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COPYRIGHT
The author has agreed that the library, Department of Civil Engineering, Institute of
Engineering, Pulchowk Campus, may make this thesis freely available for inspection.
Moreover, the author has agreed that permission for extensive copying of this thesis
for scholarly purpose may be granted by the professor who supervised the thesis work
recorded herein or, in his absence, by the Head of the Department or concerning M.
Sc. program coordinator or the Dean of the Institute where the thesis work was done.
It is understood that the recognition will be given to the author of this thesis and to the
Department of Civil Engineering, Institute of Engineering, Pulchowk Campus, in any
use of the material of this thesis. Copying or publication or other use of the thesis for
financial gain without approval of the Department of Civil Engineering, Institute of
Engineering, Pulchowk Campus and the authors written permission is prohibited.
Request for permission to copy or make any use of the material of this thesis in whole
or in part should be addressed to:
Head of Department
Department of Civil Engineering
Institute of Engineering
Pulchowk Campus
Lalitpur, Nepal.
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ABSTRACT
Nepal has large potential of hydropower resources however it is located in one of the
most tectonically active regions of the world. The hydropower resources areenvisaged not only as a supply to satisfy the domestic demand of the country rather an
export commodity. Thus, large scale projects are planned for the export orientated
power generation. These projects involve large dam structures for the impounding of
water. As the risk of failure of dam cannot be ignored due to high seismic activity, the
downstream establishment is always on greater threat.
Several number of earthquake sources are located in Nepal and nearby areas which
may cause devastating effect on large structures such as concrete gravity dam. Near-
field ground motions could cause more damaging effects on structures, as they
observed to differ dramatically from the characteristics of their far field counterparts.
Near field earthquake are characterizes by pulse type velocity time history which
cause large impulsive force on the structures.
In this study we select fifteen near-field earthquake records and five far-field records
for the same earthquake events. Further these selected near-field record are checked
for characteristics of the near field record based on the research papers. From
acceleration time history records, velocity time history records are calculated by
numerical integration using MS-Excel. Further Fourier Amplitude Spectrum is carried
out by using MS- Excels Fast Fourier Transform (FFT) tools. Finite Element
Modeling of the dam (140 m height) of proposed Tanahu hydro-electric project is
prepared on SAP2000 based on the U.S. Army Engineering Manual EM 1110-2-6051.
Linear and Nonlinear time-history analysis are used to assess earthquake performanceof non-overflow gravity dam section. The linear time history analysis is employed to
gain insight into the dynamic behavior of the dam. The nonlinear time history analysis
is employed to identify potential modes of failure. The results of linear time history
analysis are compared with the EM 1110-2-6051 performance acceptance criteria for
gravity dams. This comparison indicated that the dam would suffer significant
cracking along the base for all the fifteen selected near-field earthquake record and
should be assessed on the basis of nonlinear time-history analysis. But comparisonsfor far-field earthquake response indicate that the dam will not suffer profoundly.
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ACKNOWLEDGEMENT
I would like to express my deepest gratitude to my advisor, Dr. Hari Ram Parajuli, for
his outstanding guidance, caring, patience, and providing me with an excellent
atmosphere for doing research. I would like to thanks to Prof. Dr. Prem Nath Maskey,
Prof. Dr. Hikmat Raj Joshi, Dr. Kamal Bahadur Thapa, Dr. Rajan Suwal, Dr. Gokarna
Bahadur Motra, Er. Nabin Chandra Sharma, Er Siddhartha Shankar and all the faulty
members of Department of Civil Engineering, for their excellent course works during
M.Sc. study and valuable suggestion for the improvement of the research during the
long period.
I am indebted to Dr. Roshan Tuladhar, Senior Structural Engineer, for his guidance
and suggestion during this research. Despite being miles away, he was there to guide
me whenever I needed.
I would like to express my sincere gratitude to Dr. Krishna Prasad Dulal, Managing
Director, DK Consult Pvt. Ltd., who helped me in deciding the thesis topic and
inspired me throughout the study period. I also would like to thank Er. MaheshAcharya, Director, Tanahun Hydroelectric Company, who provided me with
necessary data about the project.
I would like to thank my colleague Er. Sandip Uprety, Hydropower Engineer, DK
Consult Pvt. Ltd., for his support and encouragement. Also, I would like to remember
Er. Soyuz Gautam, Senior Structural Engineer at Hydro Consult Pvt. Ltd, and thank
him for his constant motivation in bringing out the thesis. I would like to thanks to all
my friends for their support, knowledge sharing and encouragement throughout the
research.
Last but not the least I would like to thank my parents, relatives, my wife and
daughter for their encouragement and patience during the research.
Ravi Sharma Bhandari
Department of Civil Engineering
Institute of Engineering, Pulchowk Campus
Lalitpur, Nepal
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TABLE OF CONTENTS
COPYRIGHT .................................................................................................................... I
ABSTRACT ..................................................................................................................... III
ACKNOWLEDGEMENT ............................................................................................... V
LIST OF TABLES ....................................................................................................... VIII
LIST OF FIGURES ........................................................................................................ IX
LIST OF SYMBOLS ................................................................................................ XVIII
1. INTRODUCTION ..................................................................................................... 1
1.1.
Seismicity in Nepal .............................................................................................. 2
1.2. Research Objectives ............................................................................................. 3
1.3. Organization of Thesis ......................................................................................... 4
2. LITERATURE REVIEWS ....................................................................................... 5
3. NEAR-FAULT EARTHQUAKE RECORD CHARACTERISTICS ................... 9
3.1. Near-Field Ground Motions ................................................................................. 9
3.2. Criteria for Near-Field Records............................................................................ 9
4. GROUND MOTIONS AND THEIR CHARACTERISTICS .............................. 14
4.1. Seismic Inputs for Structures ............................................................................. 14
4.2. Selection of Ground Motion ............................................................................... 14
4.3. Characteristics of Ground Motions .................................................................... 15
4.4. Near field Ground Motion and Their Fourier Amplitude Spectrum .................. 22
5. FINITE ELEMENT MODELING OF GRAVITY DAM AND MATERIAL
PROPERTIES ................................................................................................................. 37
5.1. Introduction ........................................................................................................ 37
5.2. Analytical Modeling Procedure ......................................................................... 38
5.3. Standard Finite Element Method........................................................................ 38
5.4.
