C9-EPFL SIKA Report VersionSika

7/27/2019 C9-EPFL SIKA Report VersionSika

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DYNAMIC TESTS ON URM WALLSBEFORE AND AFTER UPGRADING

WITH COMPOSITES

EXPERIMENTAL REPORT

imac Publication No.1, May 2003

Applied computing and mechanics laboratory


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DYNAMIC TESTS ON URM WALLS BEFORE AND AFTER

UPGRADING WITH COMPOSITES

EXPERIMENTAL REPORT

Mohamed ElGawady

BSc. & MSc. Cairo University

Dr. Pierino Lestuzzi

IS-IMAC

Prof. Marc Badoux

IS-BETON

MAY 2003


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ABSTRACT

Unreinforced masonry (URM) buildings represent a large portion of the buildings stockaround the world. Most of these buildings were built with little or no considerations for

seismic design requirements. Recent earthquakes have shown that many such buildings are

seismically vulnerable; therefore, the demand for upgrading strategies of these buildings has

become increasingly stronger in the last few years. Modern composite materials offer

promising upgrading possibilities for masonry buildings. This report documents dynamic in-

plane tests carried out on URM specimens and unreinforced masonry specimens upgraded

with composites (URM-WUC). Five half-scale URM walls were built using weak mortar and

half-scale brick units. These five walls were dynamically tested as reference specimens. Then,

these reference specimens were upgraded on one face only using composites and retested

again. As consequence eleven specimens were tested on a single degree of freedom

earthquake simulator. This tests investigated the following parameters: two aspect ratios (1.4,and 0.7), two mortar types (M2.5, and M9), three composite materials (carbon, aramid, and

glass), three fiber structures (plates, loose fabric, and grids), and two upgrading configurations

(diagonal X and full surface shapes). The tests show that Fiber Reinforced Plastic (FRP)

composites can provide an upgrading alternative for URM buildings. The upgrading materials

increased the specimens lateral resistances by a factor of 1.4 to 2.9 compared to the reference

(URM) specimens. In addition, the upgrading enhanced the cracking resistance and the energy

dissipation of the upgraded specimens.

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ACKNOWLEDGEMENTS

This project was made possible through the financial and technical support of SIKA AG Companycomplemented with the financial support of the Swiss Commission for Technological Innovation

(CTI). This support is very gratefully acknowledged.

Further, deep appreciation is extended to the following organizations and individuals:

The Swiss Federal Institute of Technology in Zurich (ETHZ) for the use of the testing facility.

Special thanks to Professor Peter Marti for his openness to EPFL-ETHZ collaboration.

Federal Commission for Scholarships for Foreign Students (FCS), for providing a scholarship for

the first author of this report.

Morandi for donation of the half-scale brick units

Mr. Markus Baumann (IBK-ETHZ), the head of the laboratory, for his invaluable support duringthe dynamic tests.

Mr. Heinz Meier (SIKA) for his contribution of knowledge to this project

Mr. Victor Venetz (SIKA) for installing the composites on the masonry specimens and for

demolishing the tested specimens

Mr. Christoph Gisler, Technician (IBK-ETHZ)

Mr. Patrice Gallay, Technician (IS-IMAC-EPFL)

Mr. Rongchang Fu, Engineer

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TABLE OF CONTENTS

CHAPTER 1: INTRODUCTION ........................................................................................................ 1

1.1 Objectives and Scope of the Project .............................................................................................. 1

1.2 Organization of the Report ............................................................................................................ 2

1.3 Background.................................................................................................................................... 2

1.3.1 Historical ................................................................................................................................. 2

1.3.2 Masonry Walls ........................................................................................................................ 3

1.3.3 Composite Material ................................................................................................................. 3

1.3.4 Literature Review.................................................................................................................... 3

1.4 Performance of URM Buildings During Earthquakes ................................................................... 4

CHAPTER 2: EXPERIMENTAL PROGRAM ................................................................................. 9

2.1 Test Set-up ..................................................................................................................................... 9

2.1.1 Earthquake simulator .............................................................................................................. 9

2.1.2 Frame with movable masses ................................................................................................. 10

2.1.3 Lateral guidance .................................................................................................................... 10

2.2 URM Test Specimens .................................................................................................................. 11

2.3 Experimental Tests ...................................................................................................................... 12

2.4 Construction and Upgrading........................................................................................................ 12

2.4.1 Construction materials .......................................................................................................... 12

2.4.2 Head beam............................................................................................................................. 13

2.4.3 Foundation ............................................................................................................................ 16

2.4.4 Construction procedure ......................................................................................................... 16

2.4.5 Upgrading materials .............................................................................................................. 16

2.4.6 Composites application ......................................................................................................... 18

2.5 Loading system ............................................................................................................................ 19

2.6 Dynamic Excitations .................................................................................................................... 21

CHAPTER 3: MEASURED RESPONSE ......................................................................................... 23

3.1 Measuring system ........................................................................................................................ 23

3.2 Measured Response ..................................................................................................................... 24

3.2.1 Earthquake type and nominal intensity ................................................................................. 24

3.2.2 Earthquake real intensity....................................................................................................... 24

3.2.3 Post-tensioning force............................................................................................................. 25

3.2.4 Lateral force .......................................................................................................................... 25

3.2.5 Lateral displacement ............................................................................................................. 27

3.2.6 Natural frequencies ............................................................................................................... 27

3.2.7 Hysteresis loops .................................................................................................................... 28

3.2.8 Accelerations......................................................................................................................... 29

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3.2.9 Rocking displacement ........................................................................................................... 31

3.2.10 Plane section ....................................................................................................................... 32

3.3 Observed Response...................................................................................................................... 32

CHAPTER 4: FINDINGS AND DISCUSSION................................................................................ 37

4.1 General Performance of Test Specimens..................................................................................... 38

4.1.1 Reference specimens ............................................................................................................. 38

4.1.2 Upgraded specimens ............................................................................................................. 41

4.2 Delamination and Anchorage ...................................................................................................... 46

4.3 Maximum Strains at Failure ........................................................................................................ 47

4.4 Specimens Asymmetry ................................................................................................................ 47

CHAPTER 5: CALCULATED VERSUS MEASURED RESPONSE............................................ 49

5.1 Seismic Performance of Unreinforced Masonry Walls ............................................................... 49

5.2 Lateral Resistance of URM Walls ............................................................................................... 49

5.2.1 Flexural design ...................................................................................................................... 50

5.2.2 Shear design .......................................................................................................................... 50

5.2.3 Comparison between Measured Lateral Force and Calculated Lateral Resistance............... 53

5.3 Lateral Resistance of URM-WUC............................................................................................... 57

5.3.1 Flexural design ...................................................................................................................... 57

5.3.2 Shear design .......................................................................................................................... 59

CHAPTER 6: SUMMARY AND FINDINGS................................................................................... 63

6.1 Experimental Work...................................................................................................................... 63

6.2 Findings ....................................................................................................................................... 63

6.2.1 General .................................................................................................................................. 63

6.2.2 Impact of upgrading configuration........................................................................................ 64

