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Behaviour of retrofitted masonry shear walls subjected to cycling loading [Elektronische Ressource] / von Abdelkhalek Saber Omar Mohamed

De
195 pages
Behaviour of Retrofitted Masonry Shear Walls Subjected to Cyclic Loading Zur Erlangung des akademischen Grades eines DOKTOR-INGENIEURS von der Fakultät für Bauingenieur-, Geo- und Umweltwissenschaften der Universität Fridericiana zu Karlsruhe (TH) genehmigte DISSERTATION von M.Sc.Ing. Abdelkhalek Saber Omar Mohamed Aus Ägypten Tag der mündlichen Prüfung: 26. Novemer 2004 Hauptreferent: Prof. Dr. -Ing. L. Stempniewski Korreferent: Prof. Dipl.-Ing. Matthias Pfeifer Karlsruhe 2004 -i- Abstract The recent earthquake in different countries of the world, such as those in Iran (2003), Algeria (2003), India (2001), Turkey (1999) and Vrancea (1997) have shown, particularly masonry walls were damaged. Thus, masonry walls are the most vulnerable elements of buildings when subjected to earthquake loading. Therefore, it is necessary to find practical solutions by study the behaviour of these walls, first without and then with retrofitting under monotonic and/or cyclic seismic loading. For this study, an experimental program has been conducted using the pseudo-dynamic experimental set-up that was designed at the Institute of Reinforced Concrete Structures, at the University of Karlsruhe, Germany. Its purpose was to analyse the behaviour of masonry walls first without and then with retrofitting.
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Behaviour of Retrofitted Masonry Shear Walls Subjected to
Cyclic Loading



Zur Erlangung des akademischen Grades eines

DOKTOR-INGENIEURS

von der Fakultät für

Bauingenieur-, Geo- und Umweltwissenschaften
der Universität Fridericiana zu Karlsruhe (TH)

genehmigte


DISSERTATION

von

M.Sc.Ing. Abdelkhalek Saber Omar Mohamed

Aus Ägypten



Tag der mündlichen Prüfung: 26. Novemer 2004

Hauptreferent: Prof. Dr. -Ing. L. Stempniewski

Korreferent: Prof. Dipl.-Ing. Matthias Pfeifer




Karlsruhe 2004




-i-

Abstract

The recent earthquake in different countries of the world, such as those
in Iran (2003), Algeria (2003), India (2001), Turkey (1999) and Vrancea
(1997) have shown, particularly masonry walls were damaged. Thus,
masonry walls are the most vulnerable elements of buildings when
subjected to earthquake loading. Therefore, it is necessary to find
practical solutions by study the behaviour of these walls, first without and
then with retrofitting under monotonic and/or cyclic seismic loading.

For this study, an experimental program has been conducted using the
pseudo-dynamic experimental set-up that was designed at the Institute
of Reinforced Concrete Structures, at the University of Karlsruhe,
Germany. Its purpose was to analyse the behaviour of masonry walls
first without and then with retrofitting.

The present study had two stages; The first stage aimed to study the
behaviour of masonry walls experimentally and numerically. The
numerical study was conducted by developing a suitable constitutive
model; While the second stage concerned with the experimental and
numerical investigating of the strengthening and repairing of the masonry
walls structures, using glass fibre reinforced polymers (GFRP), that are
epoxy-bonded to the exterior surfaces of the walls. The numerical
investigation was accomplished by developing anchorage strength bond
model to study the effect of such GFRP on masonry.
Both models were programmed and incorporated into a three-
dimensional finite element code: Abaqus 6.4 [1] and they have been
verified and validated with experimental results.
In the first stage, a three-dimensional non-linear finite element model,
based on two-parameter damage coefficients has been developed to
-ii-

study the behaviour of masonry walls numerically. This model, which is
based on the continuum damage theory, takes into account for different
behaviours in tension and compression. Such an approach, revealed to
be valuable in understanding the global behaviour of masonry structures,
in particular, the numerical results are in close agreement with
experimental data.
The masonry was treated as a homogenized material, for which the
material properties were obtained by a homogenisation technique. The
damage theory proved to be a good choice to exploit in this area of
structural mechanics, due especially to its efficiency combined with
simplicity.
The numerical implementations performed gave a good description of
the failure process as well as accurate prediction of the behaviour of
masonry structures.
The numerical results have shown that the shear strength and the shear
behaviour are much influenced when loading the wall in addition to the
shear force with vertical load.
In the second stage of the work, the aim of the developed bond strength
model was to study the behaviour of the strengthened and/or repaired
masonry walls structures when using GFRP as a retrofitting material.
The comparisons of the numerical results from both models with the
experimental results have shown, generally, close agreement.

By retrofitting the pre-damaged wall with GFRP-laminates, its initial
shear stiffness could be restored, the ductility raised and the carrying
capacity increased by 60%. The results have shown that this kind of
retrofitting is effective in improving the shear capacity and ductility of
masonry walls and will be a reliable method in increasing the structural
reliability of un-reinforced masonry buildings.

