EFFECT OF MASONRY INFILL ON NONLINEAR · PDF fileeffect of masonry infill on nonlinear...

EFFECT OF MASONRY INFILL ON NONLINEAR

STRUCTURAL PERFORMANCE OF SCHOOL

BUILDINGS IN EGYPT AGAINST LATERAL

LOADS

FACULTY OF ENGINEERING, CAIRO UNIVERSITY

GIZA, EGYPT

2012

By

Eng. Nourhan Osama Hanafy Mahmoud

A Thesis Submitted to the Faculty of Engineering at Cairo University

In Partial Fulfillment of the Requirements for the Degree of

MASTER OF SCIENCE

In

Structural Engineering




LOADS


GIZA, EGYPT

2012

By




MASTER OF SCIENCE

In


Under the Supervision of

Prof. Dr. Mohamed Talat Mostafa Professor of Reinforced Concrete Structures

Faculty of Engineering

Cairo University

Dr. Islam Mohamed El-Habbal Lecturer of Structural Engineering

Higher Technological Institute

6 Oct. Branch




LOADS


GIZA, EGYPT

2012

By




MASTER OF SCIENCE

In


Approved by the Examining Committee,

…………………………………………………

Prof. Dr. Mohamed Talat Mostafa

Professor of Concrete Structures, Faculty of Engineering,

Cairo University

…………………………………………………

Prof. Dr. Mohamed El-Said Issa

Professor of Concrete Structures,

Head of Structural Engineering Dept., Faculty of Engineering,

Cairo University

…………………………………………………

Prof. Dr. Hatem Hamdy Ghith

Professor of Concrete Structures,

Housing and Building National Research Center

i

ABSTRACT

During the past few decades, it was a common practice in Egypt to design

and detail medium rise building to resist gravity loads only with no

consideration to any lateral load caused by wind or earthquakes. The amount of

damage observed in reinforced concrete buildings during the October 12th

1992 earthquake pointed out the urgent need to consider these forces in design

and detailing. Post earthquake field investigations in most earthquake regions

in the world demonstrated that school buildings are notably vulnerable due to

their typical architectural pattern. Numerous school buildings in Egypt were

damaged in past earthquakes with different levels of damage. Damage in

school buildings is attributed to their standard architectural profile

characterized by openings in the longitudinal direction and partition walls in

the transversal direction. Common failure patterns such as failure in the

longitudinal direction due to lack of walls, short-column effect due to constrain

by windowsills, and weak beam-column connections due to non-ductile

reinforcement are found during site inspections of old existing schools. In this

study, Push-over analysis for all known types of school building in Egypt is

used to determine their seismic capacity through inter-story drifts. The

structural evaluation was based on 2-D nonlinear push-over analysis using the

computer non-commercial software package SeismoStruct ver.5.2.1 developed

by SeismoSoft Ltd. Variables was studied in the types of bricks used in

construction, the thickness of the walls of buildings, brick buildings on the

distribution of roles, in addition to details of dimensions and shapes of the

holes and places in the building bricks. And has been studying the impact of the

above-mentioned variables on the values of natural frequency of buildings, and

the values of energy lost in the form of formations, as well as the distribution of

formations on the height of the building. Results were compared with levels of

performance contained in FEMA-365. According to this research, can be listed

and the preferred type of bricks used in building walls and thick to ensure the

best performance of seismic as follows: School buildings type (1), They are

ii

composed of a row of classes attached to cantilever corridor. The

columns’ main direction is arranged in the building’s short direction , in

the case of partial infilled at all floor except the ground floor is to be the best

type of cement bricks with 12 cm thickness, and also in the case of fully

infilled at all floor except the ground floor is to be the best type of cement

bricks with 25 cm thickness, and Finally, in the case of fully infilled at all floor

with the ground floor is to be the best type of red solid brick with 25 cm

thickness. School buildings type (2) is composed of two adjacent spans,

one for the corridor and the other for the class. The corridor span is

supported with square columns at the outer edge, in the case of partial

infilled at all floor except the ground floor is to be the best type of hollow red