6.2.3 Impact of upgrading product, materials and reinforcement ratio.......................................... 65

6.2.4 Design model ........................................................................................................................ 65

APPENDIX A: SPECIMEN L1-REFE ............................................................................................. 67

A.1 Observations ............................................................................................................................... 67

A.2 Measured Response .................................................................................................................... 68

APPENDIX B: SPECIMEN L1-WRAP-G-F.................................................................................... 73

B.1 Observations................................................................................................................................ 74

B.2 Measured Response..................................................................................................................... 75

APPENDIX C: SPECIMEN L1-LAMI-C-I ...................................................................................... 79

C.1 Observations................................................................................................................................ 80

C.2 Measured Response..................................................................................................................... 81

APPENDIX D: SPECIMEN L1-WRAP-G-X ................................................................................... 85

D.1 Observations ............................................................................................................................... 86

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D.2 Measured Response .................................................................................................................... 87

APPENDIX E: SPECIMEN S1-REFE .............................................................................................. 91

E.1 Observations ................................................................................................................................ 92

E.2 Measured Response ..................................................................................................................... 93

APPENDIX F: SPECIMEN S1-LAMI-C-X...................................................................................... 97

F.1 Observations ................................................................................................................................ 98

F.2 Measured Response ................................................................................................................... 100

APPENDIX G: SPECIMEN S1-WRAP-G-F.................................................................................. 105

G.1 Observations ............................................................................................................................. 107

G.2 Measured Response .................................................................................................................. 107

APPENDIX H: SPECIMEN S2-REFE............................................................................................ 111

H.1 Observations ............................................................................................................................. 111

H.2 Measured Response .................................................................................................................. 112

APPENDIX I: SPECIMEN S2-WRAP-A-F.................................................................................... 117

I.1 Observations ............................................................................................................................... 118

I.2 Measured Response .................................................................................................................... 119

APPENDIX J: SPECIMEN L2-REFE ............................................................................................ 123

J.1 Observations ............................................................................................................................... 123

J.2 Measured Response.................................................................................................................... 124

APPENDIX K: SPECIMEN L2-GRID-G-F ................................................................................... 129

K.1 Observations ............................................................................................................................. 130

K.2 Measured Response .................................................................................................................. 132

APPENDIX L: COMPARISON BETWEEN MEASURED STRAINS ....................................... 135

L.1 Delamination and Anchorage .................................................................................................... 135

L.2 Maximum Strains ...................................................................................................................... 136

L.3 Specimens Asymmetry.............................................................................................................. 136

APPENDIX M: DYNAMIC EXCITATIONS................................................................................. 141

APPENDIX N: MATERIAL PROPERTIES.................................................................................. 145

N.1 Brick Compressive Strength ..................................................................................................... 145

N.2 Mortar Compressive Strength ................................................................................................... 147

N.3 Masonry Compressive Strength................................................................................................ 148

N.4 Masonry Ultimate Strain........................................................................................................... 150

N.5 Masonry Modulus of Elasticity................................................................................................. 150

N.6 Masonry Shear Strength............................................................................................................ 150

N.6.1 Shove test ........................................................................................................................... 150

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N.6.2 Triplet test .......................................................................................................................... 150

APPENDIX O: Reinforced Concrete Elements.............................................................................. 153

APPENDIX P: EQUIPMENTS........................................................................................................ 157

APPENDIX Q: FLEXURAL LATERAL RESISTANCE OF URM-WUC................................. 159

BIBLIOGRAPHY ............................................................................................................................. 161

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LIST OF ILLUSTRATIONS

Figure 1.1: Totally Collapsed One Story Building Made of Brick Walls and Wood Roof ................ 5

Figure 1.2: No Damage to One Story Building .................................................................................. 5

Figure 1.3: Typical Deformation and Damage to URM Building ...................................................... 5

Figure 1.4: In-Plane Shear Failure...................................................................................................... 6

Figure 1.5: Out-of-Plane Failure......................................................................................................... 6

Figure 1.6: Parapet Failure.................................................................................................................. 7

Figure 1.7: Combined Out-of-Plane/In-Plane Failure ........................................................................ 7

Figure 1.8: Combined Out-of-Plane/In-Plane/Pounding Failure ........................................................ 8

Figure 1.9: Hammering-Induced Cracking......................................................................................... 8

Figure 2.1: Test Set-Up....................................................................................................................... 9

Figure 2.2: Un Upgraded Specimen Ready to Test .......................................................................... 10

Figure 2.3: Reference Building with External Structural URM Walls ............................................. 10

Figure 2.4: Long (Slender) Walls ..................................................................................................... 11

Figure 2.5: Short (Squat) Walls ........................................................................................................ 11

Figure 2.6: Overview of the Tested Long Specimens....................................................................... 14

Figure 2.7: Overview of the Tested Short Specimens ...................................................................... 15

Figure 2.8: Dimensions of Half- Scale Clay Brick Unit .................................................................. 15

Figure 2.9: Original and Half-Scale Clay Brick Units...................................................................... 15

Figure 2.10: Typical Construction Procedure..................................................................................... 17

Figure 2.11: Upgrading Bi-Directional Materials............................................................................... 18

Figure 2.12: Roughening of the Masonry Surface.............................................................................. 20

Figure 2.13: Dust Removing............................................................................................................... 20

Figure 2.14: Impregnate Epoxy Resin to Masonry Substrate ............................................................. 20

Figure 2.15: Fixation of the Fabric onto Masonry Surface................................................................. 20

Figure 2.16: Impregnating the Fabric. ................................................................................................ 20Figure 2.17: CFRP Plates Surface Cleaning....................................................................................... 20

Figure 2.18: Coating CFRP Plate with Epoxy Resin.......................................................................... 21

Figure 2.19: Spectrum-Compatible Synthetic Earthquake. ................................................................ 22

Figure 3.1: Overview of Typical Measurements For a Slender Specimen ....................................... 23

Figure 3.2: Target and Measured Acceleration Response Spectrum of Specimen L2-GRID-G-F for

Test Runs 3, 4, 10, 14, 18, and 19 .................................................................................. 26

Figure 3.3: Sample of the Variations in the Post-tensioning Forces before (L1-WRAP-G-F) and

after (L2-GRID-G-F) the Springs during an Earthquake UG1R of Real Intensity 232%..

