Performance Behavior of Confined Brick Masonry Buildings under Seismic Demand
By
AMJAD NASEER
DISSERTATION Submitted in partial fulfillment of the requirements for the degree of Doctor of
Philosophy in Civil Engineering
Department of Civil Engineering,
N-W.F.P University of Engineering and Technology,
Peshawar, Pakistan, 2009
© Amjad Naseer 2009. All rights reserved
ii
ABSTRACT
Seismic behavior of typical confined brick masonry buildings has been studied. Single
and double story reduced scale confined brick masonry building models, representing
typical single and double story residential houses in northern Pakistan, have been tested
on simple earthquake simulator. The models have been built at 1:4 reduced scale,
following the laws of complete model similitude and tested by subjecting them to a
sequence of excitations. The models were confined according to the requirements of
Eurocode 8.
The research work was divided into three distinct phases: testing of prototype masonry
materials and assemblages; simulation of reduced scale masonry materials and
assemblage; and shaking table test of reduced scale models. Prototype masonry materials
and assemblage were tested in compression, diagonal compression and cyclic test.
Typical shear failure was observed to be predominant failure mode in both single and
double story models. Although, the walls of single story severely damaged, the confining
element was able to prevent them from disintegration. Damage was concentrated at the
ground floor in the case of double story model. In-plane walls of ground floor were
severely damaged during strong shaking. Horizontal bed joint reinforcement is
recommended to connect the tie columns and ground floor masonry walls that will
improve the seismic behavior of the ground floor walls. Response modification factor of
3.0 and 2.41 was determined for single and double story models respectively, what is in
good correlation with Eurcode spectral amplification factors. The model test results
indicate that prototype single and double story buildings of the tested type will resist, with
moderate damage an earthquake with peak ground acceleration of 0.4 g and 0.25 g,
respectively. The same buildings would resist collapse when subjected to earthquakes up
to 1.0 g.
iii
ACKNOWLEDGMENT
This research work covers the first shaking table test conducted on reduced scale model
building at Earthquake Engineering Center (EEC), N-W.F.P University of Engineering
and Technology (UET), Peshawar. The test being first of its kind in Pakistan on
simulation of confined masonry buildings, many challenges were faced during the entire
research work, i.e., from the simulation of masonry materials to the data processing of the
shaking table test. This work would not have been possible without the support of many
people, especially Prof. Dr. Akhtar Naeem Khan.
I express deep gratitude to my research supervisor Prof. Dr. Akhtar Naeem Khan, who
continuously inspired and supported me during the entire research work. In spite of his
professional engagements, he remained thoroughly involved and provided valuable
suggestions and guidelines during the whole course of study.
I am also highly indebted to Prof. Dr. Miha Tomazevic, ZAG, Ljubljana, Salvenia and
Prof. Dr. Guido Magenese, Pavia University, Italy for their guidance and discussion at
different stages of the research work. I am also thankful to Prof. Miha Tomazevic and
Prof. Sergio M. Alcocer, UNAM, Mexico for sending me research papers as requested by
me during the course of the research work.
I am thankful to fellow Ph.D students Engr. Zakir Hussain, Engr Mohammad Ashraf and
Engr. Khan Shahzad for their help during the construction and testing of the reduced scale
models.
I wish to offer my thanks to the laboratory staff of Concrete, Material Testing, Structural
and EEC laboratories for working day and night with me during the fabrication and
testing of the masonry materials, assemblages and reduced scale model buildings.
Finally, this research could not have materialized without financial support of Higher
Education Commission (HEC) of Pakistan.
iv
NOMENCLATURE
Aw Area of horizontal cross section of wall.
A Net area
ai Acceleration of the ith mass
du Ultimate displacement
de Elastic displacement
E Modulus of elasticity
ft Tensile Strength,
fk Characteristics compressive strength of masonry
fb Normalized compressive strength of masonry unit
fm Compressive strength of mortar
fa & fb Frequencies on either side of the resonant frequency
fn Resonant frequency
G Modulus of Rigidity
g Gauge length
h Height of pier
H Height of specimen in diagonal compression test
∆H Horizontal extension
He Elastic Load
Hu Ultimate design load
Ke Effective Stiffness
l Thickness of the wall
L Length of pier
Mw Earthquake magnitude
mi Mass at the ith story level
v
P Applied load
Psi Pound per square inch
Pcf Pound per cubic feet
Qp Physical Quantity of prototype
Qm Physical Quantity of model
SF Scale Factor
Ss Shear Strength
t thickness of specimen in diagonal compression test
∆V Vertical shortening
W Width of specimen
γ Shear strain
µ Global Ductility Factor
α Coefficient determining the position of the inflection point along
the Height of pier
σ° Compressive stresses in the pier,
τ Tensile stresses in the pier.
σ Standard deviation
Ø Story rotation
ØRmax Story rotation at maximum resistance
Øcr Story rotation at crack limit
Øcoll Story rotation at limit of collapse
vi
ABBREVIATIONS
ASTM American Society for Testing and Material
ATC Applied Technology Council
ACI American Concrete Institute
CLS Cement-Lime-Sand
CLP Cement-Lime-Marble Powder
CLSP Cement-Lime-Sand-Marble Powder
CLSr Cement-Lime-Surkhi
CLSSr Cement-Lime-Sand-Surkhi
COV Coefficient of Variance
CS Cement Sand
CSK Cement-Sand-Khaka
EC Eurocode
EEC Earthquake Engineering Center
EERI Earthquake Engineering and Research Institute
EEFIT Earthquake Engineering Field Investigation Team
FEMA Federal Earthquake Management Agency
GI Galvanized Iron
GMT Greenwich Mean Time
IAEE International Association of Earthquake Engineers
LVDT Linear Variable Displacement Transformer
LSSr Lime-Sand-Surkhi
LSP Lime-Sand-Marble Powder
LS Lime Sand
NEHRP National Earthquake Hazards Reduction Program
NTC-M Mexico City Building Code
N-W.F.P UET N-W.F.P University of Engineering and Technology
PGA Peak Ground Acceleration
PUCP Catholic University of Peru
RC Reinforced Concrete
UBC Uniform Building Code
UNESCO United Nation Education Scientific and Cultural Organization
vii
URM Un-reinforced Masonry
UTM Universal Testing Machine
viii
TABLE OF CONTENT
ABSTRACT ............................................................................................................................ II
ACKNOWLEDGMENT ...................................................................................................... III
NOMENCLATURE .............................................................................................................. IV
ABBREVIATIONS ............................................................................................................... VI
TABLE OF CONTENT ..................................................................................................... VIII
LIST OF FIGURES .............................................................................................................XII
LIST OF TABLES ............................................................................................................. XVI
CHAPTER 1 INTRODUCTION ............................................................................................1
1.1 INTRODUCTION ............................................................................................................1
1.2 AIM AND OBJECTIVES OF THE RESEARCH WORK ..............................................2
1.3 SCOPE OF WORK ..........................................................................................................3
1.4 RESEARCH METHODOLGY ........................................................................................3
1.5 REPORT ORGANIZATION ...........................................................................................4
CHAPTER 2 LITERATURE REVIEW ................................................................................6
2.1 INTRODUCTION ............................................................................................................6
2.2 PROPERTIES OF PAKISTANI MASONRY ..................................................................7
2.2.1 Masonry Unit .............................................................................................................7
2.2.2 Mortar ......................................................................................................................10
2.2.3 Steel bar ...................................................................................................................11
2.3 FAILURE MECHANISM ..............................................................................................13
2.3.1 Un-reinforced Masonry ...........................................................................................13
2.3.2 Confined Masonry ...................................................................................................16
2.4 RESPONSE OF CONFINED MASONRY DURING EARTHQUAKES .....................20
2.4.1 Bam Earthquake (26 December 2003) ....................................................................20
2.4.2 Peru Earthquake (August 15, 2007) ........................................................................21
2.4.3 Central Java Earthquake (May 17, 2006) and Sumatra Earthquake
(December 26, 2004) ...............................................................................................23
2.4.4 Earthquakes in American continent (up to 2000) ....................................................23
2.5 CODES /GUIDELINES RECOMMENDATIONS ........................................................26
2.5.1 Specifications of Eurocode 6 & 8 ............................................................................26
2.5.2 Additional Recommendations .................................................................................28
ix
2.5.3 Confined Masonry Guidelines .................................................................................30
2.6 THEORY OF STRUCTURAL MODEL ........................................................................31
2.7 EXPERIMENTAL TESTING ........................................................................................33
2.7.1 Shaking Table Test on 24 Simple Masonry Building (D.Benedetti,
1998) ........................................................................................................................34
2.7.2 Verification of Seismic Resistance of Confined Masonry Buildings
(Tomzevic, M., 1997) ..............................................................................................34
2.7.3 Shaking Table Tests of Small-Scale Model of Masonry Building:
Advantages and Disadvantages (Tomzevic, M., 2000) ...........................................35
2.7.4 Seismic Behavior of a Three-Story Half Scale Confined Masonry
Structure (Bartolome, A.S., et al., 1992) .................................................................36
2.7.5 Seismic Response Pattern for URM Buildings (Abram 2000) ................................37
2.7.6 Experimental Study on Earthquake Resistant Design of Confined
Masonry Structures (Ishibashi, K., et al., 1992) ......................................................37
2.7.7 Cyclic Loading Tests of Confined Masonry Wall Elements for
Structural Design Development of Apartment Houses in the Third
World (Hiroto Kato et al 1992) ...............................................................................39
CHAPTER 3 EXPERIMENTAL PROGRAM: MASONRY
MATERIALS AND MASONRY ASSEMBLAGE .............................................................40
3.1 INTRODUCTION ..........................................................................................................40
3.2 PROTOTYPE MASONRY TEST .................................................................................41
3.2.1 Masonry Unit (Solid Burnt Clay Brick) ..................................................................41
3.2.2 Masonry Mortar .......................................................................................................43
3.2.3 Prototype Masonry Assemblage ..............................................................................44
3.3 MODEL MASONRY .....................................................................................................57
3.3.1 Model Masonry Unit ...............................................................................................57
3.3.2 Model Masonry Mortar ...........................................................................................59
3.3.3 Micro Concrete ........................................................................................................62
3.3.4 Reinforcing Bar .......................................................................................................63
3.3.5 Model Masonry .......................................................................................................63
3.4 COMPARISON OF MECHANICAL PROPERTIES OF PROTOTYPE
AND MODEL MASONRY ASSEMBLAGE .............................................................76
3.4.1 Masonry Materials ...................................................................................................77
x
3.4.2 Masonry Assemblage ..............................................................................................78
CHAPTER 4 EXPERIMENTAL PROGRAM: SHAKE TABLE TEST .........................79
4.1 INTRODUCTION ..........................................................................................................79
4.2 TYPICAL PAKISTANI MASONRY BUILDING ........................................................79
4.3 FABRICATION OF TYPICAL PAKISTANI MASONRY BUILDING ......................86
4.3.1 Foundation Pad ........................................................................................................86
4.3.2 Masonry Walls ........................................................................................................88
4.3.3 Confining Element ..................................................................................................89
4.3.4 Floor Slab ................................................................................................................92
4.4 PULL OUT TEST ..........................................................................................................94
4.5 DESIGN OF SLAB AND FLOOR BEAM REINFORCEMENT .................................97
4.6 ADDITIONAL FLOOR MASSES ..............................................................................101
4.7 EARTHQUAKE SIMULATOR ..................................................................................106
4.8 INSTRUMENTATIONS AND DATA ACQUISITIONS ...........................................107
4.8.1 Accelerometers ......................................................................................................107
4.8.2 Displacement Transducer and Reference Frame ...................................................110
4.9 GROUND MOTION TIME HISTORY .......................................................................111
4.10 TESTING PROCEDURE ..........................................................................................113
CHAPTER 5 SHAKE TABLE TEST RESULTS .............................................................115
5.1 INTRODUCTION ........................................................................................................115
5.2 SINGLE STORY MODEL BUILDING ......................................................................115
5.2.1 Condition of Model before Test ............................................................................116
5.2.2 Out of plane Walls .................................................................................................117
5.2.3 In-plane Walls .......................................................................................................119
5.2.4 Characteristics Parameters of Shaking Table Motions ..........................................121
5.2.5 Frequency and Damping ratio ...............................................................................122
5.2.6 Acceleration Amplification ...................................................................................124
5.2.7 Torsion Effect ........................................................................................................126
5.2.8 Base Shear .............................................................................................................127
5.2.9 Response Modification Factor of Single Story Model ..........................................130
5.3 DOUBLE STORY MODEL BUILDING ....................................................................132
5.3.1 Condition of Model before Test ............................................................................132
5.3.2 Out of Plane Walls ................................................................................................134
xi
5.3.3 In-plane Walls .......................................................................................................135
5.3.4 Characteristics Parameters of Shaking Table Motions ..........................................138
5.3.5 Torsion Effects ......................................................................................................139
5.3.6 Mode Shape ...........................................................................................................140
5.3.7 Acceleration Amplification ...................................................................................141
5.3.8 Base Shear and First Story Rotation Angle ...........................................................142
5.3.9 Response Modification Factor of Double Story Model ........................................147
5.4 SEISMIC RESISTANCE OF PROTOTYPE BUILDING ..........................................147
5.5 COMPARING SINGLE AND DOUBLE STORY BUILDING .................................149
CHAPTER 6 CONCLUSION AND RECOMMENDATION..........................................151
6.1 SUMMARY .................................................................................................................151
6.2 CONCLUSIONS AND RECOMMENDATIONS.......................................................155
6.3 FUTURE RESEARCH WORK ...................................................................................157
REFERENCES .....................................................................................................................159
APPENDIX A: LIST OF EQUIPMENT ...........................................................................165
APPENDIX B: DESCRIPTION OF EARTHQUAKE SIMULATOR ...........................167
APPENDIX C: MEASURED RESPONSE HISTORIES .................................................169
APPENDIX-D: SCHEMATIC DIAGRAMS SHOWING DAMAGE
PROPAGATION DURING DIFFERENT TEST RUN. ..................................................197
APPENDIX E: ELASTIC ANALYSIS OF SINGLE AND DOUBLE
STORY MODEL BY SAP ..................................................................................................211
xii
LIST OF FIGURES
Figure 2.1 Adobe brick manufacturing and stacking for sun drying 8
Figure 2.2 Sliding failure 14
Figure 2.3 Shear failure 14
Figure 2.4 Rocking failure and crushing of brick 15
Figure 2.5 Confined masonry walls 17
Figure 2.6 Internal forces direction in confined masonry building to lateral load 18
Figure 2.7 Flexure cracks in confined masonry 19
Figure 2.8 Separation of confining element and masonry wall (Yoshimura et al., 2004) 20
Figure 2.9 Damage to confined masonry building at opening (right side). 21
Figure 2.10 Undamaged six stories confined masonry building in Ice during 15 August, 2007
Peru earthquake (Sventlana Brzev 2007) 22
Figure 2.11 Undamaged two storeys RC confined masonry building next to a collapsed
adobe house in Ica (EEFIT 2008) 22
Figure 2.12 Collapsed confined masonry due to soft stories (EERI 2007). 23
Figure 2.13 Damage confined masonry building (1999 Tehuacan earthquake) due to non-
confinement in window (EERI, 1999) 24
Figure 2.14 Damaged confined masonry during 1985 Llolleo, Chile earthquake (Moroni et
al., 2003) 25
Figure 2.15 Stress-strain relationship of model and prototype materials in the case of
complete model similarity 32
Figure 2.16 Cyclic load test specimens and reinforcement details 38
Figure 3.1 Compressive strength test of solid brick masonry unit 42
Figure 3.2 Compression test of prototype masonry 46
Figure 3.3 Dimensions and instrumentations of prototype specimen for compression test. 46
Figure 3.4 Typical stress strain curve of prototype brick masonry in compression 48
Figure 3.5 Diagonal compression (shear) test 49
Figure 3.6 Dimensions and instrumentations of diagonal tension test 49
Figure 3.7 Dimensions and instrumentations of prototype cyclic load test 52
Figure 3.8 Cyclic test setup 52
xiii
Figure 3.9 Displacement history for prototype cyclic test. 53
Figure 3.10 Typical load-displacement hysteresis loop 54
Figure 3.11 Hysteresis envelop and bilinear idealized curve 54
Figure 3.12 Composition of Surkhi 58
Figure 3.13 Mould for model masonry unit (size 56 x 27 x 17 mm) 59
Figure 3.14 Three different types of model masonry 59
Figure 3.15 Composition of Sand 60
Figure 3.16 Dimensions and instrumentations of model walls for compression. 64
Figure 3.17 Typical stress-strain curve for model brick No.1 66
Figure 3.18 Typical stress-strain curve for model brick No.2 66
Figure 3.19 Typical stress-strain curve for model brick No.3 67
Figure 3.20 Model wall for tensile (shear) strength 68
Figure 3.21 Model wall during diagonal compression (shear) test 68
Figure 3.22 Dimensions of Model walls 69
Figure 3.23 Typical stress-strain curve for model brick No.1 71
Figure 3.24 Typical stress-strain curve for model brick No.2 71
Figure 3.25 Typical stress-strain curve for model brick No.3 72
Figure 3.26 Model wall test setup 73
Figure 3.27 Displacement-time history for model wall cyclic test 73
Figure 3.28 Load-displacement curve 74
Figure 3.29 Cracked model wall during cyclic test 75
Figure 3.30 Typical hysteresis envelope of model wall for south side loading 76
Figure 4.1 Typical single story prototype building 81
Figure 4.2 Ground floor of typical double story prototype building 82
Figure 4.3 First floor of typical double story prototype building 83
Figure 4.4 Single story confined masonry model building 84
Figure 4.5 Ground floor double story masonry model building 85
Figure 4.6 First floor double story masonry model building 86
Figure 4.7 Through holes in reinforced concrete foundation pad 87
Figure 4.8 Model rebars embedded in foundation concrete 87
Figure 4.9 Under-construction ground story wall 88
xiv
Figure 4.10 Toothing at the end and walls junction 89
Figure 4.11 Fabrication of stirrup for bond beam and tie column 90
Figure 4.12 Model bond and floor beam reinforcement 90
Figure 4.13 Rebars fixing for floor beam 91
Figure 4.14 Micro concrete pouring in tie column 91
Figure 4.15 Tie column after removal of form work 92
Figure 4.16 Concrete pouring in floor beam in double story model 92
Figure 4.17 Slab reinforcement prior to concrete pouring 93
Figure 4.18 Concrete pouring for single story floor slab 93
Figure 4.19 Pullout test specimens 94
Figure 4.20 Pullout Test Set up 95
Figure 4.21 Details of pullout Test Specimens 95
Figure 4.22 Slab reinforcement details of single story building 98
Figure 4.23 Slab reinforcement details of ground floor double story building 99
Figure 4.24 Slab reinforcement details of first floor double story building 100
Figure 4.25 Reinforcement details of floor beams and confining elements 101
Figure 4.26 Additional masses on single story model 103
Figure 4.27 Additional masses on ground floor of double story model 104
Figure 4.28 Additional masses on first floor of double story model 105
Figure 4.29 Additional masses on single story model 106
Figure 4.30 Additional masses on double story model 106
Figure 4.31 Single degree of freedom earthquake simulator (shake table) 107
Figure 4.32 Instrumentation details of single story model 108
Figure 4.33 Instrumentation details of double story model (elevation) 109
Figure 4.34 Instrumentation details of double story model (plan) 110
Figure 4.35 Reference frame for displacement transducer. 111
Figure 4.36 Prototype acceleration time history 112
Figure 4.37 Model acceleration time history 113
Figure 4.38 Lifting operation of double story building 114
Figure 5.1 Grid lines-single story model 116
Figure 5.2 Hairline cracks in roof slab and out-of-plane walls before test 117
xv
Figure 5.3 Sliding of roof slab and cracks in out of plane wall 1 after final test run 118
Figure 5.4 Cracks in out of plane wall 12 after final test run 118
Figure 5.5 Damage to in-plane wall (grid A) at the end of test 119
Figure 5.6 Damage to in-plane wall at grid C and F at the end of test 119
Figure 5.7 Fourier amplitude spectra before the start of test 123
Figure 5.8 Fourier amplitude spectra after test run R175 124
Figure 5.9 Acceleration amplification of single story model 125
Figure 5.10 Base shear coefficient and story rotation plot for single story model 129
Figure 5.11 Hysteretic envelope and idealized bilinear relation 131
Figure 5.12 Grid lines- double story model 133
Figure 5.13 Cracks in wall 1 135
Figure 5.14 Cracks in wall 9 135
Figure 5.15 Damage to ground floor wall A 136
Figure 5.16 Damage to ground floor wall F 136
Figure 5.17 Mode shapes corresponding to each test run 141
Figure 5.18 Story resistance envelop 144
Figure 5.19 Story resistance envelop 146
Figure 5.20 Hysteretic envelope and idealised bilinear relation 147
xvi
LIST OF TABLES
Table 2.1 Physical and mechanical properties of burnt clay brick ........................................... 8
Table 2.2 Absorption of burnt clay brick .................................................................................. 8
Table 2.3 Dimensions and compressive strength of concrete block ....................................... 10
Table 2.4 Compressive strength of mortar collected from field ............................................. 11
Table 2.5 Characteristics of #3 (3/8 inch diameter) bar .......................................................... 12
Table 2.6 Characteristics of #4 (1/2 inch diameter) bar .......................................................... 12
Table 2.7 Recommended allowable number of stories above ground and minimum area of
shear walls for simple buildings (EC 8) .................................................................................. 28
Table 2.8 Typical reinforcement of vertical confining element ............................................ 29
Table 2.9 Recommended maximum building height and number of stories (n) .................... 30
Table 2.10 Similitude requirements in dynamic testing ......................................................... 33
Table 3.1 Compressive strength of masonry unit (solid burnt clay brick) .............................. 42
Table 3.2 Water absorption of burnt clay brick ...................................................................... 43
Table 3.3 Compressive strength of masonry mortar .............................................................. 44
Table 3.4 Compressive strength and modulus of elasticity of prototype brick masonry ....... 47
Table 3.5 Tensile strength and modulus of rigidity of prototype brick masonry .................. 50
Table 3.6 Dimensions and mechanical properties of prototype masonry .............................. 55
Table 3.7 Target mechanical values of materials ................................................................... 57
Table 3.8 Compressive strength and density of model masonry units .................................. 59
Table 3.9 Compressive strength of cement based-masonry mortar ....................................... 61
Table 3.10 Compressive strength of lime based-masonry mortar ......................................... 62
Table 3.11 Compressive strength of micro-concrete ............................................................. 63
Table 3.12 Compressive strength and modulus of elasticity of model masonry ................... 65
Table 3.13 Tensile (shear) strength and modulus of rigidity of model masonry ................... 70
Table 3.14 Mechanical properties of model walls .................................................................. 75
Table 3.15 Actual and true scale factor for masonry materials ............................................. 78
Table 3.16 Actual and true scale factor for masonry assemblage .......................................... 78
Table 4.1 Wall-density ratios of buildings ............................................................................. 80
xvii
Table 4.2 Wall-density ratios of selected buildings ............................................................... 81
Table 4.3 Pull out test results ................................................................................................. 96
Table 4.4 Correlation of prototype to model ....................................................................... 102
Table 5.1 Characteristic parameters of shake table motion .................................................. 122
Table 5.2 Frequency and coefficient of viscous damping .................................................... 123
Table 5.3 Floor acceleration amplification ........................................................................... 125
Table 5.4 Top slab displacements during different test run .................................................. 127
Table 5.5 Base shear coefficient and rotation angle of single story model .......................... 129
Table 5.6 Base shear coefficient and story rotation at limit state levels ............................... 130
Table 5.7 Characteristic parameters of shake table motion .................................................. 139
Table 5.8 Slab displacements during different test run ......................................................... 140
Table 5.9 Acceleration amplification .................................................................................... 142
Table 5.10 Base shear coefficient and story rotation angle .................................................. 143
Table 5.11 Base shear and first story ratio at maximum and ultimate state ......................... 145
Table 5.12 Base shear and first story ratio at maximum and ultimate state ......................... 146
Table 5.13 Modeling scale factors to extrapolate model test results to prototype building . 148
Table 5.14 Parameters of seismic resistance for single story building ................................. 149
Table 5.15 Parameters of seismic resistance for double story building ................................ 149
Table 6.1 Parameters of Seismic Resistance for Single Story building ................................ 155
Table 6.2 Parameters of Seismic Resistance for Double Story building .............................. 155
1
CHAPTER 1 INTRODUCTION
1.1 INTRODUCTION
Masonry is one of the oldest construction materials providing shelter against environmental
and natural hazard. Masonry has been used in different forms in different regions of the
world, as stone masonry buildings; timber reinforced stone buildings, un-reinforced brick and
concrete block and recently as reinforced and confined brick and/or block masonry. Masonry
is also used extensively in construction as infill in the frame structure and as partition walls.
The masonry would continue to be used in the low to medium rise buildings because of its
low cost, environmental insulation and good vertical and lateral load resistance. However,
due to significant deviation from the decades old earthquake resistant traditional construction
and the use of non-engineered construction in urban nuclei, the seismic hazard posed by
masonry has alarmingly increased.
In the recent 2005 Kashmir earthquake more than 450,000 buildings were partially or fully
damaged (ADB-WB, 2005). Most of the buildings were non-engineered, un-reinforced
masonry, including adobe, rubble stone, concrete block and brick masonry buildings. Most of
the deaths and injuries were the direct results of collapse of buildings. Structural
configurations, low quality of masonry materials, workmanship and lack of confinement of
the masonry walls were responsible for the widespread building damage (Naseer, A., et al,
2009). The Kashmir earthquake proved that un-reinforced masonry buildings are vulnerable
in moderate and high seismic zones. However, the need for earthquake resistant construction
has been realized by the people and because of that in the post-earthquake scenario
construction of confined masonry single to triple story buildings has increased many folds.
The construction currently being practiced is considered to be non-engineered as no proper
analysis and design has been carried out.
The seismic analysis and design of masonry buildings require parameters of dynamic
behavior. Modern seismic building codes like Eurocode and Uniform Building Code (UBC)
2
gives these provisions. Immediately after the Kashmir earthquake, Pakistan Building Code
was developed by modifying modern international seismic building codes, for example the
Uniform Building Code (UBC 97), American Concrete Institute (ACI) and American
National Standard Institute (ANSI). However, the development of indigenous design
parameters is needed for their onward incorporation in the Pakistan Building Code.
The seismic behavior of masonry buildings depends on the configuration of buildings,
mechanical properties of masonry materials and assemblage, and workmanship. Therefore,
the evaluation of seismic behavior of typical Pakistani masonry buildings and the design
parameters is required. In this research work seismic behavior of typical confined brick
masonry buildings has been evaluated by subjecting reduced scale models to increased
intensities of ground motions on uni-axial shake table.
1.2 AIM AND OBJECTIVES OF THE RESEARCH WORK
The proper understanding of behavior of typical masonry building requires the knowledge of
masonry materials and their assemblage. In order to investigate the non-linear seismic
behavior of buildings shake table testing has been preferred over the static testing. However,
large multi-degree-of-freedom shaking tables are developed to drive large masses, testing full
size specimens is limited because of the high cost of operation and testing specimen. Reliable
test data is obtained by testing reduced scale building models on simple earthquake
simulator. Generally, global behavior of the building models is determined. Following are the
objectives of this research work:
• Seismic evaluation of typical confined brick masonry buildings,
• Evaluation of response modification factor and ductility ratio of typical confined
brick masonry buildings
• Determination of properties of typical masonry materials
• Evaluation of properties of typical masonry assemblage
The research addresses some of the goals of the Earthquake Engineering Center (EEC) to
develop indigenous design parameters for Seismic Building Code of Pakistan and improve
the current construction practice and earthquake engineering in Pakistan.
3
1.3 SCOPE OF WORK
Scope of this research work includes evaluation of the behavior of typical confined brick
masonry buildings by shake table testing of single and double story models and to provide
values of the response modification factor and ductility ratio of the typical confined brick
masonry buildings.
Evaluation of the properties of prototype masonry materials and assemblages in compression,
tension and cyclic loading was carried out. The testing of the model masonry materials and
assemblages to simulate the prototype masonry properties were also carried out.
1.4 RESEARCH METHODOLGY
The experimental programs of this research work have been divided into following phases:
• In the first phase, prototype masonry materials and assemblage have been tested to
determine their mechanical properties. Test data of bricks and reinforcing bars was
collected from the material testing laboratory of the university and analyzed to
evaluate typical properties of masonry materials. Masonry mortar samples from the
on-going construction in Peshawar, Abbottabad and Mansehra have been collected
and tested in compression. Prototype masonry assemblages were prepared from
typical materials and tested in compression, diagonal compression and, constant
vertical and cyclic lateral load.
Mortar used for the prototype masonry assemblage is typical mortar used in and
around Peshawar city, i,e., cement-sand-khaka (stone dust) mortar in the proportion
of 1:4:4 by volume. Cement-sand mortar in the proportion of 1:6 and 1:8 is also
common in Peshawar and earthquake affected area. Data collected from the material
testing laboratory represents lager part of N-W.F.P.
• In the second phase extensive research has been carried out to simulate masonry
materials properties (compressive strength of mortar and concrete, and compressive
strength and density of brick). Cement-lime-sand and cement-lime-surkhi (broken
bricks) mortar was used for preparation of model masonry mortar, micro-concrete and
model bricks. Different mixes of mortar for model masonry mortar, micro-concrete
4
and model bricks have been prepared and tested in order to obtain physical and
mechanical properties of model materials, conforming to the requirement of the
theory of models. Model masonry assemblages (model prisms and wallets) have been
tested to evaluate their strengths in compression and tension. Model walls have also
been tested in static lateral load.
• In the final phase, typical model buildings have been fabricated and tested by
subjecting them to increasing intensity of shake table motion in each test run.
Response accelerations and displacements were measured at floor levels. The data has
been analyzed to determine response modification factor.
1.5 REPORT ORGANIZATION
The report contains collection and analysis of materials data, testing of masonry assemblage
and shaking table test of typical confined brick masonry building models. The report has
been divided in to six chapters and is presented in the following manner:
Chapter 2 presents literature review. The chapter is divided into seven sections. Typical
properties of Pakistani masonry materials are presented. Failure mechanism and behavior of
confined masonry buildings during past earthquake all over the world is presented.
Provisions of codes about the confined masonry buildings are discussed. The background of
similitude laws is described. Finally the research work carried out elsewhere in the world on
shake table and cyclic test of walls are reviewed in this chapter.