Fluid-Structure Interaction ................................................................................. 40
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5.4.1. Simplified Added Hydrodynamic Mass Model ........................................ 40
5.5. Foundation-Structure Interaction ....................................................................... 43
5.6. Finite Element Model of Dam ............................................................................ 44
6. STRUCTURAL PERFORMANCE AND DAMAGE CRITERIA ..................... 46
6.1. Introduction ........................................................................................................ 46
6.2. Proposed Criteria ................................................................................................ 46
7. LINEAR TIME HISTORY ANALYSIS TECHNIQUE ...................................... 50
7.1. Introduction ........................................................................................................ 50
7.2. Equation of Motion ............................................................................................ 50
7.3. Direct Integration Method .................................................................................. 50
7.4. Mode Superposition Method .............................................................................. 51
7.5. Dynamic Characteristics .................................................................................... 52
7.6. Evaluation of Linear Response .......................................................................... 55
7.6.1. Near-Fault Response of Dam Section ....................................................... 55
7.6.2. Performance of Dam Section for Near-Fault Earthquakes ....................... 96
7.6.3. Far-Fault Response of Dam Section ......................................................... 98
7.6.4. Performance of Dam Section for Far-Fault Earthquakes ........................ 103
7.7. Result and Conclusion ...................................................................................... 104
8. NONLINEAR TIME HISTORY ANALYSIS TECHNIQUE ........................... 105
8.1. Introduction ...................................................................................................... 105
8.2. Nonlinear Modal Time-History Analysis (FNA) ............................................. 106
8.3. Nonlinear Finite-element Model ...................................................................... 106
8.4. Evaluation of Nonlinear Responses ................................................................. 109
9. CONCLUSION AND RECOMMENDATION ................................................... 111
BIBLIOGRAPHY ......................................................................................................... 113
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LIST OF TABLES
Table 3. 1 Ground motion parameters, measured characteristics and lower-
bound values (Ch.A. Maniatakis 2008) ....................................................................... 11
Table 3. 2 Selected Near-Field Ground Motion Records ............................................ 12 Table 3. 3 Ground motion parameter and measured characteristics for Fault
Normal component....................................................................................................... 13
Table 3. 4 Ground motion parameter and measured characteristics for Fault
Parallel component....................................................................................................... 13
Table 4. 1 Selected Far-Field Ground Motion records ................................................ 15
Table 4. 2 Selected Near-Field Fault Normal Ground Motion Records ...................... 19
Table 4. 3 Selected Near-Field Fault Normal Ground Motion Records ...................... 20 Table 4. 4 Far-Field Ground Motion records ............................................................... 21
Table 6. 1 Load Combination Cases for Combining Static and Dynamic
Stresses for 2-D Analysis ............................................................................................. 49
Table 7. 1 Natural Frequencies for different mode shapes .......................................... 52
Table 7. 2 Maximum Crest Displacement and Stresses due to Near Field
Earthquake Records ..................................................................................................... 97
Table 7. 3 Maximum Crest Displacement and Stresses due to Far Field
Earthquake Records ................................................................................................... 103
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Figure 7. 2 Envelops of maximum stresses (N/mm 2) (a) Horizontal Stress, (b)
Vertical Stress due to Fault-Normal component .......................................................... 56
Figure 7. 3 Envelops of maximum stresses (N/mm 2) (a) Horizontal Stress, (b)
Vertical Stress due to Fault-Parallel component .......................................................... 57
Figure 7. 4 Modified Dam Section .............................................................................. 58
Figure 7. 5 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 58
Figure 7. 7 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #6) Earthquake (FN +
V) ................................................................................................................................. 59
Figure 7. 6 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 59
Figure 7. 8 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #6) Earthquake (FP +
V) ................................................................................................................................. 60
Figure 7. 9 Time History of horizontal displacement at top of the dam due to
Imperial Valley-06 (Recording station: El Centro Array #6) Earthquake, Left:
FN-Component, Right: FP Component ....................................................................... 60
Figure 7. 10 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 61
Figure 7. 11 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 61
Figure 7. 12 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #7) Earthquake (FN +
V) ................................................................................................................................. 62
Figure 7. 13 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #7) Earthquake (FP +
V) ................................................................................................................................. 62
Figure 7. 14 Time History of horizontal displacement at top of the dam due to
Imperial Valley-06 (Recording station: El Centro Array #7) Earthquake, Left:
FN-Component, Right: FP Component ....................................................................... 63
Figure 7. 15 Envelops of maximum stresses (N/mm2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 63
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Figure 7. 16 Envelops of maximum stresses (N/mm2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 64
Figure 7. 17 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #6) Earthquake (FN +
V) ................................................................................................................................. 64
Figure 7. 18 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: El Centro Array #6) Earthquake (FP +
V) ................................................................................................................................. 65
Figure 7. 19 Time History of horizontal displacement at top of the dam due to
Loma Prieta (Recording station: LGPC) Earthquake, FN-Component ....................... 65
Figure 7. 20 Time History of horizontal displacement at top of the dam due to
Loma Prieta (Recording station: LGPC) Earthquake, FN-Component ....................... 65
Figure 7. 21 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 66
Figure 7. 22 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 66
Figure 7. 23 Time history of major principal stress at the heel of dam for
Erzican- Turkey (Recording station: Erzincan) Earthquake (FN + V) ....................... 67
Figure 7. 24 Time history of major principal stress at the heel of dam for
Erzican- Turkey (Recording station: Erzincan) Earthquake (FP + V) ......................... 67
Figure 7. 25 Time History of horizontal displacement at top of the dam due to
Erzican- Turkey (Recording station: Erzincan) Earthquake, FN-Component ............. 67
Figure 7. 26 Time History of horizontal displacement at top of the dam due to
Erzican- Turkey (Recording station: Erzincan) Earthquake, FP-Component ............. 68
Figure 7. 27 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 68
Figure 7. 28 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 69
Figure 7. 29 Time history of major principal stress at the heel of dam for Cape
Mendocino (Recording station: Cape Mendocino) Earthquake (FN + V) ................... 69
Figure 7. 30 Time history of major principal stress at the heel of dam for Cape
Mendocino (Recording station: Cape Mendocino) Earthquake (FP + V) ................... 69
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Figure 7. 31 Time History of horizontal displacement at top of the dam due to
Cape Mendocino (Recording station: Cape Mendocino) Earthquake, FN-
Component ................................................................................................................... 70
Figure 7. 32 Time History of horizontal displacement at top of the dam due to
Cape Mendocino (Recording station: Cape Mendocino) Earthquake, FP-
Component ................................................................................................................... 70
Figure 7. 33 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 71
Figure 7. 34 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 71
Figure 7. 35 Time history of major principal stress at the heel of dam for Cape
Mendocino (Recording station: Petrolia) Earthquake (FN + V) .................................. 72
Figure 7. 36 Time history of major principal stress at the heel of dam for Cape
Mendocino (Recording station: Petrolia) Earthquake (FP + V) .................................. 72
Figure 7. 37 Time History of horizontal displacement at top of the dam due to
Cape Mendocino (Recording station: Petrolia) Earthquake, FN-Component ............. 72
Figure 7. 38 Time History of horizontal displacement at top of the dam due to
Cape Mendocino (Recording station: Petrolia) Earthquake, FP-Component .............. 73
Figure 7. 39 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 73
Figure 7. 40 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Parallel component ............................................... 74
Figure 7. 41 Time history of major principal stress at the heel of dam for
Landers (Recording station: Lucerne) Earthquake (FN + V) ...................................... 74
Figure 7. 42 Time history of major principal stress at the heel of dam for
Landers (Recording station: Lucerne) Earthquake (FP + V) ....................................... 75
Figure 7. 43 Time History of horizontal displacement at top of the dam due to
Landers (Recording station: Lucerne) Earthquake, FN-Component ........................... 75
Figure 7. 44 Time History of horizontal displacement at top of the dam due to
Landers (Recording station: Lucerne) Earthquake, FP-Component ............................ 75
Figure 7. 45 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress due to Fault-Normal component ............................................... 76
Figure 7. 46 Envelops of maximum stresses (N/mm2
), Left: Horizontal Stress,Right: Vertical Stress due to Fault-Parallel component ............................................... 76
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Figure 7. 47 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Newhall - Fire Station) Earthquake (FN +
V) ................................................................................................................................. 77
Figure 7. 48 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Newhall - Fire Station) Earthquake (FP +
V) ................................................................................................................................. 77
Figure 7. 49 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Newhall - Fire Station) Earthquake, FN-
Component ................................................................................................................... 77
Figure 7. 50 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Newhall - Fire Station) Earthquake, FP-
Component ................................................................................................................... 78