........................................................................................................................................ 26

Figure 3.4: Normalized Peak Lateral Force vs. Specimen Drift....................................................... 27

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Figure 3.5: Horizontal Relative Displacement () Time-Histories of Specimen L2-GRID-G-F for

Test Runs 3, 4, 10, 14, 18, and 19 .................................................................................. 28

Figure 3.6: Fourier Amplitude Spectra for Relative Mass Accelerations of Specimen L2-GRID-G-F

for Test Runs 3, 4, 10, 14, 18, and 19 ............................................................................ 29

Figure 3.7: Lateral Force (F) vs. Relative Lateral Displacement (

) for test Runs 3, 4, 10, 14, 18,and 19 ............................................................................................................................. 30

Figure 3.8: Head Beam Horizontal Acceleration for Test Runs 3, 4, 10, 14, 18, and 19 ................. 31

Figure 3.9: Vertical Acceleration Measured on the Head Beam for Test Run 19 ............................ 31

Figure 3.10: L2-GRID-G-F after Testing (Western Face).................................................................. 34

Figure 3.11: L2-GRID-G-F after Testing (Eastern Face) ................................................................... 34

Figure 3.12: Grid Rupture in the Bottom Western North Side of L2-GRID-G-F .............................. 34

Figure 3.13: Grid Rupture in the Bottom Western South Side of L2-GRID-G-F .............................. 34

Figure 3.14: Fiber Rupture at the End of Testing L2-GRID-G-F....................................................... 34Figure 3.15: Masonry Failure in the Eastern South Side of L2-GRID-G-F ....................................... 34

Figure 3.16: The Rocking Vertical Displacement Time-Histories Measured along the Specimen Full

and Mid-Height .............................................................................................................. 35

Figure 3.17: Measured Lateral Relative Displacement and Estimated Lateral Displacement due to

Rocking .......................................................................................................................... 35

Figure 3.18: Vertical Strain Distribution along Specimen L2-GRID-G-F Cross Section .................. 36

Figure 4.1: Final Crack Pattern of Specimen L1- REFE (Eastern Face) ......................................... 40

Figure 4.2: Final Crack Pattern of Specimen L2- REFE (Western Face)......................................... 40

Figure 4.3: Final Crack Pattern of Specimen S1- REFE (Western Face) ........................................ 40

Figure 4.4: Final Crack Pattern of Specimen S2- REFE (Western Face) ......................................... 40

Figure 4.5: Final Crack Pattern of Specimen L1-LAMI-C-I (Eastern ace) ...................................... 41

Figure 4.6: The Improvement in the Lateral Resistance of the Upgrading Specimens .................... 42

Figure 4.7: Specimen L1-WRAP-G-F Ready to Test (Western Face) ............................................. 43

Figure 4.8: L2-GRID-G-F after Testing (Western Face).................................................................. 43

Figure 4.9: Specimen L1-WRAP-G-X after Testing ........................................................................ 44

Figure 4.10: Specimen S1-WRAP-G-F Ready to Test ....................................................................... 45

Figure 4.11: Specimen S2-WRAP-A-F Ready to Test ....................................................................... 45

Figure 4.12: Specimen S1-LAMI-C-X Ready to Test (Appendix F) ................................................. 46

Figure 4.13: Comparison between Measured Lateral Resistances (F) and Post-tensioning Forces (P)

for Long Reinforced Specimens L1-WRAP-G-F and L2-GRID-G-F............................ 48

Figure 4.14: Comparison between Measured Lateral Resistances (F) and Post-tensioning Forces (P)

for Short Reinforced Specimens S1-WRAP-G-F and S2-WRAP-A-F.......................... 48

Figure 5.1: In-plane Failure Modes of a Laterally Loaded URM Wall ............................................ 50

Figure 5.2: Assumptions for Rocking Resistance of Wall Failing with Toe Crushing .................... 50

Figure 5.3: Comparison of Calculated Lateral Resistance (equations. 4.1, 4.5, and 4.7) and

Measured Lateral Forces for Specimens L1-REFE and L1-LAMI-C-I ......................... 54

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Measured Lateral Forces for Specimen L2-REFE ......................................................... 55


Measured Lateral Forces for Specimen S1-REFE ......................................................... 55

Figure 5.6: Comparison of Calculated Lateral Resistance (equations. 4.1, 4.5, and 4.7) andMeasured Lateral Forces for Specimen S2-REFE ......................................................... 56

Figure 5.7: Simple Structural Model for The Test Set-Up ............................................................... 56

Figure 6.1: The Improvement in the Lateral Resistance of the Upgrading Specimens under a

Normal Force (N) of 57 kN............................................................................................ 64

Figure A.1: Specimen L1-REFE after Testing (Western Face) ......................................................... 67

Figure A.2: Final Crack Pattern of Specimen L1- REFE (Eastern Face) ......................................... 67

Figure A.3: Normalized Lateral Force vs. Wall Drift........................................................................ 69

Figure A.4: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 5, 6, 8, 9, 10, and 11

........................................................................................................................................ 70

Figure A.5: Relative Wall Displacement for Test Runs 5, 6, 8, 9, 10, and 11 .................................. 71

Figure A.6: Top Wall Acceleration for Test Runs 5, 6, 8, 9, 10, and 11........................................... 71

Figure B.1: Specimen L1-WRAP-G-F Upgraded Face..................................................................... 73

Figure B.2: Specimen L1-WRAP-G-F Ready to Test ....................................................................... 73

Figure B.3: Delamination and White Lines ................................................................................... 73

Figure B.4: Final Crack Pattern of L1-WRAP-G-F (Eastern Face) .................................................. 73

Figure B.5: Toe Crushing at The Eastern North Side after Test Run 24........................................... 75

Figure B.6: Fabric Rupture at The Bottom Western North Side after Test Run 24 .......................... 75

Figure B.7: Normalized Lateral Force vs. Wall Drift........................................................................ 75

Figure B.8: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 3, 4, 10, 14, 18, and

19.................................................................................................................................... 77

Figure B.9: Relative Wall Displacement for Test Runs 3, 4, 10, 14, 18, and 19 .............................. 78

Figure B.10: Top Wall Acceleration for Test Runs 3, 4, 10, 14, 18, and 19....................................... 78

Figure C.1: Specimen L1-LAMI-C-I Upgraded Face ....................................................................... 79

Figure C.2: Specimen L1-LAMI-C-I Ready to Test ......................................................................... 79

Figure C.3: Final Crack Pattern of Specimen L1-LAMI-C-I ............................................................ 79

Figure C.4: L1-LAMI-C-I after Testing ............................................................................................ 79

Figure C.5: Crack Propagation during L1-LAMI-C-I Test ............................................................... 81

Figure C.6: 2 mm Crack Opening during Test Run 16 ..................................................................... 81

Figure C.7: Normalized Lateral Force vs. Wall Drift........................................................................ 81

Figure C.8: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 4, 7, 10, 13, 17, and

20.................................................................................................................................... 82

Figure C.9: Relative Wall Displacement for Test Runs 4, 7, 10, 13, 17, and 20 .............................. 83

Figure D.1: Specimen L1-WRAP-G-X Upgraded Face .................................................................... 85

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Figure D.2: Specimen L1-WRAP-G-X after Testing ........................................................................ 85

Figure D.3: Final Crack Pattern of Specimen L1-WRAP-G-X (Western Face)................................ 85

Figure D.4: Diagonal Fabric Rupture after Test Run 24 of Specimen L1-WRAP-G-X.................... 85

Figure D.5: Details of Fabric Rupture at the Test End of L1-WRAP-G-X ....................................... 87

Figure D.6: Crack Propagation during L1-WRAP-G-X Test ............................................................ 87

Figure D.7: Normalized Lateral Force vs. Wall Drift........................................................................ 88

Figure D.8: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 5, 7, 10, 18, 24, and