Chapter 3 contains the testing of prototype and model masonry. Compressive strength and
water absorption of masonry units used in this research work is presented. Compressive
strength, shear strength and cyclic test of prototype masonry conducted are also presented.
The results of modeling of masonry materials and testing of model wallets constructed to
simulate the physical and mechanical properties of prototype masonry walls are analyzed and
discussed.
In chapter 4, layout of typical Pakistani single and double story masonry buildings are
selected by analyzing number of drawings. Fabrication of the models is discussed. Additional
5
masses required for simulating floor masses is determined. Instrumentations of the models
and testing procedure are also presented.
In chapter 5, results of the shaking table test are presented. The failure mechanism observed
during the shaking table test is discussed. Frequency and damping ratio measured during
different intensity of shaking is also presented. Base shear and drift ratio measured for single
and double story building is provided. Response modification factor calculated for single and
double story typical confined brick masonry are presented.
Chapter 6 presents summary and, conclusions and recommendations of the research work.
Future research works have been recommended.
6
CHAPTER 2 LITERATURE REVIEW
2.1 INTRODUCTION
Confined masonry is one of the most widely used construction systems in Latin America,
Europe and Asia. Where, the masonry system performed satisfactorily during past
earthquakes. The system has been in use for decades; however, not much experimental work
has been done for the evaluation of behavior of confined masonry. In Pakistan, confined
masonry construction is popularly used after October 08, 2005 Kashmir earthquake through
the affected area.
In this chapter an attempt has been made to present typical properties of masonry materials
used in Pakistan in section 2.2. The data presented here represent mainly N-W.F.P. However,
data of bricks and steel bars is collected from Material Laboratory of Department of Civil
Engineering and is supposed to cover much larger area than N-W.F.P. The failure mechanism
of the confined masonry is discussed in section 2.3. The behavior of confined masonry
buildings during past earthquakes in Latin American and Asian countries is presented section
2.4.
Section 2.5 presents code and guidelines recommendations about confined masonry
materials and structural requirements.
Section 2.6 provides theoretical background of similitude requirements in testing reduced
scale masonry models.
The experimental research carried out at different research institute including shaking table
tests of reduced scale models and cyclic test of walls is presented in section 2.7.
7
2.2 PROPERTIES OF PAKISTANI MASONRY
2.2.1 Masonry Unit
Burnt clay brick, sun dried clay brick (adobe brick), solid concrete block and, dressed and
undressed stone is used as masonry unit for the construction of masonry buildings in
Pakistan. In the subsequent section physical and mechanical properties are given for masonry
units. Brick data collected from Materials Laboratory, Department of Civil Engineering, N-
W.F.P UET, Peshawar has been analyzed and presented.
2.2.1.1. Brick
In the urban center solid burnt clay bricks are mostly used in the masonry building
construction and as masonry infill in the frame structures. However, in the rural areas adobe
bricks, of same size as burnt brick, are also used for the construction of single story
residential houses. The clay bricks are manually produced by pressing clay with certain
amount of sand in the wooden mould (figure 2.1). The wet bricks are first dried in the sun
and air and then transported to the brick kiln for subsequent burning process. The bricks are
burnt up to temperature of 800-900 C° in the brick kiln. As there is no temperature control in
the kiln, three different types of bricks are normally produced. The bricks are categorized as
first class with sharp edges, have comparatively low absorption and good strength. The first
class brick are recommended bricks type for building construction. The second class brick
are porous under-burnt with relatively high absorption and low strength. These types of
bricks are preferably used by low income group for construction of residential buildings. The
other types of bricks are over burnt with dark brownish color and irregular shape. These
bricks are not used for construction purposes.
The physical and mechanical properties of burnt clay bricks are given in table 2.1 and table
2.2. Data of almost 500 bricks tested in the Material Laboratory, Department of Civil
Engineering, N-W.F.P UET, Peshawar has been analyzed. The dimensions given in the table
are actual dimensions measured before crushing of the brick in universal testing machine.
The compressive strength of brick has been determined on full size brick, properly capped on
both sides.
8
Figure 2.1 Adobe brick manufacturing and stacking for sun drying
Table 2.1 Physical and mechanical properties of burnt clay brick
Length
inch (mm)
Width
inch (mm)
Height
inch (mm)
Specific Weight
pcf (kN/m3)
Strength psi
(MPa)
Maximum 9.63 (245)
5.75 (146)
2.81 (71)
125.4 (19.7)
6017.0 (41.5)
Minimum 8.00 (203)
4.00 (102)
2.50 (64)
84.8 (13.3)
617.0 (4.2)
Mean 8.71 (221)
4.21 (107)
2.71 (69)
98.1 (15.4)
2350.0 (16.2)
Coefficient of variation (%) 2% 3% 3% 22% 30%
Table 2.2 Absorption of burnt clay brick
Wet weight
lb (N)
Dry weight
lb (N) Absorption (%)
Maximum 6.98 (31.0)
7.95 (35.4) 25.84
Minimum 4.86 (22.0)
6.04 (27.0) 7.79
Mean 5.90 (26.0)
7.02 (31.0) 18.88
Coefficient of Variation (%) 37% 42% 18%
It is observed that the variability in the compressive strength as well as specific weight of the
solid burnt brick is quite large. The variation in strength and weight could be attributed to
raw materials, sun drying and burning temperature. However, it has been found from the
9
statistical evaluation of the compressive strength of masonry units in Latin America that hand
made solid clay bricks strength depended on the raw materials used in the fabrication and not
on the fabrication process itself (Alcocer, S.M., and Klingner, S.M 1994). It can be seen that
the mean compressive strength comply with the minimum strength (1000 psi or 6.89 MPa)
required by Earthquake Rehabilitation and Reconstruction Authority (ERRA) guidelines and
European standard (EN 771-1).
The absorption of brick is not directly affecting quality of masonry; however, bricks absorb
water from mortar and render the masonry weak.
2.2.1.2. Block
Solid concrete block is also becoming popular, especially in the northern part of N-W.F.P or
Azad Kashmir because of the unavailability of brick kiln and high cost of brick imported
from other part of the country. The blocks are used for construction of single or double story
buildings and also as infill masonry in the frame structure. The blocks are manufactured in
small factories in semi-automatic machines. Generally the mix proportion used for the
concrete is quite lean and there is no control of water to cement ratio. The ingredients are
mixed by volume in the proportion of 1:4:8 (one part of cement to four part of sand and eight
part of course aggregate), 1:4:6 and 1:5:7 by volume. The different sizes of blocks produced
are 12 x 8 x 6 inch (30.5 x 20.3 x 15.2 mm), 12 x 8 x 5 inch (30.5 x 20.3 x 12.7 mm) and 12
x 8 x 4 inch (30.5 x 20.3 x 10.1 mm) (length x width x thickness). Table 2.3 gives nominal
dimensions and average compressive strength of solid blocks collected from three different
factories. It is worth mentioning that the compressive strength given in table 2.3 is mean
value of three blocks, determined by testing full size unit normal to bed.
10
Table 2.3 Dimensions and compressive strength of concrete block
Length
inch (mm)
Width
inch (mm)
Height
inch (mm)
Average
Strength psi
(MPa)
1 12 (305)
6 (152)
6 (152)
220.0 (1.5)
2 12 (305)
8 (203)
6 (152)
906.0 (6.2)
3 12 (305)
8 (203)
6 (152)
750.0 (5.2)
Earthquake Reconstruction and Rehabilitation Agency (EERA) construction guideline-2006
recommends 12 x 8 x 6 inch (30.5 x 20.3 x 15.2 mm)concrete block for the construction of
building. However, the minimum compressive strength is not specified, the mix proportion of
one part of cement to three part of sand and three part of coarse aggregate (1:3:6) is specified.
The mean compressive strength of concrete block 12 x 6 x 6 (30.5 x 15.2 x 15.2) is less than
the minimum compressive strength specified in relevant European Standards (EN 771-1-6)
which is 261 psi (1.8 MPa). However, compressive strength of the concrete block 12 x 8 x 6
(30.5 x 20.3 x 15.2 mm) is more than the minimum compressive strength of both EN 771-1-6
and EC 8 for solid concrete aggregate units.
2.2.1.3. Stone
Stone masonry has been traditionally used in northern area of Pakistan. Use of un-dressed
stone units was more common in unreinforced masonry and in Dhajji type construction.
According to Eurocode 6 and Eurocode 8, the use of dimensioned stone units that are square
dressed units with parallel horizontal faces, is allowed for the construction of masonry
building in seismic zones.
2.2.2 Mortar
Mortar is used to bind masonry units, is a mixture of binding material (cement and/or lime),
aggregates (sand) and water. In the century old buildings when cement was a rare building
construction material, the mixture of lime and surkhi (burnt brick powder) were used as
mortar. The mix proportion and compressive strength of the lime-surki could not be
ascertained. With the advent of cement, the use of lime and surkhi become less significant,
11
probably, for their slow setting time. However, lime-surkhi mortar is still used for the repair
of old traditional and monumental buildings.
Mortar consisting of mixture of cement-sand and/or cement-sand-khaka (stone dust) is used
in the contemporary buildings construction. The constituent materials are manually mixed in
different proportions depending on the thickness of walls (that is double leaf full brick or
single leaf half brick wall), number of stories and economic class. The water is arbitrary
added to achieve workable paste. The addition of water and remixing with time is common
practice. Table 2.4 gives compressive strength of cement-sand and cement-sand-khaka
mortar collected from 30 under-construction building sites in Peshawar, Abbottabad and
Mensehra. The compressive strength is determined by testing 2 inch cubes specimens.
Table 2.4 Compressive strength of mortar collected from field
Compressive Strength, psi (MPa)
7 Days 28 Days
Maximum 1096.0 (7.6)
1680.0 (11.6)
Minimum 84.5 (0.58)
156.0 (1.1)
Mean 545.5 (3.8)
837.5 (5.8)
Cov (%) 102% 66%
It could be seen in table 2.4 that the variation in compressive strength of mortar is very large.
The low strength could be attributed to lean mix, use of high water to cement ratio and use of
mortar after it has been set. However, the mean compressive strength is higher than type M5
(725 psi/5 MPa) recommended by EC 8 for unreinforced and confined masonry. The scatter
of data could be attributed to mix proportion, w/c ratio, mix material and time of use of the
mortar.
2.2.3 Steel bar
In building construction, generally grade 40 (fy = 40 ksi) and grade 60 (fy = 60 ksi) bars are
used from #3 to #8 (0.375 to 1 inch diameter) deformed bars. However, plain bars have also
been used in the existing construction. #3 and #4 deformed bars are mostly used in reinforced
concrete slab in masonry buildings. #3 bars are also used for stirrups in beams and columns.
12
#4 and #6 bars are mostly used as longitudinal bars in beams. In table 2.5 and 2.6 simple
statistical analyses for yield strength, ultimate strength and elongation is presented. Data of
almost 1500 steel bars have been collected from Material Laboratory, department of Civil
Engineering, N-W.F.P UET, Peshawar and analyzed. The yield and ultimate strength given
in table correspond to grad 40 and grade 60 deformed bars.
Table 2.5 Characteristics of #3 (3/8 inch diameter) bar
Yield Strength
psi (MPa)
Ultimate Strength
psi (MPa)
Percentage
Elongation
(%)
Ultimate to
Yield Strength Ratio
Maximum 90,251.5 (622.5)
14,1628.4 (977.0) 22.66 2.45
Minimum 41,718.5 (288.0)
59,040.0 (407.0) 2.34 1.00
Mean 67,067.0 (462.5)
94,083.0 (649.0) 13.85 1.41
Cov (%) 15% 14% 25% 11%
Table 2.6 Characteristics of #4 (1/2 inch diameter) bar
Yield Strength
psi (MPa)
Ultimate Strength
psi (MPa)
Percentage
Elongation
(%)
Ultimate to
Yield Strength Ratio
Maximum 87478.5 (603.5)
130915.5 (903.0) 25.00 1.77
Minimum 40987.6 (283.0)
59938.8 (413.5) 2.34 0.94
Mean 66013.0 (455.0)
94591.5 (652.5) 15.72 1.44
Cov (%) 13% 12% 23% 7%
However, properties of grade 40 and grade 60 rebars could not be distinguished from the
data. The mean value of ratio of ultimate to yield strength is higher than 1.25 as required by
Section 1921.2.3.2 of Uniform Building Code 1997 (UBC 97). The mean elongation for both
#3 and #4 bars is more than the minimum required (9%) by ASTM A 615.
It has been concluded by a statistical study (Fakhur-us-Zaman 2003) that the probability of
obtaining yield strength between 55,000 psi/379.0 MPa and 85,000 psi/586.0 MPa for #3 and
13
#4 bars are 89.96 and 87.51 respectively, which reflects wide dispersion of yield strength
values of grade 40 bars from a specified minimum value of 40,000 psi/275.9 MPa.
2.3 FAILURE MECHANISM
In this section first the failure mechanism of un-reinforced masonry (URM) is discussed and
then the different modes of failure in the confined masonry, according to earthquake damage
analysis and experimental investigations are presented.
2.3.1 Un-reinforced Masonry
According to earthquake damage analysis and experimental investigation, four types of
failure modes have been identified. The crack patterns and failure mode of URM depend on
the axial stress, aspect ratio (height to width ratio), material strength and boundary
conditions.
• In the case of low vertical stresses and poor quality of materials, when the horizontal
shear stresses exceed the joint shear strength of the masonry, horizontal cracks at the
top and bottom of the pier develops. The upper part usually slides over the lower part
and the type of damage are called sliding failure (figure 2.2).
• Diagonal shear failure (figure 2.3) occurs where the principal tensile stresses, exceed
the tensile strength of the masonry. This is the most frequent type of failure mode.
The diagonal shear cracks either follow the mortar joint or passes through masonry
unit depending on the relative strength of mortar and unit.
• In the case of large flexure moment and improved shear resistance, horizontal cracks
at the top and bottom develop and the pier may undergo rigid body rotation (figure
2.4). This type of failure mode is known as rocking.
• The principal compressive stresses, sometimes, exceed the compressive strength of
masonry leading to crushing of masonry. As toe of the pier is usually the zone of high
compressive stresses, the crushing occurs at the toe and the failure is called toe
crushing (figure 2.4).
14
Figure 2.2 Sliding failure
Figure 2.3 Shear failure
15
Figure 2.4 Rocking failure and crushing of brick
The in-plane failure of pier is often the combination of the above failure modes. As the
nature of failures is different, so is their energy dissipation and deformation capacity. The
rocking exhibit large deformation but comparatively less energy is dissipated. Because of the
sliding action along the head and bed joint more energy is dissipated in shear failure.
However, diagonal cracks passing through units make the pier unstable and results in brittle
failure. Similar behavior of instability of pier could be expected during toe crushing.
Based on FEMA 307 (ATC 1999), the ultimate drift ratio for different mode of failure has
been summarized by Simsir C.C 2004. The pier failing in diagonal tension or toe crushing
without rocking or sliding, the ultimate drift capacity of pier is around 0.5%. While if rocking
and sliding failure is preceded by diagonal or toe crushing, the ultimate drift is larger from
1% to 2%. FEMA 274 provides the following formula for the elastic stiffness, Ke of
masonry piers based on elastic theory considering flexural and shear deformation:
α
=⎡ ⎤⎛ ⎞⎛ ⎞+⎢ ⎥⎜ ⎟⎜ ⎟
⎝ ⎠⎝ ⎠⎢ ⎥⎣ ⎦
21.2 1
we
GAK
G hhE L
(2.1)
Where:
16
Aw = horizontal area (length, L x thickness, t) of the wall.
α = coefficient determining the position of the inflection point along the height of pier
(α = 0.83 for fixed-fixed wall and 3.33 for cantilever wall)
h = height of the pier
The tensile strength, ft of masonry wall can be calculated from the theory of shear resistance
as (Turnsek and Cacovic, 1971):
( )στ°⎛ ⎞= +⎜ ⎟
⎝ ⎠21.5
2tf (2.2)
Where:
σ° = compressive stresses in the pier,
τ = Shear stresses in the pier.
2.3.2 Confined Masonry
Confined masonry is one of the widely used masonry systems in Latin America, Asia and
Europe. In this type of masonry system un-reinforced masonry wall are confined with
horizontal and vertical reinforced concrete elements or reinforced masonry elements (figure
2.5). The confining vertical elements, which are also known as tie columns, are provided to
improve the ductility and seismic resistance of building and prevent disintegration of
masonry walls during strong ground motion. The horizontal confining elements or bond
beams are used to make sure the box type behavior by tying all walls together. In confined
masonry, walls are erected first and then concrete is poured at the location of tie columns and
bond beams. The confining elements are not designed to resist any load. According to
Eurocode 6 and 8, no contribution of the confining elements should be taken in the
verification of confined masonry buildings. However, in the case of reinforced concrete
frame structure, columns and beams are part of the load resisting structure system. In frame
structure columns and beams skeleton is first constructed and it is then filled with masonry
walls. In order to be efficient construction, the bond beams and tie columns reinforcements
17
should be properly connected and anchored. Toothing should be provided at the vertical
border of walls for proper interaction of masonry walls and tie columns.
The different types of failure modes observed during earthquakes and in experimental studies
of confined masonry are classified as in-plane, out of plane and connection failure. The
evidence of observed behavior has been given; however, detailed description of experimental
testing and damage during earthquakes are provided in the subsequent sections.
Figure 2.5 Confined masonry walls
2.3.2.1. Plane Failure
The three different types of in-plane failure in the confined masonry are diagonal shear
failure, sliding shear failure and flexure failure.
• Confined masonry transfer horizontal in-plane inertia loads by diagonal strut (figure
2.6) from the upper floor level to lower floor level or to the foundation. When the
principal diagonal tensile stresses, produced by diagonal compression stresses, exceed
the tensile strength of masonry, diagonal cracks appear in the masonry. In the case of
weak mortar and strong unit, the cracks follow mortar joint in zig zag fashion and if
the unit is comparatively weak, diagonal cracks passes through masonry unit. When
the deformation continues to increase, eventually, shear cracks also appear in the
vertical confining column at the top joint. The factors which are responsible for this
type of failures are low tensile strength of mortar and weak mortar-unit bond strength.
Uniformly distributed diagonal shear cracks develop and propagate towards tie
column, thereby cracking the reinforced column. Crushing of masonry units in the
18
middle part of masonry and crushing of tie column concrete were observed at high
stress demand (Tomazevic, M., 1997; Ishibashi, K., et al. 1992). It has also been
observed during past earthquakes and in experimental studies that diagonal cracks
concentrate in the ground story (Alcocer et al., 2004; Schultz, A.E., 1994; EERI
2007).
Figure 2.6 Internal forces direction in confined masonry building to lateral load
• Sliding shear failure is the second type of in-plane failure observed in the confined
masonry buildings. This type of failure occurs in horizontal plane by the shear failure
of weak mortar brick bond. The cracks also sometime extend to vertical confining
element. Sliding shear failure are associated with the diagonal cracks.
• The third type of failure is the flexure failure. In the case of tall wall and high lateral
seismic load, large bending moments are produced at the bottom of the wall, thereby
producing tensile stresses at the one and compression stresses at the other end of the
in-plane confined wall. When the tensile stresses exceed the tensile strength of
mortar, horizontal cracks appear as shown in figure 2.7. Separation of vertical
confining element and masonry walls, and horizontal cracks in the vertical confining
element sometimes also follow.
19
Figure 2.7 Flexure cracks in confined masonry
2.3.2.2. Connection failure
Different type of connection failures are separation of masonry wall from vertical confining
element, separation of diaphragm/bond beam and masonry wall, and joint failure of
horizontal and vertical confining elements. The connection failure results in the change in the
mechanism of the masonry. The masonry walls are no longer be able to transfer tensile
stresses to vertical confining element.
• The masonry wall and vertical confining element separation could result by in-plane
or out of plane forces. This type of failure affects in-plane behavior by preventing
transfer of tension forces from the wall to the column. The failure also affects out of
plane behavior as the masonry walls are no longer supported by confining elements.
Separation of tie column and wall (figure 2.8) has been observed during earthquakes
and confined masonry testing (Paikara, S. and Rai, D.C, 2006; Yoshimura et al.,
2004; Yoshimura, K., and Kuroki, M., 2001).
• The second type of connection failure is also the result of either in-plane or out of
plane loadings. The failure results in weakening out of plane resistance and in-plane
load transfer. Horizontal cracks between floor slab and masonry wall were observed
during the 1985 Chile earthquake (Schultz, A. 1994).
• Improper anchorage of reinforcement at the confining elements joint results in the
joint failure.
20
Figure 2.8 Separation of confining element and masonry wall (Yoshimura et al., 2004)
2.4 RESPONSE OF CONFINED MASONRY DURING EARTHQUAKES
In this section, the observed behavior of confined masonry during earthquake is presented. It
has been observed that properly designed confined masonry performed satisfactorily well
during earthquakes. However, some of the buildings were severely damaged. The poor
performance of building was attributed to insufficient confinement provided to the masonry
walls, inadequate diaphragm connections, discontinuous tie beam and inappropriate
structural configuration. In the following section the experiences during Asia and Latin
American major earthquakes are given. The behavior of confined masonry during
earthquakes up to 2000 is presented in section 2.4.4.
2.4.1 Bam Earthquake (26 December 2003)
On 26 December 2003 at about 1:57 GMT, the historical city of Bam, Iran was struck by
strong earthquake, Ms of 6.7. Forty five thousand people lost their lives. PGA of 0.8g and
0.7g for the East-West and North-South horizontal components, respectively, were recorded
in the Bam station. The masonry buildings consisting of load bearing burnt brick masonry
with steel roof were as poor as adobe buildings. However, newly constructed masonry
buildings with vertical and horizontal reinforcing concrete elements performed well and
saved the lives of inhabitants (Zahrai, S. M., Heidarzadeh, M., 2004). Figure 2.9 shows a
confined masonry building damaged at opening during the earthquake. The collapse of
façade wall is also shown in the figure.
21
Figure 2.9 Damage to confined masonry building at opening (right side).
2.4.2 Peru Earthquake (August 15, 2007)
An earthquake of magnitude 7.9 struck Pisco, Peru at 6.40 p.m. local time, killing at least 519
people and injuring 1090. The modern properly engineered buildings found were the
confined masonry buildings. This type of construction consists in constructing first the clay
brick walls while leaving empty space with reinforcement which is latter filled in by
concrete, obtaining a solid joint between the RC frame and the clay bricks. In this way the
stiffer masonry walls provide most of the lateral resistance than the skeleton frame structure.
This type of building performed satisfactorily. The good performance of confined masonry
brick building up to six stories (figure 2.10) may be because of their inherent large capacity
to lateral loads (Sventlana Brzev 2007). Figure 2.11 shows undamaged two story building
next to collapsed adobe building (EEFIT report 2008). Confined masonry with soft stories
and other irregularities as well as bad detailing was severely damaged (figure 2.12).
However, well constructed confined masonry resisted the earthquake with little or no damage
(EERI report Oct 2007).
22
Figure 2.10 Undamaged six stories confined masonry building in Ice during 15 August, 2007
Peru earthquake (Sventlana Brzev 2007)
Figure 2.11 Undamaged two storeys RC confined masonry building next to a collapsed
adobe house in Ica (EEFIT 2008)
23
Figure 2.12 Collapsed confined masonry due to soft stories (EERI 2007).
2.4.3 Central Java Earthquake (May 17, 2006) and Sumatra Earthquake (December 26, 2004)
On May 27, 2006 at 5.54 am local time an earthquake of magnitude 6.3 struck Java islands,
Indonesia leaving 5,176 people dead. An estimated 154,000 houses were completely
destroyed and 260,000 suffered damage of different nature. The houses in the affected area
were divided into unreinforced masonry, confined or partially confined masonry and timber
frame houses. The post 1990 construction include confined or partially confined brick, solid
concrete block or stone masonry in cement mortar walls with flexible, pitched or hipped
timber truss or bamboo roofs covered by clay tiles. The confined masonry building
performed well (EERI 2006) in this earthquake.
In the town of Banda Aceh Sumatra, Indonesia confined masonry buildings constituted 70%
of the housing stock. During 2004 Sumatra earthquake, the buildings 1-2 stories high did not
collapse; however, ground story walls experienced out-of-plane failure by tsunami-induced
water pressure.
2.4.4 Earthquakes in American continent (up to 2000)
Observation made during past earthquakes in the North, Central and South American
countries are discussed. Generally, it has been observed that lightly loaded and regular
confined masonry performed quite well during earthquakes, particularly for one and two
24
story residential buildings. Construction deficiencies and poor quality of construction
materials were the causes of poor performance of confined masonry.
The performance of confined masonry up to four or five stories were generally good during
1985 Mexico earthquake (Mw 8.0). However, complete collapse of a three story office
building with a highly irregular floor plan was observed (Schultz, A. 1994). In the 1999
Tehuacan (Mw 6.5) and 2003 Tecoman (Mw 7.6) earthquakes, confined masonry buildings
performed generally well. However, some failures were observed due to inadequate wall
strength, poor quality of construction, inadequate number and arrangement of confining
element (figure 2.13) (EERI, 1999 & 2006).
Figure 2.13 Damage confined masonry building (1999 Tehuacan earthquake) due to non-
confinement in window (EERI, 1999)
On January 13, 2001, an earthquake of magnitude Mw=7.7 occurred in the Republic of El
Salvador in Central America. The earthquake resulted in 844 people dead and 75,000
buildings completely damaged. The use of ‘confined masonry’ walls is more popular for the
construction of residential buildings. In this system, cast-in-place, slender R/C columns are
presented at most of the extreme edges and intersections of the walls. In addition, cast-in-
place R/C collar beams are also provided. Buildings up to three and more stories are used.
The large number of existing confined masonry buildings were not severely damaged during
the earthquake, except in few cases of shear failure and separation of block masonry wall and
vertical confining column (Yoshimura, K., and Kuroki, M., 2001). It was reported by
25
Ascheim et al (2006) that ‘mixto’ confined masonry construction was used in the post-
earthquake rehabilitation following the 2001 earthquakes.
It was observed during March 31, 1983 Popayan, Colombia earthquake that adding
horizontal beams to unreinforced masonry reduced the seismic damage, while the addition of
tie column eliminate damage (Schultz, A. 1994). In the 1999 El Quindio, Colombia
earthquake (Mw 6.2), shear cracks and out of plane failure because of the inadequate
connection between wall and confining elements was observed (EERI, 2000).
The 1985 Llolleo, Chile earthquake (Mw = 7.8) caused the collapse of 66,000 buildings and
damaged upto 127,000. Out of 84,000 housing units, 13,500 were of confined masonry. The
buildings were from 3 to 5 storeys in height (Sventlana Brzev 2007). Confined masonry in
Chile has generally performed well during earthquakes; however, elimination of tie column
for economic purposes lead to the extensive inclined cracking and horizontal cracks between
floor slabs and masonry wall were observed during the 1985 Chile earthquake (Schultz, A.
1994). In the figure 2.14 below complete wall panel collapsed, after first developing diagonal
shear cracks. The tie columns can also be seen damaged.
Figure 2.14 Damaged confined masonry during 1985 Llolleo, Chile earthquake (Moroni et
al., 2003)
Damage to short residential confined masonry was observed due to structural configuration
and omission of tie members during 1990 Pomasqui, Ecuador earthquake (Schultz, A. 1994).
26
2.5 CODES /GUIDELINES RECOMMENDATIONS
The use of confined masonry has been practiced in Latin America, Asia and Europe. In most
of these countries the specification for confined masonry is part of their code or country
guidelines. The specifications are developed after experiences during the past earthquakes
and extensive experimentation. It has been observed that the confined masonry improves
both ductility and seismic resistance of the structure. In the subsequent sections, the
specifications of different codes and guidelines are discussed.
2.5.1 Specifications of Eurocode 6 & 8
According to the requirements of Eurocodes, no contribution of vertical confinement to
vertical and lateral resistance of the structure should be taken into account in the calculation
(C1.4.9, EC 6). Eurocode 6: Design of masonry structures gives some basic rules for the
confined masonry as discussed below; however, some additional requirements have been
specified in Eurocode 8: Design provisions for earthquake resistance of structures.
2.5.1.1 Construction Technique
According to Eurocode reinforced concrete or reinforced masonry vertical (tie column) and
horizontal (bond beam) confining element should be provided to the masonry wall so that
they act together during lateral action. Concrete for confining elements should be cast after
the construction of masonry wall. The confining elements should be provided at the
following locations:
• At all free edges of the structural walls,
• At the walls intersection,
• Tie columns should be placed at a maximum spacing of 13 ft (4 m) and,
• At both sides of opening having an area of more than 16 sft (1.5 m2)
• Tie beams should be provided at every floor level and at a vertical spacing of 4 m.
27
2.5.1.2 Geometric requirements in the confining masonry and area of reinforcement
The confining element should have cross-sectional area of 31 in2 (0.02 m2), with minimum
dimension of 6 inch (150 mm) in plan of the wall. In the case of double leaf wall, the
confining element should be equal to the wall thickness. The minimum wall thickness is the
one which give robust wall or determined from calculations.
The longitudinal reinforcement should be 0.8 % of the cross-sectional area of the confining
element and should not be less than 0.31 in2 (200 mm2). The stirrup should not be less than #
2 (6 mm) bar and should be provided at least at 12 inch (300 mm).
Horizontal reinforcement not less than # 2 (6 mm) diameter bars or equivalent and spaced at
12 inch (300 mm) should be provided and anchored in concrete column and in the mortar
joints.
According to additional requirements in Eurocode 8 (section 9.5.3), the minimum area of
reinforcement is 0.5 in2 (300 mm2) or 1% of the cross-sectional area of the confining
element. The stirrup should be provided at 6 inch (150 mm) center to center. The bar
diameter mentioned in Eurocode 8 is 5 mm which is slightly less #2 bar. The bars should be
spliced at length of 60 times diameter of bar.
The minimum thickness of the wall should be 9.5 inch (240 mm). The minimum effective
height to thickness ratio of the wall should be 15 and length of wall to clear height of the
opening (adjacent to the wall) should be 0.3.
2.5.1.3 Material Strength
The minimum compressive strength of masonry mortar of 730 psi (5 MPa) should be used
for confined masonry buildings.
2.5.1.4 Number of stories and wall density ratio
Eurocode 8 recommends minimum number of stories depending on the seismicity of the area
and wall density ratio. Table 2.7 gives the number of stories corresponding to minimum wall
density ratio and the maximum ground acceleration. In the table, k is a corrective factor
based on minimum unit strength of 725 psi (5 MPa) for confined masonry. Where k = 1+(lav-
28
2)/4≤2 for buildings having 70% of the shear walls under consideration are longer than 6.5 ft
(2 m), however, for all other cases k = 1. In the expression lav is average wall length.