Figure 7. 51 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 78
Figure 7. 52 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 79
Figure 7. 53 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Rinaldi Receiving Station) Earthquake (FN
+ V) .............................................................................................................................. 79
Figure 7. 54 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Rinaldi Receiving Station) Earthquake (FP
+ V) .............................................................................................................................. 80
Figure 7. 55 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Rinaldi Receiving Station) Earthquake, FN-
Component ................................................................................................................... 80
Figure 7. 56 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Rinaldi Receiving Station) Earthquake, FP-
Component ................................................................................................................... 80
Figure 7. 57 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 81
Figure 7. 58 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 81
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Figure 7. 59 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar Converter Station) Earthquake
(FN + V) ....................................................................................................................... 82
Figure 7. 60 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar Converter Station) Earthquake
(FP + V) ....................................................................................................................... 82
Figure 7. 61 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Converter Station) Earthquake,
FN-Component ............................................................................................................ 82
Figure 7. 62 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Converter Station) Earthquake,
FP-Component ............................................................................................................. 83
Figure 7. 63 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 83
Figure 7. 64 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 84
Figure 7. 65 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar - Converter Station East)
Earthquake (FN + V) ................................................................................................... 84
Figure 7. 66 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar - Converter Station East)
Earthquake (FP + V) .................................................................................................... 85
Figure 7. 67 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Converter Station East)
Earthquake, FN-Component ........................................................................................ 85
Figure 7. 68 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Converter Station East)
Earthquake, FP-Component ......................................................................................... 85
Figure 7. 69 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 86
Figure 7. 70 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 86
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Figure 7. 71 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar - Olive View Med FF) Earthquake
(FN + V) ....................................................................................................................... 87
Figure 7. 72 Time history of major principal stress at the heel of dam for
Northridge-01 (Recording station: Sylmar - Olive View Med FF) Earthquake
(FP + V) ....................................................................................................................... 87
Figure 7. 73 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Olive View Med FF) Earthquake,
FN-Component ............................................................................................................ 87
Figure 7. 74 Time History of horizontal displacement at top of the dam due to
Northridge-01 (Recording station: Sylmar - Olive View Med FF) Earthquake,
FP-Component ............................................................................................................. 88
Figure 7. 75 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 88
Figure 7. 76 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 89
Figure 7. 77 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: KJMA) Earthquake (FN + V) .................................. 89
Figure 7. 78 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: KJMA) Earthquake (FP + V) ................................... 90
Figure 7. 79 Time History of horizontal displacement at top of the dam due to
Kobe-Japan (Recording station: KJMA) Earthquake, FN-Component ....................... 90
Figure 7. 80 Time History of horizontal displacement at top of the dam due to
Kobe-Japan (Recording station: KJMA) Earthquake, FP-Component ........................ 90
Figure 7. 81 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 91
Figure 7. 82 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 91
Figure 7. 83 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: Takarazuka) Earthquake (FN + V)........................... 92
Figure 7. 84 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: Takarazuka) Earthquake (FN + V)........................... 92
Figure 7. 85 Time History of horizontal displacement at top of the dam due toKobe-Japan (Recording station: Takarazuka) Earthquake, FN-Component ............... 92
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Figure 7. 86 Time History of horizontal displacement at top of the dam due to
Kobe-Japan (Recording station: Takarazuka) Earthquake, FP-Component ................ 93
Figure 7. 87 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Normal component .............................................. 93
Figure 7. 88 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress, due to Fault-Parallel component .............................................. 94
Figure 7. 89 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: Takatori) Earthquake (FN + V) ................................ 94
Figure 7. 90 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: Takatori) Earthquake (FP + V) ................................ 95
Figure 7. 91 Time History of horizontal displacement at top of the dam due to
Kobe-Japan (Recording station: Takatori) Earthquake, FN-Component .................... 95
Figure 7. 92 Time History of horizontal displacement at top of the dam due to
Kobe-Japan (Recording station: Takatori) Earthquake, FP-Component ..................... 95
Figure 7. 93 Comparison of percentage of overstressed areas with acceptance
limits ............................................................................................................................ 96
Figure 7. 94 Comparison of cumulative duration of stress cycles with
acceptance stresses at the heel of the dam ................................................................... 96
Figure 7. 95 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress ................................................................................................... 98
Figure 7. 96 Time history of major principal stress at the heel of dam for
Imperial Valley-06 (Recording station: Coachella Canal #4) Earthquake .................. 99
Figure 7. 97 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress ................................................................................................... 99
Figure 7. 98 Time history of major principal stress at the heel of dam for Cape
Mendocino (Recording station: Eureka - Myrtle & West) Earthquake ..................... 100
Figure 7. 99 Envelops of maximum stresses (N/mm 2), Left: Horizontal Stress,
Right: Vertical Stress ................................................................................................. 100
Figure 7. 100 Time history of major principal stress at the heel of dam for
Landers (Recording station: Eureka - Amboy) Earthquake ....................................... 101
Figure 7. 101 Envelops of maximum stresses (N/mm 2), Left: Horizontal
Stress, Right: Vertical Stress...................................................................................... 101
Figure 7. 102 Time history of major principal stress at the heel of dam forNorthridge-01 (Recording station: Arcadia - Campus Dr) Earthquake ..................... 102
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Figure 7. 103 Envelops of maximum stresses (N/mm 2), Left: Horizontal
Stress, Right: Vertical Stress...................................................................................... 102
Figure 7. 104 Time history of major principal stress at the heel of dam for
Kobe-Japan (Recording station: HIK) Earthquake .................................................... 103
Figure 7. 105 Time history of instantaneous factor of safety for near field
earthquake [NGA#1084] ............................................................................................ 104
Figure 8. 1 Dam finite-element model with gap-friction elements ............................ 107
Figure 8. 2 Constitutive relations of gap-friction element ......................................... 108
Figure 8. 3 Deflected shape at the time of maximum displacement. 31 gap
elements out of 51 experienced opening and sliding (NGA#1120) ........................... 109
Figure 8. 4 Time history of sliding displacements of nodal points (heel and
toe) at the base of the dam (NGA#1120) ................................................................... 110
Figure 8. 5 Time history of horizontal displacement at the top of dam
(NGA#1120) .............................................................................................................. 110
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LIST OF SYMBOLS
PGA : Peak Ground Acceleration
PGV : Peak Ground VelocityPGD : Peak Ground Displacement
CAV : Cumulative absolute velocity
PEER : pacific Earthquake Engineering Research Center
IA : Arias Intensity
FN : Fault normal component of earthquake record
FP : Fault parallel component of earthquake record
I : Damage potential parameter : Root mean square acceleration
g : Acceleration due to gravity
NGA : New generation attenuation
: Time history of ground motion (displacement, velocity
or acceleration)
: Undamped natural frequency
: Damped natural frequency and : The cosines and sine function of amplitudes
corresponding to the nth frequency
: The amplitude corresponding to zero frequency
T : Duration of ground motion
An : Fourier Amplitude
FFT : Fast Fourier Transform
DFT : Discrete Fourier Transform
: Mass matrix of the structure
: Added hydrodynamic mass matrix having nonzero
terms only at the structure-water nodal points
: Velocity and acceleration vectors, respectively
: Overall damping matrix for the entire system
: Combined stiffness matrix for structure and foundation
region
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: Vector of nodal point displacements for the complete
system relative to the rigid base displacement
: Direction cosines to x, y and z- DOFs respectively
: Ground acceleration input in x-, y-, and z-directionrespectively
: Hydrodynamic added mass at point i
H : depth of water
: Height above the base of the dam
: Tributary surface area at point i : The normal direction cosines : Westergaard pressure coefficient : Tensile strength of concrete : Compressive strength of concrete
DCR : Demand Capacity Ratio
: Effective load vector
: Modal coordinate mass
: Modal coordinate damping
: Modal coordinate stiffness : Modal coordinate force
: Shape function for nth mode
: Modal damping ratio
FNA : Fast nonlinear analysis or modal nonlinear time history
analysis
: Stiffness matrix for the linear elastic elements
: Vector of forces from the nonlinear degrees of
freedom in the Link/Support elements
: Normal stress
: yield shear strength
c : Cohesion
: Friction angle
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1. INTRODUCTIONNepal has vast potential of hydropower resources but it is located in one of the most
tectonically active regions of the world. The hydropower resources are envisaged not
only as a source to fulfill the domestic demand of the country rather an exportcommodity. Thus, large scale projects are planned for the export orientated power
generation. These projects involve large dam structures for the impounding of water. As
the risk of failure of dam cannot be ignored due to high seismic activity, the downstream
establishment is always on greater threat.