26.................................................................................................................................... 89

Figure D.9: Relative Wall Displacement for Test Runs 5, 7, 10, 18, 24, and 26 .............................. 90

Figure D.10: Top Wall Acceleration for Test Runs 5, 7, 10, 18, 24, and 26....................................... 90

Figure E.1: Specimen S1-REFE (Eastern Face)................................................................................ 91

Figure E.2: Specimen S1- REFE after Testing (Eastern Face) ......................................................... 91

Figure E.3: Final Crack Pattern of Specimen S1- REFE (Eastern Face) .......................................... 91

Figure E.4: Final Crack Pattern of Specimen S1- REFE (Western Face) [mm] ............................... 91

Figure E.5: Normalized Lateral Force vs. Wall Drift........................................................................ 93

Figure E.6: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 3,6,9, 16, 22, and 25

........................................................................................................................................ 94

Figure E.7: Relative Wall Displacement for Test Runs 3,6,9, 16, 22, and 25 .................................. 95

Figure E.8: Top Wall Acceleration for Test Runs 3,6,9, 16, 22, and 25........................................... 95

Figure F.1: Specimen S1-LAMI-C-X Upgraded Face ...................................................................... 97

Figure F.2: Specimen S1-LAMI-C-X Ready to Test ........................................................................ 97

Figure F.3: Final Crack Pattern of Specimen S1-LAMI-C-X (Western Face) ................................. 97

Figure F.4: Specimen S1-LAMI-C-X after Testing (Western Face) ................................................ 97

Figure F.5: Final Crack Pattern of Specimen S1-LAMI-C-X (Eastern Face)................................... 99

Figure F.6: Specimen S1-LAMI-C-X after Testing (Eastern Face).................................................. 99

Figure F.7: Buckling of Plate Number 1 at the Third Brick Course of Specimen S1-LAMI-C-X ... 99

Figure F.8: Rupture of Plate Number 3 at the Top of Specimen S1-LAMI-C-X ............................. 99

Figure F.9: Hair Line Diagonal Crack in the Western Face of Specimen S1-LAMI-C-X................ 99

Figure F.10: 0.03 mm Crack Opening in The Western Face of Specimen S1-LAMI-C-X ................ 99

Figure F.11: Normalized Lateral Force vs. Wall Drift...................................................................... 100

Figure F.12: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 3,15,16, 19, 24, and

29.................................................................................................................................. 102

Figure F.13: Relative Wall Displacement for Test Runs 3,15,16, 19, 24, and 29 ............................ 103

Figure F.14: Top Wall Acceleration for Test Runs 3,15,16, 19, 24, and 29..................................... 103

Figure G.1: Specimen S1-WRAP-G-F Upgraded Face ................................................................... 105

Figure G.2: Specimen S1-WRAP-G-F Ready to Test ..................................................................... 105

Figure G.3: Final Delamination Pattern (Western Face) of Specimen S1-WRAP-G-F .................. 105

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Figure G.4: S1-WRAP-G-F after Testing (Western Face) .............................................................. 105

Figure G.5: Delamination Propagation in the Northern Side of Specimen S1-WRAP-G-F............ 107

Figure G.6: White Lines and Spots in Specimen S1-WRAP-G-F................................................... 107

Figure G.7: Normalized Lateral Force vs. Wall Drift...................................................................... 108

Figure G.8: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 2, 8, 19, 23, 32, and

34.................................................................................................................................. 109

Figure G.9: Relative Wall Displacement for Test Runs 2, 8, 19, 23, 32, and 34 ............................ 110

Figure G.10: Top Wall Acceleration for Test Runs 2, 8, 19, 23, 32, and 34..................................... 110

Figure H.1: Specimen S2-REFE after Testing (Eastern Face) ........................................................ 111

Figure H.2: Final Crack Pattern of Specimen S2- REFE (Western Face) ....................................... 111

Figure H.3: Normalized Lateral Force vs. Wall Drift...................................................................... 113

Figure H.4: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 3,6,10, 16, 19, and

22.................................................................................................................................. 114

Figure H.5: Relative Wall Displacement for Test Runs 3,6,10, 16, 19, and 22 .............................. 115

Figure H.6: Top Wall Acceleration for Test Runs 3,6,10, 16, 19, and 22....................................... 115

Figure I.1: Specimen S2-WRAP-A-F Upgraded Face ................................................................... 117

Figure I.2: Specimen S2-WRAP-A-F Ready to Test ..................................................................... 117

Figure I.3: S2-WRAP-A-F after Testing (Eastern Face)................................................................ 117

Figure I.4: S2-WRAP-A-F after Testing (Western Face) .............................................................. 117

Figure I.5: Normalized Lateral Force vs. Wall Drift...................................................................... 119

Figure I.6: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 2,7,9, 20, 26, and 30

...................................................................................................................................... 120

Figure I.7: Relative Wall Displacement for Test Runs 2, 7, 9, 20, 26, and 30 .............................. 121

Figure I.8: Top Wall Acceleration for Test Runs 2, 7, 9, 20, 26, and 30....................................... 121

Figure J.1: Specimen L2-REFE after Testing (Eastern Face) ........................................................ 123

Figure J.2: Final Crack Pattern of Specimen L2- REFE (Western Face)....................................... 123

Figure J.3: Normalized Lateral Force vs. Wall Drift...................................................................... 125

Figure J.4: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 4, 7, 8, 10, 11, and

14.................................................................................................................................. 126Figure J.5: Relative Wall Displacement for Test Runs 4, 7, 8, 10, 11, and 14 .............................. 127

Figure J.6: Top Wall Acceleration for Test Runs 4, 7, 8, 10, 11, and 14....................................... 127

Figure K.1: Specimen L2-GRID-G-F Upgraded Face..................................................................... 129

Figure K.2: Specimen L2-GRID-G-F Ready to Test....................................................................... 129

Figure K.3: L2-GRID-G-F after Testing (Western Face)................................................................ 129

Figure K.4: L2-GRID-G-F after Testing (Eastern Face) ................................................................. 129

Figure K.5: Grid Rupture in the Bottom Western North Side of L2-GRID-G-F ............................ 131

Figure K.6: Grid Rupture in the Bottom Western South Side of L2-GRID-G-F ............................ 131

Figure K.7: Fiber Rupture at the End of Testing L2-GRID-G-F..................................................... 131

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Figure K.8: Masonry Failure in the Eastern South Side of L2-GRID-G-F ..................................... 131

Figure K.9: Normalized Lateral Force vs. Wall Drift...................................................................... 132

Figure K.10: Lateral Force (F) vs. Relative Wall Displacement () for Test Runs 3, 4, 10, 14, 18, and

19.................................................................................................................................. 133

Figure K.11: Relative Wall Displacement for Test Runs 3, 4, 10, 14, 18, and 19 ............................ 134

Figure K.12: Top Wall Acceleration for Test Runs 3, 4, 10, 14, 18, and 19..................................... 134

Figure M.1: Spectrum-Compatible Synthetic Earthquake (UG1).................................................... 141

