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공학석사 학위논문

Cyclic Loading Test for Anchored Non-structural Brick Masonry Wall to

Concrete Backing

콘크리트 지지벽에 고정된 치장조적벽돌벽의

반복하중실험

2020년 2월

서울대학교 대학원

건축학과

권 종 훈

Cyclic Loading Test for Anchored Non-structural Brick Masonry Wall to

Concrete Backing

지도 교수 박 홍 근

이 논문을 공학석사 학위논문으로 제출함

2020년 2월

서울대학교 대학원

건축학과

권 종 훈

권종훈의 공학석사 학위논문을 인준함

2020 년 2 월

위 원 장 (인)

부위원장 (인)

위 원 (인)

위 원 (인)

Abstract

i

Abstract

Cyclic loading test for anchored

masonry veneer wall to concrete

backing

Kwon, Jong Hoon

Department of Architecture and Architectural Engineering

College of Engineering

Seoul National University

The brick masonry wall is the preferred cladding material in Korea due to its

appealing appearance, thermal performance and prevention of water penetration. It

is used in various buildings such as housing, school facilities, etc. The brick masonry

wall have been connected to the backing by using connectors and mechanical

fasteners. These anchors transfer the lateral load from external wall to the backing.

In the brick masonry wall, the gravity load of the brick masonry wall is supported by

the base or extended slab or shelf steel angle. The lateral load acting on the masonry

wall is transferred to the backing through the mechanical fasteners and connectors.

In recent two earthquakes in South Korea (M5.8 in 2017 and M5.4 in 2016),

exterior non-structural brick masonry wall severely damaged in many buildings

Abstract

ii

nearby the epicenter of the earthquakes. Therefore, the specifications for exterior

brick masonry wall included to the “Seismic Building Design Code”. In this code,

exterior brick masonry wall can designed by fallowing the prescriptive requirements

or calculating the demand and the capacity of the exterior brick masonry wall using

principles of mechanism. There were performance tests for brick stud backing and

steel stud backing to verify this code, but there were no tests on concrete backing.

Therefore, tests were necessary to evaluate the performance of the brick masonry

wall on concrete backing in order to verify the suitability of seismic design.

In this paper, flexural test for the masonry and the pullout test was carried out for

the mechanical fasteners and the embedded end of connectors to investigate the

lowest unit necessary to evaluate the performance of the masonry veneer wall.

Cyclic loading test for masonry unit and cyclic loading test for masonry wall

assembly were performed to investigate the seismic capacity of exterior brick

masonry wall. The masonry unit specimen reproduced the local part of the masonry

veneer wall and consisted of two bricks, a connector and a concrete block. Masonry

wall assembly consisted of masonry wall, 16 connectors, and concrete backing wall.

The test parameters were type of connector, use of insulator, and the connector fixing

method. In the masonry unit test, the peak strength was estimated by material test

results. However, insulator significantly decreased the peak strength. In the masonry

wall test assembly, the peak strength of masonry wall was reduced to about half of

the sum of masonry unit strength due to non-uniform force distribution.

Based on the cyclic loading test for masonry unit, an anchorage system strength

was proposed. Based on the both test results, the strength of exterior non-structural

masonry wall was proposed.

Abstract

iii

Keywords: Masonry veneer wall, anchorage system, cyclic loading test

Student Number: 2018-27982

Abstract

iv

Contents

Abstract ......................................................................................... i

Contents .................................................................................... iv

List of Tables ............................................................................ viii

List of Figures ............................................................................. ix

List of Symbols ......................................................................... xiv

Chapter 1. Introduction .............................................................. 1

1.1 Background .......................................................................... 1

1.2 Scope and Objectives ........................................................... 7

1.3 Outline of the master’s thesis .............................................. 8

Chapter 2. Literature Review .................................................. 10

2.1 Code review ....................................................................... 10

2.2 Cyclic test for masonry unit ............................................... 11

2.2.1 Mechanical performance of connectors for brick masonry walls .......... 11

2.2.2 Performance of corrugated connectors for brick masonry wall ............. 13

2.3 Cyclic test for exterior non-structural brick masonry wall 15 2.3.1 Cyclic test for exterior non-structural brick masonry wall with wood stud backing .................................................................................................... 15

2.3.2 Cyclic test for exterior non-structural brick masonry wall with reinforced concrete masonry backing ............................................................. 17

2.4 Shaking test for exterior non-structural brick masonry wall ........................................................................................... 20

2.4.1 Shaking test for exterior non-structural brick masonry wall with

Abstract

v

concrete masonry backing .............................................................................. 20

2.4.2 Shaking test for exterior non-structural brick masonry wall with wood stud backing. ................................................................................................... 21

Chapter 3. Material ................................................................... 24

3.1 Introduction ........................................................................ 24

3.2 Flexural test for the masonry ............................................. 26 3.2.1 Test specimen ........................................................................................ 26

3.2.2 Test setup ............................................................................................... 26

3.2.3 Test results ............................................................................................. 27

3.3 Pullout test ......................................................................... 28

3.3.1 Mechanical fastener pullout test for concrete backing .......................... 28

(1) Variables ................................................................................................ 28

(2) Test Setup .............................................................................................. 31

(3) Test results ............................................................................................. 32

3.3.2 Embedded connector pullout test form mortar joint .............................. 50

(1) Variables ................................................................................................ 50

(2) Test setup ............................................................................................... 53

(3) Test results ............................................................................................. 53

3.4 Discussion .......................................................................... 59

Chapter 4. Cyclic Tests of Masonry Unit ................................ 62

4.1 Introduction ........................................................................ 62

4.2 Test plan ............................................................................. 63

4.2.1 Variables ................................................................................................ 63

4.2.2 Test specimen ........................................................................................ 64

4.2.3 Test setup ............................................................................................... 65

4.2.4 Loading protocol ................................................................................... 66

4.2.5 Setup for LVDP and strain gage ............................................................ 67

Abstract

vi

4.3 Test results.......................................................................... 68

4.3.1 I-N-P55 .................................................................................................. 68

4.3.2 L-N-P55 ................................................................................................. 72

4.3.3 C-I-P200 ................................................................................................ 77

4.3.4 P-I-N30 .................................................................................................. 82

4.4 Discussion .......................................................................... 87

Chapter 5. Cyclic Tests of Masonry Wall ................................ 89

5.1 Introduction ........................................................................ 89

5.2 Test plan ............................................................................. 89

5.2.1 Variables ................................................................................................ 89

5.2.2 Test specimen ........................................................................................ 90

5.2.3 Test setup ............................................................................................... 94

5.2.4 Loading protocol ................................................................................... 97

5.2.5 Setup for LVDT and strain gage ............................................................ 97

5.3 Test results.......................................................................... 98

5.3.1 I-N-P55 .................................................................................................. 98

5.3.2 L-N-P55 ................................................................................................. 99

5.3.3 C-I-P200 .............................................................................................. 100

5.3.4 P-I-N30 ................................................................................................ 101

5.4 Discussion ........................................................................ 102

Chapter 6. Design of Exterior Non-structural Brick Masonry Wall ........................................................................................... 105

6.1 Anchorage system capacity (Funit) ................................... 105

6.1.1 Material capacity ................................................................................. 105

6.1.2 Anchorage system capacity ................................................................. 106

6.2 Brick masonry wall capacity (Fwall) ................................. 107

Abstract

vii

6.3 Design seismic force (Fp) ................................................ 108

6.4 Discussion ........................................................................ 109

Chapter 7. Conclusion ............................................................. 110

References ................................................................................ 114

List of Tables

viii

List of Tables

Table. 2-1 Brick-tie-brick connection subassembly types and average test results (Martins et al. 2016) ....................................................................... 12

Table. 2-2 Number of Test Specimens (Choi et al. 2004) ......................... 13

Table. 2-3 Typical Failure Mode and Average Maximum Load for Tension and Compression Specimens (Choi et al. 2004) ......................... 14

Table. 2-4 Overview of quasi-static, out-of-plane CMU wall specimens (Jo. 2010) ..................................................................................................... 18

Table. 2-5 Test results (Graziotti et al. 2016) ............................................ 21

Table. 2-6 Test results (Reneckis et al. 2003) ............................................ 22

Table. 3-1 Test results of flexural test for the masonry ........................... 27

Table. 3-2 Variables of pullout test for concrete backing ........................ 30

Table. 3-3 Test results of the mechanical fastener pullout test ............... 49

Table. 3-4 Variables of connector pullout test for mortar joint .............. 52

Table. 3-5 Test results of the mechanical fastener pullout test ............... 58

Table. 4-1 Variables of the cyclic loading test of masonry unit .............. 63

Table. 4-2 Test results of Cyclic tests of the masonry unit ...................... 88

Table. 5-1 Variables of the cyclic loading test of masonry wall assembly ....................................................................................................... 90

Table. 5-2 Test results of cyclic test of the masonry wall unit ............... 104

Table. 6-1 Design capacity and tests results of masonry wall assembly ..................................................................................................... 109

List of Figures

ix

List of Figures

Fig. 1-1 Application location of the masonry wall ..................................... 2

Fig. 1-2 Anchored brick masonry wall and adhered brick masonry wall ................................................................................................................. 2

Fig. 1-3 Details of nonstructural masonry wall without insulator ........... 3

Fig. 1-4 Details of nonstructural masonry wall with insulator ................. 3

Fig. 1-5 Type of connector ............................................................................ 4

Fig. 1-6 Damages of the masonry wall by recent earthquakes ................. 6

Fig. 1-7 Estimating the Risk to life safety during earthquakes ................ 6

Fig. 1-8 Flow chart of experimental study .................................................. 9

Fig. 2-1 Type of connector and test results (Martins et al. 2016) ........... 12

Fig. 2-2 Behavior of the exterior brick masonry veneer ......................... 16

Fig. 2-3 Type of connector .......................................................................... 18

Fig. 2-4 “Whiffle tree” apparatus ............................................................. 19

Fig. 2-5 Specimens geometry and details (Graziotti et al. 2016) ............ 20

Fig. 2-6 Displacement and elongation of brick veneer and wood frame backing (Reneckis et al. 2003) ................................................................... 23

Fig. 3-1 Section of anchored brick masonry wall .................................... 25

Fig. 3-2 Test setup for flexural test for the masonry ................................ 26

Fig. 3-3 Fabrication of concrete blocks, installation of mechanical fastener ........................................................................................................ 29

Fig. 3-4 Power-actuated tool and nail ....................................................... 30

Fig. 3-5 Dimension of plastic anchor ......................................................... 30

Fig. 3-6 Test setup for pullout strength of mechanical fastener ............. 31

Fig. 3-7 Tensile strength of mechanical fastener-compressive strength of concrete relationships of test specimen ..................................................... 35

Fig. 3-8 load-displacement relationships of nail (20 mm) with 21MPa concrete ........................................................................................................ 36

List of Figures

x




Fig. 3-12 Destruction shape of a 20 mm long nail with compressive strength of 21 MPa concrete ...................................................................... 40




Fig. 3-16 load-displacement relationships of plastic anchor (55 mm) with 21MPa concrete ........................................................................................... 43

Fig. 3-17 load-displacement relationships of plastic anchor (55 mm) with 35MPa concrete ........................................................................................... 44

Fig. 3-18 load-displacement relationships of plastic anchor (200 mm) with 21MPa concrete .................................................................................. 45

Fig. 3-19 load-displacement relationships of plastic anchor (200 mm) with 35MPa concrete .................................................................................. 46

Fig. 3-20 Destruction shape of a 55 mm long plastic anchor with compressive strength of 21 MPa concrete ................................................ 47




Fig. 3-24 Shape of connector ...................................................................... 51

Fig. 3-25 Fabrication of connector pullout test specimen ....................... 51

List of Figures

xi

Fig. 3-26 Test setup for connector pullout strength for mortar joint ..... 53

Fig. 3-27 Test results of Samwon angle’s connector ................................ 56

Fig. 3-28 Test results of Daeil Tec’s connector.......................................... 57

Fig. 3-29 failure by bending check ............................................................ 60

Fig. 4-1 Fabrication of masonry unit specimen ....................................... 65

Fig. 4-2 Section of masonry unit specimen ............................................... 65

Fig. 4-3 Test setup for the masonry unit test ............................................ 66

Fig. 4-4 Loading protocol in cyclic loading test ....................................... 67

Fig. 4-5 Load-displacement relationships of masonry unit specimens (I-N-P55 1 and 2) ............................................................................................. 69



Fig. 4-8 Failure mode of specimen (I-N-P55) ........................................... 72

Fig. 4-9 Formation of reaction force of type I connector during tensile and compressive force applied ................................................................... 72

Fig. 4-10 Load-displacement relationships of masonry unit specimens (L-N-P55 1 and 2) ............................................................................................. 74



Fig. 4-13 Failure mode of specimen (L-N-P55) ........................................ 77

Fig. 4-14 Formation of reaction force of type L connector during tensile and compressive force applied ................................................................... 77

Fig. 4-15 Load-displacement relationships of masonry unit specimens (C-I-P200 1 and 2) ............................................................................................ 79

Fig. 4-16 Load-displacement relationships of masonry unit specimens (C-I-P200 3 and 4) ............................................................................................ 80

Fig. 4-17 Load-displacement relationships of masonry unit specimens (C-

List of Figures

xii

I-P200 5 and 6) ............................................................................................ 81

Fig. 4-18 Failure mode of specimen (C-I-P200) ....................................... 82

Fig. 4-19 Formation of reaction force of type C connector during tensile and compressive force applied ................................................................... 82

Fig. 4-20 Load-displacement relationships of masonry unit specimens (P-I-N30 1 and 2) .............................................................................................. 84

Fig. 4-21 Load-displacement relationships of masonry unit specimens (P-I-N30 1 and 2) .............................................................................................. 85