Since the Northridge and Hyogoken-Nanbu (Kobe) earthquakes, there has been abundant
discussion regarding the adequacy of design practice of concrete dams.
The hazard posed by massive dams has been demonstrated since 1928 by the failure of
several dams of all kinds and in many parts of the globe. However, no failure of a
concrete dam has resulted from earthquake excitation; in reality the only complete
collapses of concrete dams have been due to failures in the foundation rock supporting
the dams 1. On the other hand, two important instances of earthquakes damage to concrete
dams occurred in the 1960s: Hsinfengkiang in China and Koyna in India. The damage
was severe enough in each case to need major repairs and strengthening, however the
reservoirs weren t released, thus there was no flooding damage. This wonderful safety
record, however, is not sufficient reason for satisfaction regarding the seismic safety of
concrete dams, as a result of no such dam has yet been subjected to must conceivable
earthquake shaking . For this reason its essential that eve ry one existing concrete dams in
tectonically active regions, also as new dams planned for such regions, be checked to see
that theyre going to perform satisfactorily throughout the great earthquake shaking to
which they might be subjected especially in the near -field regions.
1 Earthquake Engineering for Concrete Dams: Design, Performance, and Research Needs by NationalResearch Council (U.S.) Panel on Earthquake Engineering for Concrete Dams
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1.1. Seismicity in Nepal 2
Nepal is located at the boundary between Indian and Tibetan tectonic plates and therefore
lies in a very seismically active region. Historical data proof the occurrence of damaging
great earthquakes in the past.
The great earthquake that occurred in Nepal was Bihar- Nepal earthquake of 1934 A. D.,
Assam great earthquake of 1897, Kangra earthquake 1905, and Assam earthquake 1950.
The earthquake of 1833 also affected the Kathmandu Valley. The record of historical
earthquake is nt complete that poses a problem in assessing the recurrence period of great
damaging earthquakes. From the available data there has been no great damaging
earthquakes of magnitude >8.0 in the gap between the earthquakes of 1905 A. D and
1934 A. D. and there is a genuine threat that a major earthquake may occur in this gap
which will affect Western Nepal.
Figure 1. 1 Geological Map of Nepal
(Source: http://www.geocities.com/geologyofnepal/geology.html )
2 Source: National Seismological Centre, Nepal, http://www.seismonepal.gov.np
http://www.geocities.com/geologyofnepal/geology.htmlhttp://www.geocities.com/geologyofnepal/geology.htmlhttp://www.geocities.com/geologyofnepal/geology.htmlhttp://www.seismonepal.gov.np/http://www.seismonepal.gov.np/http://www.seismonepal.gov.np/http://www.seismonepal.gov.np/http://www.geocities.com/geologyofnepal/geology.html8/12/2019 Thesis Final Report Ravi Printed-libre
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Figure 1. 2 Seismic Hazard Map of Nepal
(Source: http://earthquake.usgs.gov/earthquakes/world/nepal/gshap.php )
1.2. Research Objectives
i. Performance Study of concrete gravity dams under near field earthquake pulse and
comparison to the far field earthquake effects.
ii. To show the application of linear and nonlinear time history methods to earthquake
response analysis of gravity dams.
iii. To assess stability condition of the dam.
iv. Locations of occurrence of probable cracks on dam during Earthquake.
http://earthquake.usgs.gov/earthquakes/world/nepal/gshap.phphttp://earthquake.usgs.gov/earthquakes/world/nepal/gshap.phphttp://earthquake.usgs.gov/earthquakes/world/nepal/gshap.phphttp://earthquake.usgs.gov/earthquakes/world/nepal/gshap.php8/12/2019 Thesis Final Report Ravi Printed-libre
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1.3. Organization of Thesis
Thesis work on Non -linear time history analysis of large concrete dam considering near
field earthquake e ffect is totally divided into 9 chapters.
Chapter (1) describe introduction about general background, seismicity in Nepal andresearch objective.
Chapter (2) describes related literature review for the research.
Chapter (3) describes characteristics of near-field earthquake records and criteria to select
near-field records.
Chapter (4) describes ground motion and their characteristics for the selected earthquake.
Ground motion characteristics such as amplitude, Frequency Content, duration are
described in this chapter. Special characteristics of near field record i.e. pulse type
velocity time history are also presented along with acceleration time history and Fourier
Amplitude Spectrum.
Chapter (5) describes the techniques of finite element modeling of gravity dam and
material properties used for this study. Fluid-Structure Interaction, Foundation-Structure
Interaction are also described in this chapter.
Chapter (6) Structural performance and damage criteria are described in this chapter.
Limiting values of cumulative inelastic duration and percentage of overstressed area with
different demand-capacity ratio are described based on U.S. Army Engineering Manual
EM_1110-2-6051.
Chapter (7) describes Linear Time History Numerical solution Techniques for the
evaluation of linear response of the gravity dam for selected earthquake records and
performance of dam is checked for limiting value of performance criteria.
Chapter (8) Describes nonlinear performance of dam by using Nonlinear Time History
Analysis technique.
Chapter (9) describes conclusion of linear and nonlinear response of dam for near field
and far field and recommendation for further research.
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2. LITERATURE REVIEWS(Qiumei, et al. October, 2008) analysed the gravity dam subjected to near-field pulse-like
ground motions and this study gave result that near field pulse-like ground motion will
remarkably effect on the concrete gravity dam. Thus cannot be neglected in the design of
RC gravity dam.
(US Army Crops of Engineers 22 December 2003) had developed methodology for Time
history dynamic analysis of concrete hydraulic structures (EM 1110-2-6051). Same
methodology will be used for the analysis of concrete dam and standard in contest of
Nepal will be developed. US Army Corps of Engineers also has developed methodology
for Earthquake Design and Evaluation of Concrete Hydraulic Structures (EM 1110 -2-
6053), (US Army Crops of Engineers 1 May 2007) which also be used for the evaluation
of performance of dam under Earthquake.
(Ohmachi, et al. 2003) had studied effect of near field hidden seismic fault on concrete
dam. The 2000 Western Tottory earthquake (M J 7.3), Japan, was caused by a hidden
seismic fault underlying Kasho Dam, a 46 m-high concrete gravity dam. Strong-motion
accelerometers registered peak accelerations of 2051 and 531 gal at the top of the dam
and in the lower inspection gallery, respectively. Integration of the acceleration records in
the gallery gives a permanent displacement of 28 cm to the north, 7 cm to the west, and
uplift of 5 cm. The dam survived the earthquake without serious damage, but the
reservoir water level dropped suddenly by 6 cm, followed by damped free vibration that
continued for several hours. Based on numerical simulation and field observation, the
water level change is attributed to ground displacement in the near field followed by
seiching of the reservoir. The vibration period in the upstream-downstream direction of
the dam changed noticeably during the main shock, probably due to hydrodynamic
pressure variations.