Table 2.7 Recommended allowable number of stories above ground and minimum area of
shear walls for simple buildings (EC 8)
Acceleration at
site ≤ 0.07 k.g ≤ 0.10 k.g ≤ 0.15 k.g ≤ 0.20 k.g
No of Stories Minimum sum of cross-sections areas of horizontal shear walls in each direction,
as percentage of the total floor area per storey
2 2.0 % 2.5 % 3.0 % 3.5 %
3 2.0 % 3.0 % 4.0 % N/A
4 4.0 % 5.0 % N/A N/A
5 6.0 % N/A N/A N/A
2.5.2 Additional Recommendations
However, detailed and through discussion on the earthquake resistance of masonry buildings
has been given, some additional recommendations regarding confined masonry have been
provided in addition to Eurocode specifications by (Tomazevic, M., 99). The information has
been based on actual observation of masonry during earthquake and experimental research
work carried out by the author.
Because of the lack of experimental work on the behavior of confined masonry, the amount
of reinforcement in confining element is determined on empirical basis. Table 2.8 gives
number of plain bars depending on the number of stories and seismic demand.
29
Table 2.8 Typical reinforcement of vertical confining element
No of Stories
Seismic Demand
Low
(PGA = 0.1 g)
Moderate
(0.1 g < PGA < 0.2 g)
High
(0.2 g < PGA < 0.4 g)
2 1-2 4-8 mm bars 4-10 mm bars (4#3) 4-12 mm bars (4#4)
4 1-2 4-8 mm bars 4-10 mm bars (4#3) 4-12 mm bars (4#4)
4 2-4 4-8 mm bars 4-10 mm bars (4#3) 4-12 mm bars (4#4)
6 1-2 4-10 mm bars (4#3) 4-12 mm bars (4#4) 4-14 mm bars (4#4)
6 3-4 4-8 mm bars 4-10 mm bars (4#3) 4-12 mm bars (4#4)
6 5-6 4-8 mm bars 4-10 mm bars (4#3) 4-12 mm bars (4#4)
In order to fully utilize the resistance and energy dissipation capacity of masonry, the
masonry walls should be horizontally reinforced. Specially shaped ladder-type or truss type
reinforcement should be used in horizontal mortar joint provided at vertical spacing of 24
inch (600 mm). The horizontal reinforcement should be anchored in the tie column. In such
case the EC 8 requirements for connecting tie column and masonry wall should be waived
(Tomazevic, M., 99).
The seismic resistance of the masonry buildings should be verified, however, the number of
stories and height has been recommended in table 2.9 on the basis of masonry materials, wall
density ratio and configuration of building.
30
Table 2.9 Recommended maximum building height and number of stories (n)
Design ground acceleration < 0.2 g 0.2-0.3 g ≥ 0.3 g
Unreinforced
Masonry
Height, ft (m) 39.4 (12.0) 29.5 (9.0) 20.0 (6.0)
No of stories, n 4 3 2
Confined
Masonry
Height, ft (m) 59.0 (18.0) 49.0 (15.0) 39.5 (12.0)
No of stories, n 6 5 4
Reinforced
Masonry
Height, ft (m) 79.0 (24.0) 69.0 (21.0) 59.0 (18.0)
No of stories, n 8 7 6
Concrete of minimum compressive strength of 2,200 psi/15.2 MPa (C15) is recommended
for confined masonry elements.
It is also emphasized that the configuration of the building should be simple and regular. That
is the load bearing wall should be symmetrically distributed and should not change their
position and shape along the height of the building. A detailed description is presented in
(Tomazevic 1999) about the configuration or architectural requirements.
2.5.3 Confined Masonry Guidelines
Different confined masonry guidelines are available including City University guidelines
(Virdi and Raskkoff), Catholic University of Peru (PUCP and SENCICO, 2005), the
International Association of Earthquake Engineers (IAEE) (IAEE and NICEE, 2004), and
UNESCO (Ghaidan, 2002). The guidelines are in agreement on many points. However, there
are a few points where the guidelines have some differences. Some of the guidelines have
detailed approach and discuss comprehensively all the points, while the others are very
specific. A detailed discussion on the different guidelines and item by item comparison are
given in (UBC EERI Student Chapter, 2008 report). It has been tried to evaluate the
guidelines in the light of current research on confined masonry. It was concluded that Peru
guidelines could be used. However, recommendations were provided for the improvements
in the Peru guidelines.
31
Earthquake resistant confined masonry reports (Svetlana Brzev, 2007) discusses the different
requirements of confined masonry building construction. The report discusses different
factors which affect the seismic resistance of confined masonry. Confined masonry
performance during earthquakes is presented. Chile: NCh2123.97, Mexico: Mexico City
Building Code (NTC-M 2004), Eurocode 6 & 8 and Iranian code of practice for seismic
resistant design of building (Standard 28000) are summarized. Finally, the architectural and
construction guidelines are presented. It has been concluded that confined masonry generally
performed well; however, good quality materials and simple architectural design should be
used.
2.6 THEORY OF STRUCTURAL MODEL
A structural model is defined as any structural element or assembly of structural elements
built to reduced scale which is to be tested, and for which laws of similitude must be
employed to interpret test results (Harris.G and Sabnis 1999). Any structural model must be
fabricated, loaded, tested and results interpreted according the laws of similitude
requirements. Dimensional analysis is used to determine the similitude requirements of
physical quantities of model and prototype structures. The following relationship should be
satisfied for the different physical quantities involved in the structural modeling:
p m FQ Q x S= (2.3)
Where Qp is any physical quantity required, Qm is the physical quantity measured on the
model and SF is the scale factor corresponding to the physical quantity. The different types
of models used in the experimental analysis of masonry buildings depend on the materials
used for the fabrication of the models (Tomazevic. M and Velechovshky. T 1992)
1. In the case of complete model similarity special model materials are used for the
manufacturing of model. In such cases stresses are scaled to the geometric scale.
However, strain remains the same in the prototype and model (figure 2.15 (a)).
Specific weight, poisson’s ratio and damping are also same for model and prototype.
32
2. When prototype materials are used for the construction of model, the similarity is
called simple model similarity. In such case stress and strain are similar in both
prototype and model as shown in figure 2.15 (b).
Figure 2.15 Stress-strain relationship of model and prototype materials in the case of
complete model similarity
The physical quantities involved in the dynamic testing of masonry structure with
theoretically obtained scale factor fulfilling simple and complete model similitude
requirements are given in table 2.10.
StressStress
Strain
33
Table 2.10 Similitude requirements in dynamic testing
Quantity General equation Scale Factor
Complete model Simple model
Length (L) SL = Lp/Lm SL SL
Strain (ε) Sε = εp/εm 1 1
Strength (f) Sf = fp/fm SL 1
Stress (σ) Sσ = fp/fm SL 1
Young's modulus (E) SE = Sσ/Sε SL 1
Sp. Weight Sr = rp/rm 1 1
Force (F) SF = SL2Sf SL
3 SL2
Time (t) St = SL√(SrSε/Sf) √SL SL
Frequency (Ω) SΩ = 1/St 1/√SL 1/SL
Displacement (d) Sd = SLSε SL SL
Velocity (ν) Sv = Sε√SfSr √SL 1
Acceleration (a) Sa = Sf/SLSr 1 1/SL
The scale factor of 7 is upper limit for complete model in modeling brick or block masonry
and 4 for stone-masonry buildings (Tomazevic 1992). It is important in the dynamic testing
of model that dynamic behavior as well as failure mechanism is correctly simulated. Similar
distribution of masses and stiffness is required in the prototype and model building for
fulfilling similarity of dynamic behavior. And similar working stress level in the load bearing
walls of the prototype and model should be achieved for the similarity in failure mechanism.
Both requirements of dynamic behavior and working stress are fulfilled in following
complete model similitude requirements. However, special arrangements are required for the
mass distribution and working stress level, in case of simple model requirements.
2.7 EXPERIMENTAL TESTING
In this section experimental testing on shake table and cyclic testing of confined masonry
walls are briefly presented.
34
2.7.1 Shaking Table Test on 24 Simple Masonry Building (D.Benedetti, 1998)
A total of 14 shaking table tests were carried out in the ISMES (Seriate, BG, Italy) and LEE
(Laboratory for Earthquake Engineering, NTUA, Athens, Greece). The tests were carried out
on 1:2 scaled models. Actual prototypes materials were used in the model buildings. The
acceleration and stress scales were, respectively, Sa = 1 and Sσ = 1. As same materials were
used for models and real buildings, additional masses were applied to the model to respect
the scale.
Bricks and stones were used for the construction of model buildings. Intentially, low strength
mortar and low quality workmanship were used to simulate the field situation. The models
were subjected to base excitation in three translation directions. The vertical component was
70 % of the horizontal component. After damaging the models, different techniques were
used to repair and strengthen it.
It was concluded on the basis of analysis of the test results that lateral resistance increases for
both brick and stone masonry model after strengthening. Total collapse could be avoided by
using horizontal ties.
The values of the reduction factor ‘q’ are in general slightly higher for stone masonry than
for brick masonry. ‘q’ value for both the cases is 1.5 times higher than the code
recommended values. Strengthening increased such values in some instances by a factor up
to 1.8.
2.7.2 Verification of Seismic Resistance of Confined Masonry Buildings (Tomzevic, M., 1997)
Two models of a typical three story confined masonry buildings have been tested on shaking
table at Slovenian National Building and Civil Engineering Institute (ZAG) in Ljubljana,
Slovenia. The models were scaled at 1:5, conforming to the requirements of EC-8 for simple
buildings in plan. They were subjected to a series of simulated seismic ground motions with
increased intensity of shaking.
The structural system consisted of perimetral and internal walls in both orthogonal directions
dividing the plan into four rectangles. All the perimeteral walls and an internal wall in shorter
35
direction were pierced with window and door opening. Wall to floor area was 5% in both
orthogonal directions.
Diagonal cracks were observed in all stories at maximum resistance state. Crushing of
concrete and rupture of reinforcement of tie-column was also observed at the ultimate state.
It could be concluded from the tests results that prototype buildings would withstand, with
moderate damage to all walls, strong earthquakes with peak ground acceleration of 0.8g and
withstand without collapse a sever earthquake of PGA more than 1.3g.
The value of behavior factors ‘q’ was 2.91 and 2.47 for M1 and M2 models, respectively. It
could be concluded that confined masonry buildings possess more energy dissipation
capacity than code proposed values; however, taking into account the drift limitation of story
the codal values seem reasonable. Comparing ‘q’ values from previous research on un-
reinforced and reinforced masonry buildings of similar configuration and size, EC8
underestimate their energy dissipation capacity. However, further experimental and
analytical research is needed on response modification factor.
2.7.3 Shaking Table Tests of Small-Scale Model of Masonry Building: Advantages and Disadvantages (Tomzevic, M., 2000)
In this article, experiences of reduced scale shaking table test in context of advantages and
disadvantages have been discussed. It is emphasized that significant development has been
made in the numerical techniques and numerical models; however, experimental testing of
structures and sub-assemblages is needed. Seismic behavior of buildings could be determined
by cyclic test of walls, variability in the masonry need to test complete structural system.
Similitude in the dynamic behavior as well as failure mechanism of prototype and model is
considered important factor in modeling. Distribution of masses and stiffness in the prototype
and models need to be simulated. However, the failure mechanism requires similar working
stress level that is, working stresses in load bearing walls and compressive strength of
masonry of prototype and model. Although all the structural details are not precisely
modeled, the global seismic behavior of prototype building could be accurately simulated if
the behavior of model wallets is similar to prototype. Mechanical properties such as
36
compressive strength, tensile strength, ductility and energy dissipation, are simulated in
testing walls.
It is concluded that reliable information as regards the global seismic behavior and failure
mechanism can be obtained by testing small scale models of buildings on simple earthquake
simulator, although neither the physical models nor the seismic ground motion are modeled
in great detail. Special model materials for complete or prototype materials for simple model
can be used for the construction of the models. Scale factor 7 and 4 has been found as the
practical upper limit for modeling brick and block masonry, and stone masonry respectively.
In the case of complete model the requirements of dynamic behavior and failure mechanism
is automatically fulfilled. However, special arrangement is need in the case of simple models
where prototype materials are used.
2.7.4 Seismic Behavior of a Three-Story Half Scale Confined Masonry Structure (Bartolome, A.S., et al., 1992)
A three story confined masonry building modeled at 1:2.5 scale has been tested on shake
table. The vibration properties, strength of materials and axial stress of the model were kept
similar to those of the actual buildings. May 31, 1970 earthquake record was used for the
dynamic test. Each dynamic test run was preceded by free vibration test, consisting of four
pulses of small amplitude.
Flexural crack at the wall base was first developed at 0.52g. It resulted in the vertical
reinforcement to yield. At ultimate test run (0.85g) shear failure in both first story walls
occurred. The horizontal reinforcement ruptured during the last test, showing that it
effectively worked under dynamic conditions. The time period and coefficient of damping
obtained by free vibration were smaller than the pulse test and the analytically obtained
values. Both time period and damping increased with the increased in intensity of excitation.
Damping was 4% at 0.52g and increased to 7% at the final test run when PGA was 0.85g.
Stiffness of the walls decreased in the subsequent test run.
It was concluded that shear failure could occur during strong excitation even the structure
was predicted to be failed in flexure. Therefore, the design process of a confined masonry
building should include the possibility of a shear type of failure to avoid structural collapse.
37
2.7.5 Seismic Response Pattern for URM Buildings (Abram 2000)
Two reduced scale, unreinforced masonry buildings (URM) were tested on shake table in
Newmark Laboratory, University of Illinois at Urbana Champaign, USA to highlight selected
aspects of dynamic response that help confirm or deny present engineering practices for
seismic evaluation of URM buildings. The models were constructed of clay masonry units on
three-eights scale. Type O mortar was used in a two-wythe, running bond pattern. For the
first test structure perforations in each of the two parallel shear walls were chosen so that
lateral stiffness and strength of the two wall elements were similar. For the second test, the
size and placement of perforations were varied to result in dissimilar stiffness and strengths
for two walls.
Each test structure was subjected to scaled motions measured during the 1985 Nahanni
earthquake. The time scale of the recorded earthquake motion was compressed by a factor of
1.6, which was equal to the square root of the length scale of 2.5.
It is concluded that substantial nonlinear behavior, which was largely attributed to rocking
behavior of the first-story piers was observed. The models remain stable at first story drift as
large as 0.9%. Waveforms of base shear were in phase with deflection histories suggesting a
predominant first mode response. The elastic base shear, determined from measured base
motions and measured mode shapes, was as much as 4.3 times the measured base shear
maxima and as much as 7.7 times the estimated story shear rocking capacity. Measured
lateral drifts were significantly less than anticipated elastic displacements.
2.7.6 Experimental Study on Earthquake Resistant Design of Confined Masonry Structures (Ishibashi, K., et al., 1992)
This paper presents results obtained from testing of three full scale confined masonry
specimens. Each model consisted of two wall units made with clay bricks. The first
specimen, practically lacked the flexural coupling, walls were only connected through high
strength Dywidag bars that transferred the lateral force between the walls. In the second and
third specimens, walls were linked by a cast in place reinforced concrete tie beams and slab.
Parapet wall is also provided in the third specimen. Figure 2.16 illustrates the three wall
specimens and reinforcement scheme in the confining elements. The specimens were tested
38
first applying load cycles with maximum shears equal to 5 ton, 10 ton and 18 ton which
caused first crack in the masonry panel. Then displacement cycles were applied up to 0.012
drift. The specimens were designed and constructed following the requirements of the
Mexico City Building Code.
Figure 2.16 Cyclic load test specimens and reinforcement details
It has been concluded on the basis of previous research and on this research program that
masonry strength depends on the strength of brick units, and is less depended on the mortar
characteristics. The vertical load increases the shear capacity and stiffness. However, large
vertical forces reduce the available ductility of the structures. The masonry wall confinement
improves the energy dissipation characteristics and deformation capacity. The form of the
opening clearly affected the final crack pattern. However, the mode of failure for all
specimens was governed by shear deformations in the masonry panels. The type of opening
affected the initial stiffness of the specimens, the stiffness decay was similar and follow a
parabolic curve.
39
2.7.7 Cyclic Loading Tests of Confined Masonry Wall Elements for Structural Design Development of Apartment Houses in the Third World (Hiroto Kato et al 1992)
A static cyclic test on half scale confined masonry walls of three-four story apartment house,
were carried out. However, effects of axial and shear reinforcement on the load carrying
capacity, drift ratio and damage pattern were studied in this paper, the overall objectives of
the research project were to analyze damage patterns of masonry structures, to examine
improvement methods for minimizing earthquake damage, and to prepare guidelines for
confined masonry. Several static cyclic loading and shaking table tests were planned to
clarify basic characteristics of confined masonry structure.
Four confined masonry walls were constructed with different axial and shear ratio. Specimen
A with rich axial and shear reinforcement, specimen B with rich axial and poor shear
reinforcement, specimen C with poor axial and rich shear reinforcement and specimen D is
of poor axial and shear reinforcement.
It was concluded that axial reinforcement in column can improve load carrying capacity of
the confined masonry walls. The ductility of walls can be improved with the increase in shear
reinforcement as it effectively bind the unreinforced walls and avoid brittle failure. The
subjects in seismic design are to find better combinations of the ratio of axial reinforcement
and that of shear reinforcement.
40
CHAPTER 3 EXPERIMENTAL PROGRAM: MASONRY MATERIALS AND
MASONRY ASSEMBLAGE
3.1 INTRODUCTION
In order to evaluate the behavior of reduced scale typical buildings under seismic demand,
simulation of masonry materials and assemblage is essential. Extensive experimental work
has been carried out in this study for the simulation of masonry materials and masonry
assemblage. Basically, the experimental work of this study has been divided into three
phases. In the first phase mechanical properties of prototype masonry materials and
assemblages have been determined. In the second phase, simulation study has been done for
masonry materials and assemblages. The model masonry assemblages have been tested in
compression, diagonal compression and constant vertical compression and lateral cycle load.
And in the last phase of experimental study, reduced scale models have been fabricated and
tested on unidirectional earthquake simulator (shake table). The first two phases are the part
of this chapter, while the third phase has been discussed in Chapter 4 and 5. This chapter is
organized into three main sections.
Section 3.2. In this section the mechanical properties of prototype masonry materials and
masonry assemblage have been discussed. The following tests were carried out on the
masonry units and assemblage.
Masonry Unit:
I. Compressive strength II. Water absorption and density
Masonry Assemblage:
I. Compressive strength test and Modulus of Elasticity II. Diagonal Tensile (shear) Strength Test and Modulus of Rigidity
III. Cyclic Test
Section 3.3. The mechanical properties of model masonry materials and masonry assemblage
are presented in this section as follows:
41
Model Masonry Unit:
I. Compressive Strength and Density
Model Masonry Assemblage:
I. Compressive Strength and Modulus of Elasticity, II. Diagonal Tensile (shear) Strength Test and Modulus of Rigidity
III. Cyclic Test
Section 3.4. In the third and last section of this chapter, the mechanical properties of
prototype and model are compared and discussed. The actual scale factor from this study is
also compared with the true scale factor as per complete model similitude requirements.
3.2 PROTOTYPE MASONRY TEST
3.2.1 Masonry Unit (Solid Burnt Clay Brick)
Masonry unit samples were randomly collected from the local brick kiln. As described above
compressive strength and water absorption tests have been conducted on the masonry unit.
Although water absorption is not required for simulation purposes, the test has been carried
out generally to determine the physical properties of locally available brick.
3.2.1.1 Compressive Strength of Unit
Compressive strength of brick masonry units (figure 3.1) were carried out in the 200 tonne
Universal Testing Machine (UTM-200) in accordance with ASTM C 67. According to the
standard, length of test specimen for compressive strength should be equal to one half the full
length of the unit ± 1 inch. However, in this study compressive strength of full unit was
determined. Load was applied perpendicular to the bed face (length x width). The brick was
capped on both sides with gypsum 24 hours prior to testing. The compressive strength of
masonry unit is given in Table 3.1
42
Figure 3.1 Compressive strength test of solid brick masonry unit
Table 3.1 Compressive strength of masonry unit (solid burnt clay brick)
S. No Length
in (mm)
Width
in (mm)
Height
in (mm)
Crushing
Load (t)
Compressive Strength
psi (MPa)
1 8.5 (216)
4.19 (106)
2.75 (70) 27.90 1728.0
(11.9)
2 8.5 (216)
4.25 (108)
2.85 (72) 31.10 1897.4
(13.1)
3 8.63 (219)
4.25 (108)
2.9 (74) 46.10 2771.8
(19.1)
4 8.44 (214)
4.13 (105)
2.9 (74) 42.20 2672.3
(18.4)
5 8.5 (216)
4.13 (105)
2.7 (69) 39.90 2508.0
(17.3)
6 8.5 (216)
4.19 (106)
2.75 (70) 46.0 2848.0
(19.6)
7 8.44 (214)
4.25 (108)
2.75 (70) 53.80 3307.0
(22.8)
8 8.69 (221)
4.25 (108)
2.75 (70) 25.00 1492.0
(10.3)
9 8.56 (218)
4.2 (107)
2.8 (71) 39.40 2415.0
(16.7)
10 8.5 (216)
4.15 (105)
2.75 (70) 27.90 1743.0
(12.0)
Average 8.53 (216)
4.2 (107)
2.79 (71) 37.93 2338.0
(16.0) Cov (%) 1% 1% 3% 25% 25%
According to Eurocode-8 (EC 8), the minimum acceptable normalized compressive strength
of a masonry unit, normal to the bed face, is 725 psi (5.0 MPa). However, according to
43
recently developed seismic Building Code of Pakistan (SBC-07), the minimum compressive
strength of solid burnt brick is 1196 psi (8.25 MPa). Test data of masonry unit presented in
section 2.2.1.1 and test conducted in this research work reveals that the compressive strength
of unit complies with the EC 8 and PBC 07.
3.2.1.2 Water Absorption
Water absorption was determined for the masonry units in accordance with ASTM C 67. The
test data is given in Table 3.2.
Table 3.2 Water absorption of burnt clay brick
S.No Dry Wt
lb (N)
Sat. Wt
lb (N) Absorption (%)
1 5.76 (25.6)
7.02 (31.2) 21.88
2 6.15 (27.4)
7.2 (33.4) 17.07
3 5.82 (26.0)
7.02 (31.2) 20.62
4 6.09 (27.1)
7.27 (32.3) 19.38
5 6.21 (27.6)
7.31 (32.5) 17.71
Average 6.1 (27.1)
7.16 (32.0) 19.33
Cov 10%
The absorption of the masonry unit is very important property. Brick masonry made with
highly absorptive unit would have much less shear and tensile bond strength than those of
masonry made with less absorptive brick units [Calvi, G. M., et al, 1996]. In fact, brick
absorb water from mortar, leaving small amounts of water for hydration of cement which in
turn makes the mortar weak in both tension and compression and consequently resulted in
weakening of the masonry.
Although absorption of masonry unit is not considered for simulation, however, it was
determined for prototype unit to know the general trend of locally available units.
3.2.2 Masonry Mortar
Cement-Sand-Khaka (stone dust) mortar is selected for this study. The constituent materials
were mixed in proportion of one part cement to four parts each khaka and sand by volume.
44
Water to cement ratio was kept 1.6. Sand from Nizampur and khaka from Peshawar region
were used. The proportion of mortar selected is representative of field conditions. Specimens
of mortar were cured for 7 days in water and then were kept in moist room until testing day.
The 28 days compressive strength of the mortar, given in table 3.3, is determined on 2" cube.
The mortar specimens were sampled and tested according to ASTM C 109.
Table 3.3 Compressive strength of masonry mortar
S.No Area
in2 (mm2)
Load
(t)
Compressive Strength
psi (MPa)
1 4 (2581) 1.73 953.2
(6.6)
2 4 (2581) 2.11 1162.6
(8.0)
3 4 (2581) 1.55 854.0
(5.9)
4 4 (2581) 1.70 936.7
(6.5)
5 4 (2581) 1.85 1019.3
(7.0)
6 4 (2581) 1.92 1057.9
(7.3)
Average 4
(2581) 1.81 997.3 (6.9)
Cov 11%
The mean compressive strength of mortar collected from field (section 2.2.2) and used in this
study is well above the minimum compressive strength required by EC 8 and PBC 07.
According to EC 8, the masonry mortar used for un-reinforced and confined masonry should
not be less than 725 psi (5.0 MPa). And according to PBC 07 minimum compressive strength
of mortar in seismic zone 2, 3 and 4 should be 595 psi (4.1 MPa) and not greater than 75 %
of the compressive strength of masonry unit.
3.2.3 Prototype Masonry Assemblage
The mechanical properties of the constituent materials of masonry have been reported in the
preceding section. The prototype masonry has been tested for compression, diagonal tension
and cyclic behavior. The mechanical properties from these tests are to be used for simulation
purposes. The scope of the test is discussed in the subsequent sections.
45
Same type of mortar has been used for all prototype specimens. The proportion of the mortar
has been finalized to represent the field condition. One part of cement with four part each of
Khaka (stone dust) and sand have been mixed keeping water to cement ratio of 1.6. Sizes of
specimens are different for compression, tension and cyclic test.
3.2.3.1 Compression Strength and Modulus of Elasticity
The compressive strength and modulus of elasticity are the important parameters in the axial
and seismic resistance of masonry. These mechanical properties have been determined by
testing 15¾ x 9 x 19 inch (400 x 229 x 480 mm) thickness x width x height brick prism
under uni-axial compression. The mortar joint is 3/8 to ½ inch (10-12 mm) in thickness. The
bricks are laid in running bond. The prisms have been constructed by expert local mason.
The wetting of bricks and mixing of materials for mortar have been done by the mason and a
helper in such a way so as to be representative of field conditions. Samples of mortar have
been taken for the quality control.
The masonry specimens were stored and cured in the lab. The curing was started after 48
hours of specimens preparation. The specimens were wet cured for minimum of 7 days and
kept in the moist room for the rest of the time before testing.
The specimens were capped with gypsum on both ends 24 hours prior to testing. The
specimens were tested in 200 tonne Universal Testing Machine (UTM) in the Material
Testing laboratory, N-W.F.P UET, Peshawar as shown in figure 3.2. 3/4" (19 mm) thick steel
plate was used at the top between upper platen of UTM and the specimen.
Separate load cell was used for load readings. The load cell and four displacement gages
were connected with the UCAM-70 Data logger, data acquisition system. Two of the four
gages were connected on the top of the specimen to get the overall displacement of the
specimen and two (one on each face) were connected on the mid height. The dimensions and
instrumentations are shown in figure 3.3.
The compression load was applied at an average rate of 0.4 tone/sec.
46
Figure 3.2 Compression test of prototype masonry
Figure 3.3 Dimensions and instrumentations of prototype specimen for compression test.
The compressive strength of masonry prism is calculated by dividing maximum load over the
plan area of the prism. ASTM C1314 standard requires multiplying the masonry prism
strength by correction factor. The compressive strength values in the table below are un-
corrected values. The modulus of elasticity has been determined as specified in the ASTM
C1314, that is, secant modulus of elasticity between 1/20th and 1/3rd of the maximum
compressive stress of the prism.
47
Table 3.4 gives compressive strength and modulus of elasticity of brick masonry prism and
figure 3.4 illustrates the typical stress strain curve.
Table 3.4 Compressive strength and modulus of elasticity of prototype brick masonry
S.No
Designation
Compression Strength
psi (MPa)
Modulus of Elasticity "E"
ksi (GPa)
Maximum Average COV
(%) E Avg. E COV (%)
1 CE-1 705.4 (4.8)
839.63 (5.8) 24%
211.9 (1.46)
288.0 (2.0) 23%
2 CE-2 980.9 (6.7)
340.0 (2.3)
3 CE 3 1043.5 (7.2)
312.0 (2.2)
4 CE-4 628.7 (4.3)
218.0 (1.5)
The compressive strength of masonry from the equation proposed by Miha Tomazevic (Miha
Tomazevic 1999) is as follows:
0.65 0.25 ( )k b mf Kf f MPa= (3.1)
= 5.39 MPa or 781 psi
Where:
fb = Normalized compressive strength of unit in MPa
fm = Compressive strength of mortar in MPa
k is a constant and its value depends on the classification of masonry unit. In this case k is
0.5. By comparing compressive strength from experiment and equation, good correlation is
obtained. However, the equation is an approximate approach and could not be preferred over
experimentally determined value. The value of E is 342 times the compressive strength of
masonry, which lies between the range specified in (Miha Tomazevic 99).
48
y = 2E+09x3 - 5E+07x2 + 389478xR2 = 0.9942
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
1000.0
1100.0
0 0.002 0.004 0.006 0.008 0.01 0.012
Strain (in/in)
Stre
ss (p
si)
Figure 3.4 Typical stress strain curve of prototype brick masonry in compression
3.2.3.2 Diagonal Tension (Shear) in Masonry
In order to determine the tensile strength (shear strength) of masonry five square specimens
of nominal size 28¾ x 28¾ x 9 inch (730 x 730 x 229 mm) have been prepared and tested in
accordance with ASTM C519-02. Although, ASTM standards specify 48 x 48 inch
specimen, smaller specimen have been constructed to better handle them. The specimens
were constructed in English bond with joints thickness of 3/8 to ½ inch (10-12 mm). Figure
3.5 shows the diagonal specimen during testing.
The dimensions and instrumentations are illustrated in figure 3.6. Four gages have been used
to measure vertical shortening and horizontal extensions. Two gages are connected in a way
to measure vertical shortening and the other two horizontal extensions. The specimen is
positioned in standard loading shoes on the top and bottom corners. Vertical compression
load is applied through 50 tonne actuator in a manner that the specimen failed in 3-4 minutes.
The load and displacement readings of a specimen (PTG-5) could not be recorded because of
data logger not in a recording mode.
49
Figure 3.5 Diagonal compression (shear) test
Figure 3.6 Dimensions and instrumentations of diagonal tension test
The shear strength is calculated by the following formula:
0.707sPSA
= (3.2)
Where:
P = applied load, lb,
A = net area = (W+H)t/2
W = width of specimen, inch,
50
H = height of specimen, inch,
t = thickness of specimen, inch
The shear strain is calculated as follows:
( )V Hg
γ∆ + ∆
= (3.3)
where:
γ = shear strain,
∆V = vertical shortening, inch,
∆H = horizontal extension, inch.