Fig. 4-22 Failure mode of specimen (P-I-N30) ......................................... 86

Fig. 4-23 Formation of reaction force of type P connector during tensile and compressive force applied ................................................................... 86

Fig. 5-1 Conventional masonry wall weight support mechanism .......... 91

Fig. 5-2 Dimension of concrete backing and connector installation spacing ......................................................................................................... 93

Fig. 5-3 Section of masonry wall specimen ............................................... 93

Fig. 5-4 Process of making exterior nonstructural brick masonry wall specimens. .................................................................................................... 94

Fig. 5-5 Tests set up of cyclic loading test for exterior nonstructural brick masonry wall assembly ............................................................................... 95

Fig. 5-6 Dimension of “Whiffle tree” ........................................................ 95

Fig. 5-7 Installation of “Whiffle tree” ....................................................... 96

Fig. 5-8 Point load spacing, boundary condition, and connector cover area ............................................................................................................... 96

Fig. 5-9 LVDT installation location ........................................................... 98

Fig. 5-10 Attachment location of strain gauges ........................................ 98

Fig. 5-11 Load-displacement relationships of masonry unit specimens (I-N-P55) .......................................................................................................... 99

Fig. 5-12 Load-displacement relationships of masonry unit specimens (L-N-P55) ........................................................................................................ 100

Fig. 5-13 Load-displacement relationships of masonry unit specimens (C-I-P200) ....................................................................................................... 101

List of Figures

xiii

Fig. 5-14 Load-displacement relationships of masonry unit specimens (C-I-P200) ....................................................................................................... 102

Fig. 7-1 Relationship between the results of tests .................................. 113

List of Symbols

xiv

List of Symbols

b average width of specimen, mm

d average depth of specimen, mm

Fu,c Pullout strength of embedded connector

Fu,f Pullout strength of mechanical fastener

Fu,material Lesat of strength of Fu,f or Fu,c

Fu,unit Peak strength of unit test result

Fu,wall Peak strength of masonry wall assembly test result

Fmaterial Design strength of mechanical fastener

FP Design seismic force

Funit Design strength of anchorage system

Fwall Design strength of exterior non-structural brick masonry wall

l span, mm

n Number of mechanical fastener

P Maximum applied load indicated by the testing machine, N

Ps Weight of specimen, N

R Gross area modulus of rupture, MPa

β Connector factor

γ Non-uniform distibution factor

Chapter 1. Introduction

1


1.1 Background

Exterior non-structural masonry wall is a cladding decorating the structure and it

applied to facade and aisle of the buildings (Fig. 1-1). Typically, masonry refer to

individual units placed in a mortar bed, making a distinction with panelized products.

It can be made of brick, concrete, natural stone or manufactured stone product.

Among them, the brick masonry wall is a preferred cladding material in Korea due

to its appealing appearance, thermal performance, and prevention of water

penetration. Exterior non-structural brick masonry wall is used in various buildings,

especially in school buildings.

There are two types of exterior non-structural brick masonry wall, such as

“anchored brick masonry wall” and “adhered brick masonry wall”. Anchored brick

masonry wall refer to brick masonry wall connected to the baking wall by connector

and there is an air space between the brick masonry wall and backing wall (Fig. 1-2

(a)). Adhered brick masonry wall refer to brick masonry wall attached to the backing

wall by mortar paste or glue (Fig. 1-2 (b)). The backing wall can be made of concrete

masonry, concrete, wood or metal frame. In Korea, anchored brick masonry with

concrete backing wall is usually used.


2

Fig. 1-1 Application location of the masonry wall

Fig. 1-2 Anchored brick masonry wall and adhered brick masonry wall

Fig. 1-3 show the details of typical exterior non-structural brick masonry wall

without insulator and Fig. 1-4 show the details of typical exterior non-structural brick

masonry wall with insulator. In brick masonry wall, the gravity load of the masonry

veneer wall is supported by the base or extended slab or shelf steel angle connecting

to structure, while lateral load acting on the masonry wall is transferred to the

backing wall through the mechanical fasteners and connectors.


3

Fig. 1-3 Details of nonstructural masonry wall without insulator

Fig. 1-4 Details of nonstructural masonry wall with insulator


4

Fig. 1-5 Type of connector

There are various type of connectors depending on conditions such as type of

backing wall and presence of insulator. In Korea, four different types of connectors

(Type I, Type L, Type C, and Type P) are widely used to the concrete backing (Fig.

1-5). One end of the connector is embedded in the mortar between the bricks, and

the other end is anchored to the backing wall by one or two mechanical fasteners:

two fasteners for type I or type C connectors (Fig. 1-5 (a) and (c)) and one fastener

for type L and type P (Fig. 1-5 (b) and (d)). When insulators are used between the

masonry wall and backing wall, longer mechanical fasters and connectors such as

type C and P are used to penetrate the insulator as shown in Fig. 1-4.

In the traditional seismic design methods, specifications focused to the structural

members. It defines the load applied to the building and designs each structural

member of the building. To satisfy requirements for stress and deformation, each

structural members and entire building structure were analyze and checked. The

primary objective of this traditional seismic design procedure is to ensure strength

and serviceability of the building. However, in recent two earthquakes in South

Korea (M5.8 in 2017 and M5.4 in 2016) exterior non-structural masonry walls were

severely damaged in many buildings nearby the epicenter of the earthquake (Fig.

1-6). Fortunately, these damages of exterior non-structural masonry walls were not

trigger severe human casualties. However, Beca's research shows that non-structural


5

element is significant reason for human casualties in 2010-2011 Canterbury and

2013-2014 Wellington earthquake. Total 71 % of human damage is caused by non-

structural elements, and 37 % of the injuries occurred by masonry were fatal. In

addition, the non-structural materials is not only a direct cause of human casualties,

but it can also give the psychological effect for people on the run, interrupt them

from escaping and cause secondary damage such as the destruction of gas pipes

installed outside.

Therefore, the “Seismic Building Design Code (2019)” revised and the

specifications of the anchored brick masonry wall and adhered brick masonry wall

were included. The anchored brick masonry wall design method is divided into

prescriptive requirement and alternative design. Based on previous experience, the

prescriptive requirement suggested the installation space of connectors according to

types of connector, seismic design categories, and so on. The alternative design states

that the demand and the capacity of the exterior brick masonry wall should be

calculated by using principles of mechanism. However, when applying prescriptive

requirement the types of connectors are limited and to use prescriptive requirement

unsatisfying connectors or to develop new type of veneer connectors, an alternative

design shall be applied. Connector’s capacities are unknown. In addition, thick

insulator makes it impossible to apply the prescriptive requirement and therefore it

is necessary to know the strength of the connectors for alternative design.

In 1982, experimental study for metal stud backing was conducted by Brown and

Arumala and in 2009, experimental study for wood stud backing was conducted by

Reneckis and LaFave. However, there were no experimental study for concrete

backing. Therefore, for accurate design of exterior non-structural brick masonry

walls, the test for strength of individual connector and dynamic relationship between


6

individual connector and masonry wall are required.

Fig. 1-6 Damages of the masonry wall by recent earthquakes

Fig. 1-7 Estimating the Risk to life safety during earthquakes


7

1.2 Scope and Objectives

The purpose of this study is to propose the test method of connectors and verify

strength of exterior non-structural brick masonry wall. Among the required studies

already mentioned, as preceded studies, material test, cyclic test for masonry unit,

and cyclic test for masonry wall assembly were carried out.

First, as a study to suggest a test method of connector, the masonry unit test were

performed and the strengths of individual anchorage system were proposed. The

results of the test were compared with the results of masonry wall assembly test to

see how the results of the individual masonry unit test were applied to the masonry

wall assembly. The effect of type of connector and the presence of insulator were

studied by comparing the test results for the parameters.

Next, as a study of verifying strength of exterior non-structural brick masonry wall,

the cyclic loading test for masonry wall assembly were performed and the strengths

of exterior non-structural brick masonry wall were proposed. In addition, by

comparing the test result of masonry unit test the effect of using the connector in a

group was studied. In order to know the displacement of masonry wall when equal

distribution load was applied to exterior non-structural brick masonry wall,

displacement of masonry wall by height and displacement of concrete backing were

measured.


8

1.3 Outline of the master’s thesis

The research manuscript is organized in five chapters. Chapter 3~Chapter 5 deal

with experimental studies on each research topic. A flow chart of experimental

studies in Chapter 3~Chapter 5 is illustrated in Fig. 1-8

In the Chapter 2, masonry wall specification in “Seismic Building Design Code”

was investigated. Also, previous researches for anchorage system (masonry unit

specimen), which represents a local part of the exterior non-structural brick masonry

wall, were investigated. Lastly, previous researches for exterior brick masonry wall,

which included both quasi-static test and shaking table test, were reviewed.

In 2.4, experimental studies were conducted to evaluate performance of fragile

site of exterior non-structural brick masonry wall, which composing anchorage

system. Three type of material tests, flexural test for the masonry, pullout test for

mechanical fastener, and pullout test for embedded connector were conducted and

the results were compared to investigate the failure mode and peak strength of

anchorage system.

In the chapter 4, experimental studies were conducted to evaluate performance of

anchorage system. Anchorage system represent the local part of the exterior non-

structural masonry wall and the masonry unit specimen representing anchorage

system consisted of two bricks, a concrete block, and an anchor. Total four type of

specimens, designed by the proposed installation method, were tested. All specimens

were tested under the cyclic loading. By analyzing the test results, failure mode and

peak strength were evaluated. In addition, differences in the use of insulator were

identified through comparison with material test.


9

In the chapter 5, experimental studies were conducted to evaluate performance of

exterior non-structural brick masonry wall. Total four type of specimens, designed

by the proposed installation method, were tested. All specimens were tested under

the cyclic loading. By analyzing the test results, failure mode and maximum strength

were evaluated. In addition, differences in group of connectors were identified

through comparison with masonry unit test.

Finally, summary and conclusions presented in the Fig. 1-8.

Other studies for the design of exterior non-structural brick masonry wall, a

shaking table test, can be carried out by a follow-up studies.

Fig. 1-8 Flow chart of experimental study

Chapter 2. Literature Review

10


2.1 Code review

“Seismic Building Design Code” defines anchored brick masonry wall and

adhesive brick masonry wall as an exterior non-structural brick masonry wall. For

anchored brick masonry wall, “Seismic Building Design Code” stipulates that the

conditions of general design or prescriptive requirement shall be met. The general

design requires the comparison the capacity and demand of connectors by structural

calculation or based on test results. The lateral load transmitted to the backing wall

through connectors can be calculated by means of the seismic load of the veneer wall

acting on the area covered by each connector. Pullout from the mortar bed of

connector should be suppressed.

The specification design limits various conditions in the production of exterior

non-structural brick masonry wall. The dimensions of brick thickness should be

more than 67 mm and less than 100 mm and type of connector is limited by sheet

metal type, wire type, embedded in the mortar bed type, and adjustable anchor. The

gap between the masonry wall and backing wall should be less than 120 mm. The

area, more than one connector should be installed, is limited according to type of

connector and seismic design category. The vertical and horizontal space should be

less than 600 mm and 800 mm and the thickness of mortar is more than double of

thickness of joint reinforcement. Joint reinforcement should be installed for brick

masonry wall not laid in running bond Buried length of connector is limited more

than 40 mm and at least 15mm mortar cover to the outside face.


11

2.2 Cyclic test for masonry unit

2.2.1 Mechanical performance of connectors for brick masonry walls

Martins and Vasconcelos carried out an experimental study to analyze the tension

and compression behavior of connector anchoring to masonry infill walls.

In this test, both ends of connector were buried in the mortar joint and shape of

connector was the variable. Six different connectors (Fig. 2-1) with different design,

thickness and attachment method were tested under monotonic and cyclic loading,

simulating out-of-plane loading of anchorage systems. Table. 2-1 shows the test

result including strength, stiffness of the connector.

Test results show the behavior of anchorage system and influences of variables.

Tensile resistance was influenced by connector’s design, while connector’s thickness

had influence in compression behavior. Attachment methods does not have influence

to behavior of masonry unit. This study can help to understand the contribution of

these variables for the exterior non-structural brick masonry wall under different

loading conditions. However, these test results were about the masonry infill walls.

Therefore, these tests can be the references of behavior of exterior non-structural

brick masonry wall but the test to concrete backing is needed to study behavior of

exterior non-structural brick masonry wall with concrete backing wall.


12

Fig. 2-1 Type of connector and test results (Martins et al. 2016)

Table. 2-1 Brick-tie-brick connection subassembly types and average test

results (Martins et al. 2016)

Fmax (kN)

C.O.V (%)

δmax (mm)

C.O.V (%)

E (kN/mm)

C.O.V (%)

Compression loading

T1 2.61 2.38 4.49 43.45 1.08 23.53 T2 3.19 25.09 2.73 46.51 1.18 20.91 T3 1.24 17.76 3.03 47.01 0.3 30.00 T4 1.21 14.89 2.45 58.44 0.57 8.92 T5 1.32 16.85 2.71 53.20 0.51 20.91 T6 2.49 23.67 5.38 36.44 1.07 29.00

Cyclic tension loading

T1 0.98 13.16 1.78 13.94 0.47 10.13 T2 3.12 24.00 4.68 29.61 0.89 18.32 T3 1.68 25.00 5.11 73.55 0.20 25.00 T4 2.35 4.22 9.48 35.35 0.58 17.27 T5 1.20 27.13 3.37 38.43 0.47 25.37 T6 1.00 31.12 0.81 25.62 0.41 60.46

Monotonic tension loading

T1 2.29 4.23 1.71 21.98 0.96 19.30 T2 3.13 6.72 8.04 4.40 1.09 33.29 T3 1.71 27.29 4.56 2.64 0.55 24.20 T4 2.40 5.55 13.32 3.24 0.58 26.90 T5 1.82 4.54 7.54 29.82 0.39 19.11 T6 0.82 6.19 1.66 14.48 0.33 16.28


13

2.2.2 Performance of corrugated connectors for brick masonry wall

Choi and James studied about masonry unit with corrugated shape connectors,

which using typical residential and light commercial brick masonry wall

construction in the central and southeastern U.S.