-iii-









To my father & mother;
To my brothers & sisters;
To my wife & children


















-iv-


-v-

Preface

Praise be to ALLAH with the blessings of whom the good deeds are fulfilled

The present dissertation was developed during my work as doctoral
candidate and scholarship holder at the Institute of Reinforced Concrete
Structures, at the University of Karlsruhe, Germany.

I would like to express my special thank and appreciation to Professor
Stempniewski (Chairman of the Institute) for the encouragement and
supervising for many years.

I thank also heartily Professor Eibl for his advices and suggestions
during this work.

I thank also Professor Pfeifer (Chairman of the Institute of Load-Bearing
Constructions, at the University of Karlsruhe) for undertook the co-
examiner.

My thanks are to all colleagues of the Institute for their useful and
meaningful discussions.

I thank also the Egyptian Government for the financial support through a
scholarship to make my doctor degree in Germany.

At last but not the least, I thank my father, my mother, my brothers, and
my sisters for every thing they did, and still doing for me. I am also
thankful to my wife for her unwavering patience, understanding and
encouragement and to: may sons, Mohamed and Youssef; to my
daughter, Iman, for keeping me accompanied during the accomplishment
of this dissertation. I thank also my wife’s mother for her constant support
and encouragement.

Karlsruhe, in November 2004

Abdelkhalek Saber Omar Mohamed
-vi-



-vii-

List of Contents

1 Introduction .....................................................................................1
1.1 General Remarks ___________________________________1
1.2 Fibre Reinforced Polymers (FRPs) ______________________4
1.3 Objectives and Scope ________________________________5
1.4 Contents of the Dissertation ___________________________6
2 Theoretical Background .................................................................9
2.1 Seismological Background ____________________________9
2.2 Codes and Instructions for Masonry in Seismic Areas.______12
2.2.1 Geometric Requirements for Shear Walls ........................13
2.2.2 Buildings Natural Period ...................................................14
2.2.3 Seismic Actions on the Buildings using the Response
Spectra Method...............................................................................15
2.3 Determination of Seismic Structural Response using Time-
History Method________________________________________18
2.4 Choice of the Finite Element__________________________19
2.5 Masonry Characteristics _____________________________20
2.5.1 Masonry Components.......................................................20
2.5.2 Material Properties of Masonry.........................................21
2.5.3 Masonry Properties...........................................................21
2.5.4 Masonry subjected to In-Plane Shear...............................28
2.5.5 Failure Criteria ..................................................................34
2.6 Material Behaviour under Cyclic Loading ________________44
2.7 Damage Theory Background _________________________46
2.7.1 Basic Assumptions48
2.7.2 Strain-Based Formulation .................................................49
2.7.3 Stress-Based Formulation ................................................51
2.7.4 Concepts of the Continuum Damage Mechanics..............53
2.8 Proposed Masonry Models ___________________________54
3 Developed Constitutive Law for the Analysis of Masonry ........59
3.1 Introduction _______________________________________59
3.2 Constitutive Model for the Analysis of Masonry ___________62
3.2.1 Scalar Damage Model ......................................................63
3.2.2 Homogenisation................................................................65
3.2.3 Numerical Analysis ...........................................................69
-viii-

3.3 Experimental Results of a Wall made from Autoclaved Aerated
Concrete (AAC) Blocks _________________________________82
3.4 Comparison between the Experimental and Calculation Results
of the wall made from Autoclaved Areated Concrete (AAC) Blocks87
4 Anchorage Strength Model for Fibre Reinforced Polymers (FRP)
bonded to Masonry ............................................................................93
4.1 Fibre Reinforced Polymers (FRP) Properties _____________93
4.1.1 Basic Properties of the Composite Materials....................94
4.1.2 Resin Systems..................................................................95
4.1.3 Properties of Fibres and other Engineering Materials.......98
4.1.4 Fibre Laminates Types .....................................................99
4.1.5 Laminate Mechanical Properties ....................................101
4.2 Anchorage Strength Models for FRP and Steel Plates bonded
to Concrete Blocks____________________________________102
4.2.1 Failure Modes .................................................................103
4.2.2 Existing Shear Anchorage Strength Models ...................106
4.2.3 Empirical Models ............................................................106
4.2.4 Fracture Mechanics-Based Models ................................107
4.2.5 Design Proposals110
4.3 Comparison with Experimental _______________________113
4.4 New Model by J.F. Chen____________________________115
4.4.1 Stress in Bonded Plate ...................................................119
4.5 Constitutive Model for the Analysis of Retrofitting of Masonry __
_______________________________________________121
4.5.1 Introduction .....................................................................121
4.5.2 Anchorage Strength Model for Glass Fiber Reinforced
Polymers (GFRP) bonded to Masonry ..........................................122
4.6 Experiments to determine the Performance of the Glass Fibre
Reinforced Polymers (GFRP) on the Autoclaved Aerated Concrete
(AAC) Blocks ________________________________________125
4.7 Experimental Results of Pre-Damaged-Retrofitted Wall of
Section (3.3) with the Glass Fibre Reinforced Polymers (GFRP)-
Sheets _____________________________________________128
4.7.1 Numerical Results...........................................................133
5 Summary, Conclusions and Recommendations......................141
5.1 Summary________________________________________142
5.2 Conclusions _____________________________________143