The modulus of rigidity, G is calculated as follows:
sSGγ
= (3.4)
as ASTM E519 does not specify any range of stresses for the determination of modulus of
rigidity. However, 1/20th and 1/3rd of the maximum shear stresses are taken over which
stresses are assumed linear. The shear strength and modulus of rigidity is given in table 3.5.
Table 3.5 Tensile strength and modulus of rigidity of prototype brick masonry
S.No Designation
Shear Strength
psi (MPa)
Modulus of Rigidity "G"
ksi (GPa)
Maximum Average Cov (%) G Average Cov
(%)
1 PTG-1 41.7 (0.29)
51.3 (0.35) 14%
30.6 (0.21)
28.1 (0.20) 37%
2 PTG-2 49.7 (0.34)
15.6 (0.11)
3 PTG-3 55.9 (0.39)
26.0 (0.18)
4 PTG-4 57.8 (0.40)
40.4 (0.28)
The shear strength is about 6% of the compressive strength. Shear modulus is 10% of the
elastic modulus which lies in the experimentally evaluated range of 6% to 25% suggested by
Tomazevic M., 1999. According to EC 6 specification the shear modulus, G is 40% of the
elastic modulus is much higher then the experimental results.
51
3.2.3.3 Cyclic Test of Prototype Masonry Walls
Five 36 inch square specimens were prepared in English bond for cyclic test. The mortar
joint was ¾ to ½ inch (10-12 mm) thick. Reinforced concrete beams, 9" in thickness, were
provided at the top and bottom of the masonry wall. The specimens were wet cured for 7-10
days and was kept in moist room until testing. Mortar samples were collected during
construction of the masonry specimens for quality control. The mortar samples were tested at
the same day of cyclic test. The specimens were white washed two days prior to testing for
the visibility of cracks during testing.
The dimensions and instrumentations are illustrated in figure 3.7. The specimens were tested
in straining frame, structural laboratory. Three load cells were used for applying vertical
compression and horizontal cyclic loads. A 50 tonne capacity actuator was used for applying
constant vertical compression load. Vertical load was applied on 3" (76 mm) thick steel plate
placed on 1.5" (38 mm) diameter steel rollers. The steel rollers in turn are rolling on a highly
polished 3/8" (10 mm) thick steel plate during the horizontal displacement of the specimen.
Two 25 tonne capacity actuators were used to apply horizontal cyclic load, each one applying
half cycle. Two LVDTs were connected on either side of the specimen to measure top
displacement. Two LVDTS were also connected at the bottom of the specimen to measure
shear sliding if any. A LVDT is also used to measure the slippage of the bottom concrete
beam over the steel girder (figure 3.8).
The bottom beam of the specimen is connected with a stiff steel girder with the help of four
bolts on each side.
All the instruments are connected with UCAM70 data logger for data acquisition. A list of
equipment and their specification is given in Appendix A.
52
Figure 3.7 Dimensions and instrumentations of prototype cyclic load test
Figure 3.8 Cyclic test setup
7 tonne of vertical compression load was applied on the specimen. The vertical compression
load is equivalent to 47 psi (0.32 MPa) compression stresses which is representing vertical
stresses in the pier in two story typical Pakistani masonry building (5 marlas/1361 sft typical
houses). The test was displacement control. Displacement history is illustrated in figure 3.9.
53
-14.0-12.0-10.0-8.0-6.0-4.0-2.00.02.04.06.08.0
10.012.014.0
Dis
plac
emen
t (m
m)
Figure 3.9 Displacement history for prototype cyclic test.
Figure 3.10 shows typical hysteresis loop of the cyclic test. The load-displacement envelop
(figure 3.11) was plotted by maximum load and its corresponding displacement in the first
cycle of each increment. Rocking was predominant failure mode of all specimens. One
specimen was damaged during transportation and positioning. Bilinear idealized curve is also
plotted as shown in figure 3.11.
54
Figure 3.10 Typical load-displacement hysteresis loop
Load-Displacement Curve
-5
-4
-3
-2
-1
0
1
2
3
4
5
6
-14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14
Horizontal Displacement (mm)
Hor
izon
tal L
oad,
Ton
e
Figure 3.11 Hysteresis envelop and bilinear idealized curve
Load-Displacement Hysteresis loop
-6
-4
-2
0
2
4
6
-14 -12 -10 -8 -6 -4 -2 0 2 4 6 8 10 12 14
Displacement (mm)
Hor
izon
tal L
oad
(t)
_____ Hystersis Envelope
------- Idealized Curve
55
The main parameters of seismic resistance, such as the tensile strength, ft, effective stiffness,
Ke, shear modulus G and ductility factor µ are presented in the table 3.6.
Table 3.6 Dimensions and mechanical properties of prototype masonry
Designation
h
in (mm)
l
in (mm)
t
in (mm)
E
Ksi
(GPa)
σ
psi
(MPa)
Hmax
Kips
(kN)
ft
psi
(MPa)
Ke
kips/in
(kN/mm)
G
psi
(MPa)
µ
(%)
G/E
ratio
PC-1
39.7
(1008)
36.0
(915)
8.5
(217)
290
(2)
35.8
(0.25)
0.96
(42.66)
32.2
(0.22)
82.39
(14.48)
13.4
(92.41) 3.64 5
PC-2
39.8
(1010)
36.8
(935)
8.6
(220)
290
(2)
47.0
(0.32)
1.07
(47.56)
33.3
(0.23)
100.01
(17.58)
16.75
(115.5) 4.30 6
PC-3
40.2
(1021)
37.8
(961)
8.7
(220)
290
(2)
47.0
(0.32)
1.06
(47.28)
30.5
(0.21)
93.34
(16.41)
14.41
(99.41) 3.84 5
PC-4
40.2
(1021)
37.8
(961)
8.7
(220)
290
(2)
47.0
(0.32)
1.1
(49.05)
32.1
(0.22)
112.43
(19.76)
17.53
(120.9) 6.04 6
PC-5
39.4
(1001)
36.4
(925)
8.7
(221)
290
(2)
48.7
(0.34)
1.2
(54.88)
39.0
(0.27)
45.02
(7.91)
6.9
(47.59) 2.28 2
Average
40.0
(1015)
37.1
(943)
8.6
(219)
290
(2)
44.2
(0.3)
1.0
(46.64)
32.0
(0.22)
97.04
(17.1)
15.52
(107.1) 4.02 5
Specimen PC-5 developed pre-testing horizontal crack during transportation and probably
this is reason for its low effective stiffness, Ke and modulus of rigidity, G as compared to
other specimens. The tensile strength (ft) is determined by using Turnsek equation (Turnsek
and Cacovic, 1971) as given below:
( )σ στ⎛ ⎞= + −⎜ ⎟⎝ ⎠
221.5
2 2ft (3.5)
Where:
σ = Average compressive strength in the horizontal cross-section of the wall
= vertical compression load divided by plan area (that is length x thickness) of the
wall.
τ = Maximum shear stress in the horizontal plan area of the wall
= Maximum horizontal load (Hmax) divided by plan area (Aw)
56
Modulus of rigidity, G in the table is calculated by the following formula:
=−
⎛ ⎞⎜ ⎟⎝ ⎠
21.21.2
KeG Aw Keh hh
l
(3.6)
Where:
Ke = Effective Stiffness,
Aw = Area of wall (length x thickness),
h = Height of the wall,
l = Thickness of the wall
In order to compare tensile strength from diagonal compression test and cyclic test, good
correlation is obtained. Modulus of rigidity, G obtained from the cyclic test is smaller than
those evaluated from diagonal compression test.
3.2.3.4 Target value of Prototype Materials
As discussed previously, the scale factor of 4 and complete model similitude requirements
have been selected based on simulator capacity. According to the similitude laws, the strain
and density of model should be kept same as that of the prototype materials, however, stress
should be scaled with scale factor. The prototype materials used are the actual field
representation.
The target values of prototype materials is given in Table 3.7
57
Table 3.7 Target mechanical values of materials
Description Prototype Model (Target Value) Prot/Model
Compressive Strength of Masonry unit, psi (MPa) 2338.0 (16.12)
585 (4.03) 4
Density of Masonry unit, Ib/ft3 (kN/m3) 101.0 (15.87)
101.0 (15.87) 1
Compressive Strength of Masonry Mortar, psi (MPa) 997.3 (6.88)
249 (1.72) 4
Compressive Strength of Masonry,ƒk, psi (MPa) 839.6 (5.79)
210 (1.45) 4
Tensile Strength (shear) of Masonry,ƒtk, psi (MPa) 51.27 (0.35)
13 (0.09) 4
Modulus of Elasticity of Masonry, E, ksi (GPa) 288.0 (1986.2)
72.0 (0.49) 4
Shear Modulus of Masonry, G, ksi (GPa) 28.11 (0.19)
7.03 (0.05) 4
Compressive Strength of Concrete, psi (MPa) 1500 (10.34)
375 (2.57) 4
Yield Stress of Reinforcing Steel, psi (MPa) 94,500.0 (652.0)
23,625.0 (163.0) 4
3.3 MODEL MASONRY
A series of trial mixes have been prepared for the simulating target mechanical and physical
properties of masonry materials. A number of model walls have also been constructed and
tested for subsequent analysis and extrapolation of the test results to prototype buildings.
3.3.1 Model Masonry Unit
Model masonry units have been fabricated from special mortar containing cement, lime and
surkhi. Surkhi is burnt clay brick remains. Surkhi is used instead of sand for its light weight
in the mortar mixture to fulfill the density requirement. For sand mortar the density was more
than the required. The use of Surkhi ensured that the density of model was practically same
as that of the prototype. The gradation of surkhi is illustrated in figure 3.12. Several mixes
have been tried before the final selection was made based on density and compressive
strength.
The mix proportion selected is 1:1:5. The mix is poured in the mould (figure 3.13) and
compacted in two layers. The compacted bricks are then removed from the mould by
pressing the mould against wooden blocks. The mix proportion is designed as to be easily
58
compacted and de-molded with out damaging shape of masonry unit and fulfilling the
similitude requirement. Ordinary Portland cement has been used for the mix. Surkhi from
local brick kiln near Peshawar city has been used.
Three different sizes of model bricks (figure 3.14) were fabricated. One with size 2.2 x 1.1 x
0.67 (56 x 27 x 17 mm), is the actual reduced size of the prototype bricks and is designated
as brick #1. The second with size 2.2 x 1.1 x 1.3 (56 x 27 x 34 mm), is double in height and
the third double in width that is 2.2 x 2.2 x 0.67 (56 x 56 x 17 mm) is fabricated to reduce the
number of masonry bricks required and reduce the fabrication efforts of the model building.
Model bricks double in width are designated as brick #2 and double in height as brick #3.
The density and compressive strength of the model masonry unit at 28 days is given in table
3.8. The density and compressive strength is mean value of 10 model bricks. The
compressive strength of model brick, double in width could not be determined because of its
aspect ratio. The specific mass has been obtained by weighing the brick units and measuring
the actual dimensions.
0
20
40
60
80
100
4 8 16 30 50 100
Sieve Number
Perc
ent p
assi
ng (%
)
Figure 3.12 Composition of Surkhi
59
Figure 3.13 Mould for model masonry unit (size 56 x 27 x 17 mm)
Figure 3.14 Three different types of model masonry
Table 3.8 Compressive strength and density of model masonry units
Model Masonry Unit Compressive
Strength
psi (MPa)
Cov
(%)
Density
lb/ft3 (kN/m3)
Cov
(%)
Brick #1 (56 x 27 x 17 mm)
634.79 (4.4) 7 98.10
(15.42) 1
Brick #2 (56 x 27 x 34 mm)
500.34 (3.45) 9 100.52
(15.80) 3
3.3.2 Model Masonry Mortar
Different cement and lime based mixes have been prepared for the model masonry mortar.
Indigenous materials, for example, Khaka, marble powder and surkhi are used in the mortar
60
mixes for their effects on the compressive strength and flow value. The proportions of the
mixes have been arbitrarily selected. Following are the different combination of materials:
A. Cement-Lime Based Mortar
1. Cement : Lime : Sand (CLS)
2. Cement : Lime : Khaka (CLK)
3. Cement : Lime : Marble Powder (CLP)
4. Cement : Lime : Sand : Marble Powder (CLSP)
5. Cement : Lime : Surkhi (CLSr)
6. Cement : Lime : Sand : Surkhi (CLSSr)
B. Lime Based Mortar
1. Lime : Sand : Surkhi (LSSr)
2. Lime : Sand : M. Powder (LSP)
Ordinary Portland cement and hydrated lime is used for the mixes. Sand used is the clean
river sand having size from 0-1 mm. The gradation of sand is shown in figure 3.15.
Table 3.9 and table 3.10 gives the compressive strength and flow value for the cement based
and lime based mortar mixes, respectively. Three 2" (51 mm) cube are used to determine the
compressive strength of mortar.
0
20
40
60
80
100
4 8 16 30 50 100
Sieve Number
Perc
ent p
assi
ng (%
)
Figure 3.15 Composition of Sand
61
Table 3.9 Compressive strength of cement based-masonry mortar
No Specimen
Designation
Mix
proportion
Water
content*
(ml)
Compressive Strength, psi (MPa)
7 days 28 days 90 days
Avg. Strength Avg.
Strength
Cov
(%)
Avg.
Strength
1 CLS 0411 0.4:1:11 250 15.61 (0.11) 27.55 (0.19) 9.4 -
2 CLS 1111 1:01:11 300 110 (0.76) 135.91 (0.94) 6.2 -
3 CLS 1111/F 1:01:11 300 104.69 (0.72) 120 (0.83) 8.2 -
4 CLS 0.4111/F 0.4:1:11 300 33.37 (0.23) 42.24 (0.29) 19.9 -
5 CLS 0418/F 0.4:1:8 450 87.06 (0.6) 110.2 (0.76) 5 -
6 CLS 1111/F 1:01:11 375 111.72 (0.77) 141.42 (0.98) 18 -
7 CLS 4111/F 0.4:1:11 375 56.59 (0.39) 71.63 (0.49) 7.7 -
8 CLS 1210/F 1:02:10 400 107.37 (0.74) 135.91 (0.94) 19.2 211.22 (1.46)
9 CLS 0.528/F 0.5:2:8 425 85.61 (0.59) 108.36 (0.75) 10.6 163.46 (1.13)
10 CLK 0528/F 0.5:2:8 550 120.43 (0.83) 152.44 (1.05) 4.2 163.46 (1.13)
11 CLSK05132/F 0.5:1:3:2 375 171.21 (1.18) 216.73 (1.49) 8.2 277.34 (1.91)
12 CLS0418 0.4:1:8 400 58.04 (0.4) 73.47 (0.51) 17.3 108.36 (0.75)
13 CLS125 1:02:05 475 200.23 (1.38) 253.46 (1.75) 4.3 277.34 (1.91)
14 CLS115 1:01:05 450 188.63 (1.3) 238.77 (1.65) 21.3 290.19 (2)
15 CLP1212 1:02:12 500 113.18 (0.78) 143.26 (0.99) 3.8 159.79 (1.1)
16 CLP1220 1:02:20 500 79.8 (0.55) 101.02 (0.7) 6.3 102.85 (0.71)
17 CLP1110 11:10:00 475 107.37 (0.74) 135.91 (0.94) 13 128.57 (0.89)
18 CLP126 1:02:06 575 140.74 (0.97) 178.16 (1.23) 1.8 213.05 (1.47)
19 CLP146 1:04:06 650 82.71 (0.57) 104.69 (0.72) 5.3 150.61 (1.04)
20 CLP1412 1:04:12 600 88.51 (0.61) 112.04 (0.77) 10.2 143.26 (0.99)
21 CLSP1233 1:2:3:3 500 163.96 (1.13) 207.54 (1.43) 7.7 209.38 (1.44)
22 CLSP1466 1:4:6:6 550 53.69 (0.37) 67.96 (0.47) 9.4 108.36 (0.75)
23 CLSP1433 1:4:3:3 600 105.92 (0.73) 134.08 (0.92) 11.9 104.69 (0.72)
24 CLSr1212 1:02:12 750 294.55 (2.03) 372.84 (2.57) 6.8 299.38 (2.06)
25 CLSr1220 1:02:20 750 210.39 (1.45) 266.32 (1.84) 3.2 134.08 (0.92)
26 CLSr1110 1:01:10 800 156.7 (1.08) 198.36 (1.37) 10 113.87 (0.79)
27 CLSSr1466 1:4:6:6 700 146.55 (1.01) 185.5 (1.28) 18.1 0 (0)
28 CLSSr1233 1:02:03:3 650 0 (0) 0 (0) - 214.89 (1.48)
29 CLSSr1133 1:03:03 650 194.43 (1.34) 246.11 (1.7) 3.4 185.5 (1.28)
62
Table 3.10 Compressive strength of lime based-masonry mortar
No Speciman
Designation
Mix
proportion
Water
content*
(ml)
Compressive Strength, psi (MPa)
7 days
Strength 28 days Strength
90 days
Strength
Avg.
Strength
Avg.
Strength
Cov
(%) Avg. Strength
1 LS 13/F 1:03:00 450 59.5 (0.41)
75.3 (0.52) 11.2 134.0
(0.92)
2 LSP133 1:03:03 450 94.3 (0.65)
119.4 (0.82) 25.4 113.9
(0.79)
3 LSSr133 1:03:03 650 108.8 (0.75)
137.75 (0.95) 8.0 126.7
(0.87)
4 LSSr11515 1:1.5:1.5 650 94.3 (0.65)
119.4 (0.82) 21.8 132.2
(0.91) *The water content is required for 3.90 lb (1765 g) of dry materials mixed in the proportion given in column 3 Cement lime sand mortar (CLS115) has been selected for its 28 days compressive strength
matching prototype mortar strength.
3.3.3 Micro Concrete
For the slab and confining elements concrete, different cement-sand and cement-lime-sand
mixes have been prepared. Ordinary Portland cement and hydrated lime has been used. River
sand of grain size from 0-2 mm have been used for the micro concrete. 7-days and 28-days
compressive strength data of micro concrete is presented in table 3.11.
Cement sand mortar (CS16) has been selected for floor concrete and cement-lime-sand
(CLS115) has been used for confining element. The selected mix proportion represents the
lower bound value of compressive strength of concrete as discussed in section 2.2.
63
Table 3.11 Compressive strength of micro-concrete
S.No Designation Water
content (ml)
7 days Compressive
Strength, psi (MPa)
28 days Compressive Strength
psi (MPa)
Average Cov (%) Average Cov (%)
1 CS15 550 ml 391.7 (2.7) 3.14 870.0 (6) 8.98
2 CS16 - 287.6 (1.98) 6.45 388.2 (2.68) -
3 CS110 550 ml 79.5 (0.55) 18.36 185.9 (1.28) 13.34
4 CLS114 650 ml 575.3 (3.97) 6.45 1117.8 (7.71) 14.0
5 CLS115 - 212.8 (1.47) 7.61 367.2 (2.53) -
6 CLS116 650 ml 219.8 (1.52) 15.2 322.7 (2.23) 26.45
7 CLS1110 600 ml 142.6 (0.98) 8.63 386.0 (2.66) 3.63
8 CLS1112 550 ml 123.9 (0.85) 16.58 266.6 (1.84) 27.35
9 CLS128 700 ml 108.7 (0.75) 14.7 161.4 (1.11) 8.69
10 CLS1210 600 ml 114.6 (0.79) 4.67 261.9 (1.81) 15.46
11 CLS1212 600 ml 98.2 (0.68) 15.56 173.0 (1.19) 45.87
12 CLS1215 550 ml 74.8 (0.52) 10.82 184.7 (1.27) 8.77
13 CLS148 900 ml 72.5 (0.5) 14.78 81.8 (0.56) 44.0
*The water content is required for 6.10 lb (2771 g) of dry materials mixed in the proportion given in column 2
3.3.4 Reinforcing Bar
3 mm diameter aluminum wire has been used as model reinforcing bar for confining
elements. The tensile strength of the wire is 29,000 psi (200 MPa). For the model concrete
floor, 3 mm diameter galvanized wire was used.
3.3.5 Model Masonry
In order to fulfill the simulation requirements, model masonry walls have been tested in
compression, diagonal tension and cyclic test. Modulus of elasticity, modulus of rigidity and
energy dissipation capacity has been determined for the extrapolation purposes.
3.3.5.1 Compressive Strength and Modulus of Elasticity
Model walls from all the three types of model bricks were constructed. The walls had the
same bond pattern as was followed for the prototype masonry walls. Horizontal and vertical
64
joint thickness was 2.5-3.0 mm. The walls have been built in CLS 115 mortar. No moist
curing has been done for the walls. Three walls have been built for each type of brick unit.
The walls have been instrumented with four deflection gages. Two gages were used to
measure vertical deformation. The other two gages were connected in the way to measure
deformation of overall depth of the wall. Both sides of the model walls were capped with
gypsum 24 hours prior to testing. The walls have been tested in the universal testing
machine. Deformation and load data has been acquired by data logger. The dimensions and
instrumentations of the walls for compression strength is illustrated in figure 3.16. The
compression strength and modulus of elasticity of the model wall is given in table 3.12.
Figure 3.17-3.19 shows typical stress strain curve for the three different types of bricks
prism.
Figure 3.16 Dimensions and instrumentations of model walls for compression.
65
Table 3.12 Compressive strength and modulus of elasticity of model masonry
S.No
Designation
Compression Strength
psi (MPa)
Modulus of
Elasticity "E", ksi (GPa)
fc Avg. fc Cov
(%) E Avg. E Cov (%)
1 CE 2.1/111-1 322.63 278.6
(1.92) 26%
50.86 46.28
(0.32) 29% 2 CE 2.1/111-2 316.97 56.68
3 CE 2.1/111-3 196.13 31.31
4 CE 2.1/211-1 701.36 692.9
(4.78) 4%
137.57 96.54
(0.66) 37% 5 CE 2.1/211-2 663.60 74.26
6 CE 2.1/211-3 713.77 77.78
7 CE 1.9/311-1 654.89 707.2
(4.88) 10%
70.62 56.15
(0.39) 22% 8 CE 1.9/311-2 677.11 48.11
9 CE 1.9/311-3 789.50 49.72
It could be seen from table 3.12 that compressive strength of larger sized bricks (that are
brick #2 and 3) are more than the actual model brick. The masonry constructed from brick #2
and 3, resulted in high elastic modulus than the masonry constructed of brick #1. In order to
compare compressive strength and modulus of elasticity of model and prototype good
correlation has been obtained.
Specimen designation is explained below:
CE 2 / 1 1 1 -1
Aspect ratio
Type of brick Masory mortar
Compression and Modulus of Elasticity
Mortar for Brick No. of specimen
66
y = 6E+07x3 - 4E+06x2 + 63813xR2 = 0.9838
0.0
50.0
100.0
150.0
200.0
250.0
300.0
350.0
400.0
0 0.005 0.01 0.015 0.02 0.025 0.03
Strain (in/in)
Stre
ss (p
si)
Figure 3.17 Typical stress-strain curve for model brick No.1
y = 6E+07x3 - 4E+06x2 + 63813xR2 = 0.9838
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
900.0
0 0.005 0.01 0.015 0.02 0.025
Strain (in/in)
Stre
ss (p
si)
Figure 3.18 Typical stress-strain curve for model brick No.2
67
y = 6E+07x3 - 4E+06x2 + 63813xR2 = 0.9838
-100.0
0.0
100.0
200.0
300.0
400.0
500.0
600.0
700.0
800.0
0 0.005 0.01 0.015 0.02 0.025 0.03
Strain (in/in)
Stre
ss (p
si)
Figure 3.19 Typical stress-strain curve for model brick No.3
3.3.5.2 Tensile Strength and Modulus of Rigidity
Model masonry square walls of size 6.81 x 6.81 x 2.2 (173 x 173 x 56 mm) were constructed
and tested in diagonal compression complying ASTM C 1314. Three walls, each from the
three types of bricks, were tested at the age of 28 days. The walls were constructed in English
bond with 2.5-3 mm joint thickness (figure 3.20). The modeled walls were air cured in the
laboratory at temperature 20-25 C°.
68
Figure 3.20 Model wall for tensile (shear) strength
Four displacement transducers were used to capture horizontal elongation and vertical
shortenings. The two horizontal and two vertical transducers were connected with a steel
plate as shown in figure 3.21. Steel shoes were placed on top and bottom of the specimen.
The specimens were properly caped with gypsum. The walls dimensions are illustrated in
figure 3.22.
Figure 3.21 Model wall during diagonal compression (shear) test
69
Figure 3.22 Dimensions of Model walls
The walls were tested in 200 tonne UTM. Additional load cell, connected with the UCAM 70
data logger, were used to capture load values. The displacement gages were connected with
the data logger. Results of diagonal tension test are presented in Table 3.13. Shear stress to
shear strain is plotted in figure 3.23-3.25.
70
Table 3.13 Tensile (shear) strength and modulus of rigidity of model masonry
Specimen
Designation
Specimen Dimensions Gage length
in
(mm)
Diagonal
in
(mm)
Tensile
Strength
psi
(MPa)
Modulus of
Rigidity
ksi
(MPa)
Width
inch
(mm)
Height
inch
(mm)
Thickness
inch
(mm)
Area
in2
(mm2)
Hori Vert
TG3-111
1 6.6 (169) 7.2 (183) 2.2 (56) 15.3 (9852) 11.4 (290) 11.1 (282) 24.5 (621) 33.6 (0.23) 14.1 (0.1)
2 7.1 (180) 7.5 (189) 2.2 (55) 15.7 (10110) 11.6 (295) 11.9 (302) 25.9 (658) 35.8 (0.25) 12.4 (0.09)
3 6.6 (169) 7.1 (180) 2.1 (54) 14.5 (9323) 11.6 (295) 11.1 (282) 24.5 (622) 28.5 (0.2) 23.9 (0.17)
4 7.1 (180) 7.3 (184) 2.2 (56) 15.8 (10194) 11.7 (297) 11.7 (297) 25.5 (648) 30.0 (0.21) 15.6 (0.11)
Average 32.0 (0.22) 16.5 (0.11)
Cov 10 31
TG3-211
1 7.1 (180) 7 (177) 2.2 (56) 15.5 (9968) 15.3 (389) 15.4 (391) 24.7 (626) - -
2 6.7 (170) 6.7 (170) 2.2 (55) 14.5 (9368) 15.2 (386) 15.3 (389) 23.8 (603) 95.7 (0.66) 31.1 (0.21)
3 7.1 (180) 6.7 (171) 2.2 (56) 15.1 (9735) 15.4 (391) 15.2 (386) 24.6 (625) 109.1 (0.75) 33 (0.23)
4 6.7 (171) 6.6 (167) 2.2 (56) 14.7 (9452) 14.7 (373) 15 (381) 23.7 (601) 62.4 (0.43) 84.4 (0.58)
Average 89.1 (0.61) 49.5 (0.34)
Cov 27 61
TG3-311
1 7.2 (183) 6.5 (166) 2.3 (57) 15.5 (10006) 15.1 (384) 15.4 (391) 23.9 (607) 50.2 (0.35) 33.4 (0.23)
2 7.2 (183) 6.3 (159) 2.2 (57) 15.1 (9755) 15.1 (384) 14.8 (376) 23.6 (599) 46.0 (0.32) -
3 7.1 (181) 6.4 (161) 2.3 (57) 15.2 (9806) 15 (381) 14.8 (376) 24 (610) 64.5 (0.44) 15.2 (0.1)
4 7.4 (187) 6.3 (160) 2.2 (55) 14.7 (9484) 15 (381) 14.9 (378) 24.5 (622) 52.3 (0.36) 29.6 (0.2)
Average 53.2 (0.37) 26.1 (0.18)
Cov 15 37
The shear strength and shear rigidity of masonry constructed of brick No. 2 and No. 3 are
more than the masonry constructed of brick #1. Model constructed of brick No. 2 and No. 3
would be stiff enough to represent the prototype. The strength of model would also not
represent the prototype building. The strength and stiffness of masonry from brick No. 1 is
also more than the prototype, however, the actual model bricks could be used for fabricating
the model buildings.
71
y = 6E+07x3 - 2E+06x2 + 14860x - 5.4344R2 = 0.9846
0.0
5.0
10.0
15.0
20.0
25.0
30.0
35.0
40.0
0.0000 0.0020 0.0040 0.0060 0.0080 0.0100 0.0120 0.0140
Srain (in/in)
Stre
ss (p
si)
Figure 3.23 Typical stress-strain curve for model brick No.1
y = 7E+09x3 - 5E+07x2 + 101006x - 5.2088R2 = 0.9791
0.0
10.0
20.0
30.0
40.0
50.0
60.0
70.0
0.0000 0.0005 0.0010 0.0015 0.0020 0.0025 0.0030 0.0035
Srain (in/in)
Stre
ss (p
si)
Figure 3.24 Typical stress-strain curve for model brick No.2
72
y = 6E+08x3 - 8E+06x2 + 34502x + 2.1649R2 = 0.9862
0.0
10.0
20.0
30.0
40.0
50.0
60.0
0.0000 0.0010 0.0020 0.0030 0.0040 0.0050 0.0060
Srain (in/in)
Stre
ss (p
si)
Figure 3.25 Typical stress-strain curve for model brick No.3
3.3.5.3 Cyclic Test of Model Wall
In order to evaluate the parameters which define the seismic behavior of masonry, such as
energy dissipation and ductility capacity, model walls have been constructed in English bond
with joint thickness 2.5 to 3 mm and tested under constant vertical compression load and
cyclic displacement. The walls have been constructed on 3" (76 mm) thick plain concrete
block. A 2" (51 mm) thick plain concrete beam is provided at the top of the wall to uniformly
distribute the compression load.
The model walls have been constructed in cement-lime-sand CLS115 mortar. The walls have
been kept in moist room until testing. The walls were tested at 28 days of casting. The
specimens have been tested in test set up as shown in figure 3.26. The test was displacement
control. Horizontal displacement history (figure 3.27) has been applied through two
horizontal actuators. Vertical load was applied through vertical actuator. Displacement gages
were connected to measure horizontal top displacement.
As shown in figure 3.26 the model wall was fixed with a 12 inch (30 cm) square steel girder.
The girder itself is supported on other steel girders of the straining frame. The square steel
girder was not fixed with the supporting girders. It was assumed that the self weight of the
73
girder would balance the lateral load, however, the girder was observed to rotate during the
application of lateral displacement on the specimen from north side actuator (left side in
figure 3.26). The effect of rotation of the girder could be seen in load-displacement curve,
figure 3.28.