bricks with 25 cm thickness, and also in the case of fully infilled at all floor

except the ground floor is to be the best type of hollow red bricks with 25 cm

thickness, and Finally, in the case of fully infilled at all floor with the ground

floor is to be the best type of red solid brick with 25 cm thickness. School

buildings type (3) is similar to buildings type (1) in the structural system

while different in the columns’ arrangement. Columns lying on even

axes are oriented in the building’s short direction, or vice versa , in the

case of partial infilled at all floor except the ground floor is to be the best type

of red solid bricks with 12 cm thickness, and also in the case of fully infilled at

all floor except the ground floor is to be the best type of red solid bricks with

12 cm thickness, and Finally, in the case of fully infilled at all floor with the

ground floor is to be the best type of red solid brick with 25 cm thickness. School buildings type (4) is composed of two classes and one corridor in

the same row. The columns’ arrangement is similar to the used

arrangement in type (3), in the case of partial infilled at all floor except the

ground floor is to be the best type of red solid bricks with 12 cm thickness, and

also in the case of fully infilled at all floor except the ground floor is to be the

best type of hollow red bricks with 25 cm thickness, and Finally, in the case of

fully infilled at all floor with the ground floor is to be the best type of hollow

red brick with 25 cm thickness.

iii

ACKNOWLEDGMENT

First of all, thanks to God for his grace and mercy, and for giving me the effort

to complete this work.

I am grateful for God for giving me my husband engineer Ahmed M. EL-

Mawan and his mother Dr. Marvat Ezzat that they supported me thanks for

them.

I appreciate the support of my professors, I was fortunate enough to carry out

this work under the supervision of Dr. Islam Mohamed El-Habbal for his

generous help, and it was a great honor to work with great professor like Prof.

Dr. Mohamed Talaat Mostafa.

Also, I am grateful for Dr. Saied El-Kholly thank for him. Finally, I would like

to thanks God that supported me to do this study hoping that someone can

develop it.

iv

TABLE OFCONTENTS

Page

ABSTRACT…………………………………………………………… i

ACKNOWLEDGMENT…………………………………………….… iii

TABLE OF CONTENTS……………………………………………… iv

LIST OF TABLES…………………………………………………….. ix

LIST OF FIGURES……………………………………………………. xi

CHAPTER (1): INTRODUCTION

1.1 General…………………………………………………………… 1

1.2 Objectives………………………………………………………… 2

1.3 Thesis Outlines……………………………………………………. 3

CHAPTER (2): THEORETICAL BACKGROUND AND

LITERATURE REVIEW

2.1 Introduction……………………………………………………….. 4

2.2 Theoretical Background…………………………………………... 5

2.2.1 Push-over Analysis………………………………………... 5

2.2.1.1 Description of Pushover Analysis………………. 5

2.2.1.2 Modal Pushover Analysis………………………... 6

2.2.1.3 Lateral Loading Pattern………………………….. 9

2.2.1.4 Effect of Loading Pattern On Push-over Analysis

Results……………………………………………...

10

2.2.2 Modeling Of Masonry Infill Wall…………………………. 15

2.2.2.1 Description of The Bare Frame and Infilled

Frames………..…………………………………….

15

2.3 Literature Review…………………………………………………. 20

v

2.3.1 Push-over Analysis………………………………………… 20

2.3.2 Effect of Infill on Seismic Resistance of Reinforced

Concrete Frames…………………………………....................

26

2.3.3 Modeling Of Masonry Infill Wall…………………….......... 31

CHAPTER (3): NUMERICAL MODELING OF SCHOOL

BUILDINGS FRAMES

3.1 Introduction ………………………………….……………………. 54

3.2 Properties Of The Examined Models………………………............ 55

3.2.1 Geometrical Description……………………………………. 55

3.3 Modeling of Material Behavior……………………………………. 56

3.4 Used Push-over Loading Pattern……………………………........... 57

3.5 Modeling Strategies For School Building Frames…….................... 58

3.6 Numerical Model Input Procedure………………………………… 61

3.6.1 Input Procedure for Bare Frames……………………………. 61

3.6.2 Input Procedures for infilled frame……….............................. 62

CHAPTER (4): NUMERICAL ANALYSIS RESULTS OF SCHOOL

BUILDINGS R/C FRAMES

4.1 Introduction ………………………………………………………. 81

4.2 Analysis Results For School Buildings Frames............................... 81

CHAPTER (5): DISCUSSION OF NUMERICAL RESULTS

5.1 Introduction……………………………………………………….. 141

5.2 Effect Of Studied Parameters On Structural Fundamental

Period……………………………………………………………....