In this test, the masonry unit specimens comprising two bricks, a wood stud, and

a corrugated shape connector were tested to capture the local performance of overall

wall systems rather than of just the veneer tie itself. As shown in Table. 2-2, variables

included connector’s thickness (1.6 mm, 0.8 mm, 0.4 mm), initial offset

displacement (6.4 mm), attaching method of connector to wood studs (nail, screw),

and type of loading (tension, compression, shear, cyclic, cyclic shear). Table. 2-3

shows the test result including strength, stiffness of the connector.

Table. 2-2 Number of Test Specimens (Choi et al. 2004)

Nail/Screw Tie Standard Offset

TE CO CY SH CS TE CO CY SH CS

Nail

Gauge 22

20 10 10 5 5 3 5 3 3 3

Gauge 28

5 5 5 5 5 3 3 3 3 3

Screw

Gauge 16

5 4 5 5 5 - - - - -

Gauge 22

10 5 5 - - 3 3 3 - -

Total 119 41


14

Table. 2-3 Typical Failure Mode and Average Maximum Load for Tension and

Compression Specimens (Choi et al. 2004)

Specimens Typical failure mode Strength (kN)

[average (range)] NSTE22 Pullout of nail 0.731 (0.427-1.328) NOTE22 Pullout of nail 0.775 (0.751-0.812) SSTE22 Pullout of tie 1.805 (1.084-2.403) SOTE22 Pullout of tie 0.815 (0.632-1.102)

NSTE28 Tie hole yielding or pullout of

nail 0.646 (0.562-0.720)

NOTE28 Pullout of tie 0.560 (0.492-0.611) SSTE16 Bucking of tie 1.733 (1.099-2.461) NSCO22 Bucking of tie 0.546 (0.281-0.711) NOCO22 Bucking of tie 0.433 (0.317-0.510) SSCO22 Bucking of tie 0.595 (0.391-0.785) SOCO22 Bucking of tie 0.386 (0.375-0.400) NSCO28 Bucking of tie 0.181 (0.125-0.266) NOCO28 Bucking of tie 0.157 (0.149-0.165) SSCO16 Bucking of tie 3.371 (3.202-3.746)

Test results show the behavior of anchorage system and influences of variables.

The shape of connectors and attaching method, relating strength of the anchorage of

the connector, affected the tensile resistance and the thickness of the connector

affected the compressive resistance. Connector’s thickness and eccentricity affected

tension stiffness, whereas embedment length affected tension strength. Typical

failure modes included nail pullout from the wood stud, connector pullout from the

mortar joint, and connector buckling. This study can help to understand the

contribution of these variables for the exterior non-structural brick masonry walls

under different loading conditions. However, these test results were about the wood

stud backing. Therefore, these tests can be the reference of behavior of exterior non-

structural brick masonry wall but the test to concrete backing is needed to study

behavior of exterior non-structural brick masonry wall with concrete backing wall.


15

2.3 Cyclic test for exterior non-structural brick masonry wall

2.3.1 Cyclic test for exterior non-structural brick masonry wall with wood stud backing

To evaluate the performance of exterior brick masonry walls constructed with

wood stud backing walls, Williams and McGinley were conducted the quasi-static

cyclic test for exterior brick masonry wall. In their study, the four, 4 ft x 8 ft. masonry

wall assembly specimens were tested. Each specimen was composed of a different

type of connector, the type of mechanical fastener, the presence of a joint

reinforcement, and the installation space of connector. Wall specimen was attached

to a backing wall. Forty-eight holes were drilled into the brick units, 1/4 in. e anchors

installed and the “whiffle-tree” elements and an actuator was attached to the exterior

face of the exterior non-structural brick masonry wall. The “whiffle-tree” apparatus

was configured to apply forty-eight equal point loads to the veneer. The behaviors,

the peak strength of the wall, and failure modes of the exterior non-structural brick

masonry wall were investigated.

Fig. 2-2 shows the behavior of the exterior non-structural brick masonry wall.

Before cracking, the veneer acts as a rigid body, rotating about its base and placing

larger loads on the connectors at the top and the bottom of the wall. The exterior non-

structural brick masonry wall specimens were able to resist loads equivalent to

uniform loads from 78 to 110 psf. These test results are substantially higher than

those that might be expected under maximum credible seismic events. The pullout

of the nail, or failure of the lighter gauge corrugated shape connector was

predominate failure modes for the exterior non-structural brick masonry wall. When

the thickness of connector and strength of mechanical anchor were increased the


16

failure mode of exterior brick masonry wall shifted to a pullout of connector from

the mortar joint. It is indicated that when the failure mode change, the strength of

connector is not directly related to the performance of the exterior brick masonry

wall.

Fig. 2-2 Behavior of the exterior brick masonry veneer


17

2.3.2 Cyclic test for exterior non-structural brick masonry wall with reinforced concrete masonry backing

To study the out-of-plane response of CMU walls with exterior non-structural

brick masonry wall, six reinforced concrete masonry wall specimens with exterior

brick masonry wall were tested under quasi-static cyclic loading. Three of those six

quasi-static exterior brick masonry wall specimens were tested under out-of-plane

loading, and the other three under in-plane loading.

In this test, three out-of-plane reinforced concrete masonry wall specimens with clay

masonry veneer (CMU wall specimens) were tested. Table. 2-4 shows the overview

of those wall specimens. The difference between UT CMU 1 and UT CMU 2 is the

type of connectors, and the difference between UT CMU 2 and UT CMU 2 MC is

the cementitious system used in the mortar. Two configurations of connectors and

CMU joint reinforcement were used to connect the exterior brick masonry wall to

the CMU backing. One configuration consisted of two-wire joint reinforcement with

double eye-and-pintle connector. The other configuration consisted of tri-wire joint

reinforcement (two wires in CMU walls and one wire in clay masonry veneer) with

cross wires (Fig. 2-3). Area loading was simulated to the exterior brick masonry wall

by a “whiffle-tree.” The "whiffle-tree" distributed the load from actuator into sixty-

four point (Fig. 2-4)


18

Table. 2-4 Overview of quasi-static, out-of-plane CMU wall specimens (Jo.

2010)

Specimens Loading Dimensions Reinforcement Connector Mortar

UT CMU 1

Out-of-plane, quasi-static

8-ft wide by 8-ft high

Five No. 4 bars vertically and

three No.4 bars horizontally

Double eye-and-pintle

Cement-lime

UT CUM 2 Tri-wire Cement-lime

UT CMU 2 MC

Tri-wire Masonry cement

Fig. 2-3 Type of connector


19

Fig. 2-4 “Whiffle tree” apparatus

Test results show the maximum capacity of exterior non-structural brick masonry

wall and failure modes of connectors. The double eye-and-pintle connectors failed

in tension by the double pintles pulling out of the double eyes after reaching 363 psf,

and buckling of the connectors was not observed. The maximum load recorded in

compression of the double eye-and-pintle connectors was 363 psf but the maximum

compressive load capacity was not determined because the connectors failed in

tension. In the tri-wire connectors, the maximum load in tension was 400 psf and

344 psf by low-cycle fatigue failure of the connectors. The maximum load of the tri-

wire connectors in compression was 292 psf and 356 psf by buckling of the

connectors. In both specimens, the residual load after buckling was about 190 psf,

corresponding to 12 kips. In all the three specimens, the first flexural cracking

occurred around the mid-height in both the CMU wall and the clay masonry wall.


20

2.4 Shaking test for exterior non-structural brick masonry wall

2.4.1 Shaking test for exterior non-structural brick masonry wall with concrete masonry backing

Graziotti performed shaking table tests on masonry walls with cement brick

backing structure (Fig. 2-5). The test parameter was the connector fixing method.

As shown in Table. 2-5, test results showed that the specimen with cement brick

wall resisted peak ground accelerations of 0.68g to 1.11g according to the

overburden pressure and number of connector. In this test, peak ground acceleration

that the exterior non-structural brick wall can resist was very low because of concrete

masonry backing was weak as a backing. The concrete masonry backing was

destroyed with exterior non-structural brick masonry wall.

Fig. 2-5 Specimens geometry and details (Graziotti et al. 2016)


21

Table. 2-5 Test results (Graziotti et al. 2016)

CAV-01-02 �� = 0.1 MPa, 2 ties/m2

CAV-03-02 �� = 0.3 MPa, 2 ties/m2

CAV-01-04 �� = 0.1 MPa, 4 ties/m2

Test# Input PGA(g) Peak R. (mm)



0.1 WN - - 0.1 WN - 0.1 WN - - 1.1 Gr_1 +0.04 +0.00 1.1 Gr_1 +0.08 -0.18 1.1 Gr_1 +0.03 +0.05 1.2 Gr_1 +0.09 +0.12 1.2 Gr_1 +0.12 -0.24 1.2 Gr_1 +0.09 -0.08 1.3 Gr_1 +0.12 +0.19 1.3 Gr_1 +0.17 +0.15 1.4 Gr_1 +0.13 -0.17 1.4 Gr_1 +0.17 +0.31 1.4 Gr_1 +0.21 +0.28 1.5 Gr_1 +0.17 -0.26 1.5 Gr_1 +0.21 +0.36 1.5 Gr_1 -0.08 -0.04 1.6 Gr_1 +0.21 +0.36 1.6 Gr_1 -0.08 -0.15 1.6 Gr_1 -0.12 +0.12 2.1 RWA +0.31 +0.33 1.7 Gr_1 -0.13 +0.20 1.7 Gr_1 -0.16 -0.11 2.2 RWA -0.34 -0.50 1.8 Gr_1 -0.17 -0.40 1.8 Gr_1 -0.20 -0.14 3.1 Gr_2 +0.30 +0.60 1.9 Gr_1 -0.23 -0.54 2.1 RWA +0.29 +0.65 3.2 Gr_2 +0.44 +1.47 2.1 RWA -0.22 -0.34 2.2 RWA -0.29 -0.41 3.3 Gr_2 +0.63 -2.89 2.2 RWA -0.32 -0.65 3.1 Gr_2 +0.30 +0.64 3.4 Gr_2 +0.73 -45.5 3.1 Gr_2 +0.33 -0.74 3.2 Gr_2 +0.44 +0.99 4.1 RWA -0.30 -4.66 3.2 Gr_2 +0.50 +2.45 3.3 Gr_2 +0.63 +1.70 4.2 RWA +0.31 +2.25 3.3 Gr_2 +0.60 -10.6 3.4 Gr_2 +0.75 -2.88 0.2 WN - - 4.1 Gr_1 +0.61 -42.4 4.1 RWA +0.50 +1.90 4.5 RWA +0.50 -28.8 5.1 RWA -0.32 -3.20 4.2 RWA -0.52 -2.00 4.6 RWA -0.53 -45.3 5.2 RWA -0.49 +40.42 5.1 Gr_2 +0.93 -6.12 5.1 Gr_2 +0.44 -32.9 6.1 Gr_2 +0.68 -fail 5.2 Gr_2 +1.11 -fail 5.2 Gr_2 +0.62 -fail

5.3 Gr_2 -0.49 - 5.4 Gr_2 -0.68 +fail

2.4.2 Shaking test for exterior non-structural brick masonry wall with wood stud backing.

Reneckis performed shaking table tests on masonry walls with wood backing

structure. As shown in Table. 2-6, specimens with wood stud backing resisted peak

ground acceleration of 1.07g to 2.19g according to the eccentricity of connector

installation. As shown in Fig. 2-6, the displacement of exterior non-structural brick

masonry wall was different about its height, essentially displayed rigid body rotation

about its base. Due to this deformation, fractures occurred from the top connectors.


22

Table. 2-6 Test results (Reneckis et al. 2003)

Ground Motion

PGA (g)

Top center of brick veneer Period(sec)

Peak tie elongations (centerline)

(corner)

Damage

Acc. (g) Disp.(mm) B3-W3(mm) B4-W4(mm) B5-W5(mm) B6-W6a(mm)

Wall-1

Elastic

M02 0.19 -0.38 1.0 0.10

0.5 0.5 0.6 1.0

M10 0.22 -0.47 1.6 0.4 0.5 0.7 1.5

M10 0.37 0.84 3.8 0.12

0.4 0.5 1.4 3.5 Cracks at mortar-to-concrete

foundation interface

Intermediate M10 0.51 71.09 7.3 0.6 0.8 2.0 6.6 M10 0.58 n/a n/a

0.15 n/a n/a n/a n/a Fracture : tie-1, top row

Nahanni 0.30 1.39 7.7 0.5 1.1 3.1 8.4 Fracture : tie-9, top row

ultimate M10 0.66 2.19 17.5

0.22 0.8 2.9 8.4 18.5

Fracture : tie-8, top row; tie-1, second row from top Nail pullout (~6 mm):

tie-3, top row; tie-9, second row from top

M10 0.64 -5.01 42.9 2.5 15.3 43.0 43.4 Veneer collapse

Wall-2

Elastic M02 0.19 0.79 7.2 0.17 0.8 2.6 4.8 6.8 M10 0.23 1.52 9.3

0.23

0.7 2.8 6.0 7.4

Intermediate

M02 0.20 0.68 6.2 0.9 2.1 4.5 6.5 M10 0.22 -0.91 7.8 0.8 2.0 5.0 7.5 Fracture: tie-1, top row

M02 0.24 0.75 7.8 0.9 2.0 4.8 8.3 Fracture and nail pullout: tie-1, third

row

Ultimate

M10 0.30 1.07 11.4

0.21

1.0 2.3 6.0 10.6 Crack across veneer M02 0.30 0.95 9.7 0.9 2.2 5.6 9.3 Partial fracture: tie-9, top row

M10 0.41 1.63 13.2 0.8 2.9 7.1 11.2 Partial fracture: tie-4, top row

Fracture: tie-6, top row


23

M02 0.31 1.23 11.9 0.8 3.7 8.2 11.4 Nail pullout (~3mm); tie-5, top row M10 0.49 -2.98 46.9 5.0 23.6 44.0 48.6 Veneer collapse

Wall-2b

M02 M02 0.18 0.41 2.4 0.14 0.8 0.7 1.1 2.2 M10 M10 0.22 0.53 3.7

8.2 0.14 0.8 0.7 1.2 3.0

Nahanni Nahanni 0.35 1.78 0.8 0.7 2.0 4.8 M10 M10 0.59 1.74 11.2 0.15 1.0 0.8 1.9 6.1 Slipping at anchor-A M10 M10 0.67 2.00 12.9 0.16 1.2 0.9 2.2 6.8 M10 M10 0.80 -3.00 13.4 0.17 1.0 1.4 2.7 7.5

Fig. 2-6 Displacement and elongation of brick veneer and wood frame backing (Reneckis et al. 2003)

Chapter 3. Material

24

Chapter 3. Material

3.1 Introduction

As shown in Fig. 3-1 exterior non-structural brick masonry wall consists of brick

masonry wall, connector, and backing wall. Brick masonry wall is made of bricks

laid on top of mortar bed on the outside of the backing wall. The connector connects

the brick masonry wall with the backing wall by embedding one end of the connector

in the mortar joint between the brick of brick masonry wall and anchoring to a

backing wall by one or two mechanical fasteners. In Korea, wall structures are

widely used in residential buildings such as apartments. Thus, in most cases, plastic

anchor and nail were used as a mechanical fastener for anchoring the connector.