(Jalali and Ohmachi 2000) had studied aspects of concrete dams response to near fieldground motions and summarized the result as:
Near-field ground motions differ dramatically from their far-field counterparts, and such
kind of ground motions must be treated in different ways, or even may require special
processing to accurately represent their features.
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It is important to select an appropriate suite of time histories not only based on
instrumental parameters such as PA, PV, PD, IV, and ID, or ground motion parameters
based on response spectra, but also the most reliable parameter, input energy of
earthquake ground motion. Maximum incremental velocity (IV) and maximum
incremental displacement (ID) seems to be better parameters for characterizing the
damage potential of earthquakes in near-field region.
The directional frequency contents and amplitude level of near-field ground motions have
fundamental consequences in earthquake response of dam structures. This implies that
the dynamic response of dam structures will be influenced by their orientation relative to
the ground motion and by their proximity to causative faults.
In the case of the arch dam for the most of the ground motions the increase in the
maximum arch and cantilever stresses in the FN direction is about 100 percent. However,
in some cases the maximum arch and cantilever stresses occur in FP direction. It seems
the latter cases are exceptions. It may be concluded that the FN direction is the most
critical direction regarding the stress level in most of near-field ground motions.
Stress level of arch dam is beyond the yield limit of the concrete commonly used in
constructing the dams, and dam will crack under such ground motions, and this will make
non-linear analysis of dams in highly seismic region indispensable.
For gravity dam stress level is very high, and this will lead to severe cracking of the dam
basically in the neck region and interface of the dam and foundation rock, and even
making dam unstable.
Base sliding displacements of gravity dam are dramatically large in FN direction, and
may inflict severe damages to keys, drainage systems, and grout curtains or finally may
lead to loss of reservoir.
In view of many assumptions made in the analyses performed here, the aboveconclusions should be regarded as preliminary, and this is strongly emphasized.
Additional dam heights, configurations, and different suite of strong ground motions need
to be examined. More research should be devoted to effects of large near-field
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earthquakes regarding duration of shaking and frequency contents, in addition to near-
source effects.
(ZHANG and OHMACHI 2000) had studied on seismic cracking and strengthening ofconcrete gravity dam and summarized result as:
1. Concrete gravity dams are likely to experience cracking under intensive
excitations, especially at the heel of dam body and upstream discontinuity.
2. A gentle and smooth upstream face could reduce the tensile stress in the dam
body and avoid the occurrence of cracking.
3. Reinforcing bars cannot prevent the occurrence of cracking under highly tensile
stress, but it can resist the propagation of cracks and reduce the damage of dam
body.
4. Post-tension cables can strengthen the dam body effectively, if it is adequatelydesigned.
(Burman and Reddy October, 2008) had studied on seismic analysis of concrete gravity
dams considering foundation flexibility and nonlinearity and found conclusion as:
1. The displacement and stresses are found to have increased when the flexibility of
the foundation was considered compared to the assumption of rigid foundation.
2. When the material nonlinearity of the foundation was considered, the dam showed
increased amount of displacements and stresses compared to the linear case forEl-Centro excitations. However, the foundation nonlinearity may increase or
decrease the displacement response depending on the characteristics of ground
motion, surrounding foundation properties and the type of structure.
3. The Bouc-Wen hysteretic model is capable of representing strongly nonlinear
behavior under both cyclic and random loading.
(FEMA 65 May 2005) provide a basic framework for the earthquake design and
evaluation of Dams. The general philosophy and principles for each part of the
framework are described in sufficient detail to achieve a reasonable degree of uniformity
in application among the Federal agencies involved in the planning, design, construction,
operation, maintenance, and regulation of dams. The guidelines deal only with the
general concepts and leave the decisions on specific criteria and procedures for
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accomplishing this work up to each agency. Because these guidelines generally reflect
current practices, it will be necessary to make periodic revisions, additions, and deletions
to incorporate state-of-the-practice earthquake engineering.
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3. NEAR-FAULT EARTHQUAKE RECORD CHARACTERISTICS
3.1. Near-Field Ground Motions
A lot of major dam sites is located near to active faults and so could be subjected to near-
field ground motions from massive earthquakes. Information of ground motion in thenear-field region of damaging earthquake is limited by the inadequacy of recorded data.
The near-field of an earthquake is the region within which distinct pulse-like ground
motion are observed due to release and propagation of huge energy from the fault rupture
process. The near-field ground motions are characterized by high peak acceleration
(PGA), high peak velocity (PGV), high peak displacement (PGD), pulse-like time
history and distinct spectral content . The character of near-field ground motions differs
significantly from that of far-field ground motions. The damaging earthquake data clearly
show the presence of systematically larger ground motions in the fault normal direction
than in the fault parallel direction near to faults. The ratio of fault normal to fault parallel
motions increases with increase in magnitude, increase in fault proximity and increase in
period. Further, recent massive earthquakes have shown signs of damage occurring in
chosen directions that correspond to fault normal (north in the 1994 Northridge
earthquake and northwest in the 1995 Kobe earthquake).
3.2. Criteria for Near-Field Records 3
Criteria for Near-Field earthquake record are evaluated based on the paper
Identification of Near-Fault Earthquake record Characteristics by Ch.A.
Maniatakis, I.M. Taflampas and C.C. Spyrakos. The parameters used to select the records
attempt to address the complexity of strong seismic ground motion, such as frequency
content, amplitude and direction, given the fact that it is impossible to characterize strong
motion accurately using any single parameter (Jenning, 1985).
This procedure has been applied in the selected ground motion data from PEER groundmotion database (peer .berkeley.edu/ peer _ ground _ motion _ database) to recognize near-field
records. The following parameters have been selected:
3 The 14 th World Conference on Earthquake Engineering, October 12-17, 2008, Beijing, ChinaIdentification of Near-Fault Earthquake Record CharacteristicsCh.A. Maniatakis, I.M. Taflampas and C.C. Spyrakos
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i) Peak horizontal ground acceleration (PHGA) or (PGA)
ii) Cumulative absolute velocity (CAV), defined as
Where t r is the total duration of the acceleration trace.
iii) Peak horizontal ground velocity (PHGV) or (PGV) which has been found to
be a better indicator of damage potential than PGA (Akkar and Ozen, 2005)
for structures with fundamental frequency in the intermediate range
iv) Arias intensity (I A) (1970), defined as
Where a g(t), is the ground acceleration and I E the integral of the squared ground
acceleration.
v) The damage potential parameter proposed by Fajfar et al. (1990), (I), defined
as
Where t D is the duration of strong motion, according to Trifunac and Brady (1975). The
index incorporates the effects of strong motion duration.
vi) The root mean square acceleration (a rms), defined as
This index accounts for the effects of amplitude and frequency content of strong-motion
record and is directly proportional to the square root of the gradient of the specified
interval of Arias Intensity.
Table 3.1 presents the lower bounds of the parameters listed above that serve as criteria to
identify that correspond to seismic intensities .