141

5.3 Effect Of Studied Parameters On Structural Ductility…………….. 142

5.4 Effect Of Studied Parameters On Story Drift………………............ 143

CHAPTER (6): SUMMARY AND CONCLUSIONS

6.1 Introduction ………………………………………………………. 165

6.2 Summary …………………………………………………............. 166

vi

6.3 Conclusions……………………………………………………….. 169

6.4 Recommendations for Future Research …………………….......... 171

References……………………………………………………………… 172

ix

List of Tables

Table 2. 1 Design spectrum according to ECP-2003……………………….15

Table 2.2 Push Over Analysis Results…………………………………...30

Table 4.1 (a)Percentage change of fundamental period for model (1) with 12

cm wall thick………………….………………………………….131

Table 4.1 (b) Percentage change of fundamental period for model (1) with 25

cm wall thick ……………………..………………………….…..131

Table 4.2 (a) Percentage change of fundamental period for model (2) with 12

cm wall thick……………….………………….…………………132

Table 4.2 (b) Percentage change of fundamental period for model (2) with 25

cm wall thick………………………………….…………………132

Table 4.3 (a) Percentage change of fundamental period for model (3) with 12

cm wall thick…………………………………….……..….……133

Table 4.3(b) Percentage change of fundamental period for model (3) with 25

cm wall thick………………………………….…………………133

Table 4.4 (a) Percentage change of fundamental period for model (4) case (1)

with 12 cm wall thick…………..………………………………..134

Table 4.4 (b) Percentage change of fundamental period for model (4) case (1)

with 25 cm wall thick…………..………………………………..134

Table 4.5 (a) Percentage change of Absorbed Energy for model (1) with 12 cm

wall thick….………………………………………………….….135

Table 4.5 (b) Percentage change of Absorbed Energy for model (1) with 25 cm

wall thick…….…………………………………………………..135


wall thick………………………………………………………...136


wall thick.......................................................................................136

x


wall thick………………………………………………………...137


wall thick………………………………………………………...137

Table 4.8 (a) Percentage change of Absorbed Energy for model (4) case (1)

with 12 cm wall thick………………………………………..…..138

Table 4.8 (b) Percentage change of Absorbed Energy for model (4) case (1)

with 25 cm wall thick………………………………………..…..138


with 12 cm wall thick……………………………………..……..139


with 25 cm wall thick……………………………………..……..139


with 12 cm wall thick…………………………..………………..140


with 25 cm wall thick…………………………...…………….…140

Table 5.1 Inter-story Drift Limit States (ASCE 2000)………...…………...143

xi

List of Figures

Fig. 2. 1 Global Capacity (Pushover) Curve of a Structure ………….........……..42

Fig. 2.2 View, plan, and typical reinforcement of the columns of the example

structures…………………………………….…………………….………….42

Fig. 2.3 The moment–rotation relationship for the plastic hinges in the columns

and beams, and the force–displacement relationship for the diagonal struts

representing the masonry infill…….……………….………………...…….43

Fig. 2.4 The force–displacement relationships of the diagonal struts

(incompression), measured in the horizontal direction….……………...43

Fig. 2.5 Calculated and experimental time-histories for the third-storey drift of the

bare frame, and for the first-storey drift of the partially infilled

frame…….........................................................................................................44