Figure 3.26 Model wall test setup
-4.0
-2.0
0.0
2.0
4.0
Disp
lace
men
t (m
m)
Figure 3.27 Displacement-time history for model wall cyclic test
74
Figure 3.28 Load-displacement curve
It could be seen from the load-displacement curve that more resistance has been shown in the
upper half of the cycle as compared to the lower half cycle. It could be attributed to the
lifting (rotation) of steel girder. In other words the input energy has been partly used to
overcome the weight of the girder. However, because the steel girder was placed touch with
the steel column of the straining frame, no sign of rotation was observed while applying
displacement from south actuator (right side in the figure 3.26).
The walls were observed to fail in rocking mode. A horizontal crack developed at the
interface of masonry wall and base slab/beam or at the second last mortar joint (figure 3.29).
Almost same manner of cracks have been observed in the prototype walls during cyclic
testing. Cracks were also observed in the un-reinforced base slab/beam.
-0.2
-0.1
0
0.1
0.2
0.3
0.4
0.5
0.6
-4.0 -3.0 -2.0 -1.0 0.0 1.0 2.0 3.0 4.0
Displacement (mm)
Horiz
onta
l Loa
d (t)
75
Figure 3.29 Cracked model wall during cyclic test
The lateral resistance parameters evaluated during cyclic test of the model walls are given in
table 3.14. One wall has been damaged during transportation and fixing operation. It is worth
mentioning that behavior of wall to lateral displacement from the south actuator has only
been analyzed and present in the table. The rotation of the girder could not be filtered from
the upper half cycle to obtain the actual behavior of the wall. The hysteresis envelopes are
shown in figure 3.30. The idealized bilinear curve is also plotted in the same figure to
evaluate effective stiffness, Ke and ductility ratio, µ.
Table 3.14 Mechanical properties of model walls
Designation
h
inch
(mm)
l
inch
(mm)
t
inch
(mm)
E
psi
(GPa)
σ
psi
(MPa)
Hmax
kips
(kN)
ft
psi
(MPa)
Ke
kips/in
(kN/mm)
G
ksi
(MPa)
µ
(%)
G/E
Ratio (%)
MC-111-1 8.3
(210)
9.4
(238)
2.2
(56)
46.4
(0.32)
11.6
(0.08)
0.31
(1.39)
17.4
(0.12)
9.73
(1.71)
5.02
(34.59) 3.76 11%
MC-111-2 8.5
(215)
9.1
(230)
2.2
(57)
46.4
(0.32)
11.6
(0.08)
0.52
(2.31)
33.35
(0.23)
5.23
(0.92)
2.74
(18.88) 3.3 6%
Average 8.4
(213)
9.2
(234)
2.2
(56.5)
46.4
(0.32)
11.6
(0.08)
0.41
(1.85)
24.65
(0.17)
7.45
(1.31)
3.88
(26.74) 3.53 8%
Prototype 40
(1015)
37.1
(943)
8.6
(219)
290.0
(2)
43.5
(0.3)
10.45
(46.64)
31.9
(0.22)
97.05
(17.06)
15.52
(107.06) 4.45 5%
Theoretical S.F 4 4 4 4 4 64 4 16 4 1
Actual S.F 4.8 4.0 3.9 6.2 4 25.2 1.3 13 4 1.3
76
Load-Displacement Curve
-0.160
-0.140
-0.120
-0.100
-0.080
-0.060
-0.040
-0.020
0.000-3.0 -2.5 -2.0 -1.5 -1.0 -0.5 0.0
Horizontal Displacement (mm)
Hor
izon
tal L
oad,
Ton
e
Figure 3.30 Typical hysteresis envelope of model wall for south side loading
It could be seen from the table that full compliance with the complete model similarity
requirements has not been obtained in some of the parameters. However, stiffness Ke and
modulus of elasticity and ductility ratio are adequately modeled. The experimental set up for
the cyclic test of model walls could be attributed to the non-compliance.
3.4 COMPARISON OF MECHANICAL PROPERTIES OF PROTOTYPE AND
MODEL MASONRY ASSEMBLAGE
In this section, the physical and mechanical properties of model and prototype masonry
materials are compared. The mechanical properties of model walls are extrapolated to
prototype and compared with the actual experimentally determined mechanical properties of
prototype walls. Actual scale factor is compared with the theoretical scale factor for
compression strength, modulus of elasticity, tensile (shear) strength and modulus of rigidity
and other parameter of the cyclic load test of masonry assemblage.
77
3.4.1 Masonry Materials
As mentioned earlier, different trial mixes have been prepared for simulating compressive
strength of masonry mortar, micro concrete and masonry unit. Cement-lime-sand mortar
(CLS 115) is selected as masonry mortar for its extrapolated 28 days compressive strength
close to 28 days compressive strength of prototype mortar. The 28 days compressive strength
of model mortar was 239 psi (1.65 MPa) and its extrapolated value becomes 956 psi (6.6
MPa) as compared to 997 psi (6.9 MPa). The prototype mortar is representing the field
condition.
Although, prototype concrete has not been designed and tested in this research work,
however, decision was made to assume 1500 psi (10.35 MPa) as target value. The
compressive strength for prototype concrete represents lower bound used in the current
masonry construction practice in Peshawar and earthquake affected area. However, relatively
high compressive strength of 2175 psi/15 MPa (C15) has been recommended by researchers
(Miha Tomazevic 99) for the confining element. Cement-lime-sand (CLS 115) having
compressive strength of 367 psi (2.53 MPa) was finalized as micro-concrete for confining
elements. However, relatively high strength micro concrete (Cement-sand CS16) was
designed for floor slabs.
However, the data of masonry unit analyzed in section 2.2 is scattered; the prototype
masonry unit used in this study is considered as reference for modeled units. Different mortar
mixes for simulating compressive strength and density of masonry unit have been prepared.
The two main types of combination of constituent materials were cement-lime-sand and
cement-lime-surkhi. Density of modeled brick from cement-lime-sand mix was high when
extrapolated to prototype. Cement-lime-surkhi (CLSr 125) mix has been finalized. As
mentioned earlier, three different shapes of model bricks have been prepared. The simulation
was done on the actual model brick.
The physical and mechanical properties of model and prototype masonry materials are
compared in table 3.15. In the table, the actual and theoretical scale factor is also compared.
It could be seen that good correlation exists between true and theoretical scale factor.
78
Table 3.15 Actual and true scale factor for masonry materials
Description Prototype Model Scale Factor
Actual True
Masonry Unit Dimensions (length x width x thickness); inch; (mm)
8.7x4.2x2.75 (222x107x70)
2.2x1.1x0.67 (56 x27x17) 4.0 4.0
Compressive Strength of Masonry Mortar; psi; (MPa) 997.3 (6.9)
238.8 (1.7) 4.2 4.0
Compressive Strength of Masonry unit, psi; (MPa) 2338.0 (16.1)
634.8 (4.4) 3.7 4.0
Density of Masonry unit, lb/ft3; (kN/m3) 101.0 (15.9)
98.0 (15.4) 1.03 1.0
Compressive Strength of Concrete, psi; (MPa) 1500 (10.3)
367 (2.53) 4.1 4.0
Yield Stress of Reinforcing Steel, psi; (MPa) 94,500 (652.0)
29,000 (200.0) 3.3 4.0
3.4.2 Masonry Assemblage
Table 3.16 summarized the results of prototype and model masonry assemblage. It is worth
mentioning that the mechanical properties of model masonry assemblage is representing the
actual model brick (Model Brick No. 1, 56 x 27 x 17)
Table 3.16 Actual and true scale factor for masonry assemblage
Description Prototype Model Scale Factor
Actual True
Compressive Strength of Masonry,ƒk, psi; (MPa) 839.6 (5.8)
278.6 (1.92) 3.01 4.00
Tensile Strength (shear) of Masonry,ƒtk, psi; (MPa) 51.27 (0.35)
31.97 (0.22) 1.60 4.00
Modulus of Elasticity of Masonry, E, ksi; (GPa) 288.0 (1.98)
46.28 (0.32) 6.22 4.00
Shear Modulus of Masonry, G, ksi; (GPa) 28.11 (0.19)
16.53 (0.11) 1.70 4.00
It is observed that the mechanical properties of masonry materials are satisfactorily modeled,
the modeled masonry assemblage showed a higher trend. This could be attributed to the
increase in bond strength in the model masonry (Calvi, G. M., et al., 1996). It could be
concluded that, however, properties of masonry materials are very well scaled, the
mechanical properties of model masonry have not ben scaled as required by complete model
similarities. The actual scale factor should be used for extrapolating model masonry results to
prototype masonry.
79
CHAPTER 4 EXPERIMENTAL PROGRAM: SHAKE TABLE TEST
4.1 INTRODUCTION
In order to determine the behavior of typical masonry building by testing small scale model
buildings, the requirements of strength as well as dynamic characteristics must be fulfilled. In
the case of complete model similitude laws, as described earlier, the compressive stresses in
the walls should be scaled so that failure mechanism in prototype and model is same. For the
dynamic behavior to be same, mass and stiffness requirements should be fulfilled.
The selection of typical Pakistani masonry building, fabrication of different phases of model
buildings, calculation of additional load to simulate floor finishing, instrumentation and data
acquisition and finally the testing procedure is discussed in this chapter. The chapter is
divided into ten sections. Pullout test is conducted on model aluminum bar is presented in
section 4.4. Different parameters of selected ground motion are discussed in section 4.9.
4.2 TYPICAL PAKISTANI MASONRY BUILDING
The diversity in materials of construction and configuration is high in Pakistani residential
buildings. Solid fired clay brick, solid and hollow concrete block, adobe brick, and mud is
used for the construction of residential buildings in both rural and urban areas. The fired clay
brick load bearing walls are typically double leaf of 9 inch (229mm) thickness, are laid in
English bond. 4½ inch (115 mm) thick walls, laid in running bond are typically used as non-
load bearing walls including boundary and parapet walls. Solid and hollow concrete blocks,
typically of 12 x 8 x 6 inch (30.5 x 20.3 x 15.2 cm) size are laid in stretcher bond to construct
load bearing walls or non-load bearing infill in frame structure. In rural areas adobe brick
wall of the same size as burnt brick walls or mud walls of comparatively larger size is used
for single story load bearing walls.
Cement-sand, cement-Khaka (stone dust)-sand or mud mortar is used for the construction of
masonry walls. The proportion of mortar varies from place to place and from building to
building and also varies with the wall thickness. Comparatively weak mortar is used in 9 inch
80
thick wall than 4½ inch thick wall (half brick thickness). In rural area mud mortar is used for
the construction of walls.
Floor slab is mostly rigid reinforced concrete 5 or 6 inches (127 or 152 mm) thick. Wooden
and/or steel truss with galvanized iron (GI) sheet is used in hilly terrain for roofing. Steel W-
section girder and T-section supporting fired clay tiles and heavy 6-8 inches (152-203 mm)
thick mud load is also used for roofing in some areas. Foundation is either of stone masonry,
stepped brick masonry, plain concrete or in very rare cases of reinforced concrete. The
masonry buildings are typically of one to two stories high. However, three and four stories
masonry building are available in old urban areas. The story height is 10 to 12 ft (3.0-3.7 m).
For this study, up to 64 building drawings have been collected from Peshawar, Abbottabad
and Mansehra. The plot area for these buildings ranges from 5-7 Marlas (1360-1904 sq.ft or
126.0-177 m2). The buildings represent single and double story brick masonry residential
buildings. All load bearing walls are typically of 9 inch (229 mm) thickness. The drawings
have been analyzed on the basis of wall density ratio in both orthogonal directions. Finally a
single and double story typical brick masonry building have been selected for their wall
density ratio close to mean wall density ratios.
Table 4.1 gives range of wall density ratios in both orthogonal direction for single and double
story buildings and Table 4.2 gives wall density ratio of the selected single and double story
building. Figure 4.1-4.3 shows the selected prototype buildings. The dimensions of the model
building have been slightly reduced in both directions to accommodate the model on the
shake table. However, wall density ratio has not been significantly reduced. The non-load
bearing walls are not considered in the model building construction.
Table 4.1 Wall-density ratios of buildings
S. No. Type of Building Wall-Density Ratios
Long Direction Short Direction
1 Single-Story Buildings 4.55% to 10.34% 2.81% to 7.98%
2 Double-Story Buildings - Ground Floor 3.92% to 12.78% 2.28% to 7.30%
Double-Story Buildings - First Floor 3.00% to 9.69% 1.86% to 6.03%
81
Table 4.2 Wall-density ratios of selected buildings
S. No. Type of Building Wall-Density Ratios*
Long Direction Short Direction
1 Single-Story Buildings 8.16 5.64
2 Double-Story Buildings - Ground Floor 8.17 3.87
Double-Story Buildings - First Floor 7.81 5.99
Figure 4.1 Typical single story prototype building
82
Figure 4.2 Ground floor of typical double story prototype building
83
Figure 4.3 First floor of typical double story prototype building
The building has been confined according to the requirements of EC8. Tie columns, 9x9
inch, have been provided at the wall junctions and 9x6 inch (229x152 mm) have been
provided at the end of the walls. All doors and windows openings greater in size than 4x4 ft
(1.22x1.22 m) are confined with 9x6 inch (229x152 mm) confining element. A 9x6 inch
(229x152 mm) bond beam has been provided over wall at the lintel level. Tie columns are
provided at maximum horizontal spacing of 13 ft (3.96 m). The confining elements are
84
reinforced with 4#4 longitudinal bars. # 3 bar stirrups are provided at 6 inch (152 mm) in the
horizontal and vertical confining element.
The prototype building dimensions have been reduced by a scale factor of 4. Commercially
available 3.1 mm aluminum wire has been used as model reinforcement in the confining
element to simulate #4 longitudinal bars. The #3 bar stirrups have modeled with 1 mm mild
steel wire woven twice to make the effective diameter of 2 mm. Figure 4.4-4.6 illustrate the
confining element location in single and double story building.
Figure 4.4 Single story confined masonry model building
85
Figure 4.5 Ground floor double story masonry model building
86
Figure 4.6 First floor double story masonry model building
4.3 FABRICATION OF TYPICAL PAKISTANI MASONRY BUILDING
In the subsequent sections, the different stages of construction of model are discussed.
4.3.1 Foundation Pad
The model buildings have been constructed on foundation pad. The foundation pad has been
designed to support shear and flexure action during lifting operation of the specimen and of
the overhang portion when the specimen is fixed with the shake table top. The pad is 5 inches
(127 mm) in thickness and is reinforced with # 3 deformed reinforcing bar @ 6" c/c in both
87
directions. Through holes, 0.51 inch (13 mm) in diameter, were provided in the foundation
pad for fixing model building with the table top (shake table platform) by steel bolts. Model
rebars were tied with the foundation steel prior to concrete pouring. While in the other case
holes have been drilled in the concrete, rebars were then fixed in the holes with epoxy resin.
In the former case there was problem of positioning of flexible modeled bars during concrete
pouring. Pull out test has been carried out for the later case (section 4.4). U-type hooks were
also provided near four corners for lifting purposes. The different stages of construction of
foundation pad are shown in figure 4.7-4.8.
Figure 4.7 Through holes in reinforced concrete foundation pad
Figure 4.8 Model rebars embedded in foundation concrete
88
4.3.2 Masonry Walls
Markings have been made for walls and tie columns on the foundation pad. The foundation
was roughened with chisel for proper bond between foundation pad and first layer of bricks.
Special arrangement had been made for keeping walls aligned. Plumbness of the walls is
checked with water level. 2-3 mm joint thickness is maintained throughout the model
building construction. The bricks were laid in English bond. At the end and at the junction of
walls toothings were provided with 1/4th of brick projection. The practice of construction of
the prototype was respected in the construction of the model buildings. Figure 4.9 shows
construction of wall and figure 4.10 shows under construction model with toothing at the end
and junction of walls.
Figure 4.9 Under-construction ground story wall
89
Figure 4.10 Toothing at the end and walls junction
4.3.3 Confining Element
Tie columns reinforced with 4 bars are provided at the specified locations. The bond beams
are provided when all the walls are erected up to lintel level (7 ft/2.1 m from floor level). The
longitudinal reinforcement of tie columns has been anchored in the foundation slab. The
reinforcement of tie columns and beams are tied together with binding wire. The longitudinal
reinforcement of tie beams at the end of wall are provided 90-degree hook. Micro concrete
has been poured into the tie column after the wall has been constructed. However, in this case
the micro concrete is manually vibrated with a steel wire for better filling in the wall
toothing, in the case of prototype construction good consistency of concrete as well as
mechanical vibration is required. Figure 4.11-4.16 show modeled rebars, their fixing during
construction of model, concrete pouring in modeled confining element.
90
Figure 4.11 Fabrication of stirrup for bond beam and tie column
Figure 4.12 Model bond and floor beam reinforcement
91
Figure 4.13 Rebars fixing for floor beam
Figure 4.14 Micro concrete pouring in tie column
92
Figure 4.15 Tie column after removal of form work
Figure 4.16 Concrete pouring in floor beam in double story model
4.3.4 Floor Slab
Floor slab has been cast after walls and tie columns have been constructed. The slab
reinforcements have been fabricated and fixed at desired spacing. Sufficiently rigid farm
work has been erected. Polyethylene sheet is provided over the plywood form work as to
prevent absorption of water from micro concrete. The slab reinforcement mesh has been
brought and positioned on slab form work. The tie column’s reinforcements have been bent
with the roof slab reinforcement before concrete pouring. The slab concrete has been cured
for about 7 days. The slab form was removed after 28 days of concrete pouring. In the case of
93
ground floor of the double story model, the form work was kept until the second floor (roof
slab) has been cast. After the slab was sufficiently strong, marking was made for the location
of additional steel masses, simulating floor finishing and live load, and holes were drilled in
the slab. Figure 4.17 and figure 4.18 shows floor slab reinforcement and concreting.
Figure 4.17 Slab reinforcement prior to concrete pouring
Figure 4.18 Concrete pouring for single story floor slab
94
4.4 PULL OUT TEST
In order to check the adequacy of model rebar anchorage in foundation pad fixed in drilled
holes by epoxy resin, pull out tests have been carried out. The tests were also aimed to check
the anchorage of the bar in tie columns and bond beams. However, there exist a standard test
method, ASTM A 944-99 for comparing bond strength of prototype steel reinforcing bars to
concrete using beam-end specimens, a simplified pull out test method has been designed for
testing model rebar anchorage.
Two types of mortar, cement-sand (CS 1:6) and cement-lime-sand (CLS 1:1:5), and two
types of bar anchorage were used. In one type straight bar was anchored in fresh concrete
with anchorage length of 3.75 inch (95 mm), calculated according to ACI Code 12.2.3. In
other type hook bar was anchored with hook length of 12 times diameter of bar. Three
specimens were prepared of each mortar and anchorage type. Three specimens were prepared
fixing bar by epoxy resin in a drilled hole. In such case the anchorage length was 1½ ".
Figure 4.19 and figure 4.20 show pull out specimen and test set up. Figure 4.21 illustrate
different pull out specimens and anchorage details. Table 4.3 gives failure mode and stress at
pulling during pull out.
Figure 4.19 Pullout test specimens
95
Figure 4.20 Pullout Test Set up
33 4"
3"
6"
6"
A A
PLAN
SECTION A-A
STRAIGHT WIRE INMODEL CONCRETE
3mm Ø ALUMINUM WIRE
33 4"
3"
6"
6"
A A
PLAN
SECTION A-A
HOOKED WIRE INMODEL CONCRETE
3mm Ø ALUMINUM WIRE
112"
11 2"
3"
6"
6"
A A
PLAN
SECTION A-A
STRAIGHT WIRE INPROTOTYPE CONCRETE
3mm Ø ALUMINUM WIRE
EPOXY
DRILLEDHOLE
Figure 4.21 Details of pullout Test Specimens
96
Table 4.3 Pull out test results
Specimen Dia of Wire
(in)
Area of Wire
(sq. in)
Stress at pulling (% age of
Yield Strength) Failure Mode
Straight Bar (Embedment length = 3.75" or 95 mm), 1: 6 micro concrete
1 0.125 (3.18) 0.0123 (7.94) 95% Pulled out
2 0.125 (3.18) 0.0123 (7.94) 97% Pulled out
3 0.125 (3.18) 0.0123 (7.94) 90% Pulled out
Hooked Bar (Embedment = 3.75" or 95 mm & Hook length = 1.5" or 38 mm), 1: 6 micro concrete
1 0.125 (3.18) 0.0123 (7.94) 122% Wire Broke
2 0.125 (3.18) 0.0123 (7.94) 139% Wire Broke
3 0.125 (3.18) 0.0123 (7.94) 139% Wire Broke
Straight Bar (Embedment length = 3.75" or 95 mm), 1: 1: 5 micro concrete
1 0.125 (3.18) 0.0123 (7.94) 80% Pulled out
2 0.125 (3.18) 0.0123 (7.94) 85% Pulled out
3 0.125 (3.18) 0.0123 (7.94) 90% Pulled out
Hooked Bar (Embedment = 3.75" or 95 mm & Hook length = 1.5" or 38 mm), 1: 1: 5 micro concrete
1 0.125 (3.18) 0.0123 (7.94) 130% Wire Broke
2 0.125 (3.18) 0.0123 (7.94) 139% Wire Broke
3 0.125 (3.18) 0.0123 (7.94) 139% Wire Broke
Straight Bar (Embedment length = 1.5"or 38 mm) with epoxy
1 0.125 (3.18) 0.0123 (7.94) 130% Wire Broke
2 0.125 (3.18) 0.0123 (7.94) 130% Wire Broke
3 0.125 (3.18) 0.0123 (7.94) 100% Pulled out
It was observed that all the hooked bars in both types of mortars ruptured. The straight bars,
however, pulled out but the stress at the pulling was more than 80 % of yield strength in both
mortar specimens. Two out of three bars ruptured and the third pull out at 100 % of yield
strength in case of epoxy fixed bar specimens. It is worth mentioning that the age of micro
concrete at testing was 14 days. Compressive strength of micro concrete CS 1:6 and CLS
1:1:5 at 14 days was 480 psi (3.3 MPa) and 250 psi (1.52 MPa) respectively. The bond
between micro concrete and modeled wire would have increased with age and strength of
97
concrete, the hooked bars and epoxy fixed bars would develop the yield strength with out
pulling.
4.5 DESIGN OF SLAB AND FLOOR BEAM REINFORCEMENT
Floor slab and floor beams have been designed as per ACI-code. The slabs are designed for
supporting live load of 40 psf (1.92 kN/m2), floor finishing load of 35 psf (1.67 kN/m2) and
self weight of the slab. The minimum thickness calculated is 5 inch (127 mm) for both single
and double story building. Negative reinforcements have been provided in top of the slab
over all internal walls. Floor beams have been provided in the ground floor of double story
building. The beams have been designed for supporting ground floor load, upper story wall
load and self weight of the beam. Figure 4.22-24 illustrate the reinforcement of single and
double story buildings. Figure 4.25 shows cross sections of floor beam (beam 1) at mid span
and near support, and reinforcement details of confining element.
98
Figure 4.22 Slab reinforcement details of single story building
99
Figure 4.23 Slab reinforcement details of ground floor double story building
100
Figure 4.24 Slab reinforcement details of first floor double story building
101
Figure 4.25 Reinforcement details of floor beams and confining elements
4.6 ADDITIONAL FLOOR MASSES
In order to simulate the live load and floor finishing, additional masses have been attached.
The masses have been distributed and attached with floor slab in such a way as to fulfill the
requirements of compressive stresses in the walls but would not affect the dynamic
characteristics of the model.
The masses have been calculated on the basis of actual densities of the prototype and model
materials. The densities of materials are determined by measuring actual weight and
dimensions of prototype and model walls.
Prototype Masonry = 101.0 pcf (15.87 kN/m3)
Model Masonry = 95.31 pcf (14.98 kN/m3)
Micro Concrete = 98.83 pcf (15.53 kN/m3)
102
However, the densities of prototype reinforced concrete and floor finishes are assumed to be
150 pcf (23.57 kN/m3) and 140 pcf (22.0 kN/m3) respectively. In the calculation of additional
masses for the model building, self weight of the floor slab and 3 inch floor finishes (35 psf)
has been considered. The mass of wall to slab ratio of prototype and model is adequately
correlated (table 4.4). The mass of slab includes additional masses, floor finishes and self
weight of slab.
Table 4.4 Correlation of prototype to model
Prototype Mass (lb) Model Mass (lb)
Wall, (A) Slab (B) A/B Wall, (A) Slab (B) A/B
Single Story 57,267.0
(25,983.2)
63,280.0
(28,711.4) 0.90
841.6
(382.4)
877.8
(398.3) 0.96
Ground floor, Double Story 123,037.0
(55,824.4)
69,981.3
(31,752.0) 1.76
1,808.2
(820.4)
963.2
(437.62) 1.88
First Floor, Double Story 59,880.4
(27,169.0)
76,160.0
(34,555.4) 0.79
880.0
(400.0)
1,010.8
(459.2) 0.87
Circular steel weights 22 lb (10 kg) each is used as additional mass. The masses are
uniformly distributed and fixed by nut and bolts with model slab so that no movement was
possible during shaking of the model. The location of additional masses on the slab is
illustrated in figure 4.26-4.28. The masses can also be seen in figure 4.29-4.30 after fixing
with models.
103
Figure 4.26 Additional masses on single story model
104
Figure 4.27 Additional masses on ground floor of double story model
105
Figure 4.28 Additional masses on first floor of double story model
106
Figure 4.29 Additional masses on single story model
Figure 4.30 Additional masses on double story model
4.7 EARTHQUAKE SIMULATOR
Earthquake Engineering Center (EEC), N-W.F.P University of Engineering and Technology,
Peshawar has 5.0 x 5.0 ft (1.5 m x 1.5 m) single degree of freedom and 20.0 x 20.0 ft (6.0 m
x 6.0 m) six degree of freedom earthquake simulators (shake tables). At the time of this study
the later facility was under construction, therefore, the reduced scaled models were tested on
single degree of freedom shake table (figure 4.31).
107
Figure 4.31 Single degree of freedom earthquake simulator (shake table)
The seismic simulator consists mainly of 5 ft x 5 ft (1.5 m x 1.5 m), 2.5 inch (64 mm) thick
aluminum table and an actuator. The table moves to and fro on a rail. The actuator drives the
table, is connected at one end with the table and the other end is fixed with a reaction arm.
The actuator is displacement control. Desired acceleration time history is fed in the computer
in the control room which is converted to displacement time history by controller to drive the
actuator. An external accelerometer connected with table and a internal LVDT is used for
feedback. The detailed description of the shake table, its components and controller is given
in Appendix B.
4.8 INSTRUMENTATIONS AND DATA ACQUISITIONS
Global response of the model building is captured through two types of instruments,
accelerometers and displacement transducers. The accelerometers are used to measure
absolute response acceleration and displacement transducers are used to measure relative
displacement response of the model. The following sections provide details of the
instrumentation plan and data acquisition.
4.8.1 Accelerometers
Two types of accelerometers were used in this study. 10g capacity accelerometers were
connected at mid depth of floor slab to capture model response in the direction of shaking. A
total of 4 accelerometers were used in single story model connected at the floor slab at
108
location of the four in-plane walls. Four accelerometers were also used in the double story
model building, two connected at each floor at the location of in-plane exterior walls. A 2g
capacity Dytran accelerometer was used to capture response of base slab and to compare the
result with the table top for possible relative slip. An additional accelerometer was also
connected at the bottom side of the shake table top to measure table acceleration. The
instrumentation plans for single and double story model are shown in figure 4.32-4.34.
Figure 4.32 Instrumentation details of single story model
109
Figure 4.33 Instrumentation details of double story model (elevation)
110
Figure 4.34 Instrumentation details of double story model (plan)
4.8.2 Displacement Transducer and Reference Frame
String pot displacement transducers were used to measure the relative displacement response
of the models. The displacement instruments were connected at the same locations where
accelerometers were connected in both single and double story model as shown in figure
4.32-3.34. The string pot transducers were connected with specially designed reference frame
erected off the table. Tube steel section was used in the design and fabrication of the
reference frame. The frame is designed and fixed on strong floor in such a way that minimum
floor noise has been transferred to the instruments. For this purpose an accelerometer was
also installed on the frame to measure noise level during testing operation. Reference reframe
is shown in figure 4.35
111
Figure 4.35 Reference frame for displacement transducer.
4.9 GROUND MOTION TIME HISTORY
Kobe 1995 North-South component earthquake acceleration record has been used for the
motion of shake table. The peak acceleration of the earthquake record is 0.833 g. The record
is originally of 50 second duration but first 30 second strong motion record is taken for shake
table motion. The record is used on the basis of its predominant period of 0.36 second.
As complete model similitude requirements are to be fulfilled, therefore, the earthquake
record is to be compressed in time duration by square root of scale factor but the amplitude
or acceleration of the record is not scaled. The duration and peak acceleration of the modeled
record becomes:
Prototype:
Duration of earthquake record = 30 sec,
Peak Acceleration = 0.833 g
Model:
Duration of earthquake record = 304
= 15 sec,
Peak Acceleration = 0.833 g
112
The prototype and model earthquake accelerogram is shown in figure 4.36 and figure 4.37
respectively.
Since the behavior of the models is to be assessed from low level of shaking to high level, the
shake table motion is applied in increasing increments. The different intensities of shaking
applied on the model are 5 %, 10 %, 20 %, 40%, 60%, 80%, 100%, 125%, 150%, 175% and
200%. The different intensities of shaking is chosen to have enough points for plotting base
shear to drift ratio curve and assessing the response modification and ductility factor.
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Time (see)
Acc
eler
atio
n (g
)
Prototype Acceleroram
Figure 4.36 Prototype acceleration time history
113
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
1 3 5 7 9 11 13 15 17 19 21 23 25 27 29
Time (see)
Acc
eler
atio
n (g
)
Model Accelerogram
Figure 4.37 Model acceleration time history
4.10 TESTING PROCEDURE
As discussed earlier the models were constructed on the reinforced concrete slab. Hooks
were provided at the corners of the base slab. Special arrangements were made to lift (figure
4.38) the models from its construction location to the shake table by 20 tonne overhead
crane. The model was fixed to the table top with nuts and bolts. The roof slab was hanged
with the overhead crane by belt in such a way that it would hold the slab in case of model
collapse and to avoid instrument damage and would not interfere in the dynamic
characteristics of the model shaking.
114
Figure 4.38 Lifting operation of double story building
Both single and double story models were tested in their weak axis. The models were given
different motions in increasing increments. Before each incremental motion, a free vibration
test was carried out to find natural frequency and coefficient of viscous damping ratio of the
model by hitting the model with impact hammer. An 18 inch (46 cm) wooden piece was
placed on the center of the top slab and then the wooden piece was hit with steel hammer.