Figure M.2: Spectrum-Compatible Synthetic Earthquake (UG1R) ................................................. 142

Figure M.3: Spectrum-Compatible Synthetic Earthquake (UG1RR)............................................... 142

Figure M.4: Spectrum-Compatible Synthetic Earthquake (UG1RRR)............................................ 143

Figure M.5: Spectrum-Compatible Synthetic Earthquake (UG3). ................................................... 144

Figure N.1: Testing a Brick Unit in a Lengthwise........................................................................... 145

Figure N.2: Early Cracking of Brick Unit ....................................................................................... 146

Figure N.3: The Test End of Brick Unit .......................................................................................... 146

Figure N.4: Typical Failure of Mortar Cube ................................................................................... 147

Figure N.5: Compression Test of Masonry Assemblage ................................................................. 149

Figure N.6: Compression Failure of Assemblage............................................................................ 149

Figure N.7: Shove Test .................................................................................................................... 151

Figure N.8: Triplet Test of Masonry Assemblage ........................................................................... 151

Figure N.9: Triplet Test of Masonry Assemblage (a) at Test Beginning and (b) at the Test End... 152

Figure O.1: Execution Drawings for Foundation ............................................................................ 153

Figure O.2: Modified Foundation.................................................................................................... 153

Figure O.3: Foundation Reinforcement........................................................................................... 154

Figure O.4: Head Beam Execution Drawing for Long Walls.......................................................... 155

Figure O.5: Head Beam Execution Drawing for Short Walls ......................................................... 155

Figure O.6: Long Walls Head Beam Typical Reinforcement ......................................................... 156

Figure P.1: Overview of Typical Measurements for a Slender Specimen ...................................... 158

Figure P.2: Overview of Typical Measurements for a Squat Specimen ......................................... 158

Figure Q.1: Strain, Stresses, Internal, and External Forces in Upgraded Brick Masonry Specimen159

XIV


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LIST OF TABLES

Table 1.1: Summary of The Tested Specimens ...................................................................................... 2

Table 2.1: List of the Tested Specimens............................................................................................... 12Table 2.2: Legend for Specimens Names............................................................................................ 13

Table 2.3: The Different Mixes of Mortars .......................................................................................... 13

Table 2.4: FRP Used in the Experimental Program ............................................................................. 17

Table 3.1: Loading History and Main Peak Measured Response of Specimen L2-GRID-G-F ........... 24

Table 4.1: Summary of The Dynamic Tests......................................................................................... 37

Table 4.2: Summary of The Peak Measured Forces and Displacements in the North Direction ......... 38

Table 4.3: Summary of The Peak Measured Forces and Displacements in the South Direction ......... 38

Table 5.1: Parameters Used in Assessment of Reference Specimens .................................................. 56

Table 5.2: Calculated Lateral Resistance and Measured Lateral Forces for Specimens L1-REFE and

L2-REFE ............................................................................................................................. 57

Table 5.3: Theoretical Resistance and Measured Lateral Forces of Reference Squat Specimens ....... 58

Table 5.4: Summary of Flexural Assessment ....................................................................................... 59

Table 5.5: Fiber Contribution to Lateral Resistance in case of Shear Failure ...................................... 61

Table 5.6: Theoretical Lateral Resistance and Measured Lateral Forces of Squat Specimens ............ 61

Table A.1: Loading History and Measured Response of Specimen L1-REFE ..................................... 68

Table B.1: Loading History and Measured Response of Specimen L1-WRAP-G-F............................ 74

Table C.1: Loading History and Measured Response of Specimen L1-LAMI-C-I .............................. 80

Table D.1: Loading History and Measured Response of Specimen L1-WRAP-G-X ........................... 86

Table E.1: Loading History and Measured Response of Specimen S1-REFE...................................... 92

Table F.1: Loading History and Measured Response of Specimen S1-LAMI-C-X............................. 98

Table G.1: Loading History and Measured Response of Specimen S1-WRAP-G-F .......................... 106

Table H.1: Loading History and Measured Response of Specimen S2-REFE.................................... 112

Table I.1: Loading History and Measured Response of Specimen S2-WRAP-A-F .......................... 118

Table J.1: Loading History and Measured Response of Specimen L2-REFE .................................. 124

Table K.1: Loading History and Measured Response of Specimen L2-GRID-G-F............................ 130

Table L.1: Measured Vertical Strains along the Specimen Mid-Height and Bottom for Specimen L1-

WRAP-G-X at Different Test Runs .................................................................................. 138

Table L.2: Measured Vertical Strains along Specimen Heights for Upgraded Slender Specimens at

Different Test Runs ........................................................................................................... 138

Table L.3: Measured Vertical Strains along Specimen Heights for Upgraded Squat Specimens at

Different Test Runs ........................................................................................................... 139

Table L.4: Measured Concentrated Strains at Specimen Bottom for Slender Specimens at Different

Test Runs........................................................................................................................... 139

XV


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Table L.5: Measured Concentrated Strains at Specimen Bottom for Squat Specimens at Different Test

Runs................................................................................................................................... 140

Table N.1: Compression Test on Brick Units in Lengthwise.............................................................. 146

Table N.2: Compression Test on Brick Units in Heightwise .............................................................. 147

Table N.3: Compressive Strength of Mortar Type 0........................................................................... 147



Table N.6: Compressive Strength of Masonry Assemblage Made with Mortar Type 2 ..................... 149

Table N.7: Compressive Strength of Masonry Assemblage Made with Mortar Type 1 ..................... 150

Table N.8: Initial Shear Strength of Masonry Assemblage Made with Mortar Type 2 ...................... 151

Table P.1: List of Gages Used in Data Collection.............................................................................. 157

XVI


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Chapter 1: INTRODUCTION 1

1 INTRODUCTION

Unreinforced masonry (URM) buildings represent a large portion of the buildings around the world.Most of these buildings were built with little or no considerations for seismic design requirements.Recent earthquakes have shown that many such buildings are seismically vulnerable; therefore, thedemand for upgrading strategies of these buildings has become increasingly stronger in the last fewyears, implying the evaluation of lateral resistance of existing URM buildings. Evaluation of thelateral resistance of URM buildings in many times clouded because of uncertainties associated withestimating shear or flexural strength of individual walls [Ab 92]. Moreover, based on modern designcodes most of the existing URM buildings need to be upgraded. For example, under the URMBuilding Law of California, passes in 1986, the buildings evaluation showed that approximately 96%of the URM buildings needed to be retrofitted, which would result in approximately $4 billion inretrofit expenditure [ED 02]. In Switzerland, a recent research [La 02] carried out on a target area in

Basel shows that from 45% to 80% of the existing URM buildings, based on construction details, willexperience heavy damage or destruction during an earthquake event. Thereby, improving existing anddeveloping better methods of upgrading existing seismically inadequate buildings is an urgent need.

Numerous techniques are available to increase the strength and/or ductility of URM walls. Thereseems to be a reliability issue with some of the commonly used techniques. Modern compositematerials offer promising upgrading possibilities for masonry buildings. This report documentsdynamic in-plane tests carried out on unreinforced masonry specimens and unreinforced masonryspecimens upgraded with composites (URM-WUC).