When connecting the masonry wall to the concrete backing wall, the failure modes

expected in anchored brick masonry wall include flexural fracture of the brick

masonry wall, pullout of mechanical fastener from the concrete backing wall, pullout

of connector from mortar joint, and destruction of the connector itself. Therefore,

before the cyclic loading test for masonry unit, material tests were conducted to

predict the peak strength of each expected failure mode. Material tests included the

following: flexural test for the masonry, mechanical fastener pullout test for concrete

backing and connector pullout test form mortar joint. The destruction strength of

connector itself were calculated in cross-section with the property of the material of

connector. In this chapter, each of those tests is described, and the corresponding

results are presented.

Chapter 3. Material

25

Fig. 3-1 Section of anchored brick masonry wall

Although the number of mechanical fastener used for anchoring the connector and

point of applied load varies depending on the type of connector, the mechanical

fastener pullout test was conducted to check the strength of one mechanical fastener

in a direct tension direction. The load applied in the tensile direction at the center for

the mechanical fastener. Although type I and type C connector is consisted stamped

plate and wire tie (Fig. 1-5), only wire tie, which embedded in mortar joint were

tested in connector pullout test. In the connector pullout test form mortar joint,

interaction between stamped plate and wire tie doesn’t considered, only pullout

strength of wire tie was tested.

Chapter 3. Material

26

3.2 Flexural test for the masonry

3.2.1 Test specimen

A flexural test for the masonry was performed to predict the strength of fracture

by bending. The dimension of the one brick was 90 mm x 190 mm x 57. A

specimen consisted of seven bricks and mortar joints. The dimension of a specimen

were 190 mm x 90 mm x 460 mm along ASTM E518/E8518M-15 (Fig. 3-2 (a)).

Mortar joint was 13 mm with a compressive strength of 11MPa. The specimen was

cured for 28 days.

3.2.2 Test setup

For the measurement of the flexural bond strength of masonry, flexural tests for

the masonry were performed according to ASTM E518/E8518M-15 using a 2,000

kN UTM as shown in Fig. 3-2 (c). The third-point loading method was used. The

span between the supports was 300 mm, and the distance between each support and

the adjacent distributed point load is 100 mm. The load was applied at a constant

speed that allowed the total test time to be more than 1 minute and less than 3 minute

(1.5 kN/min).

Fig. 3-2 Test setup for flexural test for the masonry

Chapter 3. Material

27

3.2.3 Test results

The weight of specimen, maximum applied load, and gross area modulus of

rupture are detailed in Table. 3-1. The gross area modulus of rupture was calculated

as follow equation. The meanings of each symbol are shown in Table. 3-1. The

average gross area modulus of rupture was 0.75 MPa (0.55~1.05 MPa) and

coefficient of variance (COV) was 0.238. These loads are substantially higher than

those that be expected under maximum seismic events.

S2

0.75(P P ) lR

bd

+= (3-1)

Table. 3-1 Test results of flexural test for the masonry

Test number

Weight of specimen (N)

Maximum applied load (N)

Gross area modulus of rupture (MPa)

1 155.04 3700 0.74

2 154.84 5280 1.05

3 155.34 2920 0.59

4 156.21 4080 0.82

5 155.62 2720 0.55

Average 155.43 3740 0.75

R = gross area modulus of rupture, MPa P = maximum applied load indicated by the testing matching, N Ps = weight of specimen, N l = span, mm : 300 mm b = average width of specimen, mm : 90 mm d = average depth of specimen, mm : 190 mm Standard deviation : 0.060 Coefficient of variance : 0.238

Chapter 3. Material

28

3.3 Pullout test

3.3.1 Mechanical fastener pullout test for concrete backing

(1) Variables

Depending on the type of connector and type of backing wall, there were various

ways to fix the connector to the backing wall. When using cement block or brick

walls as a backing wall, both ends of connector were embedded in the mortar joint.

Nail or plastic anchor was used for attaching the connector to concrete backing wall,

wood stud backing wall, and steel stud backing wall. In Korea, nail or plastic anchors

are usually used to concrete backing wall, so in the mechanical fastener pullout test

for concrete backing, the nails and plastic anchors fixed in concrete backing were

tested.

Since there is no existing standard for strength of nail and plastic anchor, the test

variables were decided according to the recommendation by fastener company Hilti.

In Hilti’s recommendation, the compressive strength of the concrete backing wall

and the length of the nail affect the pullout strength of the nail. The Compressive

strength of concrete, commonly used compressive strength of concrete in Korea, 21

MPa and 35 MPa were used as variables. According to the mechanical fastener

installation recommendation, the dimension of concrete block is 140 mm (width) x

140 mm (length) x 120 mm (thickness).

A mechanical fastener was installed in the center of the concrete block so that the

distance of the mechanical fastener was 70 mm from all edges of the concrete block.

Nails were installed by power-actuated tool (Fig. 3-4 (a)). 20 mm and 32 mm long

nails were used as variables (Fig. 3-4 (b)). 20 mm long nail, which have been used

Chapter 3. Material

29

in construction sites, was chosen a variable and a 32 mm long nail was chosen as a

variable to compare with a 20 mm long nail. 55 mm and 200 mm long plastic anchors

were used as variables (Fig. 3-5). When connector is anchored to backing wall

without insulator, a 55 mm long plastic anchor was used and when insulator is

installed on a backing wall, the a 200 mm long plastic anchor was used to anchor the

connector by penetrating the insulator and securing it to the backing. The diameter

of the holes drilled in the concrete to install both plastic anchors was 6 mm. Because

of insulator’s thickness, the depth of the holes drilled to install the 55 mm and 200

mm plastic anchors was 55 mm and 45 mm, and the length of the expansion of the

plastic anchor inside the concrete block was 25 mm (Fig. 3-5). In the mechanical

fastener pullout test for concrete backing mechanical fasteners are installed with a

slight amount of space (2 mm) considering the thickness of connector and gripping

device as shown in Fig. 3-3 (b). The variables are summarized in Table. 3-2.

Fig. 3-3 Fabrication of concrete blocks, installation of mechanical fastener

Chapter 3. Material

30

Fig. 3-4 Power-actuated tool and nail

Fig. 3-5 Dimension of plastic anchor

Table. 3-2 Variables of pullout test for concrete backing

Variable Type of mechanical

fastener Length of mechanical

fastener (mm) Embedded

length (mm) Compressive strength of concrete backing (MPa)

1

Plastic anchor

55 55 21

2 55 35

3 200

45 21

4 45 35

5

Nail

20 20 21

6 20 35

7 32

32 21

8 32 35

Chapter 3. Material

31

(2) Test Setup

Because there was no mechanical fastener pullout test method on concrete, to

measure the pullout strength of mechanical fastener, pullout test for mechanical

fastener were performed according to the ASTM D1761-12 using 2,000kN UTM as

shown in Fig. 3-6. ASTM D1761-12 was originally a valid test on wood, but since

the same test method also valid on plastic, it was judged that this test method can be

applied to other typed of materials. The test was conducted by applying the same test

setting of ASTM D1761-12. A gripping device shaped to fit the base of the fastener

head was produced to allow accurate specimen positioning and to apply true axial

loading. A clamping assembly was produced to hold the concrete block to one platen

of the UTM. For the basic loading method for fastener withdrawal, the load was

applied throughout the test at a uniform rate of 2.5 mm/min.

Fig. 3-6 Test setup for pullout strength of mechanical fastener

Chapter 3. Material

32

(3) Test results

The relationship between the pullout strength of the mechanical fastener with

compressive strength of concrete blocks are shown in Fig. 3-7. The horizontal axis

of the graph represents the compressive strength of concrete and the vertical axis

represents the pullout strength of mechanical fastener. In Fig. 3-7 (a), classifying

with length of nail, a 20 mm long nail was represented by circle, a 32 mm long nail

was represented by rectangular, and the filling in the shape indicates the concrete

with a compressive strength of 35 MPa. Unfilled shapes indicate concrete with a

compressive strength of 21 MPa. In Fig. 3-7 (b), classifying with length of plastic

anchor, a 55 mm long plastic anchor was represented by circle, a 200 mm long plastic

anchor was represented by rectangular, and the filling in the shape indicates the

concrete with a compressive strength of 35 MPa. Unfilled shapes indicate concrete

with a compressive strength of 21MPa.

In concrete block with compressive strength of 21MPa, the pullout strength of the

nail was measured larger as the depth of the embedment of nail was deeper. The

average pullout strength of a 32 mm long nail was 1,848 N (820~3,360 N), 24%

greater than the average pullout strength of a 20 mm long nail (1,490 N (320~2,800

N)). The COV of 20 mm nail and 32 mm nail was 0.52 and 0.48 respectively. In

concrete backing with compressive strength of 35MPa, the average pullout strength

of nail does not show any definite difference in length of nail. The average pullout

strength of a 20 mm long nail was 1,622 N (520~2,300 N) and the average pullout

strength of a 32 mm long nail was 1,658 N (260~2,800 N).

When comparing the results of tests at 21MPa and 35MPa, the strength of 20 mm

nail was increase and the strength of 32 mm nail was decrease as the compressive

Chapter 3. Material

33

strength of concrete increased 21MPa to 35MPa. This result is similar to that of

Hilti’s recommendation for different recommend strengths depending on the length

of the nail and the compressive strength of the concrete. The reason for this

difference in relation between pullout strength of nail and compressive strength of

concrete is presumed due to the difficulty of settling in concrete with higher strength

as the length of nail is longer. The COV of 20 mm nail and 32 mm nail was 0.32 and

0.48 respectively. The reason for the big COV is that the failure mode of the nail is

related to tensile destruction of the concrete, resulting in brittle destruct

In plastic anchor, two specimens showed excessive strength (178 % and 169 % of

average strength respectively). The specimen with a pullout strength of 178 % of the

average strength did not observe the destruction due to the limit of the test setting.

Except for the two specimens, the Fig. 3-7 shows that the standard deviation of

plastic anchor is less than one-third the standard deviation of the nail. The 55 mm

plastic anchor is embedded 55 mm and the 200 mm plastic anchor is embedded 45

mm in the concrete block. There is no relationship between the two plastic anchors

because the shape of the plastic anchor is completely different.

The average strength of a 200 mm plastic anchor in 35 MPa concrete was 2,098

N (1,820~2,420 N), which was 6 % larger than the average pullout strength of a 200

mm plastic anchor in 21MPa concrete (1980 N (1,620~2,460 N)). The average

strength of 55 mm plastic anchor in 35 MPa concrete was 1,810N(1,460~2,160 N),

which was 2% larger than the average strength in 21 MPa concrete, except for two

specimens with higher strength than the average pullout strength of 55 mm long

plastic anchor in 21 MPa concrete (1768 N (1,760~1,920 N)).

When two test specimens were included, the average strength is greater than the

Chapter 3. Material

34

average strength in 35MPa concrete (2,084 N), and the coefficient of variance is 0.34,

tree times that of the other plastic anchor specimens. In the 21 MPa concrete, the

COV of 55 mm nail and 200 mm plastic anchor was 0.12 and 0.13 respectively. In

the 35 MPa concrete, the COV of 55mm and 200 mm plastic anchor was 0.14 and

0.09 respectively. The test results of plastic anchor shows lower COV than nail,

because the failure of plastic anchor was not accompanying destruction of concrete.

The load-displacement relationships of nail are shown in Fig. 3-8 to Fig. 3-11. Fig.

3-8 to Fig. 3-11 shows the test results of a 20 mm long nail with compressive strength

of 21 MPa concrete, a 20 mm long nail with compressive strength of 35MPa concrete,

a 32 mm long nail with compressive strength of 21 MPa concrete, and a 32 mm long

nail with compressive strength of 35MPa concrete respectively. In the graphs, all

subjects reached the maximum strength of each specimen and failure in brittle

manners.

When destruction occurred, the strength of specimens were zero and the nails were

completely removed from the concrete block as shown in Fig. 3-12 to Fig. 3-15. Fig.