Fig. 2.6 Calculated and experimental storey shear versus storey drift relationships

for the bare frame (third storey), and for the partially infilled frame (first

storey)………………………………………………………………………....44

Fig. 2.7 Pushover Curves for all models……………………………………….….…45

Fig. 2.8 Plastic hinges…………………………………………….…………………....46

Fig. 2.9 Displacement versus Story Number for all Models of Structures…….…47

Fig. 2.10 Relative Displacements for all Models of Structure……………….........47

Fig. 2.11 Max. Plastic Hinge Rotation for all Models of Structures……………...48

Fig. 2.12 Envelope of the constitutive law…………………...……………………...48

Fig. 2.13 Force vs. displacement in an empty frame under monotonic loading (a)

Test (b) Numerical simulation with Abaqus…………..…...……….…....49

Fig. 2.14 Force vs. displacement in an infilled frame under monotonic loading (a)

Test (b) Numerical simulation with Abaqus….……...………………......50

Fig. 2.15 Force vs. displacement under cyclic loadings (a) _ D 2 (b) _ D 5 (c) _ D

1…………………………………………………….……………………..…..51

Fig. 2.16 Force vs. displacement in an empty frame under cyclic loading (a) Test

(b) Numerical simulation with Abaqus………….…….………………..….52

Fig. 2.17 Fluency moment vs. Plastic rotation……………..…………………....….52

xii

Fig. 2.18 Force vs. displacement in an infilled frame under cyclic loading (a) Test

(b) Numerical simulation with Abaqus………………………..…………53

Fig. 2.19 Parametric study on the softening parameters for rn = 0.1 MPa (a) α = 100

m_1; and (b) α= 1000 m_1……………………...…………………….......53

Fig. 3.1 (a) School Building Type (1)………………………….………………….63

Fig. 3.1 (b) School Building Type (2).....…………………...…………………….64

Fig. 3.1 (c) School Building Type (3)…………………………………..…………65

Fig. 3.1 (d) School Building Type (2) ……….………...………………...…….…66

Fig. 3.2 Details of Type (1),(3) Geometry and Reinforcement of Beams and

Columns used in the Investigated Frames (Before 1992)……….……...67

Fig. 3.3 Details of Type (2) Geometry and Reinforcement of Beams and Columns

used in the Investigated Frames (Before 1992)… ……………………...68

Fig. 3.4 Details of Type (4) Geometry and Reinforcement of Beams and Columns

used in the Investigated Frames(Before 1992)………………..…………69

Fig. 3.5 Concrete Confinement factor module……………………………………….70

Fig. 3.6 Triangular Lateral Load Pattern for Models (1&3)……………………...70

Fig. 3.7 The triangular lateral load pattern for Model (2)………...……………..71

Fig. 3.8 The triangular lateral load pattern for Model (4)…...…………………..71

Fig. 3.9 Seismicstruct Graphical User Inter Face……...……………………………..72

Fig. 3.10 Selection of Seismostruct Modeling Wizard...…...………………………….72

Fig. 3.11 Choice of Structural Analysis Model……………………………………...73

Fig. 3.12 Definition of Structural Dimension……………………...………………...73

Fig. 3.13 Reference Nominal Base Shear ……………………………...……………74

Fig. 3.14 Overall View of Modeled Frame…………...……………………………...74

Fig. 3.15 Sections Data Entry Screen……...…………………………………………....75

Fig. 3.16 Definition of Column's Dimensions and Reinforcement…..……………….75

Fig. 3.17 Definitions of Beam's Dimensions and Reinforcement...…………………..76

Fig. 3.18 Definitions of Cantilever's Cross-Sectional Dimensions and

Reinforcement…...………………………………….………….……………76

Fig. 3.19 Definitions of Permanent Loads through Applied Loading Tab……...….….77

Fig. 3.20 Selection of Analysis Output Members………..………………………..…77

xiii

Fig. 3.21 Running analysis Form.………………………………………………….78

Fig. 3.22 Infill Element Classes Module...………………………………………….78

Fig. 3.23 Parameters of Infill Wall panel…..….……………………………………79

Fig. 3.24 Properties of Blocks Used in Frame...…………………………………....79

Fig. 3.25 Wall Connectivity for each Floor………………………………………...80

Fig. 4.1 Analytical comparison of fundamental period for model (1) with different types