1.1 Objectives and Scope of the Project

The scope of the research included an experimental study of the in-plane behavior of URM and URM-WUC under earthquake loading. The following primary objectives were followed throughout thecourse of this study:

to examine, in near real conditions, the seismic in-plane behavior of unreinforced masonry (URM)specimens that have been upgraded on one face using composites

to study the effect of various fiber types and structures on the upgraded specimen behavior

to compare the behavior of various upgrading configurations

to compare available design models with the test results for URM specimens and URM specimens

that have been upgraded using composites (URM-WUC).

Five half-scale URM walls were built using weak mortar and half-scale brick units. These five wallswere dynamically tested as reference specimens. Then, these reference specimens were upgradedusing composites and retested. As consequence a total of eleven specimens were tested on theearthquake simulator of ETHZ. This research has investigated the following parameters (Table 1.1):

the aspect ratio: slender (aspect ratio of 1.4) and squat (aspect ratio of 0.7)

the fiber type: aramid, glass, and carbon

the upgrading configurations: diagonal shape (X) and wrapping

the fiber structures: plates, fabrics, and grids

the mortar compressive strength: weak (M2.5) and strong (M9).


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2 Chapter 1: INTRODUCTION

Table 1.1: Summary of The Tested Specimens

SpecimenName

SlendernessUpgrading Material1

and Fiber ProductUpgradingConfiguration

Mortar Type

L1-REFE Slender No upgrading Strong

L2-REFE Slender No upgrading WeakS1-REFE Squat No upgrading StrongS2-REFE Squat No upgrading WeakL1-LAMI-C-I Slender CFRP Plates 2 Vertical plates StrongL1-WRAP-G-F Slender GFRP Fabric Full face StrongL2-WRAP-G-F Slender GFRP Grid Full face WeakL1-WRAP-G-X Slender GFRP Fabric X Pattern StrongS1-WARP-G-F Squat GFRP Fabric Full face StrongS2-WRAP-A-F Squat AFRP Fabric Full face WeakS1-LAMI-C-X Squat Plates of CFRP XX Pattern Weak

1. All specimens were upgraded on one face only. The materials used for upgrading were Glass (G),Carbon (C), and Aramid (A) FRP.

The following issues were not included in this research:

the anchorage of the Fiber Reinforced Plastic (FRP). Although the anchorage of externally bondedreinforcement is a recognized crucial aspect, it was not the goal of this research to test theanchorage of the upgrading system. The anchorage can be studied using simple tests (e.g. directtension tests). To ensure that anchorage failure did not occur, steel plates were used at the end ofthe FRP to anchor the FRP to the walls using steel bolts.

the out-of-plane behavior of URM walls and URM-WUC. The out-of-plane behavior of URMwalls and URM-WUC were extensively discussed experimentally and theoretically in the literature(e.g. [KEC 03], [AEC 01], [HD 01], [HMM 01], [VE 00a], [VE 00b], and [ESV 99]).

1.2 Organization of the Report

The report is divided into 6 chapters. Specimen design, upgrading materials and configurations,construction procedure, instrumentation, and the synthetic earthquakes are detailed in Chapter 2. Themeasured dynamic responses are described in Chapter 3. The complete measured data are collected inappendices A to K. The most important findings appear in Chapter 4. Chapter 5 covers the staticresponse calculated with conventional methods. A summary of the report and the main conclusions are

provided in Chapter 6. The measured strains at delamination and failure are appeared in Appendix L.More details about the dynamic excitations are available in Appendix M. Appendix N gives the

material properties. The dimensions and reinforcements of the reinforced concrete elements (headbeam and foundations) are given in Appendix O. Appendix P presents a list of the equipments used inthe measurements. Finally, Appendix Q gives the complete derivation of the mathematical equations,which used to calculate the flexural capacity of URM-WUC.

1.3 Background

1.3.1 Historical

Masonry is one of the oldest construction materials. Clay units have been in use for over 10,000 years.Sun dried bricks were widely used by early civilizations in Babylon, Egypt, Spain, South and North


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America. Wide usage is illustrated by the word adobe which is now incorporated in the Englishlanguage but is a Spanish word based on the Arab word atob meaning sun-dried brick. Someenduring masonry structures include the Pyramids of Egypt and the Great Wall of China. Masonry wasoften used in the construction of simple small dwelling units. But multistory masonry buildings werecommon long time ago. For example, the Romans built apartments blocks up to five or more stories

high [Mu 87].There are many reasons for the extensive use of masonry as a construction material. The simplicity ofconstruction process and local availability of materials are among these reasons. Many materials have

been used for masonry construction, those locally available being most convenient. The most commonmasonry materials used today are stone, clay, calcium silicate, and concrete.

Masonry is used as structural element for walls, columns, pilasters, beams, and lintels as well as it maybe used to enclose and subdivide the interior architectonic space of a building. Masonry has manyadvantages as a construction material including, good acoustic and thermal insulation; moreover,masonry construction is fire retardant.

1.3.2 Masonry Walls

There are various types of masonry walls. The function of a wall, the load it carries, and its location inthe building are some of the factors to be considered in choosing the wall type. Depending on thenumber of wythe, we can define four types of masonry walls: single-wythe (leaf), solid and composite,cavity, and veneer walls. The first type is the most common type in Europe, and it was used during thisresearch. The leaf type can be built in a running bond (half or one third bond), stack pattern, or anopen bonded pattern. The last two types are for decorative purpose while the first one can be used forload bearing and non-load bearing applications. The leaf wall can be grouted and reinforced but doesnot have to be. This research concerns leaf-unreinforced masonry walls built in half running bondusing hollow clay brick.

1.3.3 Composite Material

Development of fiber composites began for military and aerospace applications at the beginning of the20th century. Since the 1960s, application of advanced composites in military aircraft has becomecommon. With time, the potential benefits for structural engineering applications were recognized.

Composite fiber materials, most commonly known as fiber-reinforced polymer (FRP), are made ofdifferent kinds of fibers (carbon, glass, aramid, etc.) impregnated in a polymeric matrix. Present FRPshave several well-known advantages including negligible specific weight, corrosion immunity, andhigh tensile strength. The unique properties of fiber composite materials have led to a rapidly growingnumber of applications, in particular the retrofitting of existing structures. Moreover, their flexibilityand ease of application allow a wide range of intervention scenarios for upgrading.

1.3.4 Literature Review

A complete literature review is presented in [ElG 04]; nevertheless, the survey of the literature reviewshows the following:

Different post earthquakes surveys have been done (e.g. [Pa 91], [Br 95], and [Ke 96]). Thesemissions noted the different modes of failure of URM buildings; also, they discussed some

behavioral differences between different construction issues (e.g. the effect of concrete

and wooden floor on masonry behavior, the wall-floor connection, etc.).


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Several researchers examine experimentally the behavior of URM walls (e.g. [BMT 80], [KM88], [Ab 92], [MC 92], [MC 94], and [AMM 94]). These experiments demonstrated that the

behavior of URM walls is highly dependent on the applied axial load and wall aspect ratio, withmaterial properties playing a smaller role.