3-12 to Fig. 3-15 shows the destruction shape of a 20 mm long nail with compressive

strength of 21 MPa concrete, a 20 mm long nail with compressive strength of 35MPa

concrete, a 32 mm long nail with compressive strength of 21 MPa concrete, and a 32

mm long nail with compressive strength of 35MPa concrete respectively. As the nails

are pulled out with the destruction of concrete surrounding nail, the length of the

displacement is different and less than 10 mm in all the specimens.

Chapter 3. Material

35

Fig. 3-7 Tensile strength of mechanical fastener-compressive strength of

Chapter 3. Material

36

concrete relationships of test specimen

Fig. 3-8 load-displacement relationships of nail (20 mm) with 21MPa concrete

Chapter 3. Material

37


Chapter 3. Material

38

Fig. 3-10 load-displacement relationships of nail (32 mm) with 21MPa

concrete

Chapter 3. Material

39


Chapter 3. Material

40

Fig. 3-12 Destruction shape of a 20 mm long nail with compressive strength of

21 MPa concrete


35 MPa concrete

Chapter 3. Material

41


21 MPa concrete


35 MPa concrete

The load-displacement relationships of plastic anchor are shown in Fig. 3-16 to

Fig. 3-19. Fig. 3-16 to Fig. 3-17 shows the test results of a 55 mm long plastic anchor

with compressive strength of 21 MPa concrete and a 55 mm long plastic anchor with

compressive strength of 35MPa concrete. Fig. 3-18 to Fig. 3-19 shows a 200 mm

long plastic anchor with compressive strength of 21 MPa concrete and a 200 mm

long plastic anchor with compressive strength of 35MPa concrete respectively. In

the graphs, the strength of the test specimen decreases rapidly after the maximum

Chapter 3. Material

42

strength is reached, but is not destroyed immediately. The strength gradually

decreases from rapidly decreased strength to zero until all the embedded length of

the plastic anchor is pulled out.

When the plastic anchors were completely removed from concrete backing as

shown in Fig. 3-20 to Fig. 3-23, the tests of 55 mm a long plastic anchor were ended

between 50 mm and 60 mm displacement and the tests of 200 mm long plastic anchor

were ended near displacement 30 mm. Fig. 3-20 and Fig. 3-21 shows the destruction

shape of a 55 mm long nail with compressive strength of 21 MPa concrete and a 55

mm long nail with compressive strength of 35MPa concrete. Fig. 3-22 and Fig. 3-23

shows a 200 mm long nail with compressive strength of 21 MPa concrete, and a 200

mm long nail with compressive strength of 35MPa concrete respectively.

Displacement reaching maximum strength is also similar. 55 mm long plastic

anchors reached the maximum strength near the displacement of 10 mm and 200 mm

long plastic anchor reached the maximum strength near the displacement of 5 mm.

Chapter 3. Material

43

Table. 3-3 show the test results

Fig. 3-16 load-displacement relationships of plastic anchor (55 mm) with

21MPa concrete

Chapter 3. Material

44


35MPa concrete

Chapter 3. Material

45


21MPa concrete

Chapter 3. Material

46


35MPa concrete

Chapter 3. Material

47

Fig. 3-20 Destruction shape of a 55 mm long plastic anchor with compressive

strength of 21 MPa concrete



Chapter 3. Material

48





Chapter 3. Material

49

Table. 3-3 Test results of the mechanical fastener pullout test

Mechanical fastener Nail Plastic anchor

Compressive strength of concrete (MPa)

21 35 21 35

Total length (mm) 20 32 20 32 55 200 55 200

Embedded length (mm)

17 24 17 22 55 30 55 30

Fastener diameter (mm)

3 3 3 3 6 6 6 6

Pullout strength (N)

1 1400 2200 1280 1700 1280 2220 1500 1900

2 680 1000 1820 1240 1760 2220 1460 2040

3 2060 3360 1260 1740 3700 2000 1800 2140

4 320 820 2300 260 1920 1780 2000 1980

5 2000 900 1820 2800 3000 1620 1880 2040

6 920 2380 1700 2260 1860 1820 1640 2140

7 2100 1360 2180 1580 1780 1780 2160 2420

8 2800 3060 1400 2100 1780 2460 2080 2280

9 880 1500 1940 540 1880 2060 1980 1820

10 1740 1900 520 2360 1880 1840 1600 2220

Average 1490 1848 1622 1658 2084 1980 1810 2098

Coefficient of Variance

0.52 0.48 0.32 0.48 0.34 0.13 0.14 0.09

Chapter 3. Material

50

3.3.2 Embedded connector pullout test form mortar joint

(1) Variables

Brick masonry wall is connected to the backing wall by burying connector in

mortar bed between bricks. Various shape of connector be buried in mortar bed

depending on the type of connector. Steel plate (type L and P) and the wire tie (type

I and C) are mostly used in Korea. Two companies’ steel plate and wire tie were used

as variables to check the performance difference of the same type of connector made

by different company. Assuming that the connector is bonded to the mortar, the

strength of the attachment was related to the area where the connector contacts the

mortar, so the depth of the connector was also used as a variable. The steel plate,

regardless of length, has the same shape of the part buried in mortar, but the length

of the wire tie changes the shape of the part buried in mortar (Fig. 3-24), so in the

wire ties, different lengths of wire tie also added as a variables. 80 mm and 100 mm

long DaeilTec’s wire tie were used and 100 mm and 120 mm long Samwon angle’s

wire tie were used. The depth of the embedment was 45 mm and 75 mm, which

depths are half of the brick width 90 mm or satisfying the minimum mortar thickness

of 15 mm. Compressive strength of mortar was 11 MPa to satisfy Korean Standard

(KS). The spacing of mortar between bricks was 13 mm as construction convention.

The variables of connector pullout test for mortar joint is summarized in

Chapter 3. Material

51

Table. 3-4. The specimens were fabricated according to the above variables as

shown in Fig. 3-25

Fig. 3-24 Shape of connector

Fig. 3-25 Fabrication of connector pullout test specimen

Chapter 3. Material

52

Table. 3-4 Variables of connector pullout test for mortar joint

No Number of specimen

Company Type of

connector

Compressive strength of mortar

(MPa)

Depth of connector

(mm)

Embedment length (mm)

1 5

Samwon angle

Wire 11 100 45 2 5 Wire 11 120 45 3 5 Wire 11 120 75 4 5 Plate 11 100 45 5 5 Plate 11 120 75 6 5

DaeilTec

Wire 11 80 45 7 5 Wire 11 100 45 8 5 Wire 11 100 75 9 5 Plate 11 100 45 10 5 Plate 11 120 75

Chapter 3. Material

53

(2) Test setup

For the measurement of the pullout strength of the connector from mortar joint, c

pullout test for mortar joint were performed according to ASTM E754 using a 2,000

kN UTM as shown in Fig. 3-26. Auxiliary pulling apparatus is shown in Fig. 3-26.

These fixtures are provide with swivel joints to eliminate lateral restraint and

bending when applying the pullout loads. The apparatus shall be designed to have

enough strength and stiffness to prevent its yielding and to maintain uniform

distribution of the axially applied test loads until failure of specimen occurs. The

loading was rate in 20 % expected resistance /minute.

Fig. 3-26 Test setup for connector pullout strength for mortar joint

(3) Test results

The relationship between the pullout strength of embedded connector in mortar

joint with embedded length of connectors are shown in Fig. 3-27 and Fig. 3-28. The

horizontal axis of the graph represents the length of embedded length of connector

and the vertical axis represents the pullout strength of embedded connector. In Fig.

3-27 (a) and (b), the results of the test were shown using connector of Samwon angle,

Chapter 3. Material

54

and in Fig. 3-28 (a) and (b), the results of the test were shown using connector of

Daeil Tec. In Fig. 3-27 (a) and Fig. 3-28 (a), classifying with length of connector, a

80 mm long wire tie was represented by circle, a 100 mm wire tie was represented

by rectangular, and filling in the shape indicates the a 75 mm long embedded length .

Unfilled shapes indicate a 45 mm long embedded length. In Fig. 3-27 (b) and Fig.

3-28 (b), classifying with length of connector, a 100 mm long plate anchor was

represented by circle, a 120 mm plate anchor was represented by rectangular.

In Fig. 3-27 (a), the tendency of increasing pullout strength according to the

embedded length change is not visible on the wire tie of Samwon angle. The average

strength of 100 mm wire tie with 45 mm buried, 120 mm wire tie with 45 mm buried,

and 120 mm wire tie with 75mm buried were 4.04 kN (3.34~4.64 kN), 3.98 kN

(2.78~5.72 kN), and 4.23 kN (3.60~5.62 kN) respectively. The average strength is

strongest in the specimen with a 120 mm long connector buried 75 mm. However,

the length of the buried wire tie was increased 67% from 45 mm to 75 mm, but the

pullout strength was increased by 6%, so the increase in length was not considered

significant. In Fig. 3-27 (b), the average pullout strength of the 45 mm and 75 mm

buried specimen in steel plate were 4.24 kN (3.08~5.08 kN) and 4.98kN (3.50~6.20

kN), with 17% increase in strength in the 75 mm buried specimens.

In Fig. 3-28 (a), the average strength of 80 mm wire tie with 45 mm buried, 100

mm wire tie with 45 mm buried, and 100 mm wire tie with 75mm buried were 4.54

kN (2.90~5.82 kN), 5.22 kN (2.38~8.02 kN), and 3.28 kN (2.50~4.18 kN)

respectively. For a 100 long wire tie, the average strength of 45 mm embedded

specimen was 59% stronger than that of 75 mm embedded specimen. This is because

the failure modes of the 75 mm buried specimen and the 45 mm buried specimen

Chapter 3. Material

55

were different. Two bricks were separated from the main failure mode of the 75 mm

buried specimen, and in the main failure mode of the 45 mm buried specimen, mortar

in the area where the wire tie was buried was destroyed while the bond of the brick

was maintained. Shape of DaeilTec's wire tie did not change depending on length,

so the test results of the specimens embedded same length were assumed to be same.

However, one of the specimen showed a strength that was well above the average

(8.02 kN, 154 % of average); a 100 mm long wire tie specimen showed 15% higher

average strength than that of an 80 mm long wire tie specimen. The mean, except

for one of the specimen showed a strength that was well above the average from the

mean, is 4.52 kN (2.38~5.68 kN). This is similar to the average strength of 80 mm

wire tie with 45 mm buried.

In Fig. 3-28 (b), the results of the test showed the pullout strength of the steel plate

increased with the increase of the buried length. The reason for this is that the size

of surface area appears to have played a major role in steel plate, since the wire tie

is settled in mortar in the form of hooks and the steel plate is settled with the adhesion

of the surface except for slight flection. The increase in strength according to the

length of the buried steel plate specimens is more noticeable in the test specimen of

Daeil Tec, as the steel plates in Samwon angle had hole, and the the steel plate of

Daeil Tec close to pure steel plate.

Chapter 3. Material

56

Fig. 3-27 Test results of Samwon angle’s connector

Chapter 3. Material

57

Fig. 3-28 Test results of Daeil Tec’s connector

Chapter 3. Material

58

Table. 3-5 Test results of the mechanical fastener pullout test

Samwon angle Daeil Tec

Type of connector Wire Plate Wire Plate

Dimension of connector (mm)

φ4 30 x 2 φ4 30 x 1.6

connector length (mm) 100 120 120 100 120 80 100 100 100 120

Embedded length (mm)

45 45 75 45 75 45 45 75 45 75

Pullout strength (kN)

1 4.36 3.26 3.80 4.76 3.50 4.50 4.74 4.02 2.86 3.68

2 4.32 2.78 4.06 5.08 6.20 5.58 2.38 4.18 3.76 4.80

3 3.52 2.78 3.60 4.04 5.74 2.90 5.68 2.50 3.18 5.68

4 4.64 5.34 4.06 3.08 4.48 3.90 5.26 2.90 3.70 4.66

5 3.34 5.72 5.62 - - 5.82 8.02 2.80 1.96 5.42

Average 4.04 3.98 4.23 4.24 4.98 4.54 5.22 3.28 3.09 4.85

Coefficient of Variance

0.14 0.36 0.19 0.21 0.25 0.27 0.39 0.23 0.24 0.16

Chapter 3. Material

59

3.4 Discussion

In the material test, the tests were carried out on expected failure modes to verify

the strength of each expected failure modes. The flexural test for the masonry was

performed for masonry specimen with 11MPa mortar joint. The pullout test for

mechanical fastener from concrete backing and for connector from mortar joint were

performed.

(1) In flexural test for the masonry, the average gross area modulus of rupture was

0.75 MPa. Assuming the worst-case scenario that could be applied to the

masonry veneer according to the following equation in “Seismic Building

Design Code”, the gross area modulus of rupture of veneer wall was

calculated. In the worst-case scenario (�� = 1, �� = 1.5, �� = 1.5, � =

0.54, � = ℎ ), the available vertical space between connectors was 2.04 m.

Because the limitation maximum vertical space between connector was 0.6 m,

it was determined that in exterior brick masonry wall, there would not be

failure by bending.

0.41 2p DS P

P

P

P

a S W zF

hR

I

= +

(3-2)

1.6P DS P PF S I W= (3-3)

0.3P DS P PF S I W= (3-4)

Where,

FP : Design seismic force acting on the center of mass of non-structural

element

Chapter 3. Material

60

aP : Amplification factor of non-structural elements

IP : Criticality factor of non-structural factor

h : Average height of the roof layer from the base of the structure

RP : Response correction factor for non-structural elements

SDS : The acceleration of the design spectrum in a short period

WP : Weight considering operating conditions of non-structural elements

z : Height with non-structural element attached to the underside of the

structure

Fig. 3-29 failure by bending check

(2) In the mechanical fastener pullout test for concrete backing, four type of nail

specimens and four type of plastic anchor specimens were tested, classified as

the length of the nails and the compressive strength of the concrete blocks.