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Table 3. 1 Ground motion parameters, measured characteristics and lower-bound values(Ch.A. Maniatakis 2008)
Ground
Motion
parameters
Ground Motion Characteristics
Amplitude Frequency
Content
Duration Energy Lower-
BoundPGA 0.2 gCAV 0.30 g secPGV 20 cm/s
IA 0.4 m/secI 30 cm sec -
arms 0.5 m/sec
Seven earthquake events recorded at fifteen different recording stations are selected for
the evaluation of response of gravity dam. Selected ground motion record (Table 3.2) are
evaluated according to above characteristics and presented in Table 3.3 and Table 4.4.
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Table 3. 2 Selected Near-Field Ground Motion Records
SN NGA# Event Year Station Mag. MechanismEpc.Dist.(km)
Low.freq (Hz)
1 181 ImperialValley-06 1979 El Centro Array #6 6.53 Strike-Slip 0 0.12
2 182 ImperialValley-06 1979 El Centro Array #7 6.53 Strike-Slip 0.6 0.12
3 779 Loma Prieta 1989 LGPC 6.93 Reverse-Oblique 0 0.12
4 821 Erzican-Turkey 1992 Erzincan 6.69 Strike-Slip 0 0.12
5 825 CapeMendocino 1992 Cape Mendocino 7.01 Reverse 0 0.07
6 828 CapeMendocino 1992 Petrolia 7.01 Reverse 0 0.07
7 879 Landers 1992 Lucerne 7.28 Strike-Slip 2.2 0.1
8 1044 Northridge-01 1994 Newhall - Fire Sta 6.69 Reverse 3.2 0.12
9 1063 Northridge-01 1994 Rinaldi Receiving Sta 6.69 Reverse 0 0.11
10 1084 Northridge-01 1994 Sylmar - Converter Sta 6.69 Reverse 0 0.41
11 1085 Northridge-01 1994 Sylmar - Converter StaEast 6.69 Reverse 0 0.41
12 1086 Northridge-01 1994 Sylmar - Olive ViewMed FF 6.69 Reverse 1.7 0.12
13 1106 Kobe- Japan 1995 KJMA 6.9 Strike-Slip 0.9 0.06
14 1119 Kobe- Japan 1995 Takarazuka 6.9 Strike-Slip 0 0.36
15 1120 Kobe- Japan 1995 Takatori 6.9 Strike-Slip 1.5 0.36
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Table 3. 3 Ground motion parameter and measured characteristics for Fault Normal component
SN Event Mag Station
PGA(g)
CAV(g sec)
PGV(cm/s)
IA(m/s)
I(cm s -0.75)
arms (m/s 2)
1Imperial Valley-
06 6.53 El Centro Array #6 0.44 1.05 111.87 1.77 208.71 0.94
2Imperial Valley-
06 6.53 El Centro Array #7 0.46 0.81 108.97 1.67 195.52 0.99
3 Loma Prieta 6.93 LGPC 0.94 2.16 97.02 8.24 198.70 1.71
4 Erzican- Turkey 6.69 Erzincan 0.49 0.89 95.42 2.03 177.38 1.02
5 Cape Mendocino 7.01 Cape Mendocino 1.27 1.09 59.55 2.90 124.89 0.97
6 Cape Mendocino 7.01 Petrolia 0.61 1.51 82.10 3.67 175.12 1.05
7 Landers 7.28 Lucerne 0.71 2.45 141.02 6.76 338.35 1.13
8 Northridge-01 6.69 Newhall - Fire Sta 0.72 1.74 120.27 6.47 239.47 1.60
9 Northridge-01 6.69 Rinaldi Receiving Sta 0.87 1.87 167.20 8.22 339.31 1.74
10 Northridge-01 6.69 Sylmar - Converter Sta 0.59 1.22 130.27 5.35 301.63 1.17
11 Northridge-01 6.69Sylmar - Converter Sta
East 0.84 1.06 116.56 4.08 236.81 1.25
12 Northridge-01 6.69Sylmar - Olive View
Med FF 0.73 1.35 122.72 3.80 225.21 1.43
13 Kobe- Japan 6.9 KJMA 0.85 2.21 96.27 9.41 197.23 1.82
14 Kobe- Japan 6.9 Takarazuka 0.65 1.03 72.65 2.92 134.81 1.23
15 Kobe- Japan 6.9 Takatori 0.68 2.41 169.58 10.36 355.39 1.84
Table 3. 4 Ground motion parameter and measured characteristics for Fault Parallel component
SN Event Mag Station
PGA(g)
CAV(g sec)
PGV(cm/s)
IA(m/s)
I(cm s -0.75 )
arms (m/s 2)
1 Imperial Valley-06 6.53 El Centro Array #6 0.40 0.98 64.72 1.47 120.03 0.862 Imperial Valley-06 6.53 El Centro Array #7 0.33 0.66 44.53 0.89 74.99 0.81
3 Loma Prieta 6.93 LGPC 0.54 1.44 72.18 3.40 149.51 1.07
4 Erzican- Turkey 6.69 Erzincan 0.42 0.77 45.33 1.27 88.20 0.74
5 Cape Mendocino 7.01 Cape Mendocino 1.43 1.41 119.44 5.44 250.03 1.33
6 Cape Mendocino 7.01 Petrolia 0.63 1.52 60.74 3.57 128.75 1.05
7 Landers 7.28 Lucerne 0.79 2.51 48.12 6.78 115.60 1.138 Northridge-01 6.69 Newhall - Fire Sta 0.65 1.32 50.57 3.56 102.84 1.13
9 Northridge-01 6.69 Rinaldi Receiving Sta 0.42 1.45 62.71 3.52 128.91 1.11
10 Northridge-01 6.69 Sylmar - Converter Sta 0.80 1.03 93.30 4.28 213.24 1.04
11 Northridge-01 6.69Sylmar - Converter Sta
East 0.50 0.91 78.36 2.87 152.16 1.15
12 Northridge-01 6.69Sylmar - Olive View
Med FF 0.60 1.34 54.67 3.82 109.23 1.22
13 Kobe- Japan 6.9 KJMA 0.55 1.60 53.67 4.39 107.16 1.31
14 Kobe- Japan 6.9 Takarazuka 0.70 1.15 83.23 4.06 155.72 1.43
15 Kobe- Japan 6.9 Takatori 0.60 1.94 62.82 6.20 149.10 1.11
Table 3.3 and Table 3.4 shows that all the characteristics of near-fault ground motion
satisfied by the selected ground motion according to Table 3.1.
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4. GROUND MOTIONS AND THEIR CHARACTERISTICS
4.1. Seismic Inputs for Structures
Seismic inputs are the earthquake data that are necessary to perform different types of
seismic analysis. In the context of seismic analysis and design of structures, variousearthquake records may be required depending upon the nature of analysis being carried
out. Seismic inputs for structural analysis are provided either in the time domain or in
frequency domain or in both time and frequency domains. In addition, a number of
earthquake parameters are also used as seismic inputs for completeness of the
information that is required to perform different types of analysis. They include
magnitude, intensity, peak ground acceleration/velocity/displacement, duration,
predominant ground frequency, and so on.
The most general way to describe a ground motion is with a time history record. The
motion parameters may be acceleration, velocity, or displacement, or all the three
combined together. Generally, the directly measured quantity is the acceleration and the
other parameters are the derived quantities.
4.2. Selection of Ground Motion
For this study, we have considered 15 near-field ground motion records (fault-normal and
fault-parallel components) and for the same earthquake events 5 far-field ground motions(recorded one component only) are considered.