Different conventional upgrading techniques are available for in-plane upgrading of URM walls:shotcrete, Ferro-cement surface coating, center core, grouting, [AL 01] [MEE 96]. In manycases, these techniques were not able to significantly improve the behavior of theupgrading specimens. In addition, Northridge (1994) post-earthquake surveys showed thatmore than 450 buildings upgraded, before the earthquake, using conventional techniques failedafter the earthquake [Ke 96].

Few researchers have focused on the in-plane behavior of URM-WUC under static cyclic (e.g.[HH 02], [HSH 02], [AL 01], and [Sc 94]) or dynamic loading [AH 99]. Most of these researchersused either glass and/or carbon fiber; also, different upgrading configurations were tested. Theupgrading materials were applied on one face (e.g. [AH 99], and [Sc 94]) and/or on both faces(e.g. [HH 02], [HSH 02], [AL 01], and [Sc 94]). The results of these researches have shown that

composites could improve significantly the lateral resistance of URM walls.

All the previous researchers concentrate their effort on experimental investigations. No physicaldesign models have been developed for design of URM-WUC. Researchers tried to either useconventional design methods of reinforced concrete elements to design URM-WUC (e.g. [ESV99]) or use empirical formulae to calculate the shear resistance of URM-WUC (e.g. [Tr 98]).

1.4 Performance of URM Buildings during Earthquakes

The potential vulnerability of old, unreinforced masonry buildings was observed a long time ago(Figure 1.1); however, there is evidence that URM buildings can survive major earthquakes (Figure1.2). The conditions required for satisfactory performance are not fully understood, and the usualmodern analytical tools are often unable to discriminate appropriately [Br 94a].

Although the structural typology of masonry buildings varies in different regions, their damageresulting from earthquakes can be classified in an uniform way. Figure 1.3 demonstrates typicaldeformations and damages to structural walls of a simple masonry building subjected to seismic loads.Moreover, Figures (1.4 to 1.9) summarize some major failure patterns of URM buildings that have

been observed during past earthquakes.


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Compton Junior High School, Long Beach Earthquake, 1933

Figure 1.1: Totally Collapsed One Story Building Made of Brick Walls and Wood Roof

(Courtesy of EERC Library)

Coalinga Library, Coalinga Earthquake, 1983

Figure 1.2: No Damage to One Story Building (Courtesy of EERC Library)

Figure 1.3: Typical Deformation and Damage to URM Building (Courtesy of [To 99])
mailto:[email protected]:[email protected]


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Santa Monica, Northridge Earthquake, 1994 Watsonville, Loma Prieta Earthquake, 1989

Arvin, Kern County Earthquake, 1952 Long Beach Earthquake, 1933

Figure 1.4: In-Plane Shear Failure (Courtesy of EERC Library)

North of Coalinga, Coalinga Earthquake, 1983 Downtown Coalinga, Coalinga Earthquake, 1983

Figure 1.5: Out-of-Plane Failure (Courtesy of EERC Library)
mailto:[email protected]


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Watsonville, Loma Prieta Earthquake, 1989 Hollister Area, Loma Prieta Earthquake, 1989

Figure 1.6: Parapet Failure (Courtesy of EERC Library)

Whittier, Whittier Narrows, 1987(Courtesy of EERC Library)

GUJARAT, Bhuj Earthquake, 2001(Courtesy of Langenbach / UNESCO)

Figure 1.7: Combined Out-of-Plane/In-Plane Failure
mailto:[email protected]:[email protected]


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.

Santa Cruz Area, Loma Prieta Earthquake, 1989

Figure 1.8: Combined Out-of-Plane/In-Plane/Pounding Failure (Courtesy of EERC Library)

Hollister Area, Loma Prieta Earthquake, 1989

Figure 1.9: Hammering-Induced Cracking (Courtesy of EERC Library)


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Chapter 2: EXPERIMENTAL PROGRAM 9

2 EXPERIMENTAL PROGRAM

Five half-scale walls were constructed for the experimental program. The test walls were constructedof half-scale clay brick units and weak mortar to represent common structures in central Europe in the

early half of the 20th

century. The test specimens were constructed and tested in the laboratory of the

structural engineering institute IBK of the Swiss Federal Institute of Technology Zurich ETHZ.

This research has investigated the effect of the aspect ratio, the mortar type, the upgrading material

and the upgrading configurations on the specimens dynamic behavior. The specimens have been

tested on the earthquake simulator using synthetic earthquakes. This chapter describes the test set-up,

the test specimens, the construction procedure, the upgrading configurations, and the dynamic

excitations.

2.1 Test Set-up

The test set-up used for the dynamic tests was constructed and successfully used in a previous research

for dynamic tests of reinforced concrete shear walls. A complete description of the test set up is

available in [LWB 99]. In general, the test set-up consisted of three parts (Figures 2.1 and2.2): an

earthquake simulator, a frame with movable masses, and the lateral guidance of the specimens.

a. Shake table

b. Test specimen (1600 x 1600)

c. Separate test set-up for the masses

d. Additional frame for the laterally guidance

e. Moveable car for mass (M=12 t)

f. Hinged connecting member

g. External post-tensioningh. Jack for the post-tensioning

i. Footing connection: M16 bolt

j. Shock absorber

k. Reaction structure

l. Servo-hydraulic actuator

m. Room

n. Valve 120 l/min

o. Hinge

p. Rail guidance

+/- 0.0

+1125

+4020

a

b

g

j

k

n

lpj

o

m

d

2400 1200 1200

1600

350

350

350

400

c

e

i+1700

+3060

+4420

f

h

Figure 2.1: Test Set-Up

2.1.1 Earthquake simulator

The earthquake simulator includes the following equipments:

An uniaxial (horizontal) shaking table measures 2m by 1m. The maximum displacement of the

table from the rest position is 100 mm.


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10 Chapter 2: EXPERIMENTAL PROGRAM

A 100 kN servo-hydraulic actuator supplied by a 280 bar hydraulic pump with a total capacity of

240 l/min drives the table.

A control system controls the table displacements.

Figure 2.2: Un Upgraded Specimen Ready to Test

2.1.2 Frame with movable masses

R R R R

L~H

R

H

H

H

H

H

Figure 2.3: Reference Building withExternal Structural URM

Walls

In order to simulate the inertia mass of the floor, the dark

gray area in Figure 2.3, a separate frame with movable

mass is used. This structure consists of a three

dimensional steel frame (element c in Figure 2.1)

supports three carts, each cart supports 12 ton mass. The

mass consists of 28 steel bars. The maximum

displacement of the car is 200 mm. A low friction

guidance of the car was implemented with cam rollers.

Coefficient of friction in order of 0.5% can be achieved

for this wheels system.

During this research, only a single mass was used: either

the lower or the middle mass in case of squat or slenderspecimens, respectively.

The axial force was applied by two external post-

tensioning bars (element g in Figure 2.1)

2.1.3 Lateral guidance

To guide laterally the specimens, additional lateral frames were constructed (element d inFigure2.1).