of masonry……………………………………….…………………..………103


of masonry…………………………..………………………….………........104


of masonry……..………………..……………………………………..…….105

Fig. 4.4 Analytical comparison of fundamental period for model (4) case (1) with

different types of masonry…………...……………………..……………….106

Fig. 4.5 Analytical comparison of absorbed energy relative to overall structure weight for

model (1) with different types of masonry .......................................……....107


model (2) with different types of masonry………………...…………..…...108


model 3 with different types of masonry………………….………………..109


model (4) case (1) with different types of masonry………………………..110





Fig. 4.11 Push over curves of model (1) for partially infilled frames (F150) using different

types of masonry……….…………………………………………….……..113

Fig. 4.12 Push over curves of model (1) with fully infilled frames (F1100) using different

types of masonry…………………….….……………………………….….114

Fig. 4.13 Push over curves of model (1) with fully infilled frames with ground floor wall

(F1100G) using different types of masonry………………..………………..115

xiv

Fig. 4.14 Push over curves of model (2) with partially infilled frames (F250) using

different types of masonry……………………….…………………………116


types of masonry………………..……..…………………………………….117


(F2100G) using different types of masonry………………………………...118

Fig. 4.17 Push over curves of model (3) with partially infilled frames (F350) using

different types of masonry…………………………………………………..119


types of masonry……………………………………………………………..120


(F3100G) using different types of masonry………………………………...121

Fig. 4.20 Push over curves of model (4) case (1) with partially infilled frames (F450) using

different types of masonry………………………………………….………122

Fig. 4.21 Push over curves of model (4) case (1) with fully infilled frames (F4100) using


Fig. 4.22 Push over curves of model (4) case (1) with fully infilled frames with ground

floor wall (F4100G) using different types of masonry……………………..124


different types of masonry………………………………………………..…125






different types of masonry…………………………………...………..…….128





Chapter (1)

1

CHAPTER (1)

INTRODUCTION

1.1 General

Prior to October 1992 Cairo earthquake, it was a common

practice in Egypt to design and detail medium rise building to resist

gravity loads only. With no consideration to any lateral load caused by

wind or earthquakes. In fact, the majority of public buildings were

designed according to this concept. In addition, structural ductility did

not represent a major concern for engineers due to lack of scientific

research in the field of structural performance during earthquakes and

wind gusts.

Accordingly, there were no special recommendations for

reinforcement details at critical zones. Special reinforcement details

were not present for beam-column connections to ensure weak-beam

strong-column concept. Effect of lengths and locations of steel lap

splices on structural ductility was not well studied yet. Moreover,

relation between minimum reinforcement ratio in columns and column

slenderness ratio was not followed seriously during structural design.

For these reasons, old existing RC buildings are believed to be

vulnerable to damage from lateral loading caused by severe earthquakes.

Some of mid-rise buildings survived from collapse during 1992

October earthquake due to existence of masonry walls. Masonry infill

walls are found in most existing concrete frame building systems. These

masonry infill walls which are constructed after completion of concrete

frames are considered as non-structural elements. Although they are

designed to perform architectural functions, infill walls have a

considerable strength and stiffness and they have significant effect on

the seismic response of the structural system with substantial structural

Chapter (1)

2

action. There is a general agreement among researchers that infilled

frames have greater strength as compared to frames without infill walls.

The presence of the infill walls increases the lateral stiffness

considerably. Due to the change in stiffness and mass of the structural

system, the dynamic characteristics change, as well. Thickness, heigh t,

and type of masonry infill walls were noticed to affect overall structural

performance during lateral loads.

Post-earthquake field investigations in most earthquake regions

in the world demonstrated that school buildings are notably vulnerable

due to their typical architectural pattern. The school buildings and pre -

school facilities in Egypt are mainly represented by two constructive

systems: bricks and RC frame-panel, which constitute the major portion

of the school buildings stock, and a few buildings are made up of adobe

bricks. Therefore, it was found to be worthy to study structural

performance of RC frame panels used in school buildings with variable

arrangement of infill walls for common types of school buildings in

Egypt.