After analyzing displacement and acceleration data, it was found that the frequency and
damping ratios were not representative of the model. Then a small amplitude forced motion
was given after each test run for dynamic characterization. The motion was given manually
to the shake table. Fourier amplitude spectra were used for determining the dynamic
characteristics.
The response of the models was measured with the help of accelerometers and displacement
transducers as explained earlier. All the accelerometers and string pots were connected with
data acquisition system. The instruments were checked before the start of the first test run by
giving low level excitation to the shake table and observe their functioning qualitatively. For
each test run data was collected for 40 second. After each test run, cracks were marked on the
model and photographed. The cracks were also mapped on the drawing. Two video cameras
were used to capture the response of the model during shaking.
115
CHAPTER 5 SHAKE TABLE TEST RESULTS
5.1 INTRODUCTION
In this chapter the measured response of reduced scale model on shake table test has been
analyzed to evaluate the behavior of single and double story brick masonry building. The
chapter is basically divided into five sections. In section 5.2, the behavior of single story
model and data analysis has been discussed. The section is subdivided into nine sections. The
general condition of single story model before commencing shake table test and then damage
propagation and failure mechanism during different shake table tests with increasing
intensity has been discussed. Base shear and story rotation evaluated on the basis of
measured response acceleration and response displacement is presented. The response
modification factor for single story model evaluated from global ductility factor and elastic
response has also been presented.
In section 5.3, the behavior of double story model has been discussed. In section 5.4, the
seismic resistance parameters of single and double story model has been extrapolated to
prototype building.
In section 5.5 the behavior of single and double story model has been compared.
5.2 SINGLE STORY MODEL BUILDING
As explained in the preceding sections, visual observations were made after each test run for
damage propagation. The internal and external walls of the models were white washed before
start of the test. The cracks were marked on the model and photographs were taken after each
test run. The cracks were also mapped on the drawing after each test run. Video was prepared
during each test run and after the test.
For the reporting purposes, the out of plane and in plane walls were divided in different grids
as shown in figure 5.1. Walls are designated after grids lines. For example, walls parallel to
116
grid A, B, C and F are designated a wall A, wall B, wall C and wall F. Similarly, walls
parallel to grid 1, 5, 6 and 12 are designated as wall 1, wall 5, wall 6 and wall 12.
Figure 5.1 Grid lines-single story model
5.2.1 Condition of Model before Test
The model was carefully lifted with the help of overhead crane from the location of its
construction and fixed on the shake table. The model was thoroughly observed for any cracks
before lifting and white washing operation. Horizontal hairline cracks between first and
second layer of bricks in the out-of-plane wall 12 were observed. This could be because of
the shrinkage of the micro-concrete and deflection of the floor slab. Hairline cracks were also
observed on the upper side of the roof slab. The cracks marked with black marker are shown
in figure 5.2. After the model has been fixed, it was again inspected for any damage during
lifting and fixing operation. However, no damage has been observed.
117
Figure 5.2 Hairline cracks in roof slab and out-of-plane walls before test
5.2.2 Out of plane Walls
The out of plane walls were comparatively less damaged during shake table tests. There were
no cracks in the out of plane walls (grid 1, 5, 6 & 12) until test run R60. During test run R60
horizontal hairline cracks were observed in wall 1 (panel between grid A and B) almost at
mid height between bond beam and foundation pad. A horizontal hairline crack was also
observed in the bottom course (panel between grid A and B), propagating in zig zag fashion
towards tie column. The wall on grid 12 has developed horizontal hairline cracks in the
second last course (panel between F and C). In the subsequent test run 80, a new vertical
crack formed between masonry and tie column (1B) interface propagating from top slab
towards bond beam. In the same test run, a shear stepped crack was observed on right side of
window in wall 6.
During test run 125, some new cracks formed in both out of plane walls 1 and 12.
Propagation of existing cracks was also observed. A hairline cracks developed at second
course from the slab in wall 1. In the test run R175, the shaking was so intense that slab
corner (where the accelerometer was also installed), at tie column A1 location, cracked and
Hairline
Cracks
118
subsequently disintegrated. The sliding of slab at existing horizontal cracks could be noticed
in grid 1 and 12 (figure 5.3 and 5.4). The internal wall at grid 5 could not be observed during
the testing phases. Figures D1-D9 in Appendix D shows schematic diagrams of crack
propagation during each test run. The figures show propagation of the existing cracks and
newly developed cracks in each test run. However, the overall damage to walls has been
presented in the last test run.
Figure 5.3 Sliding of roof slab and cracks in out of plane wall 1 after final test run
Figure 5.4 Cracks in out of plane wall 12 after final test run
Cracks in wall 1
Cracks in wall 12
119
5.2.3 In-plane Walls
The in plane walls were severely damaged at the end of test. Crushing of concrete in the tie
column, falling and crushing of brick and separation of masonry walls from the tie columns
were observed. The reinforcement in the tie column buckled at the beam-column joints.
However, all the in-plane walls severely damaged, the confining element prevented the in-
plane walls from disintegration and model from collapse. Damaged external walls at the end
of shaking table test are shown in figure 5.5 and 5.6. Figures D10-D15 in Appendix D shows
schematic of the cracks propagation in the in-plane walls during shake table test.
Figure 5.5 Damage to in-plane wall (grid A) at the end of test
Figure 5.6 Damage to in-plane wall at grid C and F at the end of test
120
In the in-plane walls no cracks have been observed until test run R60. During the test run a
hairline stepped shear cracks were observed originating from bottom of right window and
propagated upward towards tie column (grid A). Another crack during the same test run was
also observed near column A5 between roof slab and bond beam. However, during test run
R80 some cracks have been observed in Grid C and F. An inclined shear crack was observed
in wall C between roof slab and bond beam. Another hairline crack was observed almost at
mid height between bond beam and base slab. A horizontal hairline crack was also observed
in Grid F. No significant new crack was observed in the subsequent test run until R125,
except the propagation of the old crack.
The model was seriously damaged during test run R125. Major shear cracks were developed
wall of the model. Inclined stepped shear cracks propagating from bottom corners of the
window in wall A were observed running towards bottom corners of the tie columns.
Horizontal cracks have also been observed propagating from the two windows. The cracks
developed in a scissor crack in the pier between the windows, which also pass through the tie
column (A5) concrete. Vertical crack at the interface of tie column A12 and masonry wall
was also observed. Inclined shear cracks following mortar joint appeared in the in-plane
walls having doors. The cracks propagated from the top and bottom end of the door confining
element (tie column) and join almost at the center of the wall panel. These types of cracks
were observed in all internal and external in-plane walls. The cracks also shear micro-
concrete at the top and bottom end of the tie column. Spalling of concrete cover at the top of
tie column was also observed.
During test run R175, the model was significantly damaged. Some new cracks were
observed. Existing cracks opened up and propagated. Falling of part of already cracked
masonry from the sides of the window was observed (wall A). Opening and closing of
existing cracks could be clearly seen in the close up video clips. Because of the increased
drift demand, the concrete at the top and bottom of tie column crushed. The rebars buckled at
this location. Bricks near top and bottom joint of tie column were also crushed. Separation of
tie column and masonry wall was also observed. Horizontal crack at the roof level could also
be seen.
121
However, the in-plane walls were heavily damaged, no out of plane failure of walls were
observed. This could be attributed to the effect of confining element. The test has been
terminated after the heavy damaged to in-plane walls, crushing of concrete and buckling of
steel in the confining element.
5.2.4 Characteristics Parameters of Shaking Table Motions
Maximum acceleration and displacement of shaking table motion are compared with that of
input model accelerogram in table 5.1. It is observed that the shaking table satisfactorily
simulated the acceleration record. However, the measured acceleration is comparatively
larger than the input model acceleration. Because of the malfunctioning of the shake table
during test run R175, base acceleration of 2.01g was recorded. As the controlling parameter
was acceleration, no clear trend was seen in the shake table measured displacement and input
displacement. The input displacement is calculated after twice integrating the input
acceleration. However, the input motion could not be exactly achieved by some technical
deficiencies; the aim of the reduced scale model would be achieved. The small difference
between input and the achieved motion is inevitable and were experienced in research on
simple simulators (Roko Zarnic et al 2001). The comparative difference between input and
shake table motion could be attributed to the model-platform interaction, friction between the
moving parts of the testing facility and dynamic characteristics of the system (Tomazevic
1992).
Shake table acceleration could not be recorded above 2.0g because upper limit of the
accelerometer installed on the shake table and base slab was reached. The capacity of the
accelerometer connected with table top for controlling actuator was 10g, however, only the
maximum value could be recorded. The displacement and acceleration time histories,
recorded during the shaking table test are presented in figure C1-C100 in appendix C.
122
Table 5.1 Characteristic parameters of shake table motion
Test Run
Input Model Accelerogram Shake Table Motion
Max. Acceleration
(g)
Displacement
(mm)
Max. Acceleration
(g)
Displacement
inch (mm)
5 0.0417 0.092 (2.34) 0.0603 0.216 (5.485)
10 0.0833 0.184 (4.679) 0.1073 0.213 (5.409)
20 0.1666 0.368 (9.359) 0.1955 0.282 (7.161)
40 0.3332 0.737 (18.718) 0.4853 0.716 (18.181)
60 0.4998 1.105 (28.078) 0.5761 1.018 (25.849)
80 0.6664 1.474 (37.437) 0.9659 1.139 (28.922)
100 0.8330 2.176 (55.276) 0.8825 1.757 (44.64)
125 1.0413 2.303 (58.495) 1.0433 2.387 (60.637)
150 1.2495 2.764 (70.194) 1.3192 2.538 (64.471)
175 1.4578 3.224 (81.893) 2.0100 2.778 (70.565)
60R 0.4998 1.105 (28.078) 0.4000 1.018 (25.849)
100R 0.8330 2.176 (55.276) 0.8200 1.834 (46.595)
150R 1.2495 2.764 (70.194) 1.4900 -
5.2.5 Frequency and Damping ratio
Natural frequency and coefficient of viscous damping has been determined before the start of
test and after each test run. The natural frequency after the initial few test runs has been
determined by hitting middle of the top slab with hammer. A wooden strip placed in contact
with the middle of the slab, was hit with the steel hammer as direct impact on the slab could
have damaged the slab. However, after observing impression of the wooden strip on the slab
and masonry, a small impulse was given after each test run to determine the natural
frequency of vibration and coefficient of viscous damping. Table 5.2 gives natural frequency
and damping ratio of single story model. The natural frequency has been determined by
plotting fourier amplitude of the acceleration recorded at the top of the slab. Fourier
amplitude spectra before the start of test and after test run R175 has been shown in figure 5.7
and 5.8. Half-power band width method (Chopra, A, K., 2004) was used to estimate
coefficient of equivalent viscous damping, ζ.
123
2b a
n
f ff
ξ−
= (5.1)
Where:
fa & fb = frequencies on either side of the resonant frequency at which amplitude is
1/√2 times the resonant amplitude, and fn is the resonant frequency.
Table 5.2 Frequency and coefficient of viscous damping
Test Run Frequency, Hrz Coefficient of
Viscous Damping (%)
R00 30.11 3.98
R010 31.35 4.18
R020 29.34 4.13
R040 27.54 5.30
R060 25.66 5.35
R080 21.54 5.89
R100 19.87 6.65
R125 16.33 6.32
R150 16.14 6.68
R175 9.27 10.52
150R 8.34 10.56
0
0.005
0.01
0.015
0.02
0.025
0 10 20 30 40 50 60 70 80
Frequency (Hrz)
Four
ier
Am
plitu
de
Figure 5.7 Fourier amplitude spectra before the start of test
f = 30.11 Hrz,
ζ = 4.98 %
124
0
0.01
0.02
0.03
0.04
0.05
0.06
0.07
0.08
0.09
0 10 20 30 40 50 60 70 80
Frequency (Hrz)
Four
ier
Am
plitu
de
Figure 5.8 Fourier amplitude spectra after test run R175
It can be seen from the table that frequency decreases and damping ratio increases as the
damage to model increases with the sequence of test run. There is a good correlation between
decrease in frequency and damage propagation. However, the damping ratio increased at the
end of test, there were some readings which were less than their preceding values. The
damping ratio should be interpreted with caution as the values would be larger if obtained
from higher amplitude tests (Clough and Penzien, 1993).
5.2.6 Acceleration Amplification
Acceleration amplification has been determined by dividing maximum response acceleration
with maximum input base acceleration during each test run. The response accelerations of
channel 1 and 2 (figure 4.32) are averaged. The acceleration amplifications are given in table
5.3. The data is plotted in figure 5.9. Acceleration amplification corresponding to test run 80
is not plotted as its acceleration is more than the test run 100. The amplification values of
repeated test run 60R and 150R are also not plotted.
f = 9.27 Hrz,
ζ = 10.52
125
Table 5.3 Floor acceleration amplification
Test Run
Max. Shake Table
Acceleration
(g)
Max. Avg. Response
Acceleration
(g)
Amplification
R5 0.0603 0.0995 1.65
R10 0.1073 0.1307 1.22
R20 0.1955 0.1913 0.98
R40 0.4853 0.5395 1.11
R60 0.5761 0.6391 1.11
R80 0.9659 0.9964 1.03
R100 0.8825 1.0118 1.15
R125 1.0433 1.1672 1.12
R150 1.3192 1.5988 1.21
R175 2.0100 2.7372 1.36
60R 0.4000 0.6391 1.60
150R 1.4900 4.1050 2.76
0.0
0.3
0.5
0.8
1.0
1.3
1.5
1.8
2.0
0.0 0.5 1.0 1.5 2.0 2.5
Peak base acceleration (g)
Peak
top
acce
lera
tion/
peak
bas
e ac
cele
ratio
n
Figure 5.9 Acceleration amplification of single story model
126
The highest amplification of 2.76 was observed during test run 150R. This could be
attributed to the resonance effect. Because at this test run the model has developed sever
damage to the masonry wall. The frequency and stiffness are also decreased at this stage.
However, it is generally expected that the amplification factor decreased as the damaged in
the model is increased.
5.2.7 Torsion Effect
Table 5.4 gives displacement values from channel 10 (at A1) and channel 7 (at F6) and
average of channel 8 and 9 readings. The left and right channels displacements are
normalized with the average of the maximum middle displacements. In the table the average
of the maximum middle displacements measured in all test runs are also given. It is worth
mentioning that left and right displacements are taken at the same instant of time when
maximum middle displacements were taken. All the top displacements are average of six
absolute maximum displacements.
Although, plan irregularity exist in the model, no significant torsional motion has been
observed after the analysis. However, in the last three test run (60R, 100R and 150R) left side
observed more displacement because of the comparatively less rigidity and extensive damage
on this side.
127
Table 5.4 Top slab displacements during different test run
Test Run Normalized Displacement
Average maximum
displacement
inch (mm)
Left
(Channel 7)
Middle
(avg. of channel 8 & 9)
Right
(channel 10) Middle
R5 0.955 1.000 1.003 0.231 (5.867)
R10 0.969 1.000 0.957 0.31 (7.874)
R20 1.050 1.000 1.075 0.729 (18.517)
R40 1.040 1.000 1.013 1.027 (26.086)
R60 1.020 1.000 0.947 1.17 (29.718)
R80 1.031 1.000 0.993 1.729 (43.917)
R100 0.979 1.000 1.000 2.361 (59.969)
R125 1.024 1.000 1.003 2.617 (66.472)
R150 0.996 1.000 0.987 2.814 (71.476)
R175 0.995 1.000 0.990 1.027 (26.086)
60R 1.020 1.000 0.947 1.87 (47.498)
100R 1.010 1.000 0.975 4.805 (122.047)
150R 1.012 1.000 0.998 0.231 (5.867)
5.2.8 Base Shear
Base shear is the sum of inertia forces acting on each story level produced as a result of
excitation at the base. The inertia force at a story level has been evaluated by the mass of
story and acceleration with which the mass has been excited. It has been assumed in
calculating base shear that the model under consideration is characterized by first mode of
vibration. If the shape of the vibration is stable in time, the base shear is given by the
following expression:
i ii
Base shear m a⋅ = ∑ (5.2)
Where:
mi = mass at the ith story level
ai = acceleration of the ith mass
128
The equation 5.2 can also be written as
ii
Base shear S⋅ = ∑ (5.3)
Where:
S3 = m3a3max, is the third story shear
S2 = S3+m2a2max, is the second story shear
Base shear = S2+m1a1max, is the total shear at the base
Base shear has been calculated for the model for each test run by multiplying floor masses
with the average of floor accelerations. Table 5.5 gives average acceleration and base shear
during each test runs. The accelerations corresponding to maximum displacement in channel
# 9 were considered. Floor masses calculated in chapter 4 were used for the determination of
base shear. The floor masses include weight of slab, additional masses attached to the slab
and upper half of the wall mass:
Weight of the floor slab = 436 lb (197.82 kg);
Weight of the upper half of the walls = 787.22 lb (357.18 kg);
Additional weights attached to the slab = 440.8 lb (200 kg)
Weight of the model which would contribute to the inertia forces = 1664 lb (755 kg)
Total weight of the model = 2347.26 lb (1065 kg)
Table 5.5 also gives base shear coefficient and rotation angle of the model. Base shear
coefficient are calculated by dividing base shear with total weight of the model. Story
rotation is calculated by dividing story displacement with story height. The base shear
coefficient is plotted versus story rotation angle in figure 5.10. The graph is called seismic
resistance envelopes.
129
Table 5.5 Base shear coefficient and rotation angle of single story model
Test Run Acceleration
(g)
Displacement
inch (mm)
Story mass
lb (kN)
Shear force
lb (kN)
Base Shear
Coefficient
Rotation
Angle
(%)
5 0.0939 0.0043 (0.1092) 1664.0 (55) 156.27 (0.695) 0.0666 0.014%
10 0.1286 0.0059 (0.1499) 1664.0 (755) 214.02 (0.952) 0.0912 0.020%
20 0.1908 0.0138 (0.3505) 1664.0 (755) 317.56 (1.413) 0.1353 0.046%
40 0.5800 0.0236 (0.5994) 1664.0 (755) 965.13 (4.295) 0.4112 0.079%
60 0.6900 0.0307 (0.7798) 1664.0 (755) 1148.17 (5.109) 0.4892 0.102%
80 0.9883 0.0358 (0.9093) 1664.0 (755) 1644.61 (7.319) 0.7007 0.119%
100 1.2000 0.0484 (1.2294) 1664.0 (755) 1996.82 (8.886) 0.8507 0.161%
125 1.7000 0.0748 (1.8999) 1664.0 (755) 2828.83 (12.588) 1.2052 0.249%
150 2.4000 0.2362 (5.9995) 1664.0 (755) 3993.65 (17.772) 1.7014 0.787%
175 2.6000 0.3543 (8.9992) 1664.0 (755) 4326.45 (19.253) 1.8432 1.181%
150R 1.8000 0.4724 (11.999) 1664.0 (755) 2995.24 (13.329) 1.2761 1.575%
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2% 1.4% 1.6% 1.8%
Story Drift Rotation (%)
Bas
e Sh
ear
Coe
ffic
ient
Figure 5.10 Base shear coefficient and story rotation plot for single story model
Three limit states have been defined to characterize the model. Damage limit state represents
the occurrence of first significant crack and the change (decrease) in the first stiffness of the
130
model. The second characteristic state occurs when the model shows maximum resistance to
the lateral forces. The third state is ultimate state where the model is close to collapse or
where significant damage to structural walls has occurred and the model is beyond repair.
The base shear coefficient and story rotation angle for the three limit states are given in table
5.6.
Table 5.6 Base shear coefficient and story rotation at limit state levels
Description of limit state Base shear
Coefficient
Story Rotation
angle (%)
Elastic limit (R125) 1.205 0.25
Maximum Resistance (R175) 1.843 1.18
Ultimate state (R125) 1.276 1.57
It can be seen from table 5.6 that story rotation angle is 0.25 % at damage or elastic limit
state that is where stiffness of the model significantly changed. The story rotation angle was
found to be between 0.25-0.30 % in test carried out elsewhere on un-reinforced and confined
masonry of two different masonry materials and configuration. However, values of story
rotation varied from 0.28-1.39 % in cases of semi-confined and fully confined masonry
model (Tomzavic, et al. 2004).
5.2.9 Response Modification Factor of Single Story Model
Response modification factor is simply defined as ratio of seismic force when the structure is
fully elastic to the seismic force when structure intrinsic non-linear behavior has been taken
into account. That is the ratio between elastic load, He and ultimate design load, Hu is called
response modification factor, R. The following relation describes the definition.
eHR
Hu= (5.4)
Response modification factor, R can be used to reduce the seismic force determined from
elastic analysis of the structure thereby considering the energy dissipation capacity of the
structure. Therefore explicit non-linear analysis of the structure could be avoided. Response
modification factor can also be evaluated by the following expression:
131
( )µ= −2 1uR (5.5)
Where µu = du/de, is global ductility factor.
The base shear coefficient and story drift ratio relation (figure 5.10) has been idealized by
bilinear curve as shown in figure 5.11. In order to idealize the curve, 20% degradation from
the maximum resistance is taken.
0
0.2
0.4
0.6
0.8
1
1.2
1.4
1.6
1.8
2
0.0% 0.2% 0.4% 0.6% 0.8% 1.0% 1.2% 1.4% 1.6% 1.8%
Story Drift Rotation (%)
Bas
e Sh
ear
Coe
ffic
ient
Figure 5.11 Hysteretic envelope and idealized bilinear relation
The response modification factor according to the definition of global ductility factor is given
below:
du = Ultimate displacement of the idealized bilinear curve = 0.435 inch (11.05 mm)
de = displacement at the elastic limit of the idealized bilinear curve = 0.085 inch (2.15 mm)
Global ductility ratio, µu = 5.13 and,
Response modification factor, R from expression 5.5 = 3.04
In order to determine the response modification factor according to equation 5.4, the reduced
scale building has been modeled in SAP2000. The input and output data has been given in
Appendix E. The model has been analyzed by subjecting it to maximum acceleration
_____ Hystersis Envelope
------- Idealised Curve
132
(recorded shake table acceleration during test run R175). The base shear evaluated during the
SAP analysis is given below:
Elastic base shear He = 8410 lb (3816.0 kg)
Experimentally determined base shear Hmax= 4326 lb (1963.0 kg)
Ultimate base shear Hu = 3893.4 lb (1767.0 kg)
Response modification factor, R, according to equation 5.4 = 2.16
The response modification factor given by Eurocode 8 for confined masonry buildings is 2.0-
3.0. Comparing the evaluated response modification factor with that of Eurocode, it could be
concluded that the Eurocode values are adequate.
5.3 DOUBLE STORY MODEL BUILDING
The double story model has been given the same increasing excitation as given to single
story model. The shake table could not produce the desired input excitation. Instruments,
measuring response were removed from the double story model after test run R30. The
model has been excited with increased ground motion until severe damage to in-plane walls
in ground story. The peak shake table acceleration could only be noted as complete time
history file of the shake table motion could not be retrieved. The data analysis and damage
propagation during each test run is discussed in the subsequent sections.
5.3.1 Condition of Model before Test The double story model has been divided into grids in both horizontal directions. The grids in
ground and first floor are shown in figure 5.12. The model has been inspected thoroughly
before white washing. Horizontal hairline cracks have been observed in wall H at the
interface of first floor masonry wall and ground floor slab. A horizontal crack in the second
last mortar joint from the ground story slab was also observed as shown in figure D17,
appendix D. Horizontal cracks of the same nature were also observed in wall 1 in the second
mortar joint from the ground floor slab (figure D18, appendix D). In wall A a horizontal
hairline crack was observed, at the ground floor slab and first floor masonry wall interface
(figure D16). The cracks in walls could be attributed to shrinkage. The model was carefully
133
lifted by overhead crane and fixed on the shake table top. No damage to any wall was
observed during the lifting and fixing operations. The model was white washed prior to
ground shaking.
Figure 5.12 Grid lines- double story model
134
5.3.2 Out of Plane Walls The out of plane walls survived any severe damage or out of plane failure because of the
confining effects. However, separations of masonry wall from tie columns, sliding with floor
and bond beam were observed. Significant out of plane movement could be seen in video
clip, in Wall 9 (towards actuator) of ground story, during the shaking table test
There was no crack in the out of plane walls until Test run 30 except horizontal hairline
cracks as discussed above. A horizontal crack was observed in ground floor at mid height
between bond beam and foundation pad in wall 1 at test run 30. Horizontal hairline crack at
the interface of ground floor slab and first floor masonry wall was also observed in wall 1.
Some horizontal cracks were observed in wall 9 in the ground floor near floor level. A
stepped crack was noted in panel FJ. The crack runs between tie columns. A horizontal crack
at the interface of bond beam and masonry over the beam in the first floor level was also
marked during the test run 30. During last test run (PGA – 3.65g) significant movement of
the out of plane wall of ground floor was observed. In a video clip, wall 9 could be seen
rocking at the base slab and mid height between base slab and ground floor bond beam.
Separation of masonry wall and tie column in panel AB was also visible in the video. Out of
plane sliding of wall 4 in panel EF was observed. However, a few hairline horizontal cracks
were observed in first floor out of plane walls, the damage was relatively small. This could
be also confirmed from its rigid body movement during shaking in the video clips replay.
It could be concluded that some damage to out-plane-walls were observed during strong
shaking (PGA = 3.65g), the confining elements prevented the out of plane failure of the walls
perpendicular to excitation. Figure 5.13 and 5.14 shows cracks in the out of plane walls at the
end of test. Figure D19-D24 of the Appendix D shows schematic of damage propagation to
out-of-plane walls during test runs.
135
Figure 5.13 Cracks in wall 1
Figure 5.14 Cracks in wall 9
5.3.3 In-plane Walls The in-plane walls were severely damaged at the end of testing. External and internal in-
plane walls in ground floor almost collapsed. However, there was no significant damage to
both external and internal wall in first story level at the end of the test. Micro-concrete of
column in the ground floor crushed and model rebars buckled. Crushing of bricks was also
observed in the severely damage zones. Figure 5.15 and 5.16 shows the severely damaged
double story model at the end of test. The schematics of damage propagation to in-plane wall
are shown in figure D22-D27, appendix D. The newly developed cracks and propagation of
136
existing cracks are shown in each figure corresponding to different test runs. The overall
damage to walls are shown in the last test run (figure D26 and D27).
Figure 5.15 Damage to ground floor wall A
Figure 5.16 Damage to ground floor wall F
A hairline crack was observed in in-plane walls during test run 20. Separation crack at the
interface of tie column of window and masonry wall was observed in wall F. A horizontal
crack at the sill level of window was observed, propagating towards window confining
element. A horizontal crack at the interface of bond beam and masonry wall over the beam
was observed to propagate from its pre-testing condition. Hairline cracks at two locations
were marked in wall A during test run 20.
137
First significant damage to in-plane walls were observed during test run R30 when inclined
cracks were developed in ground floor masonry wall. Scissor type cracks were developed in
the ground floor masonry piers of wall A (Grid A). In all the three priers cracks penetrated in
the tie column concrete at the location of bond beam and tie column joint. The cracks from
both directions intersect each other at mid height between bond beam and foundation slab.
Cracks running at the interface of masonry wall and tie column could also be seen, separating
the wall from confining column. Cracks at different locations were also observed in wall F
during test run R30. The cracks in wall F were mostly horizontal. However, the cracks
stepping downward following mortar joint were observed. Short length vertical and inclined
cracks were also marked. At this stage no crushing of brick or micro concrete were
observed.
Wall D (Grid D) was severely damaged during test run R30. Inclined cracks in both
directions were developed. The cracks propagated into tie columns and bond beam, shearing
micro concrete. Cracks at the interface of masonry wall and tie column was also seen.
During the last test run, sever shaking having PGA of 3.65 was observed because of
malfunctioning of shake table. Almost all the ground floor in-plane walls collapsed and/or
severely damaged. Crushing of brick unit was observed in the damage/collapsed walls.
Micro-concrete of the tie column was crushed and model rebars were made visible. The
rebars in the tie columns buckled and deflected out from the original alignment. No
significant crack in the in-plane first floor walls was observed. However, propagation of
existing cracks was noticed. This could be attributed to the concentration of damage to
ground floor and the rigid body motion of the first floor over the ground floor. The
concentration of damage to ground floor could be attributed to soft story effect because of the
more wide openings in the ground floor. The wall density ratio as given in section 4.2 was
3.87 in the ground floor and 5.99 in the first floor.
In closely focused video clips it could be concluded that heavy damage to wall is the result of
crushing of concrete in tie column near joints and/or separation of wall and tie column. The
wall pushed the tie columns out ward and disintegration started at the middle part of the
walls.
138
However, the model did not collapse; the common assumption that the confining elements
would prevent the masonry walls from disintegration did not work. It has been observed
during testing confined masonry walls that the confinement would prevent the wall from
disintegration at certain level of drift. However, at increased demand the separation of
masonry walls from tie column and ultimately collapse of wall could not be prevented.
Horizontal reinforcement in the bed joint, which connect the masonry wall and tie column
certainly improves the inelastic behavior and could prevent the collapse of walls (Tomzvic,
M., et al 1996; IIBA, M., et al 1996). Column confined with enough shear reinforcement
could avoid brittle failure of walls (Kato, H., et al 1992; Salim, A, H., 1982).
It could be concluded that even with strong ground motion; the confining elements prevent
collapse of the masonry building. However, in-plane walls were severely damaged during
strong shaking; the provision of horizontal reinforcement could prevent disintegration of the
masonry walls as reported by other authors during confined masonry walls test. Keeping in
view the economic condition of the people, horizontal reinforcement to connect tie columns
and masonry wall in the ground floor is only recommended. Figure D22-D27 of Appendix
shows schematic of damage propagation during test run.
5.3.4 Characteristics Parameters of Shaking Table Motions
Maximum acceleration and displacement of shaking table motion are compared with that of
input model accelerogram in table 5.7. The shaking table could not satisfactorily produce the
acceleration record. The reasons of the unusual behavior were not verified. However, the
response acceleration and displacements were used to calculate the response behavior of the
model. Instruments were removed from the model as it could be damaged because of the un-
predicted response of shake table motion. Maximum shake table accelerations were recorded
and crack propagation observed during subsequent test run.
139
Table 5.7 Characteristic parameters of shake table motion
Test Run
Input Model Accelerogram Shake Table Motion
Max.
Acceleration
(g)
Displacement
inch (mm)
Max.