The average strength of the nails was between 1,490 N and 1,848 N,

depending on the length and the compressive strength of the concrete. The

length of the nail in the 21 MPa concrete block affected the pullout strength,

Chapter 3. Material

61

but the length of the nail in the 35 MPa concrete block did not affect the

pullout strength. The strength of the plastic anchors was between 1,810 N and

2,098 N, depending on the compressive strength of the concrete and type of

plastic anchor. The compressive strength of concrete doesn’t affect to the

pullout strength of the plastic anchor. The COV for nails were 0.32 - 0.52 and

the COV for plastic anchors were 0.09 - 0.14. The range of the strength of the

nails is greater than the range of the strength of the plastic anchor, which has

more uncertainty in the strength.

(3) In the connector pullout test for mortar joint, the pullout strength of the

connector was between 3.09 kN and 4.98 kN. This is about twice the strength

of the mechanical fastener and the failure mode is the shear failure of mortar

and the extraction of connector.

(4) When comparing the results from (1) to (3), the failure mode of the anchorage

system were expected to be the failure of the mechanical fastener. The pullout

strength of embedded connector form mortar is twice the strength of the

mechanical fastener, so if two mechanical fastener are used, the two failure

modes (failure of mechanical fastener and failure of connector from mortar

joint) are expected to coexist.

Chapter 4. Cyclic Tests of Masonry Unit

62


4.1 Introduction

The anchorage system resists the lateral forces applied to the exterior non-

structural brick masonry wall. The load applied to the center of gravity of the exterior

non-structural brick masonry wall is transferred to the connector embedded in mortar

between bricks, and the veneer connector transferred load to the backing wall

connected by mechanical fastener. Therefore, flexural failure of the non-structural

masonry wall, pullout failure of connector from mortar joints, and the pullout failure

of the mechanical fastener were expected as a failure mode of exterior non-structural

brick masonry wall. The failure mode and strength of the anchorage system were

predicted through the results of preceding individual material test. However, unlike

material tests with vertical loads on the center of gravity, the strength and failure

modes may differ from the material test results because of the eccentricity depending

on the type of connector, the number of mechanical fasteners used in the connector,

and the presence of insulator. In order to predict the strength of the exterior non-

structural brick masonry wall, a test represent the anchorage system is needed. Thus,

before the test of masonry wall assembly, test of the masonry unit that represent local

part of exterior non-structural brick masonry wall, consisting of two brick, connector,

and a concrete block was preceded. The four failure modes of flexural failure of the

masonry wall, fracture of connector, pullout failure of mechanical fastener, and

pullout failure of connector from the mortar joint are expected. As a result of the test,

the strength of masonry unit was compared with the results of the material test.


63

4.2 Test plan

4.2.1 Variables

The major variables of the cyclic test of masonry unit test were classified with

type of connector, the use of insulator, and the number of mechanical fastener using

in connector as shown in Table. 4-1. Type I and C connectors were consist of wire

tie and stamped plate, and using two mechanical anchor to anchor. Type L and P

connectors were steel plate, and using one mechanical anchor to anchor. Type I and

L connector is directly touched and installed on the surface of the backing wall. Type

C connector is touched on the surface of insulator attached to backing wall and

installed in the surface of backing wall by 200 mm long plastic anchor. Type P

connector is installed on the backing wall by penetrating the insulator. Connectors

used with insulator shall either be penetrated the insulator by itself or the mechanical

fastener penetrated the insulator and secured to the backing wall (Fig. 1-5)

Table. 4-1 Variables of the cyclic loading test of masonry unit

No Specimen Connector Insulator Mechanical fastener Number of fastener

1 I-N-P55 Type I None Plastic anchor

(55 mm) 2

2 L-N-P55 Type L None Plastic anchor

(55 mm) 1

3 C-I-P200 Type C Installed Plastic anchor

(200 mm) 2

4 P-I-N30 Type P Installed Nail

(30 mm) 1


64

4.2.2 Test specimen

Masonry unit specimen was consisted of two brick, connector, and concrete block.

In order to avoid the effects of weather during the curing process of mortar, the test

specimens were constructed inside the container box (Fig. 4-1). The dimensions of

brick was 190 mm (width) x 90 mm (length) x 57 mm (thickness) and the thickness

of the mortar was 13 mm same as the thickness used in construction site. According

to the mechanical fastener installation recommendation and number of installed

mechanical fastener, two concrete blocks were made. The dimension of concrete

block is 140 mm (width) x 140 mm (length) x 120 mm (thickness) and 140 mm

(width) x 300 mm (length) x 120 mm (thickness). The small concrete block was

using for specimens with type L and P connector, which anchored the connector, by

using one mechanical fastener. The larger concrete block was using for specimens

with type I and C connector, which anchored the connector by using two mechanical

fasteners. The mechanical fasteners were installed at the centerline of the concrete

block so that the distances from the all edge of the concrete block were more than 70

mm. In specimens with type I and L connector, connector is embedded 45 mm in the

mortar joint and is installed to the concrete using 55 mm long plastic anchor. In

specimens with type C and P connector, connector is buried 45 mm in the mortar

joint and 155 mm of insulator is attached to the concrete block. In C-I-P200 specimen

with type C connector, 200 mm long plastic anchor penetrate the insulator and anchor

the connector to the backing wall. In P-I-N30 specimen with type P connector,

connector itself penetrate the insulator and 30 mm nail anchored the connector to the

backing wall. The section of the specimen is shown in the Fig. 4-2


65

Fig. 4-1 Fabrication of masonry unit specimen

Fig. 4-2 Section of masonry unit specimen

4.2.3 Test setup

The test setup was shown in Fig. 4-3. Pair of apparatus were constructed to secure

concrete block and brick part of specimen for repeated application of tensile and

compressive force. The masonry unit specimen was fixed to the upper and lower part

of the 2,000kN capacity universal testing machine (UTM). The lower apparatus fixed

the bricks to the bottom of the UTM and the UTM applied load to the upper apparatus

fixing concrete block.


66

Fig. 4-3 Test setup for the masonry unit test

4.2.4 Loading protocol

The cyclic loading was applied in two phases as shown in Fig. 4-4 in accordance

with ASTM C1201. First, 20, 40, 60, 80, and 100 percent of the expected capacity

(i.e. the results of material test) was applied in the load control. At each load step, 3

load cycles were repeated. Then, 150, 200, 300, and 500 percent of the displacement

at the expected capacity were applied in displacement control. However, yield

plateau occurred for all the specimens under the load control step. Then, 150, 200

percent of the displacement at the expected capacity were applied in displacement

control.


67

Fig. 4-4 Loading protocol in cyclic loading test

4.2.5 Setup for LVDP and strain gage

The LVDT and strain gage were installed as shown in Fig. 4-3 to check the load-

displacement relationship of the specimen. The displacement of concrete block was

measured by LVDT and deformation of connector was measured by strain gauge.

The LVDT and strain gage were installed in the same method for all specimen.


68

4.3 Test results

4.3.1 I-N-P55

In I-N-P55 with type I connector, the average peak strength was 3.51 kN

(0.50~4.78kN) with the coefficient of variation of 0.4. Fig. 4-5 to Fig. 4-7 shows the

load-displacement relationship of I-N-P55. The stiffness in tension direction and

compression direction were different due to the differences of resisting methods. In

tension, under cyclic loading, the wire tie and stamped anchor plate were loosened.

The large slips occurred in the load-displacement relationships (Fig. 4-5 to Fig. 4-7).

On the other hand, in compression, the lateral force was transferred by the contact

between the wire tie and the backing wall (Fig. 4-9). After reaching the maximum

load, the failure occurs with brittle manner. As expected from the results of the

material test, the failure modes of the pullout failure of connector and the pullout

failure of plastic anchor were coexisted (Fig. 4-8 (a) and (b)). Only three specimens

out of six specimens attained the pullout strength of mechanical fastener failure.

However, the other three specimens showed low strength due to the early pullout

failure of the embedded connector. Strength of the pullout of the connector from

mortar point failure was 1.4kN and 2.75kN, which were only 26% and 52%

performance compared to the results of the material test. This is because in the

masonry unit, under cyclic loading, the pullout strength of embedded connector was

lower than that of the material tests. Because the strength varies from failure mode,

showing large COV. The last specimen, failed due to a defect of the plastic anchor

(Fig. 4-8. (C))


69

Fig. 4-5 Load-displacement relationships of masonry unit specimens (I-N-P55

1 and 2)


70

Fig. 4-6 Load-displacement relationships of masonry unit specimens (I-N-P55 3

and 4)


71

Fig. 4-7 Load-displacement relationships of masonry unit specimens (I-N-P55 5

and 6)


72

Fig. 4-8 Failure mode of specimen (I-N-P55)

Fig. 4-9 Formation of reaction force of type I connector during tensile and

compressive force applied

4.3.2 L-N-P55

In L-N-P55 with type L connector, the average peak strength was 1.64 kN

(0.6~2.21kN) with the coefficient of variation of 0.24. Fig. 4-10 to Fig. 4-12 shows


73

the load-displacement relationship of L-N-P55. The stiffness in tension direction and

compression direction were different due to the differences of resisting methods. In

tension, under cyclic loading, the type L connector had a permanent deformation.

The slips occurred in the load-displacement relationships (Fig. 4-10 to Fig. 4-12). In

compression, the lateral load was transferred by the direct contact between the

connector and backing wall (Fig. 4-14). After reaching the maximum load, the

failure occurs with brittle manner. After failure, the strength decreases rapidly and

than the strength gradually decreases from rapidly decreased strength to zero until

all the embedded length of the plastic anchor is pulled out.(Fig. 4-13 (b)). As

expected from the results of the material test, for all specimen the failure modes was

of the pullout failure of connector (Fig. 4-13 (a)). Four specimen out of six attained

the pullout strength of plastic anchor or similar. Two specimens showed low strength

due to the bad quality of the plastic anchor. Average peak strength rate of masonry

unit specimen to material test specimen was 0.84.


74

Fig. 4-10 Load-displacement relationships of masonry unit specimens (L-N-

P55 1 and 2)


75

Fig. 4-11 Load-displacement relationships of masonry unit specimens (L-N-P55

3 and 4)


76

Fig. 4-12 Load-displacement relationships of masonry unit specimens (L-N-P55

5 and 6)


77

Fig. 4-13 Failure mode of specimen (L-N-P55)

Fig. 4-14 Formation of reaction force of type L connector during tensile and


4.3.3 C-I-P200

In C-I-P200 with C type connector, the average peak strength was 1.64 kN


78

(1.03~2.31kN) with the coefficient of variation of 0.32. Fig. 4-15 toFig. 4-17 shows

the load-displacement relationship of C-I-P200. Type C connector consists of a

stamped plate and wire tie, as type I connector, but the stiffness in tension direction

and compression direction were close to each other since both tension and

compression loads were resisted by bending of stamped plate. In C-I-P200, due to

the stamped plate is on the surface of insulator stamped plated can bended in both

direction (tension and compression). In both tension and compression, under cyclic

loading, the wire tie and stamped anchor plate were loosened. The large slips

occurred in the load-displacement relationships. After reaching the maximum load,

the failure occurs with brittle manner. After failure, the strength decreases rapidly

and then the strength gradually decreases from rapidly decreased strength to zero.

As expected from the results of the material test, the failure modes of the pullout

failure of connector and the pullout failure of plastic anchor were coexisted (Fig.

4-18 (a) and (b)). The first three specimens failed due to pullout of plastic anchor.

The other three specimen failed due to pullout of embedded connector. However, the

peak strengths did not reach the pullout strength obtained from the material test. This

is because in the masonry unit, it is very difficult to assure the straightness and the

embedded length of the plastic anchor because of the use of insulators. Further, under

cyclic loading, the pullout strength of embedded connector was lower than that of

the material tests. Because the strength varies from failure mode, showing large COV.


79

Fig. 4-15 Load-displacement relationships of masonry unit specimens (C-I-

P200 1 and 2)


80

Fig. 4-16 Load-displacement relationships of masonry unit specimens (C-I-P200

3 and 4)


81

Fig. 4-17 Load-displacement relationships of masonry unit specimens (C-I-P200

5 and 6)


82

Fig. 4-18 Failure mode of specimen (C-I-P200)

Fig. 4-19 Formation of reaction force of type C connector during tensile and


4.3.4 P-I-N30

In P-I-N30 with type P connector, the average peak strength was 1.65 kN


83

(1.46~1.85kN) with the COV of 0.17. Fig. 4-20 to Fig. 4-21 shows the load-

displacement relationship of P-I-N30. After reaching the maximum load, the failure

occurs with brittle manner (Fig. 4-19). The unit specimen was made inside the

container box because of the cold weather. Due to the bottom of the container box

absorbs the impact of the power-actuated tool, the nail failed to settle properly. Only

four specimens were tested because of the fabrication mistaken. The failure modes

were the pullout failure of mechanical fastener (Fig. 4-22 (a)) and failure of

connector itself (Fig. 4-22 (b)). The failure of connector itself did not occur in other

specimens, but in type P connector, the failure of connector itself occurred in narrow

section of type P connector. Particularly, the connector plate buckling occurred at

initial loading. Thus, the test specimens showed low capacity in the deformation as

well as the strength, because of the low performance of nails and the bucking of the

connector.


84

Fig. 4-20 Load-displacement relationships of masonry unit specimens (P-I-N30

1 and 2)


85

Fig. 4-21 Load-displacement relationships of masonry unit specimens (P-I-N30

1 and 2)


86

Fig. 4-22 Failure mode of specimen (P-I-N30)

Fig. 4-23 Formation of reaction force of type P connector during tensile and



87

4.4 Discussion

The test result of the masonry units were shown in Table. 4-2. In the test of

specimen without insulator (type I and type L) the peak strengths of the masonry unit

test were similar to the material test (115% and 84% respectively). On the other

hands in the test of specimen with insulator (type C and type P) the peak strengths

of the masonry unit test were about half (40% and 66% respectively). This is because

that the presence of the insulator caused early failure of the mechanical fasteners.