1.2 Objectives

The main objective of this study is to study the effect of infill wall

panels on the overall structural performance of old existing school buildings

against lateral loads. In this research, the effect of masonry infill on the seismic

response of school buildings using push over analysis is studied numerically

using non-linear numerical techniques. A comparison has been made with the

behavior of bare frame. The numerical analysis results indicated that the infill

can completely change the distribution of damage throughout the structure. The

infill can have a beneficial effect on structural response, provided that they are

placed regularly throughout the structure.

Chapter (1)

3

1.4 Thesis Arrangement

Besides this introductory chapter, thesis is organized in 5 chapters as

follows. In chapter 2, the philosophy of analysis using various pushover

techniques is introduced. Past studies that discussed the modal pushover

analysis and standard lateral load patterns such as triangular, uniform, first

mode, and IBC are discussed, in addition to studies related to numerical

modeling for masonry infill wall and their effect on seismic resistance of

reinforced concrete frames.

In chapter 3, the layout and design details of old existing school

buildings are represented. These buildings consists of four models. They are

designed before 1992. Details of numerical analysis performed for previously

mentioned structures using standard pushover analysis are representing.

Analysis details represent material modeling, geometrical description,

designation, …etc. for studied models.

Chapter 4, discuss results of different analyses procedures performed

for the studied frames. Listed analysis results in this chapter are, fundamental

period and energy absorbed of each frame and the relation between base shear

and percentage of story drift.

In chapter 5, a detailed statistical analysis of the seismic responses

obtained by triangular pushover load pattern is presented. And conclusions

from the results of these different analyses procedures for the studied frames

are presented.

In chapter 6, the main conclusions of this study are reported, in

addition to some recommendation for future studies.

Chapter (2)

4

CHAPTER (2)

THEORETICAL BACKGROUND AND

LITERATURE REVIEW

2.3 Introduction

It has been observed by most researchers, that infill masonry

panals are seldom included in the analysis of reinforced concrete (R/C)

frames. Most engineers consider masonry panals as non-structural

elements especially in skeleton structure. However, experimental tests

showed a significant difference in structural response of R/C masonry

infilled frames compared to R/C bare frames especially under lateral

loading.

Accordingly, a lot of research efforts have been directed in recent

years to explore the effect of masonry infill panals on the structural

behavior of R/C frames under seismic loads. Moreover, other research

efforts have been directed to find the most convenient methods to

numerical modeling of masonry infilled R/C frames. The following

sections review both the theoretical background and the available

literature for pushover analysis methods for R/C frames and modeling of

masonry infill panels.

Chapter (2)

5

2.4 Theoretical Background

2.4.1 Push-over Analysis.

2.2.1.1 Description of Pushover Analysis

Pushover analysis is an approximate analysis method in which the

structure is subjected to monotonically increasing lateral forces with an

invariant height-wise distribution until a target displacement is reached.

Pushover analysis consists of a series of sequential elastic

analyses, superimposed to approximate a force-displacement curve of

the overall structure. A two or three dimensional model which includes

bilinear or trilinear load-deformation diagrams of all lateral force

resisting elements is first created and gravity loads are applied initially.

A predefined lateral load pattern which is distributed along the building

height is then applied. The lateral forces are increased until some

members yield. The structural model is modified to account for the

reduced stiffness of yielded members and lateral forces are again

increased until additional members yield. The process is continued unt il

a control displacement at the top of building reaches a certain level of

deformation or structure becomes unstable. The roof displacement is

plotted with base shear to get the global capacity curve, as shown in Fig.

(2.1).

Pushover analysis can be performed as force-controlled or

displacement controlled. In force-controlled pushover procedure, full

load combination is applied as specified, i.e, force-controlled procedure

should be used when the load is known (such as gravity loading). Also,

in force-controlled pushover procedure some numerical problems that

affect the accuracy of results occur since target displacement may be

associated with a very small positive or even a negative lateral stiffness

because of the development of mechanisms and P-delta effects. Analysis

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