Acceleration
(g)
Displacement
inch (mm)
5 0.04165 0.092 (2.34) 0.0638 0.156 (3.97)
10 0.0833 0.184 (4.679) 0.1381 0.235 (5.97)
20 0.1666 0.368 (9.359) 0.3726 0.407 (10.34)
30 0.3332 0.737 (18.718) 0.6356 0.818 (20.77)
60 0.4998 1.105 (28.078) ---- ----
80 0.6664 1.474 (37.437) ---- ----
100 0.833 2.176 (55.276) ---- ----
125 1.04125 2.303 (58.495) ---- ----
150 1.2495 2.764 (70.194) ---- ----
175 1.45775 3.224 (81.893) ---- ----
5.3.5 Torsion Effects Table 5.8 gives displacement values from channel 10 (at A1) and channel 7 (at F6) and
average of channel 8 and 9 readings at the ground floor slab. The response displacement
measured at the first floor slab level by channel 13 to 16 is also given. Displacements
measured by middle channels (14 and 15) are averaged. In the table right and left
displacements are from channel 7 and 10 at ground floor level and 13 and 16 at first floor
level, respectively. The displacements are normalized with the average of middle
displacements. In table the average displacement is also given.
Differences have been observed in the displacement measured at left and right side. This
could be because of torsion in the model and the same is confirmed from the damage
concentration which was more at one side than the other.
140
Table 5.8 Slab displacements during different test run
Test Run Story Normalized Displacement
Maximum
average
displacement
inch (mm)
right Middle left Middle
5 2 1.299 1.000 1.140 0.003 (0.081)
1 1.852 1.000 1.491 0.002 (0.051)
10 2 0.765 1.000 0.859 0.007 (0.19)
1 0.986 1.000 1.346 0.004 (0.103)
20 2 0.986 1.000 0.967 0.013 (0.324)
1 0.995 1.000 1.252 0.014 (0.359)
30 2 0.947 1.000 0.967 0.03 (0.757)
1 1.112 1.000 0.971 0.027 (0.697)
40 2
1
5.3.6 Mode Shape
Mode shapes have been determined by normalizing story displacements with the top
displacements. The story displacement has been obtained by averaging response
displacements measured at four locations in each story corresponding to maximum
displacement in Channel 9. The base displacement is average of two displacements
corresponding to maximum displacement in Channel 9. The mode shapes corresponding to
each test run is shown in figure 5.17.
141
Figure 5.17 Mode shapes corresponding to each test run
The mode shapes represent that the double story model is vibrating in fundamental mode of
vibration. It could be seen from the mode shapes that displacement of the ground story
increases as the model becomes non-linear. This is in agreement with the cracks propagation
and damage concentration in the ground story. However, data was not measured at large
shaking table excitation, the video clips reveals that the first story had rigid body motion.
5.3.7 Acceleration Amplification Acceleration amplification has been determined by dividing maximum response acceleration
with maximum input base acceleration during each test run. The maximum response
accelerations measured at story level during each test run is averaged. The acceleration
amplification and maximum shake table and maximum average response acceleration is
given in Table 5.9. The maximum amplification recorded is 1.88 in the first floor. However
1
0.28
00
1
2
0 0.5 1 1.5
R05
1
0.51
00
1
2
0 0.5 1 1.5
R20
1
0.46
00
1
2
0 0.5 1 1.5
R10
1
0.81
00
1
2
0 0.5 1 1.5
R30
142
response data has not been recorded after test run 30 where the model is significantly
damaged, the acceleration amplification is expected to decrease.
Table 5.9 Acceleration amplification
Test
Run Story
Max. Shake
Table
Acceleration
(g)
Max. Avg.
Response
Acceleration
(g)
Amplification
5 2 0.0638 0.1064 1.67
1 0.1000 1.57
10 2 0.1381 0.2058 1.49
1 0.1883 1.36
20 2 0.3726 0.6988 1.88
1 0.6119 1.64
30 2 0.6356 1.1053 1.74
1 1.0690 1.68
60 2 - - -
1 - - -
5.3.8 Base Shear and First Story Rotation Angle Base shear is the sum of story shear forces. The story shear forces have been calculated by
multiplying masses concentrated at the story with the acceleration measured at the
corresponding story. The story shear for the double story model has been calculated for each
test run by multiplying floor masses with the average of floor accelerations. Table 5.10 gives
average accelerations and base shear during each test runs. The accelerations corresponding
to maximum displacement in channel # 9 were considered. Floor masses calculated in
chapter 4 were used for the determination of base shear. The floor masses include weight of
slab, additional masses attached to the slab and upper half of the wall mass:
Ground Floor:
Weight of the ground floor slab = 492 lb (223 kg);
Weight of the upper half of the walls = 880 lb (399 kg);
Additional weights attached to the first floor slab = 485 lb (220 kg)
143
Ground floor weight = 1857 Ib (842 kg)
First Floor:
Weight of the ground floor slab = 482 lb (219 kg);
Weight of the upper half of the walls = 1808 lb (820 kg);
Additional weights attached to the first floor slab = 485 lb (220 kg)
First floor weight = 2775 lb (1259 kg)
Total weight of the model which would contribute to the inertia forces = 4,632.6 lb (2100kg)
Table 5.10 also gives base shear coefficient and rotation angle of the model. Base shear
coefficient are calculated by dividing base shear with total weight of the model. Story
rotation is calculated by dividing story displacement with story height.
Table 5.10 Base shear coefficient and story rotation angle
Test Run Story
Relative
Acceleration
(g)
Relative
Displacement
inch (mm)
Story mass
lb (kg)
Shear force
lb (kN)
Base Shear
Coefficient
Rotation
Angle
5 2 0.0254 0.0011 (0.0284) 1847.3 (838.2) 47.02 (0.209) 0.010 0.09%
1 0.0608 0.0009 (0.0227)2785.3 (1263.7) 216.4 (0.963) 0.047 0.08%
10 2 0.1132 0.0013 (0.0327) 1847.3 (838.2) 209.24 (0.931) 0.045 0.11%
1 0.1628 0.001 (0.0256) 2785.3 (1263.7) 662.72 (2.949) 0.143 0.12%
20 2 0.1667 0.002 (0.0512) 1847.3 (838.2) 307.97 (1.37) 0.066 0.02%
1 0.1834 0.0013 (0.0335)2785.3 (1263.7) 818.84 (3.644) 0.177 0.17%
40 2 0.4199 0.0031 (0.0782) 1847.3 (838.2) 775.86 (3.453) 0.167 0.26%
1 0.4658 0.0042 (0.1066)2785.3 (1263.7) 2073.45 (9.227) 0.448 0.36%
60 2 0.6511 0.0031 (0.0782) 1847.3 (838.2) 1201.01 (5.345) 0.259 0.40%
1 0.7010 0.0093 (0.2362)2785.3 (1263.7) 3151.16 (14.023) 0.680 0.70%
The base shear coefficient and story rotation angle are ploted in figure 5.18. The data upto
test run 60 could only be plotted. Data for higher test run were not measured as the
instruments were romoved from the model. The model could have resisted story forces
more than the measured corresponding to test run, however, it is assumed that the maximu
resistance is observed during test run 60 on the basis of damage propogation. The cracks
144
developed during test run 30 were opened up and propagated in to the confining element and
sheared the mico-concrete.
0
0.5
1
0.0% 0.5% 1.0% 1.5%
Story Drit Rotation (%)
Bas
e Sh
ear
Coe
ffici
ent
Figure 5.18 Story resistance envelop
The first story rotation angle corresponding to significant cracks is 0.28 % and the
corresponding base shear coefficient is 0.447. It is worth mentioning that the model has been
tested untill the in-plane walls practically collapsed or severely damaged. The maximum
ground motion (PGA) recorded at this stage was 3.65 g. However, the ultimate limit states
could not be characterised by the experiemental resistance envolpe, available visual
information and experiemental resistance envelope of single story model of this research, and
test carried out on confined masonry buildings at other institutes could be utilised to define
the limit states.
The ratios of base shear coefficient (BSC) and first story rotation angle at maximum
resistance and ultimate state to damage limit state has been determined for different confined
masonry models and is summerized in table 5.11. The number of story and wall density ratio
of each model is also provided. It could be seen from the table that no specific coorelation
has been obtained in BSC and drift ratio and wall density or number of storires.
145
Table 5.11 Base shear and first story ratio at maximum and ultimate state
Model
Designation
No of
story
of model
building
Wall Density
ratio (%)
Maximum
Resistance/Damage Limit
Ultimate state/Damage
Limit
Reference
BSC
First Story
Drift,
Ф
BSCFirst Story Drift,
Ф (%)
M1/1d 2 3.5 1.38 5.2 0.6 10.37 Tomazevic, M., 2004
M1/1c 2 3.5 1 1 0.433 15 Tomazevic, M., 2004
M1 3 5.0 1.57 1.36 0.533 43 Tomazevic, M., 1996
M2 3 5.6 2.04 4.64 1.057 67.9 Tomazevic, M., 1996
M1 1 - 1.1 1.86 0.62 5.1 Alcocer, S.M., 2004
M3 3 4.1 1.1 1.85 0.91 6.73 Alcocer, S.M., 2004
Single story 1 5.64 1.53 4.72 1.06 6.28 This research
The scatter of the data of first story rotation angle at ultimate limit is large as it depends on
the structural system, type of materials used (fired clay brick, concrete block etc) and
structural configuration of the building used.
The following BSC and story drift ratios are expected at ultimate state for the double story
model studied in this research work:
Ratio of Base Shear Coefficient at Ulitmate and Damage limite state = 0.75
Ratio of First Story Drift at Ulitmate and Damage limite state = 5.5
The base shear coefficient and first story drift ratio at the ultimate state comes out to be 0.336
and 1.43 % respectively. A similar attempt has also been made by (Tomazevic, M., 2007) to
correlate the observed damage with displacement capacity and limit states. The ranges of
values for story rotation assigned to characteristic limit states are given as under:
Crack limit, Øcr = 0.2 % to 0.4 %,
Maximum Resistance, ØRmax = 0.3 % to 0.6 % and,
Limite state at collapse, Øcoll = 2.0 % to 4.0 %.
The base shear coefficient and story rotation angle for the three limit states for double story
model are given in table 5.12. The maximum ground acceleration (pga) measured during the
146
last test run was 3.65 g which resulted in the disintegation of ground floor in-plane walls.
However, in order to prevent the disintegraton of wall at the ultimate state, a lower value of
PGA is conisdered. The PGA measured at the late test run is reduced by 30%. The hysteretic
envelop is plotted in figure 5.18.
Table 5.12 Base shear and first story ratio at maximum and ultimate state
Description of limit state Base shear coefficient Story rotation angle
(%)
Maximum Ground
Acceleration (g)
Elastic Limit (R30) 0.448 0.26% 0.636
Maximum Resistance (R60) 0.680 0.70% 1.153
Ultimate State 0.336 1.43% 2.55
By comparing the values of rotation angle at the three limit states, it could be concluded that
experimentally obtained rotation angle at damage limit state is within the range assessed by
(Tomazevic, M., 2007). However, the rotation angle at ultimate state is less than the assessed,
the value is close to the upper bound at the maximum limit state.
0
0.2
0.4
0.6
0.8
0.00% 0.25% 0.50% 0.75% 1.00% 1.25% 1.50%
Story Drift Rotation (%)
Bas
e Sh
ear
Coe
ffic
ient
Figure 5.19 Story resistance envelop
147
5.3.9 Response Modification Factor of Double Story Model
The base shear coefficient and story drift ratio has been idealized by bilinear curve as shown
in figure 5.19. 20% degradation from the maximum resistance limit is considered in the
idealization of the curve. The different parameters of the idealized curve are given below:
du = Ultimate displacement of the idealized bilinear curve = 0.36 inch (9.14 mm)
de = displacement at the elastic limit of the idealized bilinear curve = 0.11 inch (2.72 mm)
Global ductility ratio, µu = 3.4 and,
Response modification factor, R from equation 5.5 = 2.41
The response modification factor evaluated for double story building on the basis of global
ductility factor seems small as suggested by other authors. This could be partly because of
the reasons that full response upto collapse were not measured and maximum resistnace was
conservatively assumed at lower value. Secondly, the response accelerations corresponding
to displacement in channel # 9, considered for the evaluation of base shear, are small as
compared the maximum acceleration in each test run.
0
0.2
0.4
0.6
0.8
0.00% 0.25% 0.50% 0.75% 1.00% 1.25% 1.50%
Story Drift Rotation (%)
Bas
e Sh
ear
Coe
ffic
ient
Figure 5.20 Hysteretic envelope and idealised bilinear relation
5.4 SEISMIC RESISTANCE OF PROTOTYPE BUILDING
The results obtained during shaking table test of the single and double story models are
extrapolated to prototype building by taking into consideration the laws of model similarity.
_____ Hystersis Envelope
------- Idealised Curve
148
The maximum shake table motion during characteristics limit states should be converted to
maximum ground motion which would cause these limit state in the real building. Similarly,
the properties of model observed during the shaking table such as frequency and damping
during each test run, and base shear and drift at the three limit states should be scaled to the
prototype building.
However, properties of masonry materials and masses over each floor are adequately
simulated; the mechanical properties of masonry assemblage are not correctly modeled.
Actual relationship developed as a result of experimentally obtained properties of prototype
and model assemblage should be used to extrapolate model result to prototype.
As discussed earlier, shear was predominant mode of failure in both the models, scale factors
for each physical quantity is calculated as a result of scale factor corresponding to shear
strength. Table 5.13 gives the actual scale factors calculated keeping the geometric scale
factor of 4 and strength factor of 1.6. The scale factors for acceleration and time comes out to
be 0.4 and 3.16 respectively.
Table 5.13 Modeling scale factors to extrapolate model test results to prototype building
Physical Quantity Relationship Scale factor
True Model This Study
Length (L) SL = Lp/LM 4 4
Strength (f) Sf = fp/fm =SL 4 1.6
Strain (ε) Sε = εp/εm 1 1
Sp. Mass (γ) Sγ=γp/γM 1 1
Displacement (d) Sd = SL 4 4
Force (F) SF = SL2 Sf 64 25.6
Time (t) St = SL √(Sε Sγ/ Sf) 2 3.16
Frequency 1/ St 0.5 0.316
Velocity Sv = √(SεSf/ Sγ) 2 1.26
Acceleration Sf /(SL Sγ) 1 0.4
Table 5.14 and 5.15 give base shear and story drift corresponding to limit states of prototype
single and double story building respectively. The table also gives ground motion defined by
peak ground acceleration. The peak ground acceleration is determined by multiplying
149
maximum shake table acceleration with acceleration scale factor (0.4). The same acceleration
scale factor is used to convert the base shear force for model to prototype building.
Table 5.14 Parameters of seismic resistance for single story building
Description of limit state Base shear
Coefficient
Story Rotation
angle (%)
Maximum Ground
Acceleration
(g)
Elastic limit (R125) 0.482 0.25 0.42
Maximum Resistance (R175) 0.778 1.18 0.81
Ultimate state (R150) 0.18 2.1 1.15
Table 5.15 Parameters of seismic resistance for double story building
Description of limit state Base shear
Coefficient
Story Rotation
angle (%)
Maximum Ground
Acceleration
(g)
Elastic limit (R30) 0.180 0.37 0.254
Maximum Resistance (R60) 0.272 0.55 0.461
Ultimate state 0.134 0.80 1.02
It could be seen from the tables that both single and double story models designed according
to Eurocode could be used in high seismic zones of Pakistan Building code 2007. Both the
models properly constructed and designed could resist strong earthquake. However, the
double story model because of its small wall area in the short direction of the ground floor
would significantly be damaged. Separation of walls from tie column and/or collapse of walls
would result as a consequence of strong earthquake.
5.5 COMPARING SINGLE AND DOUBLE STORY BUILDING
Single story building is comparatively more rigid than the double story building. The wall
density ratio of single story in the short direction (parallel to excitation) is 5.64 % as
compared to 3.87 % in the ground floor and 5.99 % in the second floor. This could be the
reason for the double story model that ground floor was more damaged than the first floor.
However, concentration of damage in the ground floor has also been observed by other
researchers. Damage limit state was observed at 0.42 g in the single story model, however
first significantly crack in the double story has been observed at 0.22 g.
150
However, significant degradation has been observed in single story model at the last test run,
the confining elements keep the walls from disintegration. At the last test run, separation of
walls and buckling of model rebars in the confining element were observed. The in-plane
walls in the ground floor of the double story on other hand disintegrated at the last test run.
The confining element could not prevent the walls disintegration at strong ground shaking.
The single story buildings are much stiffer. Designed according to Euro code, the single story
buildings could survive collapse at strong ground motion.
It is concluded that the double story building cracks at lower PGA value than the single story
building. As discussed earlier the walls disintegrated after their separation from tie columns.
It is recommended to provide horizontal reinforcement to connect the tie columns and
masonry walls at ground floor. As the first story is comparatively stiffer than the ground floor
and the damage is also small, the toothing would work to keep the integrity of masonry walls
and tie columns.
151
CHAPTER 6 CONCLUSION AND RECOMMENDATION
The objective of this research work was to determine the behavior of typical confined brick
masonry buildings subjected to seismic loadings. Response modification and ductility ratio of
the confined brick masonry building was evaluated. The research work was aimed at the
growing demand of confined brick masonry buildings after 2005 Kashmir earthquake which
resulted in the destruction of more than 450,000 buildings.
6.1 SUMMARY
A survey of building typology and inventory has been carried out in Peshawar city and
earthquake affected area, including Abbottabad and Mansehra city. About 65 building
drawings have been collected from these cities and analyzed. Typical single story and double
story buildings have been selected on the basis of wall density ratio close to mean value of
the analyzed drawings.
Masonry materials survey has also been made, including survey of mortar, bricks and rebars.
Masonry mortar samples were collected in Peshawar as well as in Abbottabad and Mansehra
city from the construction sites. The survey shows that cement-sand and cement-sand-khaka
(stone dust) mortar were the typical mortar used in the area. The popular mix proportions are
1:6, 1:8 in cement-sand and 1:4:4 in cement-sand-khaka by volume. The mean compressive
strength of masonry mortar was found to be 837 psi (5.77 MPa). Test data of fired clay brick
and rebars was collected from Material Testing Lab, N-W.F.P UET, Peshawar. Mean
compressive strength of the brick was 2350 psi (16.2 MPa). Grade 40 and 60 deformed bar
are mainly used in buildings. Grade 40 bars are mostly used in residential buildings from 3/8
to 6/8 inch diameter. Data about compressive strength of structural concrete was; however,
not collected. Compressive strength of concrete cores cut from existing buildings vary from
1500 (10.34 MPa) to 2500 psi (17.24 MPa). The mean compressive strength of masonry unit
and masonry mortar comply with minimum requirements of Pakistan building code 2007 and
Eurocode 6.
152
The experimental work has been divided into three phases. In the first phase properties of
prototype masonry have been determined. In the second phase, properties of model materials,
including masonry mortar, masonry unit and micro-concrete have been simulated. The
mechanical properties of model masonry have been evaluated. In the last and final phase
model buildings have been fabricated and tested on shake table to evaluate their seismic
response.
In order to fulfill the requirements of complete model similitude law extensive experimental
work has been carried out for modeling masonry mortar, model brick and micro concrete.
Mixes with different proportions have been prepared and tested in compression to simulate
the masonry mortar. Cement-sand, cement-sand-lime, cement-lime-surkhi (brick remains),
cement-lime-marble powder and lime-surkhi were used in different proportions. Almost 40
batches of masonry mortar have been tested. Finally, cement-lime-sand (1:1:5), has been
selected as masonry mortar. Cement-lime-sand (1:1:5), having coarser sand than used in
masonry mortar, has been selected as micro concrete. Cement-lime-surkhi (1:1:2) has been
used for fabricating model masonry unit. Surkhi (burnt brick remains) passed through sieve
no 8 and retained on sieve 30 has been used to simulate specific weight of the prototype brick
as cement-lime-sand resulted in high specific weight. In order to reduce the fabrication
efforts, model bricks were fabricated in three different dimensions. That is actual model brick
of dimensions 2.2x1.1x0.67 (56x27x17 mm) (length x width x height), model brick with
double height 2.2x1.1x1.34 inch (56x27x34 mm) and model brick double in width with
dimensions 2.2x2.2x0.67 (56x56x17 mm) are used in model masonry wallets.
The prototype and model masonry assemblage has been tested in compression, diagonal
compression and cyclic test. Modulus of elasticity and rigidity has been determined. The
compression strength of prototype masonry was 828 psi (5.7 MPa) and modulus of elasticity
was 290 psi (2.0 MPa). Diagonal shear strength of prototype masonry was 51.0 psi (0.35
MPa) and modulus of rigidity was 26.0 psi (0.18 MPa). Model masonry walls of all the three
type of bricks have been tested. It was concluded that model bricks doubled in height and
width resulted in high strengths than actual model brick walls.
153
A small scale model of single and double story building has been tested on single degree of
freedom shake table. Scale factor four and complete model similarity has been adopted for
the models construction on the basis of capacity of the shake table and economy.
Kobe accelerogram compressed in time with square root of scale factor but with the same
PGA value as original record has been used for shaking table test of the reduced model. The
models have been subjected to increasing intensity of vibration in each test run. The models
have been instrumented with accelerometers and displacement transducers connected at the
floor slab at front of the in-plane walls. Four accelerometers and four string pots have been
used in single story model. However, four string pots and two accelerometers have been
connected at each floor in double story models to measure response acceleration and
displacement at the floor level. Additional weights are attached to each floor of the model to
simulate the dead load of flooring. The confining elements (tie columns and bond beams) are
designed according to Eurocode requirements. However, horizontal reinforcement were not
provided to connect tie columns and masonry walls.
Both the models failed in shear. Cracks initiated in masonry walls were confined by the
confining elements. However, with the increased intensity of shaking, the cracks propagated
and damaged the tie columns. During the final intensity of shaking, crushing of masonry
units at the corners of walls, crushing of concrete and buckling of rebars in the tie columns
have been observed. In the case of double story building model, damage was concentrated in
the ground floor. However, the in-plane walls were severely damaged at high intensities of
shaking; the confining elements prevented the collapse of model. The confining elements
also prevented collapse of out-of-plane walls which are generally vulnerable in the URM
buildings. Separation of masonry walls from the tie columns at early stages of shaking could
be attributed to the absence of horizontal reinforcement. It is, therefore, recommended to
provide horizontal reinforcement to connect the tie columns and masonry walls. However,
further research work should be carried out to evaluate the effect of horizontal reinforcement
on the ductility and energy dissipation capacity of confined masonry walls. However, further
research work should be carried out to evaluate the effect of horizontal reinforcement on the
ductility and energy dissipation capacity of confined masonry walls.
154
Seismic resistance and deformation capacity of the model have been evaluated on the basis of
measured acceleration and displacement response. Base shear is determined by multiplying
the response acceleration, measured at the attainment of maximum response displacement
with masses concentrated at floor level. A graph of base shear coefficient, that is base shear
divided by total weight of the model and first story rotation angle, first story drift divided by
height of first story has been plotted. The curve is idealized as bilinear curve. Complete
elastic analysis has also been carried out by modeling the reduced scale building in SAP,
computer software. The response modification factor, R of single story model determined on
the basis of global ductility ratio is 3.04 and the ductility ratio, µ comes out to be 5.13 for
single story building. However, response modification factor determined by dividing elastic
base shear over ultimate base shear comes out to be 2.16 for the single story model. The
response modification factor evaluated for double story model on the basis of ductility ratio
is 2.41 which is conservative value.
In order to extrapolate the shaking table parameters and response characteristics of the model
to the prototype earthquake and building, laws of complete model similarity have been taken
into consideration. However, actual scale factor is to be considered instead of theoretical. The
actual scale factor is determined as the relation between properties of the prototype that are
target values to that of properties measured on model masonry. As the basic failure mode in
the single and double story model was shear, therefore shear strength should be kept as the
basis of the true scale factor. The scale factors for other physical quantities are determined on
the basis of geometric scale factor and the strength factor. The base shear and shake table
accelerations at the three characteristic states have been extrapolated to the prototype
building. The limit states are damage limit state where the first significant crack occurs or
where there is significant drop in the stiffness, the maximum resistance limit state and
ultimate limit state that is before collapse and where the structural walls in the first story are
severely damaged. Base shear and the acceleration at the three limit states are given in table
5.14 and 5.15. The tables are reproduced as given below.
155
Table 6.1 Parameters of Seismic Resistance for Single Story building
Description of limit state Base shear
Coefficient
Story Rotation
angle (%)
Maximum Ground
Acceleration
(g)
Elastic limit (R125) 0.482 0.25 0.42
Maximum Resistance (R175) 0.778 1.18 0.81
Ultimate state (R200) 0.18 2.1 1.15
Table 6.2 Parameters of Seismic Resistance for Double Story building
Description of limit state Base shear
Coefficient
Story Rotation
angle (%)
Maximum Ground
Acceleration
(g)
Elastic limit (R30) 0.180 0.37 0.254
Maximum Resistance (R100) 0.272 0.55 0.461
Ultimate state (R300) 0.134 0.80 1.02
It can be seen that both single and double story building would be able to resist with minor
damage an earthquake with PGA 0.40g and 0.25g and without collapse an earthquake with
PGA 1.1g and 1.0g respectively. It is concluded that properly constructed and designed
single and double story models could be used in high seismic zones (Pakistan Building Code
2007). On the basis of observed behavior and wall density ratio it could be concluded that the
Eurcode requirements are stringent for single story building.
6.2 CONCLUSIONS AND RECOMMENDATIONS
Based on the experimental work, the following conclusions and recommendations are made.
Further, research areas are identified to investigate vulnerability in the masonry buildings and
its subsequent mitigation.
Conclusions:
• Shear is the predominant failure mode in both single and double story models
• The analysis of measured response and observed behavior of the single story model reveals that the typical single story building would withstand with minor damage an earthquake of PGA 0.40g and would not collapse under an earthquake of PGA 1.15 g.
156
• The typical double story building would withstand with minor damage an earthquake of PGA 0.25g and without collapse an earthquake of PGA 1.0g.
• Single and double story confined masonry buildings properly designed and constructed could be used in high seismic zones (zone 3 and 4 of Pakistan Building Code 2007).
• The ground story walls could collapse or severely damaged during strong ground motion (that is PGA 0.8 and higher) because of the absence of horizontal reinforcement.
• The confining elements could prevent collapse of out-of-plane walls of both single and double story buildings at strong earthquake, if proper monolithic behavior of tie columns and masonry walls is achieved.
• The eurocode requirements for the design of confined masonry buildings seems stringent for single story building.
• The provision of toothing in walls could not prevent separation of walls from confining element at strong ground motion.
• The response modification factor of single story building confined according to Eurocode 8 is 3.0. Response modification factor for double story building designed according to Eurocode is determined to be 2.41. The Eurocode requirements for response modification factor are found adequate.
• The mean compressive strength of masonry unit, 2350 psi (16.2 MPa), tested in the Material Laboratory, N-W.F.P UET, Peshawar, comply with the minimum requirements of Pakistan Building Code 2007 and Eurocode 6.
• The mean compressive strength of masonry mortar collected from field in Peshawar, Abbotabad and Mansehra after Kashmir earthquake comply with the minimum requirements of Pakistan Building Code 2007 and Eurocode 6.
Recommendations:
• In order to delay extensive damage to masonry wall, it is recommended to provide horizontal bed joint reinforcement to connect the masonry walls and tie-columns.
• Wall density ratio should not be less than 5 % in seismic zone 3 and 4.
• The building should be regular in plan and elevation.
157
• Minimum thickness of masonry wall should be kept at 9 inch (229 mm).
• Minimum thickness of confining element should be 9 inch (229 mm).
• Minimum 1% longitudinal reinforcement should be provided in the confining element.
• Stirrups of 3/8 inch (10 mm) diameter bars should be provided in the confining elements at a maximum spacing of 6 inch (152 mm) c/c.
• At least 48 diameters splice length should be provided.
• The longitudinal reinforcement of tie-columns should be adequately anchored in foundation and bond beam/floor slab. The reinforcement must be tied with foundation reinforcement at the bottom as well as with the bond beam/floor slab reinforcement at the top.
• Tie-column should be provided at 16 ft (4.2 m) c/c horizontal spacing.
• Not more than two stories building should be constructed in zone 4 and three stories in zone 3.
• Minimum compressive strength of brick, mortar and concrete should be1800 psi (12.4 MPa) , 800 psi (5.5 MPa) and 2000 psi (13.8 MPa), respectively.
6.3 FUTURE RESEARCH WORK
• Numerical analysis of the typical confined brick masonry buildings is recommended.
• As real earthquake is three dimensional phenomenons, experimental testing of typical confined brick masonry building model on 6-degree of freedom shake table is recommended.
• Cyclic testing of full-scale confined brick masonry walls with different dimensions of confining elements and reinforced with different reinforcement ratio should be carried out. The optimum dimensions of confining element and reinforcement ratio could be suggested and made part of the Pakistan Building Code 2007.
• Shake table test of single story building model with smaller dimensions and less reinforcement ratio as required by Eurocode for both horizontal and vertical confining element should be tested and compared with the results of this research.
158
• Effect of different earthquake accelerograms on the typical confined masonry building should be carried out.
• Confined masonry walls with different horizontal reinforcement ratio should be carried out and the effect of horizontal reinforcement on the seismic resistance and ductility should be investigated in future studies.
• Shake table testing of typical confined masonry building with flexible diaphragm should be carried out to study its behavior.
• The study of seismic behavior of typical confined block masonry buildings is recommended for future research work.
159
REFERENCES
Abram D.P., “Seismic Response Pattern for URM Buildings”, Journal of the Masonry
Society, Vol 18, No.1, 2000.
ACI 318-63, “American Concrete Institute Building Code requirements for Reinforced
Concrete”, American Concrete Institute, Michigan, 1963.
ADB-WB. “Preliminary Damage and Needs Assessment-Pakistan 2005 Earthquake”, Asian
Development Bank and World Bank, Islamabad, Pakistan, 2005.
Alcocer, S. M., and Klingner, R. E., “Masonry Research in the America”, Masonry Research
in Americas, ACI (SP-147), pp, 239-262.
Alcocer, S. M., Arias, J. G., Vazquez., A., “Response Assessment of Mexican Confined
Masonry Structures Through Shaking Table Tests”, proc. 13th World Conference on
Earthquake Engineering, Vancouver, B.C., Canada, paper No. 2130.
Ali. Qaisar, “Seismic Risk Assessment of Un-reinforced Brick Masonry Buildings System of
Northern Pakistan”, Ph.D thesis, Department of Civil Engineering, N-W.F.P UET, Peshawar,
2004.