88

Table. 4-2 Test results of Cyclic tests of the masonry unit

Specimen I-N-P55 L-N-P55 C-I-P200 P-I-N30

Connector Type I Type L Type C Type P

Insulator None None Installed Installed

Mechanical fastener Plastic anchor Plastic anchor Plastic anchor Nail

Mechanical fastener length

(mm) 55 55 200 30

Embedded length (mm) 55 55 45 30

Number of fastener 2 1 F

1.202 1

Failure mode

Strength (kN)

1 M

1.40

F

1.80

F

1.03

F

1.85

2 F

4.31

F

0.60

F

1.60

F

0.45

3 M

2.75

F

1.10

M

2.26

F

0.45

4 F

4.78

F

1.50

M

1.46

F

-

5 F

4.31

F

2.21

M

2.31

C

1.46

6 F

0.50

F

1.60

M

2.31

F

-

Avg 3.51 1.64 1.64 1.65

COV 0.40 0.25 0.32 0.17

Fu,unit / Fu,material 0.90 0.84 0.40 0.61

Note: M : pullout of connector form the mortar joint, F : pullout of mechanical fastener, C : Failure of

connector, Fu,unit : Average pullout strength of masonry unit test, Fu,material : Average pullout strength of

material test

Chapter 5. Cyclic Tests of Masonry Wall

89


5.1 Introduction

A masonry wall is an assembly of several individual bricks placed on a mortar bed.

Because non-structural brick masonry wall does not resist horizontal force on its own,

connectors are embedded between the mortar beds to connect non-structural brick

masonry wall with a backing wall that can resist horizontal force. Several connectors

are used to transfer the horizontal force of masonry wall to the backing wall, and the

performance of the connectors in an exterior non-structural brick masonry wall may

differ from the performance of individual connector. According to Reneckis, in the

out-of-plane shaking table test, the masonry wall rotates around the base before crack

occurs in the masonry wall, thus, the gap between the masonry wall and backing wall

varies depending on masonry wall’s height. The gap at the top produces more

deformation than the gap at the bottom. This difference causes the difference of the

deformation of connector and un-uniformness of load distribution. Thus, cyclic

loading test for masonry wall assembly was conducted to investigate the reduced

strength of connector in masonry wall assembly by the effect of non-uniform load

distribution.

5.2 Test plan

5.2.1 Variables

The major variables of the cyclic test of masonry wall assembly were classified

with type of connector, the use of insulator, and the number of mechanical fastener

using in connector as shown in Table. 5-1. Type I and C connectors were consist of


90

wire tie and stamped plate, and using two mechanical anchor to anchor. Type L and

P connectors were steel plate, and using one mechanical anchor to anchor. Type I and

L connectors were directly touched and installed on the surface of the backing wall.

Type C connector is touched on the surface of insulator attached to backing wall and

installed in the surface of backing wall by 200 mm long plastic anchor. Type P

connector is installed on the backing wall by penetrating the insulator. Connectors

used with insulator shall either be penetrated the insulator by itself or the mechanical

fastener penetrated the insulator and secured to the backing wall (Fig. 1-5)

Table. 5-1 Variables of the cyclic loading test of masonry wall assembly

5.2.2 Test specimen

Considering the actual details in Fig. 1-3 and Fig. 1-4, Masonry wall assembly

specimen was consisted of masonry wall, 16 connectors, and concrete backing wall.

The size of brick was 190 mm (width) x 90 mm (length) x 57 mm (thickness) and

the thickness of the mortar was 13 mm same as the thickness used in construction

site. The dimension of concrete backing wall was 2500 mm (width) x 1350 mm

(height) x 300 mm (thickness) and the dimension of foundation was 3500 mm (width)

x 575 mm (height) x 1300 mm (depth) as shown in Fig. 5-2. The thickness of the

concrete backing wall was determined to install connector on both side of concrete

backing wall and the height of foundation was determined by considering the space

of holes in the reaction wall of the laboratory. The concrete compressive strength of

No 1 2 3 4

Specimen I-N-P55 L-N-P55 C-I-P200 P-I-N30

Connector Type I Type L Type C Type P

Insulator None None Installed Installed

Mechanical fastener Plastic anchor

(55 mm)

Plastic anchor

(55 mm)

Plastic anchor

(200 mm)

Nail

(30 mm)

Number of fastener 2 1 2 1


91

the backing wall was 35 MPa. In “Building Code Requirements for Masonry

Structures”, anchored brick masonry wall is required the weight of the masonry wall

shall be supported by noncombustible construction at each story above 9.14 m height.

To satisfy this requirement, the brick masonry wall, which laid on the level of 1st

floor, is supported by base and the brick masonry wall, which laid above 9.14 m

height, is supported by extended slab or shelf steel angle anchored to backing wall

as shown in Fig. 5-1. Two perpendicular brick masonry walls were possible

connected or separated at the corner. To prevent the crack on the brick masonry wall,

expansion joints were inserted in a span of less than 9 m. In this test, top and both

sides of brick masonry wall were open.

Fig. 5-1 Conventional masonry wall weight support mechanism

In “Seismic Building Design Code” for anchored masonry veneer specifications, at


92

least one connector is required per 0.25 m2 of wall area. Thus, the connectors were

anchored at a horizontal space of 700 mm and a vertical space of 335 mm (Fig. 5-2).

Total 16 connectors were used and one connector covered a wall area of 0.23 m2. For

I-N-P55 and C-I-P 200, a 100 mm wire tie (Fig. 1-5) was used. For L-N-P55, a 100

mm L shaped connector was used. The anchors embedded in the mortar joint was 45

mm long thus the gap between the inner face of the masonry wall and outer face of

the backing wall or insulator was 55 mm. For specimen P-I-N30, 275 mm long type

P connector and a 155 mm thick insulator were used. The connector embedded in

the mortar joint was 45 mm and thus, the gap between the inner face of the masonry

wall and outer face of the insulator was 30 mm. For specimen C-I-P55, a 200 mm

long plastic anchor used to penetrate the insulator and anchor the connector to the

backing wall. For specimen P-I-N30, a 275 mm long connector penetrated the

insulator with power-actuated tool and 30 mm nail anchored the connector to the

backing wall. The masonry wall was laid in running bond using mortar with

compressive strength of 11MPa. The lower part of veneer wall is installed on the

foundation and higher part of veneer wall is installed on extended slab or the veneer

support. To simulate masonry wall located more than two stories high, the masonry

veneer was installed on the shelf steel angle (Fig. 5-2). The section of the specimen

is shown in the Fig. 5-3. Fig. 5-4 show the process of making exterior non-structural

brick masonry wall specimens.


93

Fig. 5-2 Dimension of concrete backing and connector installation spacing

Fig. 5-3 Section of masonry wall specimen


94

Fig. 5-4 Process of making exterior nonstructural brick masonry wall

specimens.

5.2.3 Test setup

The test setup was shown in Fig. 5-5. In the present study, a “Whiffle tree” was

used to simulate uniformly distributed load to the masonry veneer wall through 32-

point loads. Following the study of McGinley3 and Jo4 “Whiffle tree” consisted of

one steel beam (H 350 x 350 x13 x 13), 30 steel tubes (two SHS 150 x 150 x 9, four

SHS 100 x 100 x 6, eight plus sixteen SHS 50 x 50 x 6), and 62 threaded rods (four

27 mm. rods, eight 20 mm. rods, sixteen 14 mm. rods, and thirty - two 8 mm. rods)

(Fig. 5-6). 32-point loads were spaced with space of 310 mm and at a vertical space

of 330 mm. The 'whiffle tree' and the veneer were connected by adhesive anchors

for the load transfer. The installed “Whiffle tree” and typical connection between

steel tubes were shown in Fig. 5-7


95

Fig. 5-5 Tests set up of cyclic loading test for exterior nonstructural brick

masonry wall assembly

Fig. 5-6 Dimension of “Whiffle tree”


96

Fig. 5-7 Installation of “Whiffle tree”

Fig. 5-8 Point load spacing, boundary condition, and connector cover area


97

5.2.4 Loading protocol

The cyclic lateral loading was applied in two phases as shown in Fig. 4-4 in

accordance with ASTM C1201.13 First, 20, 40, 60, 80, and 100 percent of the

expected capacity (i.e. the results of material test) was applied in the load control. At

each load step, 3 load cycles were repeated. Then, 150, 200, 300, and 500 percent of

the displacement at the expected capacity were applied in displacement control.

However, yield plateau occurred for all the specimens under the load control step.

Then, 150, 200 percent of the displacement at the expected capacity were applied in

displacement control.

5.2.5 Setup for LVDT and strain gage

LVDT and strain gage were installed as shown in Fig. 5-5 to check the load-

displacement relationship of the specimen. Total 12 displacements were installed in

the masonry wall specimen. As same height of connectors were connected, 6

displacements were installed at the outer faces of exterior non-structural brick

masonry wall and 6 displacement were installed at the opposite faces of concrete

backing wall (Fig. 5-9). 16 strain gauges were attached to each connectors to

estimate the force distribution. Fig. 5-10 show the attachment location of strain

gauges.


98

Fig. 5-9 LVDT installation location

Fig. 5-10 Attachment location of strain gauges

5.3 Test results

5.3.1 I-N-P55

In I-N-P55 with I type connector, the peak strength was +27.48 kN and -57.92 kN

in the tension and compression directions, respectively (Fig. 5-11). Sum of 16

anchorage systems capacity also presented in Fig. 5-11. The compression was


99

transmitted by the contact between the wire tie and the backing wall, on the other

hand, in tension, a large slip occurred because of the gap between the wire tie and

the stamped plate. Thus, the stiffness and strength in the tension and compression

directions were significantly different. Bending occurred in the stamped plate under

tension. After reaching the maximum load, drastic decrease of strength was not

observed.

Fig. 5-11 Load-displacement relationships of masonry unit specimens (I-N-

P55)

5.3.2 L-N-P55

In L-N-P55 with type L connector, the peak strengths in the tension and

compression direction were +9.41 kN and -34.58kN, respectively (Fig. 5-12). Sum

of 16 anchorage systems capacity also presented in Fig. 5-12. The tensile strength

were determined by the fastener. The stiffness in the tension and compression


100

direction were different due to the different resisting methods. The compression

force was transferred by the contact between connector and backing wall. The

Bending occurred in the type L connector under tension.

Fig. 5-12 Load-displacement relationships of masonry unit specimens (L-N-

P55)

5.3.3 C-I-P200

In C-I-P200 with type C connector, the peak strengths in the tension and

compression direction were +12.41 kN and -46.01 kN respectively (Fig. 5-13). Sum

of 16 anchorage systems capacity also presented in Fig. 5-13. Because of the

insulators, the stiffness and strength were less than those of I-N-P55. Both tension

and compression load were resisted by bending of stamped plate. Further,

deformation in compression was also large due to the insulators.


101


P200)

5.3.4 P-I-N30

In P-I-N30 with type P connector, the peak strength was +11.22 kN and -10.57 kN

in the tension and compression directions (Fig. 5-14). Sum of 16 anchorage systems

capacity also presented in Fig. 5-14. The type P connector was buckled, the strength

was lower in compression than in tension. The pullout failure of nail occurred in

tension. The test specimens showed low capacity in the deformation as well as the

strength, because of the low performance of nails.


102


P200)

5.4 Discussion

The test results were summarized in Table. 5-2. I-N-P55 with two plastic anchors

and without insulator showed the greatest strength 27.48 kN. In tension the tensile

strength of the C-I-P200 with two plastic anchors with insulator was 12.41kN,

showing 45% strength of the I-N-P55. The comparison results of two specimens

showed that the presence of insulator reduces the strength of the masonry wall. L-

N-P55 with one anchor showed only 34% of the strength of I-N-P55. P-I-N30

specimen was nails, showed the lowest tension direction deformation. Further, due

to buckling of connector, the compressive strength was lower than the tensile

strength. When Compared with the results of the masonry unit test results, there was

no significant change in the presence of insulator as the test results in masonry unit


103

tests already included variables for insulator. Compared with the results of material

tests that did not reflect the effects of insulator, the strength of the masonry veneer

wall was reduced more than in the absence of insulator. In type P specimen with nail,

the failure occurred in significantly smaller displacements than those of other

specimens.

Based on the test results for masonry unit and for masonry veneer wall assembly,

the relationships between the peak strength of masonry veneer wall to the peak

strength of masonry unit pullout strength Fu,wall/Fu,unit was shown in Table. 5-2

The strength ratios Fu,wall/Fu,unit were less than 49 % (36%~49%) as shown in Table.

5-2. In the masonry wall, the displacement of the veneer wall varied with its height

of the specimens. Thus, while the load-carrying capacity of the connector at the top

row reached to the maximum load, in connectors at different heights, it did not reach

the maximum load. In a horizontal direction, difference of connector cover area made

a non-uniform force distribution. Because individual anchorage systems are brittle,

anchorage systems do not reach the maximum strength at the same time. Accounting

for these non-uniform distributions, the design capacity of the masonry veneer wall

assembly should be as less than half the sum of anchorage system capacities.