The PGAs of 15 near -field fault normal ground motions ranges between 0.44 1.27 and
PGAs of 15 near -field fault parallel ground motions ranges between 0.33 1.43 are
considered. For the same events, PGAs of 5 far -field ground motion records ranges
between 0.09 0.15 are selected. The PGAs and duration of ground motions ra nges
from low to high and frequency content ranges from resonating to non-resonating
frequencies. Near-Field ground motion records are presented in Table 3.1 and Table 3.4.
Far Field records are presented below.
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Table 4. 1 Selected Far-Field Ground Motion records
Far-Field Ground Motion Records
SN
NGA#
Event Year Station Magnitude
Mechanism
Epicentral
Distance
PGA(g)
1 166 Imperial Valley-06 1979 Coachella Canal #4 6.53 Strike-Slip 50 0.12
2 826 Cape Mendocino 1992 Eureka - Myrtle &West 7.01 Reverse 42 0.15
3 832 Landers 1992 Amboy 7.28Strike-Slip 69 0.12
4 948 Northridge-01 1994 Arcadia - Campus Dr 6.69 Reverse 41 0.09
5 1105 Kobe- Japan 1995 HIK 6.9Strike-Slip 95 0.14
4.3. Characteristics of Ground Motions
It is necessary to describe the characteristics of the ground motion that are of engineering
significance and to identify a number of ground motion parameters that reflect those
characteristics. For engineering purpose, three characteristics of earthquake motions (1)
amplitude, (2) frequency content, and (3) duration of the motion are important to be
studied. Plenty of different ground motion parameter have been proposed, each of which
provides information about one or more of these characteristics. In practice, it is usually
necessary to use more than one of these parameters to characterize a particular ground
motion adequately (Kramer 1996). These (amplitude, frequency, duration) characteristics
differ dramatically between near-field and far-field ground motions.
Current study is on comparison of the response of concrete gravity dam subjected to
effects caused by near-fault ground motions with the effects caused by far-field ground
motions of the same event. Near-fault ground motions are different from ordinary ground
motions in that they often contain strong pulse like velocity time history and permanent
ground displacements. The dynamic motions are dominated by a large long period pulse
of motion that occurs on the horizontal component normal to the strike of the fault,
caused by rupture directivity effects. Forward rupture directivity causes the horizontal
strike-normal component of ground motion to be systematically larger than the strike-
parallel component at periods longer than about 0.5 seconds (Somerville 2002). However,
near fault recordings from recent earthquakes indicated that the pulse is a narrow band
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pulse whose period increases with magnitude, causing the response spectrum to have
peak whose period increases with magnitude, such that the near-fault ground motions
from moderate magnitude earthquakes may exceed those of larger earthquakes at
intermediate period. Parameter like rupture directivity, recording close to the epicenters,
faulting mechanism and duration can cause changes in characteristics of near-fault
ground motions.
Amplitude : Horizontal accelerations have commonly been used to describe the ground
motions. The peak horizontal acceleration for a given component of motion is simply the
largest (absolute) value of horizontal acceleration obtained from the acceleration of that
component. The largest dynamic forces induced in certain types of structures (very stiff)
are closely related to the peak horizontal accelerations (Kramer 1996).
Frequency Content : Only the simplest analyses are required to show that the dynamic
response of structures is very sensitive to frequency at which they are loaded. Earthquake
produce complicated loading with components of motion that span a broad range of
frequencies. The frequency content describes how the amplitude of a ground motion is
distributed among different frequencies. Since the frequency content of an earthquake
motion will strongly influence the effect of that motion, characterization of the motion
cannot be complete without consideration of its frequency content (Kramer 1996).
As the response of any structure depends on the ratio between the natural frequency of
the structure and the frequency of excitation, it is important to know the frequency
contents of the ground motion (Datta 2010). The most common way of providing this
information is by way of Fourier synthesis of the time history of the ground motion.
Assuming that the time history of the ground motion repeats itself with a period equal to
the duration of the ground motion, it can be represented as sum of an infinite number of
harmonic functions by
(4.1)
where
is the time history of ground motion (displacement, velocity or acceleration)
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is the nth frequency
and are the cosines and sine function of amplitudes corresponding to the nth
frequency
is the amplitude corresponding to zero frequency, respectively.
The amplitudes are given by: (4.2)
(4.3)
(4.4)
Where
(4.5)
T is the duration of ground motion.
The Fourier amplitude gives the amplitude of the harmonic at frequency and is given
by:
(4.6)Equation 4.1 can also be represented in the form
(4.7)
In which is the same as
; ; and is given by
(4.8)
The plot of versus frequency is called the Fourier amplitude spectrum and that of
versus is the Fourier phase spectrum.
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To obtain the Fourier amplitude spectrum of a time history of ground motion, integrations
given by Equations 4.2 4.4 need to be performed. As is an irregular function of
time, the integration is carried out by a numerical technique. This operation is performed
very efficiently by discrete Fourier transform (DFT), which is programmed as FFT and
available in most mathematical software. In FFT, the Fourier synthesis of a time history
record is mathematically treated as a pair of Fourier integrals in the complex domain as
given below.
(4.9)
(4.10)
The first integral provides frequency contents of the time history in a complex form,while the second one provides the time history back, given the complex frequency
contents. The second one is performed using IFFT (inverse Fourier transform).
The standard input for FFT is the time history of ground motion sampled at discrete time
interval. IF N is the number of discrete ordinates of the time history at an interval of time
given as the input to FFT, then N numbers of complex quantities are obtained as the
output. The first N/2 complex quantities provide frequency contents of the time history
with amplitude at frequency as:
j = 0, .. , N/2 Where and are the real and imaginary parts of the jth complex quantity,
respectively.
Generally band width is measured at a level of
times of maximum Fourier
amplitude.
Duration : the duration of strong ground motion can have a strong influence on
earthquake damage. It is related to the time required for accumulation of strain energy by
rupture along the fault. There are different procedures for calculating the duration of
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ground motion, out of which we have considered Trifunac and Brady (1975) method for
calculating the duration of ground motion.
Trifunac and Brady Duration (1975) is based on the time interval between the points at
which 5 % and 95 % of the total energy has been recorded.
Details of the ground motions with magnitude, epicentral distance, PGA, duration and
frequency range are given below in table 4.2 to table 4.4. Further the ground motions and
their Fourier Amplitude Spectrums are given in figure 4.1 to figure 4.15.