Applied Technology Council (ATC). NEHRP Commentary on the Guidelines for the Seismic
Rehabilitation of Buildings. Publication No.274, Federal Emergency Management Agency,
Washington, D.C. (FEMA-274), 1997b.
Aschheim, M., et al, “Improving The Earthquake Resistance And Sustainability of Confined
Masonry (Mixto) Dwellings in El Salvador” Proc. of the 8th U.S. National Conference on
Earthquake Engineering, San Francisco, USA, Paper No. 1462.
ASTM C67, “Test Methods for Sampling and Testing Brick and Structural Clay Tiles”, 4th
Ed., Philadelphia.
ASTM C 109, “Standard Test Method for Compressive Strength of Hydraulic Cement
Mortars (using 2-inch or 50 mm cube specimens)”, 4th Ed., Philadelphia.
ASTM E519, “Standard Test Method for Diagonal Tension (Shear) in Masonry
Assesmblages”, 4th Ed., Philadelphia.
160
ASTM C1314, “Standard Test Method for Compressive Strength of Masonry Prisms”, 4th Ed,
Philadelphia.
ASTM C615, “Standard Test Method for Compressive Strength of Masonry Prisms”, 4th Ed,
Philadelphia.
Bartolome, A. S., et al, ‘Seismic Behavior of a Three Story Half Scale Confined Masonry
Structure’, proc. Earthquake Engineering, 10th WCEE, 1992 Balkema, Rotterdam, pp 3527-
3531.
Calvi, G. M., Kingsley, G. R., and Magenese, G., Testing of Masonry Structures for Seismic
Assessment, Earthquake Spectra, Vol. 12, No. 1, pp 145-162, Feb 1996.
Chopra, A,.K, 2004, “Dynamics of Structures: Theory and Applications to Earthquake
Engineering” 2nd edition, Pearson Education.
Cough, R.W., and J. Penzien, “Dynamics of structures”, Second edition, McGraw-Hill, Inc,
1993.
Crewe, A. J., and Taylor, C. A., “Shaking table Tests of 1:4 Reduced Scale Models of
Masonry in-filled Reinforced Concrete Frame Buildings”, Earthquake Engineering and
Structural Dynamics, 30:819-834, 2001.
D.Benedetti, P. Carydis and P. Pezzoli, ‘Shaking Table Test on 24 Simple Masonry Building’
Earthquake Engineering and Structural Dynamics, Vol. 27, 67-90 (1998).
EERI (1999). The Tehuacan, Mexico, Earthquake of June 15, 1999. EERI Special
Earthquake Report. Newsletter. Earthquake Engineering Research, California, September
1999.
EERI (2000). El Quindio, Colombia Earthquake, January 25, 1999: Reconnaissance report.
An EERI learning from earthquakes Project. Earthquake Engineering Research Institute,
California.
EERI (2006). The Tecoman, Mexico Earthquake January 21, 2003. An EERI and SMIS
Learning from Earthquake Reconnaissance Report, Technical Editor S.M. Alcocer and R.E.
Klingner. Earthquake Engineering Research Institute, Oakland, California, March 2006.
161
EERI (2006), ‘The Mw 6.3 Java, Indonesia, Earthquake of May 27, 2006’, 2006 August
EERI Special Report.
EERI (2007). ‘Learning from Earthquake: The Pisco, Peru, Earthquake of August 15, 2007’
EERI Special Earthquake Report-October 2007.
EERI (2007). ‘2007 August 15 Magnitude 7.9 Earthquake near the Coast of Central Peru’,
EERI Field Mission 5-12 September 2007/Final Report.
Eurocode 6: Design of masonry structures, Part 1-1: Common rules for reinforced and
unreinforced masonry structures. ENV 1996-1-1: 2004:E (CEN, Brussels)
Eurocode 8: Design provisions for earthquake resistance of structures, Part 1-2: General
rules, seismic actions and rules for buildings. ENV 1996-1-1: 2004:E (CEN, Brussels)
FEMA 274, NEHRP Commentary on the Guidelines for the Seismic Rehabilitation of
Buildings”, Federal Emergency Management Agency, Washington, D.C., October, 1997.
FEMA 307, “Evaluation of Earthquake Damage Concrete and Masonry Wall Buildings,
Technical Resource”, Federal Emergency Management Agency, Washington, D.C., 1999.
Fukhur-ur-Zaman, “Optimum Utilization of Mild Steel Residual Strength”, M.Sc thesis
report, N-W.F.P University of Engineering and Technology, Peshawar, 2003-04.
Hiroto Kato et al, ‘Cyclic Loading Tests of Confined Masonry Wall Elements for Structural
Design Development of Apartment Houses in the Third World’ proc. of 10 WCEE, Balkema,
Rotterdam, pp 3539-3544, 1992.
IIBA, M., Mizuno, H., Goto, T., and Kato, H., “Shaking Table Test on Seismic Performance
of Confined Masonry Wall”, proc of 11th WCEE, pp 659, 1996.
Ishibashi, K., Meli, R., Alcocer, S. M, Leon, F., Sanchez, T.A., ‘Experimental Study on
Earthquake Resistant Design of Confined Masonry Structures’ proc. 10th WCEE, 1992
Balkema, Rotterdam, pp 3469-3474.
Javed. M, “Seismic Risk Assessment of Un-reinforced Brick Masonry Buildings System of
Northern Pakistan”, Ph.D thesis, Department of Civil Engineering, N-W.F.P UET, Peshawar,
2009.
162
Kato, H., Goto, T., and Mizuno, H., “Cyclic Loading Tests of Confined Masonry Wall
Elements for Structural Design Development of Apartment Houses in the Third World”,
proc. 10th WCEE, Balkema, Rotterdam, pp. 3539-3544, 1992.
Meli, R., “Structural Design of Masonry Buildings: The Mexican Practice”, Masonry
Research in Americas, ACI (SP-147), pp, 239-262.
Moroni, M., et al., 2003, “Confined Block Masonry Buildings. Chile, Report 7, World
Housing Encyclopedia, Earthquake Engineering Research Institute (www.world-housing.net)
Naseer, A., Khan, A, N., Ali, Q., Hussain, Z., “Observed Seismic Behavior of Buildings in
Northern Pakistan During Kashmir Earthquake”, Earthquake Spectra, 2009 (under review).
Salim, A, H., “Experimental Investigations on the Behavior of Masonry Walls with
Confinement Reinforcement”, proc. of 2nd Canadian Masonry Symposium, Ottawa, June,
1980.
Schultz, A., “Performance of Masonry Structures During Extreme Lateral Loading Events”,
Masonry Research in Americas, ACI (SP-147), pp, 85-125.
Simsir, C, C., “Influence of Diaphragm Flexibility on the Out-of-Plane Dynamic Response of
Unreinforced Masonry Walls”, Ph.D thesis, University of Illinois at Urbana-Champaign,
2004.
Svetlana Brzev, “Earthquake-Resistant Confined Masonry Construction”, NICEE, ITTK,
Indian, 2007 report.
Tianyi Yi, “Experimental Investigation and Numerical Simulation of an Unreinforced
Masonry Structure with Flexible Diaphragms”, Ph.D thesis, Georgia Institute of Technology,
2004.
Tim Mathews et al, “Evaluation of confined masonry guidelines for earthquake resistant
housing”, UBC EERI, 2007 report.
Tomazevic, M., “Damage as a measure for earthquake-resistant design of masonry structures:
Slovenian experience”, Candian Journal of Civil Engineers, 34: 1403-1412 (2007)
163
Tomazevic, M., Bosiljkov, V., and Weiss, P, 2004 “Structural Behavior Factor for Masonry
Structures”, 13th World Conference on Earthquake Engineering, Vancouver, B.C., Canada,
paper No. 2642.
Tomazevic, M., ‘Shaking Table Tests of Small-Scale Model of Masonry Building:
Advantages and Disadvantages’ Munchner Massivbau-Seminar 2000.
Tomazevic, M., and Velechovsky, T., ‘Some Aspects of Testing Small Scale Masonry
Building Models on Simple Earthquake Simulators’, Earthquake Engineering and Structural
Dynamics, Vol. 21, 945-963 (1992).
Tomazevic, M., Klemenic, I., Petkovic, L., Lutman, M., “Seismic Behavior of Confined
Masonry Buildings”, part 1: shaking table test of model building M1 and M2-test results,
report ZAG/PI-95/04, Ljubjana, 1996.
Tomazevic, M., and Klemenc, I., ‘Verification of Seismic Resistance of Confined Masonry
Buildings’ Earthquake Engineering and Structural Dynamics, Vol. 26, 1073-1088 (1997).
Tomzevic, M., 1999, ‘Earthquake Resistant Design of Masonry buildings’ Imperial College
Press.
Tomazevic, M., Klemenc, I., Petkovic, L., and Lutman, M., “Seismic Behavior of Confined
Masonry Buildings, Part 1: Shaking-Table Tests of Model Buildings M1 and M2-Test
Results”, Report ZAG/PI-95/04, ZAG (Slovenian National Building and Civil Engineering
Institute), Ljubljana, Slovenia.
Turnsek, V., Cacovic, F., ‘Some experimental results on the strength of brick masonry walls’,
proc. of the 2nd International Brick-Masonry Conference, Stoke-on-Trent, pp.149-156 (1971).
UBC 1997, “Uniform Building Code, Volume 2, International Conference of Building
Officials, Whittier, California, 1997.
Virdi, K., and Raskoff, R., “Low Rise Residential Construction Detailing to Resist
Earthquake: Confined Brick Masonry”, http://www.staff.city.ac.uk/earthquakes/Masonry
Brick/References htm
164
Yoshimura, K., and Kuroki, M., ‘Damage to Masonry Buildings Caused by the El Salvador
Earthquake of January 13, 2001’ Journal of Natural Disaster Science, Vol. 23, No. 2, 2001,
pp53-63.
Yoshimura, k., et al., “Experimental Study For Developing Higher Seismic Performance of
Brick Masonry Walls”, proc. of the 13th World Conference on Earthquake Engineering,
Vancouver, Canada, Paper No. 1597, 2004.
Zahrai, S. M., Heidarzadeh, M., ‘Seismic Performance of Existing Buildings during the 2003
Bam Earthquake’, 13th WCEE, Vancouver, B.C., Canada, No. 1715, 2004.
165
APPENDIX A: LIST OF EQUIPMENT
A1.0 Dynamic Test
A 1.1 Dytran Accelerometers
Model 3191A
Weight = 775 grams
Sensitivity = 10.0 V/g
Maximum range = ±2g
Frequency Range = 0.1 to 1000 Hz
A 1.2 Dytran Model 3056B3 Accelerometers
Weight = 10 grams
Sensitivity = 500 mV/g
Acceleration range = ±10g
Frequency Range = 0.1 to 10,000 Hz
A 1.3 Celesco String pots
PT1DC Series
Maximum Range 0-20 inch,
Accuracy = 0.15 %
A2.0 Static Material Test
Shimadzu Universal Testing Machine (UTM), UH-200
Load Capacity = 200 t
Loading speed = 0-50 mm/min
A3.0 Straining Frame (Static Cyclic)
A3.1 Kyowa Loading Cell
Load Capacity = 50 t (2 Nos)
Load Capacity = 25 t (2 Nos)
Macros Hyraulic Power Supply (HPS)
A3.2 Data Acquisition Sytem
Kyowa UCAM 70 Data Logger
166
Maximum Channels = 30+30 (strain gages+dispacement gages ports)
Maximum Frequency = 20 Hrz/Channel
167
APPENDIX B: DESCRIPTION OF EARTHQUAKE
SIMULATOR
The earthquake simulator (shake table) used in this study is horizontal single degree of
freedom vibration facility driven by a servo-hydraulic actuator. The shake table is anchored
to the reinforced concrete foundation with dimensions of 20 x 20 x 5 ft (6 x 6 x 1.5 m) in the
Earthquake Engineering Center (EEC), N-W.F.P University of Engineering and Technology.
The actuator is connected to the backstop and aluminum table top via ball joint assemblies.
These bass joints allow a small amount of transverse and rotational adjustment flexibility for
alignment.
Following are the capabilities and characteristics of the shake table:
• Table size 5 ft x 5 ft (1.5 x 1.5 m) aluminum table top with M14 tapped holes on 7-7/8 inch (20 cm) both directions,
• Uni-axial horizontal motion,
• A total of 8 linear roller bearings on 4 linear rails to guide table motion and prevent vertical, side to side, roll, and yaw motion,
• Peak to peak displacement is 10 inch (25.4 cm),
• Peak velocity (with 4000 kg test specimen) is 43.3 inch/see (1.1 m/s ),
• Peak acceleration (with a 4000 kg test specimen) is 1.1 g,
• Maximum test item weight; 8000 kg. Test items above 4000 kg leads to significant system performance degredation,
• frequency range is 0.15 to 50 Hrz
• Maximum test item eccentricity is 10.0 ton-m
Data Acquisition and Control Characteristics
The data acquisition and control system for the shake table is a Data Physics SignalStar
Vector Vibration Controller operating on a Dell desktop computer. The system allows for a
feedback accelerometer on the moving table, a PC-based digital control system reading this
168
acceleration, and the same PC system producing an analog drive signal to the actuator servo
controller. The Data Physics provides a total of 16 channels for table accelerometers, for
response measurements of specimen etc)
Hydraulic System:
The hydraulic actuator is supplied by Gardner Systems. The actuator has a 13 inch (33.0 cm)
stroke with 1.0 inch (25.0 cm) of cushion and 15 mm of bumper/hard stop. The actuator is
rated at 11 kips (5 metric tons) and includes three-two stage Moog G761-3005 servo valves
rated at 15 GPM (56.8 LPM), Delta P compensation, and a magnetostrictive Balluf
displacement transducer to measure actuator displacement.
Shake table system is supplied with 5 GMP hydraulic pump with 3 micron filtering and water
cooling. The system has 40 gallon reservoir. The system is supplied with two accumulators.
These are identical 10 gallon 3000 psi bladder accumulators to provide for peak flow
capacity during high velocity seismic events.
169
APPENDIX C: MEASURED RESPONSE HISTORIES
C.1 Acceleration Time Histories: Single Story Model
Time [sec]
3029.52928.52827.52726.52625.52524.52423.52322.52221.52120.52019.51918.51817.51716.51615.51514.51413.51312.51211.51110.510
Acc
eler
atio
n [g
]
0.1
0.05
0
-0.05
-0.1
Figure C1 Acceleration during test run R05 in channel 00
Time [sec]
3029.52928.52827.52726.52625.52524.52423.52322.52221.52120.52019.51918.51817.51716.51615.51514.51413.51312.51211.51110.510
Acc
eler
atio
n [g
]
0.1
0.05
0
-0.05
-0.1
Figure C2 Acceleration during test run R05 in channel 01
Time [sec]
3029.52928.52827.52726.52625.52524.52423.52322.52221.52120.52019.51918.51817.51716.51615.51514.51413.51312.51211.51110.510
Acc
eler
atio
n [g
]
0.1
0.05
0
-0.05
-0.1
Figure C 3 Acceleration during test run R05 in channel 02
Time [sec]
3029.52928.52827.52726.52625.52524.52423.52322.52221.52120.52019.51918.51817.51716.51615.51514.51413.51312.51211.51110.510
Acc
eler
atio
n [g
]
0.1
0.05
0
-0.05
-0.1
Figure C 4 Acceleration during test run R05 in channel 03
Time [sec]
3029.52928.52827.52726.52625.52524.52423.52322.52221.52120.52019.51918.51817.51716.51615.51514.51413.51312.51211.51110.510
Acc
eler
atio
n [g
]
0.1
0.05
0
-0.05
-0.1
Figure C 5 Acceleration during test run R05 in channel 04
170
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.53
Acc
eler
atio
n [g
] 0.1
0.05
0
-0.05
-0.1
Figure C 6 Acceleration during test run R10 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.53
Acc
eler
atio
n [g
] 0.1
0.05
0
-0.05
-0.1
Figure C 7 Acceleration during test run R10 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.53
Acc
eler
atio
n [g
] 0.1
0.05
0
-0.05
-0.1
Figure C 8 Acceleration during test run R10 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.53
Acc
eler
atio
n [g
] 0.1
0.05
0
-0.05
-0.1
Figure C 9 Acceleration during test run R10 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.53
Acc
eler
atio
n [g
] 0.1
0.05
0
-0.05
-0.1
Figure C 10 Acceleration during test run R10 in channel 04
171
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.150.1
0.050
-0.05-0.1
-0.15
Figure C 11 Acceleration during test run R20 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 12 Acceleration during test run R20 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 13 Acceleration during test run R20 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 14 Acceleration during test run R20 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 15 Acceleration during test run R20 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 16 Acceleration during test run R40 in channel 00
172
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 17 Acceleration during test run R40 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 18 Acceleration during test run R40 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 19 Acceleration during test run R40 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 20 Acceleration during test run R40 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 21 Acceleration during test run R60 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 22 Acceleration during test run R60 in channel 01
173
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 23 Acceleration during test run R60 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 24 Acceleration during test run R60 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 25 Acceleration during test run R60 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 26 Acceleration during test run R80 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 27 Acceleration during test run R80 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 28 Acceleration during test run R80 in channel 02
174
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 29 Acceleration during test run R80 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 0.4
0.2
0
-0.2
-0.4
Figure C 30 Acceleration during test run R80 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
1
0.5
0
-0.5
-1
Figure C 31 Acceleration during test run R100 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
1
0.5
0
-0.5
-1
Figure C 32 Acceleration during test run R100 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 33 Acceleration during test run R100 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 34 Acceleration during test run R100 in channel 03
175
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 35 Acceleration during test run R100 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 36 Acceleration during test run R125 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 37 Acceleration during test run R125 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 38 Acceleration during test run R125 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 39 Acceleration during test run R125 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 1
0.5
0
-0.5
-1
Figure C 40 Acceleration during test run R125 in channel 04
176
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
21.5
10.5
0-0.5
-1-1.5
-2
Figure C 41 Acceleration during test run R150 in channel 00
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
21.5
10.5
0-0.5
-1-1.5
-2
Figure C 42 Acceleration during test run R150 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
21.5
10.5
0-0.5
-1-1.5
-2
Figure C 43 Acceleration during test run R150 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
21.5
10.5
0-0.5
-1-1.5
-2
Figure C 44 Acceleration during test run R150 in channel 03
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
21.5
10.5
0-0.5
-1-1.5
-2
Figure C 45 Acceleration during test run R150 in channel 04
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
3
2
1
0
-1
-2
-3
Figure C 46 Acceleration during test run R175 in channel 00
177
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
3
2
1
0
-1
-2
-3
Figure C 47 Acceleration during test run R175 in channel 01
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
]
3
2
1
0
-1
-2
-3
Figure C 48 Acceleration during test run R175 in channel 02
Time [sec]
2019.51918.51817.51716.51615.51514.51413.51312.51211.51110.5109.598.587.576.565.554.543.532.521.510.50
Acc
eler
atio
n [g
] 4
2
0
-2
-4
Figure C 49 Acceleration during test run R175 in channel 03
C.2 Displacement Time History:
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 51 Displacement during test run R05 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 52 Displacement during test run R05 in channel 08
178
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 53 Displacement during test run R05 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.30.250.2
0.150.1
0.050
-0.05
Figure C 54 Displacement during test run R05 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 55 Displacement during test run R05 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 56 Displacement during test run R10 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 57 Displacement during test run R10 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 58 Displacement during test run R10 in channel 09
179
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 59 Displacement during test run R10 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.20.150.1
0.050
-0.05-0.1
-0.15-0.2
Figure C 60 Displacement during test run R10 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.2
0.1
0
-0.1
-0.2
Figure C 61 Displacement during test run R20 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.2
0.1
0
-0.1
-0.2
Figure C 62 Displacement during test run R20 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.2
0.1
0
-0.1
-0.2
Figure C 63 Displacement during test run R20 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.2
0.1
0
-0.1
-0.2
Figure C 64 Displacement during test run R20 in channel 10
180
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
0.2
0.1
0
-0.1
-0.2
Figure C 65 Displacement during test run R20 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
) 0.4
0.2
0
-0.2
-0.4
Figure C 66 Displacement during test run R40 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
) 0.4
0.2
0
-0.2
-0.4
Figure C 67 Displacement during test run R40 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
) 0.4
0.2
0
-0.2
-0.4
Figure C 68 Displacement during test run R40 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
) 0.4
0.2
0
-0.2
-0.4
Figure C 69 Displacement during test run R40 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
) 0.4
0.2
0
-0.2
-0.4
Figure C 70 Displacement during test run R40 in channel 11
181
Time [sec]4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 71 Displacement during test run R60 in channel 07
Time [sec]4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 72 Displacement during test run R60 in channel 08
Time [sec]4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 73 Displacement during test run R60 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 74 Displacement during test run R60 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 75 Displacement during test run R60 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 76 Displacement during test run R80 in channel 07
182
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 77 Displacement during test run R80 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 78 Displacement during test run R80 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 79 Displacement during test run R80 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1
0.5
0
-0.5
-1
Figure C 80 Displacement during test run R80 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1.51
0.50
-0.5-1
-1.5
Figure C 81 Displacement during test run R100 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1.51
0.50
-0.5-1
-1.5
Figure C 82 Displacement during test run R100 in channel 08
183
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1.51
0.50
-0.5-1
-1.5
Figure C 83 Displacement during test run R100 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1.51
0.50
-0.5-1
-1.5
Figure C 84 Displacement during test run R100 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
1.51
0.50
-0.5-1
-1.5
Figure C 85 Displacement during test run R100 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
2
1
0
-1
-2
Figure C 86 Displacement during test run R125 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
2
1
0
-1
-2
Figure C 87 Displacement during test run R125 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
2
1
0
-1
-2
Figure C 88 Displacement during test run R125 in channel 09
184
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
2
1
0
-1
-2
Figure C 89 Displacement during test run R125 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
2
1
0
-1
-2
Figure C 90 Displacement during test run R125 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 91 Displacement during test run R150 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 92 Displacement during test run R150 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 93 Displacement during test run R150 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 94 Displacement during test run R150 in channel 10
185
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 95 Displacement during test run R150 in channel 11
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 96 Displacement during test run R175 in channel 07
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 97 Displacement during test run R175 in channel 08
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 98 Displacement during test run R175 in channel 09
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 99 Displacement during test run R175 in channel 10
Time [sec]
4038363432302826242220181614121086420
Dis
plac
emen
t (in
)
3
2
1
0
-1
-2
-3
Figure C 100 Displacement during test run R175 in channel 11
186
C.3 Acceleration Time History: Double Story Model
Figure C 101 Acceleration during test run R05 in channel 00
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 102 Acceleration during test run R05 in channel 01
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 103 Acceleration during test run R05 in channel 02
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 104 Acceleration during test run R05 in channel 03
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 105 Acceleration during test run R05 in channel 04
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 106 Acceleration during test run R10 in channel 00
187
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 107 Acceleration during test run R10 in channel 01
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 108 Acceleration during test run R10 in channel 02
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 109 Acceleration during test run R10 in channel 03
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 110 Acceleration during test run R10 in channel 04
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.4
0.2
0
-0.2
-0.4
Figure C 111 Acceleration during test run R20 in channel 00
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.4
0.2
0
-0.2
-0.4
Figure C 112 Acceleration during test run R20 in channel 01
188
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.6
0.4
0.20
-0.2
-0.4
-0.6
Figure C 113 Acceleration during test run R20 in channel 02
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.4
0.2
0
-0.2
-0.4
Figure C 114 Acceleration during test run R20 in channel 03
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.4
0.2
0
-0.2
-0.4
Figure C 115 Acceleration during test run R20 in channel 04
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 116 Acceleration during test run R30 in channel 00
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
1
0.5
0
-0.5
-1
Figure C 117 Acceleration during test run R30 in channel 01
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
1
0.5
0
-0.5
-1
Figure C 118 Acceleration during test run R30 in channel 02
189
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 119 Acceleration during test run R30 in channel 03
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.6
0.4
0.2
0
-0.2
-0.4
Figure C 120 Acceleration during test run R30 in channel 04
190
C.3 Displacement Time History: Double Story Model
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.05
0
-0.05
Figure C 121 Displacement during test run R05 in channel 07
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 122 Displacement during test run R05 in channel 08
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 123 Displacement during test run R05 in channel 09
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 124 Displacement during test run R05 in channel 10
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 125 Displacement during test run R05 in channel 11
191
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 126 Displacement during test run R05 in channel 12
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 127 Displacement during test run R05 in channel 13
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 128 Displacement during test run R05 in channel 14
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 129 Displacement during test run R05 in channel 15
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.1
0.05
0
-0.05
-0.1
Figure C 130 Displacement during test run R05 in channel 16
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 131 Displacement during test run R10 in channel 07
192
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 132 Displacement during test run R10 in channel 08
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 133 Displacement during test run R10 in channel 09
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 134 Displacement during test run R10 in channel 10
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 135 Displacement during test run R10 in channel 11
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 136 Displacement during test run R10 in channel 12
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 137 Displacement during test run R10 in channel 13
193
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 138 Displacement during test run R10 in channel 14
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 139 Displacement during test run R10 in channel 15
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.2
0.1
0
-0.1
-0.2
Figure C 140 Displacement during test run R10 in channel 16
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 141 Displacement during test run R20 in channel 07
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 142 Displacement during test run R20 in channel 08
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 143 Displacement during test run R20 in channel 09
194
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 144 Displacement during test run R20 in channel 10
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 145 Displacement during test run R20 in channel 11
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 146 Displacement during test run R20 in channel 12
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.30.20.1
0-0.1-0.2-0.3
Figure C 147 Displacement during test run R20 in channel 13
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.2
0
-0.2
Figure C 148 Displacement during test run R20 in channel 14
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.2
0
-0.2
Figure C 149 Displacement during test run R20 in channel 15
195
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.2
0
-0.2
-0.4
Figure C 150 Displacement during test run R20 in channel 16
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 151 Displacement during test run R30 in channel 07
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 152 Displacement during test run R30 in channel 08
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 153 Displacement during test run R30 in channel 09
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 154 Displacement during test run R30 in channel 10
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.60.40.2
0-0.2-0.4-0.6-0.8
Figure C 155 Displacement during test run R30 in channel 11
196
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g]
0.60.40.2
0-0.2-0.4-0.6
Figure C 156 Displacement during test run R30 in channel 12
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 157 Displacement during test run R30 in channel 13
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 156 Displacement during test run R30 in channel 14
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 157 Displacement during test run R30 in channel 15
Time [sec]
4038363432302826242220181614121086420
Acce
lera
tion
[g] 0.5
0
-0.5
Figure C 158 Displacement during test run R30 in channel 16
197
APPENDIX-D: SCHEMATIC DIAGRAMS SHOWING
DAMAGE PROPAGATION DURING DIFFERENT TEST RUN. D.1 Single Story Model
Figure D1 Hairline cracks in wall 12 before start of test
Figure D2 Crack propagation in wall 1 during test run R60
198
Figure D3 Crack propagation in wall 12 during test run R60
Figure D4 Crack propagation in wall 6 during test run R80
199
Figure D5 Crack propagation in wall 6 during test run R80
Figure D6 Crack propagation in wall 1 during test run R125
200
Figure D7 Crack propagation in wall 12 during test run R125
Figure D8 Crack propagation in wall 1 during test run R175
201
Figure D9 Crack propagation in wall 12 during test run R175
Figure D10 Crack propagation in wall A during test run R80
202
Figure D11 Crack propagation in wall C during test run R80
Figure D12 Crack propagation in wall F during test run R80
203
Figure D13 Crack propagation in wall A during test run R175
Figure D14 Crack propagation in wall C during test run R175
204
Figure D15 Crack propagation in wall F during test run R175
205
D.2 Double Story Model
Figure D16 Hairline cracks before start of test in wall A
Figure D17 Hairline cracks before start of test in wall H
206
Figure D18 Hairline cracks before start of test in wall 1
Figure D19 Crack propagation in wall 1 during test run R30 (Pga = 0.636g)
207
Figure D20 Crack propagation in wall 9 during test run R30 (Pga = 0.636g)
Figure D21 Crack propagation in wall 9 during last test run (Pga = 3.65g)
208
Figure D22 Crack propagation in wall F during test run R20 (Pga = 0.33g)
Figure D23 Crack propagation in wall A during test run R20 (Pga = 0.33g)
209
Figure D24 Crack propagation in wall H during test run R30 (Pga = 0.56g)
Figure D25 Crack propagation in wall A during test run R30 (Pga = 0.56g)
210
Figure D26 Crack propagation in wall H during last test run (Pga = 3.65g)
Figure D27 Crack propagation in wall A during last test run (Pga = 3.65g)
211
APPENDIX E: ELASTIC ANALYSIS OF SINGLE AND
DOUBLE STORY MODEL BY SAP
The elastic analysis of single and double story model has been carried out by modeling
building in SAP2000, computer software. The confining beams and columns are modeled as
frame element and masonry walls are modeled as shell element of SAP2000.
E-1.0 Material Properties:
E-1.1 Masonry
Modulus of Elasticity = 46.28 ksi,
Weight per unit volume = 95.3 pcf,
E-1.2 Micro Concrete
Compression Strength = 367 psi
Modulus of Elasticity = 1092 psi
Weight per unit volume = 98.8 pcf,
E-1.3 Frame Sections
Tie Column-1 (C6x9) = 1.5 x 2.25 inch
Tie Column-2 (C9x9) = 2.25x2.25 inch
Bond Beam (B6x0) = 1.5x2.25 inch
Slab (S5) = 1.25 inch
Wall (W9) = 2.25 inch
Time History Function
212
Figure E 1 Time History Function
Figure E 2 Single Story Model in SAP
213
Figure E 3 Double Story Model in SAP
E-2.0 Results:
E-2.1 Maximum Displacement:
Maximum Top Displacement in single story model = 0.4 mm
Maximum Top Displacement in Double Story Model = 3.17 mm
Maximum Ground Floor Displacement in Double Story Model = 2.47 mm
E-2.1 First Natural Frequency:
Single Story Model = 0.0266 Hrz
Double Story Model = 0.0535 Hrz
214
VITA
Amjad Naseer was born in Lakki Marwat, N-W.F.P, Pakistan, on May 12, 1972. He
graduated from Department of Civil Engineering, N-W.F.P University of Engineering and
Technology, Peshawar in 1995 with a degree in civil engineering. Amjad Naseer completed
his M.Sc degree in Structural Engineering from the same institution. Following the 2005
Kashmir earthquake, Amjad Naseer started work on the evaluation of typical confined brick
masonry buildings in his Ph.D studies. He completed his Ph.D degree in 2009, which was
funded by Higher Education Commission of Pakistan under the Indigenous 5000 scholarship
scheme, batch-I.