104

Table. 5-2 Test results of cyclic test of the masonry wall unit

Notes: M : Pullout of connector from mortar joint, F : Pullout of mechanical fastener, Fu, wall : Test result of masonry wall test, Fu, unit : Average pullout strength of 16 masonry unit,

Fu, material : Average pullout strength of 16/32 material

Specimen Veneer anchor Insulator Mechanical fastener

(embedded length) Number of fastener

Test results

Failure mode Strength (kN) Fu, wall /

Fu, material

Fu, wall /

Fu, unit

I-N-P55 Type I None Plastic anchor

(55 mm) 2 F 27.48 0.44 0.49

L-N-P55 Type P None Plastic anchor

(55 mm) 1 F 9.41 0.30 0.36

C-I-P200 Type C Installed Plastic anchor

(200 mm) 2 F 12.41 0.19 0.47

P-I-N30 Type P Installed Nail

(30 mm) 1 F, M 11.22 0.26 0.42

Chapter 6. Design of Exterior Non-structural Brick Masonry Wall

105


Through the tests in Chapter 4~6, it was confirmed that the strength of the exterior

non-structural brick masonry wall is affected by the strength of mechanical fastener,

the type of connector, the use of insulator, and the in installation space of connector.

To design the exterior non-structural brick masonry wall, capacity of individual

anchorage system and effect of spacing should be determined. Design seismic force

demand can be calculated according to “Seismic Building Design Code”. By

comparing the design seismic force and the anchorage system capacity the number

of connectors were decided.

6.1 Anchorage system capacity (Funit)

Anchorage system capacity (Funit) can be decided by using the material capacity

or test results of cyclic test of the masonry unit.

6.1.1 Material capacity

In anchorage system, failure modes were pullout of mechanical fastener and

pullout of embedded connector. Both failure modes showed big COV and brittle

failure mode like anchor. Material capacity can be decided by using the test results

of material test. Because of high COV, material capacity should be based on the 5

percent fractile of the basic individual material strength as in the test for anchor’s

nominal strength.

Anchorage system capacity (Funit) can be decide by using material capacity or the

test results of cyclic test of the masonry unit. When using material capacity type of


106

connector, presence of insulator, and the number of mechanical fasteners should be

considered. Anchorage system capacity without insulator and anchorage system

capacity with insulator of 155 mm or less in thickness can be calculated following

equation.

unit materialF nFβ= (6-1)

Where,

β : Connector factor

n : Number of mechanical fastener

Reflecting the test results of the chapter 3 and 4, β is 0.8 for an anchorage

system without insulator and β is 0.4 for an anchorage system with insulator of

155 mm or less in thickness. In the case insulator thickness more than 155 mm,

anchorage system capacity should be decided by test. Funit must be less than the

capacity of the material capacity of the embedded connector.

6.1.2 Anchorage system capacity

For new type of connector and the case of connector with insulator thickness more

than 155 mm, anchorage system capacity should be decided by test. As like material

capacity, anchorage system capacity should be based on the 5 percent fractile of the

basic individual material strength as in the test for anchor’s nominal strength.


107

6.2 Brick masonry wall capacity (Fwall)

In exterior non-structural brick masonry wall, several connectors connect the brick

masonry wall and the concrete backing wall. The test result of chapter 6 shows that

when using group of connectors the capacity was reduced due to non-uniform force

distribution and brittle failure mode of anchorage system. This non-uniform force

distribution occurred by the difference of connector cover area and the boundary

condition of masonry wall. Because of the dimension of brick vertical space was

limited to a multiple of 200 mm. Horizontal spacing was not limited by dimension

of brick, but the convenience of construction, multiple 100 mm space were used.

These vertical and horizontal spaces make differences in connector cover area at the

center, edge, and corner of the exterior non-structural masonry wall. For a brick

masonry wall the expansion joints were inserted in a span of less than 9 m and brick

masonry wall was separated in a vertical direction due to the shelf steel angle

installed on each floor to share the load of the masonry wall. By considering these

construction practice, boundary conditions of brick masonry wall at the top and both

side were open and the condition at the bottom were between hinge and roller support.

When uniform distributed load was applied in brick masonry wall, these boundary

conditions made brick masonry wall rotating about its base.

wall unitF Fγ= (6-2)

Where,

γ : Non-uniform distribution factor, 0.33


108

Non- uniform distribution factor (γ ), was decided by most unfavorable condition

of connector. When connectors were arranged equally spaced in a horizontal row, in

the most unfavorable case, the connector at the both side ends can be half the

connector cover area located in the center. The connector in the center reached its

capacity and failed before the connectors in both ends. When the three connectors

were located at the center and both ends of the wall, the ratio of the capacity of brick

masonry wall to that of the sum of anchorage system capacity was the lowest. In this

case, the brick masonry wall capacity was the 66 % of the sum of anchorage system

capacity. When connectors were arranged equally spaced in a vertical row, due to the

rotation of brick masonry wall the connector in the top reached its capacity and failed

before the connectors in other locations. When the number of connectors installed in

brick masonry wall were increased, the ratio of the capacity of brick masonry wall

to that of the sum of anchorage system capacity was decreased up to 50%.

Considering unfavorable horizontal and vertical arrangement condition, the Non-

uniform distribution factor (γ ) was decided to 0.33.

6.3 Design seismic force (Fp)

Design seismic force of exterior non-structural brick masonry wall can be

calculated by using equations in “Seismic Building Design Code”. In these equations,

types of non-structural elements should be classified to decide amplification factor,

reduction factor, and overstrength factor. Exterior non-structural brick masonry wall

can be classified as veneer. When the ductility capacity of exterior non-structural

brick masonry wall was unknown, amplification factor, reduction factor, and

overstrength factor should be used for low deformation capacity member and


109

attachment. When the ductility capacity of exterior non- structural brick masonry

wall was known by test, amplification factor, reduction factor, and overstrength

factor should be used for member and attachment with limited deformation.

6.4 Discussion

When using the equation in 6.2 and the average cyclic test results of the masonry

wall, the brick masonry wall capacity can be calculated. The brick masonry wall

capacities with 16 type I, L, C, and P connectors and the test results of cyclic test of

the masonry wall assembly were summarized in Table. 6-1. Due to the non-uniform

distribution factor decided with assumption of the most unfavorable condition all

design capacities were lower than that of test results.

Table. 6-1 Design capacity and tests results of masonry wall assembly

Specimen I-N-P55 L-N-P55 C-I-P200 P-I-N30 Brick masonry wall capacity (Fwall,kN) 18.72 8.75 8.75 8.80

Test results of cyclic tests of the masonry wall assembly (Fu,wall, kN)

27.48 9.41 12.41 11.22

Fwall / Fu,wall 68 % 93 % 70 % 78 % Notes: F wall = Design pullout strength of masonry unit, Fu, wall = Tested pullout strength of masonry wall

Chapter 7. Conclusion

110


In this study, for design the exterior non-structural brick masonry wall, following

studies were conducted on the level of material, masonry unit, and masonry wall

assembly. Relationship between the results of material test, unit test, and wall

assembly test is shown in Fig. 7-1.

[1] In the level of material, to acquire the properties of the materials, flexural test

for masonry, pullout test for mechanical fastener, and pullout test for embedded

connector were conducted.

Gross area modulus of rupture was presented by flexural test for masonry. This

test result showed that the possibility of bending fracture of brick masonry wall was

low.

In the pullout test for mechanical fastener, 4 type of mechanical fasteners (20 mm

nail, 32 mm nail, 55 mm plastic anchor, 200 mm plastic anchor) were tested. The

test results showed that the strengths of nail were lower than that of plastic anchor

and the Cov of nail were larger than that of plastic anchor. The use of a plastic anchor

was recommended because it is superior in both strength and deviation. When using

the nails, it is recommended to use two or more nails to prevent low strength.

The pullout strength of embedded connector was presented by pullout test of

embedded connector. Two type of connector ends (wire tie and steel plate) were test.

The pullout strength of embedded connector was bigger than that of mechanical

fastener. In case of wire tie (type I and C connectors), the pullout strength was more


111

than twice of pullout strength of plastic anchor and in case of steel plate (type L and

P connectors), the pullout strength was more than pullout strength of plastic anchor.

Through this, the failure mode of anchorage system and the strength of anchorage

system were expected and in order to take into account the large variation in the

results, material capacities should be based on the 5 percent fractile of the basic

individual material strength.

[2] In the level of masonry unit, the masonry unit specimens comprising two

bricks, a wood stud, and a connector were tested to capture the local performance of

exterior non-structural brick masonry wall systems rather than of just the connector

itself. 4 type of connectors (type I, L, C, and P connector) were tested to investigate

the difference by type of connectors. Test results showed that strength of anchorage

system was proportional to the number of mechanical fasteners and pullout strength

of mechanical fastener.

When using insulator, presence of insulator decrease the strength of anchorage

system less than that of material test 66 % (40 ~ 66 %). This is because that the

presence of the insulator caused early failure of the mechanical fasteners.

Due to the anchorage systems showed large COV (0.17~0.40), the anchorage

system capacities should be based on the 5 percent fratile of the basic individual

material strength. The failure mode of anchorage system showed brittle failure.

[3] In the level of masonry wall assembly, to investigate the non-uniform force

distribution through brick masonry wall, cyclic tests of the masonry wall assembly

were conducted. Test results showed that the peak strengths of masonry wall

assembly were less than 49 % (36~ 49%) than that of anchorage system. This is

because non-uniform force distribution made by boundary condition of brick


112

masonry wall and difference in connector cover area.

By measuring the displacement by height, the difference of deformation according

to height was verified. The masonry wall assembly showed the ductility due to the

redistribution of force after the failure of the most stressed connector.

Through these results, the design capacity of brick masonry wall capacity was

proposed. The anchorage system capacity was determined account for number of

fasteners and the presence of insulator. The brick masonry wall capacity was

determined account for the non-uniform distribution of force. By using cyclic tests

for the masonry wall assembly, it was proposed that after verifying the ductility

capacity, masonry wall assembly could be applied as a member and attachment with

limited deformation.

In this study, for design the exterior non-structural brick masonry wall, studies on

the out-of-plane strength of exterior non-structural brick masonry wall were focused.

However, further studies are needed besides included in this study. In addition to the

in-plane strength of exterior non-structural brick masonry wall, interaction of out-

of-plane and in-plane loading, and the effect of rapid repetition should be considered.

These considerations are expected to be addressed in future studies.


113

Fig. 7-1 Relationship between the results of tests

References

114

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Experimental study on the mechanical performance of steel ties for brick

masonry veneers. In 16th International Brick and Block Masonry

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performance of brick veneer walls on wood frame

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[4] McGinley, W. M., & Hamoush, S. (2008). Seismic Masonry Veneer:

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[9] ASTM D1761-12 (2014). Standard Test Method for Mecanicla

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Energy Conservation Design Standards. Building Energy Conservation

Design Standards, Korea.

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콘크리트 지지벽에 고정된 치장조적벽돌벽의

반복하중실험

권 종 훈

서울대학교 건축학과 대학원

치장 벽돌벽은 매력적인 외형, 단열성능, 방수 효과로 한국에서

선호되는 외장재다. 치장벽돌벽은 주택, 학교시설 등 다양한 건물에서

사용된다. 치장 벽돌벽은 연결철물과 못, 칼블럭 등을 사용하여 지지벽에

연결된다. 연결철물은 수평방향 하중을 치장 벽돌벽에서 지지벽으로

전달한다. 이때 치장 벽돌벽의 자중은 기초 또는 연장된 슬래브, 또는

지지벽에 연결된 앵글을 통해 지지벽으로 전달된다.

최근 한국에서 발생한 두 차례의 지진에서 진원진 인근 건물에서

외부 치장 벽돌벽이 심하게 파손되었다. 이에 따라 “건축물 내진설계

기준”에 외부 치장 벽돌벽에 대한 내용이 포함되었다. 이 기준에서, 외부

치장 벽돌벽은 사양설계를 만족하도록 연결철물을 배치하거나 역학

원리에 부합하도록 치장 벽돌벽의 강도와 지진하중을 계산하여

설계하도록 하고 있다. 사양설계의 내용을 검증하기 위하여 나무

샛기둥과 강재 샛기둥에 연결된 치장 벽돌벽의 성능 실험이

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진행되었지만 콘크리트벽체에 연결된 치장 벽돌벽의 성능실험은

진행되지 않았다. 따라서 기준에서 제시한 내진설계의 적합성을

검증하기 위해 콘크리트 벽체에 연결된 치장 벽돌벽의 성능을

평가하기위한 실험이 필요했다.

본 연구에서는 치장 벽돌벽의 성능을 평가하는 데 필요한 실험

단위를 조사하귀 위해 구조체 정착부 뽑힘실험, 연결철물 뽑힘실험, 치장

벽돌 유닛 반복하중실험, 치장 벽돌벽체 반복하중 실험을 수행하였다.

치장 벽돌 유닛 실험체는 치장벽돌벽의 연결철물 연결부를 재현하였으며

벽돌 2개, 연결철물 1개, 그리고 콘크리트 블록으로 구성되었다. 치장

벽돌벽체 실험체는 외부 치장 벽돌벽, 16개의 연결철물, 콘크리트

지지벽으로 구성되었다. 실험의 변수는 연결철물의 종류, 단열재의

사용여부 및 연결철물의 고정 방법이었다. 구조체 정착부 뽑심실험과

연결철물 뽑힘실험의 결과로 치장 벽돌 유닛 반복하중 실험의 결과를

예측하였다. 단열재를 사용한 경우 벽돌 유닛 반복하중 실험체의 강도는

현저히 감소되었다. 치장 벽돌벽체 반복하중실험에서는 균일하지 않은

힘 분포로 인해 치장 벽돌벽의 최대 강도는 설치된 벽돌 유닛의 강도의

합의 약 절반으로 감소하였다.

벽돌 유닛 반복하중 실험 결과에 근거하여, 연결철물 시스템의 강도를

제안하였다. 두 가지 실험 결과를 바탕으로 외부 치장 벽돌벽의 강도가

제안되었다.

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주요어 : 치장 벽돌벽, 연결철물, 반복하중실험

학 번 : 2018-27982

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