Table 4. 2 Selected Near-Field Fault Normal Ground Motion Records
Near-Field Fault Normal Ground Motion
SN NGA#
Event Year Station Magnitude
Mechanism
Epicentral
Distance
PGA(g)
Duration
(sec)
Frequency(Hz)
1 181 ImperialValley-06 1979El Centro Array
#6 6.53Strike-Slip 1.35
0.44 12.12 0.24 - 0.39
2 182 ImperialValley-06 1979El Centro Array
#7 6.53Strike-Slip 0.56
0.46 10.37 0.24 - 1.37
3 779 LomaPrieta 1989 LGPC 6.93Reverse-Oblique 3.88
0.94 17.59 1.27 - 1.61
4 821 Erzican-Turkey 1992 Erzincan 6.69Strike-Slip 4.38
0.49 11.95 0.34 - 1.51
5 825 CapeMendocino 1992 Cape Mendocino 7.01 Reverse 6.961.27 19.34 0.37 - 7.35
6 828 Cape
Mendocino1992 Petrolia 7.01 Reverse 8.18 0.61 20.7 1.12 - 2.34
7 879 Landers 1992 Lucerne 7.28 Strike-Slip 2.20.71 33.13 0.20 -12.35
8 1044 Northridge-01
1994 Newhall - FireSta 6.69 Reverse 5.920.72 15.72 0.73 - 1.95
9 1063 Northridge-01
1994 RinaldiReceiving Sta 6.69 Reverse 6.50.87 16.96 0.68 - 1.32
10 1084 Northridge-01
1994 Sylmar -Converter Sta 6.69 Reverse 5.350.59 28.74 0.88 - 0.88
11 1085 Northridge-01
1994Sylmar -
Converter StaEast
6.69 Reverse 5.19 0.84 17.04 0.34 - 1.37
12 1086 Northridge-01
1994 Sylmar - OliveView Med FF 6.69 Reverse 5.30.73 11.34 0.37 - 3.30
13 1106 Kobe-Japan 1995 KJMA 6.9Strike-Slip 0.96
0.85 17.62 0.98 - 1.49
14 1119 Kobe-Japan 1995 Takarazuka 6.9Strike-Slip 0.27
0.65 11.86 0.49 - 4.37
15 1120 Kobe-Japan 1995 Takatori 6.9Strike-Slip 1.47
0.68 19.29 0.46 - 0.90
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Table 4. 3 Selected Near-Field Fault Normal Ground Motion RecordsNear-Field Fault Parallel Ground Motion
SN NGA#
Event Year Station Magnitude Mechanism
Epicentral
Distance
PGA(g)
Duration(sec)
Frequency(Hz)
1 181 ImperialValley-06 1979 El Centro Array#6 6.53 Strike-Slip 1.35 0.40 11.84 0.39 - 1.22
2 182Imperial
Valley-06 1979El Centro Array
#7 6.53 Strike-Slip 0.56 0.33 8.04 0.34 - 1.42
3 779Loma
Prieta 1989 LGPC 6.93Reverse-
Oblique 3.88 0.54 18.4 1.56 - 1.76
4 821Erzican-
Turkey 1992 Erzincan 6.69 Strike-Slip 4.38 0.4214.3
3 0.39 - 3.52
5 825Cape
Mendocino 1992Cape
Mendocino 7.01 Reverse 6.96 1.43 19.2 2.12 - 7.47
6 828Cape
Mendocino 1992 Petrolia 7.01 Reverse 8.18 0.6320.1
8 1.32 - 1.98
7 879 Landers 1992 Lucerne 7.28 Strike-Slip 2.2 0.7933.3
111.43 -11.43
8 1044Northridge-01 1994
Newhall - FireSta 6.69 Reverse 5.92 0.65 17.1 1.39 - 4.03
9 1063Northridge-01 1994
RinaldiReceiving Sta 6.69 Reverse 6.5 0.42
17.86 2.64 - 3.27
10 1084Northridge-01 1994
Sylmar -Converter Sta 6.69 Reverse 5.35 0.80
27.28 0.54 - 1.81
11 1085Northridge-01 1994
Sylmar -Converter StaEast 6.69 Reverse 5.19 0.50
14.22 0.63 - 1.27
12 1086Northridge-01 1994
Sylmar - OliveView Med FF 6.69 Reverse 5.3 0.60
15.94 1.25 - 2.25
13 1106 Kobe-Japan 1995 KJMA 6.9 Strike-Slip 0.96 0.55 15.9 1.86 - 3.0
14 1119Kobe-
Japan 1995 Takarazuka 6.9 Strike-Slip 0.27 0.7012.2
5 0.61 - 2.20
15 1120Kobe-
Japan 1995 Takatori 6.9 Strike-Slip 1.47 0.6031.7
2 0.56 - 0.93
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Table 4. 4 Far-Field Ground Motion records
SN NGA# Event Year Station
Magnitude Mechanism
EpicentralDistance
PGA(g)
1
166 Imperial
Valley-
1979 Coachella
Canal #4
6.53 Strike-Slip 50 0.12
2826 Cape
Mendoc
1992 Eureka -
Myrtle & West7.01 Reverse 42 0.15
3832 Landers 1992 Amboy 7.28 Strike-Slip 69 0.12
4948 Northrid
ge-011994 Arcadia -
Campus Dr6.69 Reverse 41 0.09
51105
Kobe-
Japan1995 HIK 6.9 Strike-Slip 95 0.14
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4.4. Near field Ground Motion and Their Fourier Amplitude Spectrum
(a) (d)
(b) (e)
(c) (f)
Figure 4. 1 Imperial Valley -06 (Recording Station: El Centro Array #6) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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-0.4
-0.2
0
0.2
0.4
0 10 20 30 40 A c c e l e r a t i o n
( g )
Time (Sec.)
-150
-100
-50
0
50
100
0 20 40
V e
l o c i t y
( c m / s )
Time (Sec.)
-60
-40
-20
0
20
40
60
0 10 20 30 40 V e
l o c i t y
( c m
/ s )
Time (Sec.)
-0.005
0.000
0.005
0.010
0.015
0.020
0.025
0.030
-5 5 15 25
F o u r i e r A m p
l i t u
d e
Frequency (Hz)-0.005
0.000
0.005
0.010
0.015
0.020
-5 5 15 25 F o u r i e r A m p
l i t u
d e
Frequency (Hz)
-0.6
-0.4-0.2
0
0.2
0.4
0.6
0 10 20 30 40
A c c e
l e r a t i o n
( g )
Time (Sec.)
(a) (d)
(b) (e)
(c) (f)
Figure 4. 2 Imperial Valley -06 (Recording Station: El Centro Array #7) near-field(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c) Fault
Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e) Fault
parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 3 Loma Prieta (Recording Station: LGPC) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 4 Erzican- Turkey (Recording Station: Erzincan) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 5 Cape Mendocino (Recording Station: Cape Mendocino) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 6 Cape Mendocino (Recording Station: Petrolia) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 7 Landers (Recording Station: Lucerne) near-field(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 8 Northridge-01 (Recording Station: Newhall - Fire Station) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 9 Northridge-01 (Recording Station: Rinaldi Receiving Station) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 10 Northridge-01 (Recording Station: Sylmar - Converter Station) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 11 Northridge-01 (Recording Station: Sylmar - Converter Station East) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 12 Northridge-01 (Recording Station: Sylmar - Olive View Med FF) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 13 Kobe-Japan (Recording Station: KJMA) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 14 Kobe-Japan (Recording Station: Takarazuka) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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Figure 4. 15 Kobe-Japan (Recording Station: Takatori) near-field
(a) Fault Normal acceleration time history, (b) Fault normal velocity time history, (c)
Fault Normal Fourier amplitude Spectrum, (d) Fault parallel acceleration time history, (e)
Fault parallel velocity time history, (e) Fault parallel Fourier amplitude spectrum
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5. FINITE ELEMENT MODELING 4 OF GRAVITY DAM ANDMATERIAL PROPERTIES
5.1. Introduction
Concrete gravity dam are massive concrete structures that
retain the impounded water by resisting the forces imposed
on them mainly by their own weight (Figure 5.1). They are
designed so that every unit of length is stable independent
of the adjacent units.
Traditionally, analysis of gravity dam considered a very simple
mathematical model of the structure. Such a method was based on the concept that the
resistance to external forces was 2-D in nature, so only a unit slice of the dam taken in the
upstream-downstream direction was analyzed. The earthquake forces were expressed as
the product of a seismic coefficient and were treated simply as static forces. Only the
effects of horizontal ground motion applied in the upstream-downstream direction were
considered. However, to represent the resistance mechanism realistically, it now has
become standard practice to use some form of finite element model in th