Two steel beams rested on lateral frames, are used to guide the specimen at the reinforced concrete

head beam level. To minimize the friction between the head beam and the steel guides layers of Teflon

connected to the steel beams were used.


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2.2 URM Test Specimens

Due to the size and capacity limitations of the test set-up, half-scale walls were devised. A total of 5

half-scale brick masonry walls were constructed for the research program. Two wall families were

tested. The first family consisted of slender walls (herein after referred to as long walls). The second

family consisted of squat walls (herein after referred to as short walls). The nominal dimensions of along wall were 1.600 m height, 1.570 m length, and 0.075 m width. For a short wall the height was

reduced to 0.700 m height. The main geometric features of the constructed walls are illustrated in

Figures 2.4 and 2.5.

1

1

3.

05

1.

60

0.

35

0.30

1.600.600.400.60

0.

20

0.

36

0.

25

0.150.10

0.40

0.15

Mass

Level(4.020)

Table Top

Level (1.125)

0.075

0.36

Sec (1-1)

b

a

c c

b

a

d

a. Head beam (R.C.)

b. Masonry specimen

c. Foundation (R.C.)

d. Post-tensioning bars

1.57

Figure 2.4: Long (Slender) Walls [m]

1

1

0.

70

1.

95

0.601.60 0.36

0.0750.60

0.

19

0.40

0.40

0.

18

(1.125)

(2.660)

0.

30

0.

33

Sec (1-1)

0.

25

Level

Mass

Level

Table Top

a. Head beam (R.C.)b. Masonry specimenc. Foundation (R.C.)d. Post-tensioning bars

1.57

b

c

ad

c

b

a

Figure 2.5: Short (Squat) Walls [m]


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2.3 Experimental Tests

The test walls were tested twice; first, the URM specimens were tested, as reference specimens, till a

predefined degree of damage; secondly, these reference specimens were upgraded using composites

and retested. The specimens were upgraded on one face only; since in many upgrading intervention

scenarios one face upgrading is frequently preferred over two faces ones, either for convenience ofconstruction (when added to the wall exterior surface) or to leave the exterior faade of the building

unaltered. This way of upgrading was successfully used in different research programs for upgrading

of URM walls using either composite material [Sc 94] or other upgrading materials such as shotcrete

[KF 92a].

Table 2.1 gives a complete list of the tested specimens. Also, Figures 2.6and 2.7show summary of

the tests that were carried out on the specimens. The following comments complete the table and

figures:

Each specimen is designated by a name reflects their characteristics, Table 2.2 explains the

specimens names. For instance, L1-WRAP-G-X means long specimen (L) with mortar type (1)

upgraded with fabric (WRAP) of glass (G) fiber in a diagonal shape (X) configuration. To study the shear resistance of such slender specimens, there was one virgin URM specimen

upgraded with plates of CFRP (L1-LAMI-C-I). The goal of this specimen was to increase the

flexural resistance of the specimen with minimum increase of its shear resistance in order to force

a shear failure. As such, this specimen herein after is considered as a reference specimen.

After testing of L1-LAMI-C-I and S1-LAMI-C-X the CFRP plates were taken off using hammer

and chisel. These specimens were upgraded, one more time, using glass fiber and retested again as

L1-WRAP-G-X and S1-WRAP-G-F respectively.

Table 2.1: List of the Tested Specimens

Tests carried out on slender specimens with type 1 mortarL1-REFE Reference specimen

L1-WRAP-G-F Specimen L1-REFE after upgrading with fabrics of glass fibers

L1-LAMI-C-I Specimen has been upgraded with plates of carbon fiber and is considered as a referencespecimen

L1-WRAP-G-X Specimen L1-LAMI-C-I after taking off the carbon plates and re-upgrading the specimen

with fabrics of glass fiber

Tests carried out on slender specimens with type 2 mortar

L2-REFE Reference specimen

L2-GRID-G-F Specimen L2-REFE after upgrading with grids of glass fibers

Tests carried out on squat specimens with type 1 mortar

S1-REFE Reference specimen

S1-LAMI-C-X Specimen S1-REFE after upgrading with plates of carbon fibersS1-WRAP-G-F Specimen S1-LAMI-C-X after taking off the carbon plates and upgrading it with fabrics of

glass fibers

Tests carried out on squat specimens with type 2 mortar

S2-REFE Reference specimen

S2-WRAP-A-F Specimen S2-REFE after upgrading with fabrics of aramid fibers

2.4 Construction and Upgrading

2.4.1 Construction materials

Test specimens were intended to represent structures built in the middle of the 20th

century in

Switzerland. It was important that materials were selected such that test specimens would reflect


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structural characteristics of an old masonry wall. Based on this criterion, it was decided that hollow

clay masonry with relatively weak mortar would be used for the construction of test specimens. The

construction material properties are available in Appendix N.

Table 2.2: Legend for Specimens Names

Slenderness Mortar Type

L Long (Slender) 1 Type 1

S Short (Squat) 2 Type 2

Upgrading Products Upgrading Materials

WRAP Loose Fabric A Aramid fibers

GRID Rigid Fabric C Carbon fibers

LAMI Plates G Glass fibers

REFE REFERENCE - -

Upgrading Configurations

F One Face Fully Covered I Vertical Elements

X Diagonal Elements - -

Brick

A commercial firm specially produced the brick units, used in the experimental program, tobe one-

half scale of original Hollow Clay Masonry (HCM) units. The original HCM unit is 300 X 150 X 190

mm; this resulted in a scale brick nominally measuring 150 X 75 X 95 mm (Figures 2.8 and 2.9). This

scaled HCM units had been produced with the same materials and procedure like the original one. The

only difference between the original HCM unit and the scale HCM one was that the scaled one had

one end frog while the original had frogs at both ends.

Mortar

Two types of weak mortars, type 1 and 2, were used in the construction of the test walls. A few jointsof the test walls required a stronger mortar, so type 0 was used. This strong mortar was used in the first

layer of mortar just after the foundations and the last layer between the foundation and the head beam.

This strong mortar (type 0) was not used in the last two walls (specimens S2-REFE and L2-REFE).

For bed joints the nominal size were 5 mm, which was consistent with the half-scaled bricks.

Table 2.3: The Different Mixes of Mortars

Proportions of Components by VolumeMortar Type

Cement Hydrated Lime Sand*

0 1 0.25 3

1 1 2 9

2 1 1 12* The maximum aggregate size was 3 mm to be consistent with the half-scale specimens

2.4.2 Head beam

Two reinforced pre-cast-concrete head beams, 1.600 m length, were used (see Appendix O for

concrete dimensions and reinforcements). The beams served the following functions:

To apply and distribute the post-tensioning axial forces.

To connect the test specimen to the moveable mass in the separate structure. The head beam web

was connected by steel pin element (element f inFigure 2.1) to the movable mass.

The web provided an anchorage surface for the composite material.


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L1-REFE L1-WRAP-G-F

+ Fabrics of Glass FRP

L1-LAMI-C-I L1-WRAP-G-X

- Plates of Carbon FRP

+ Fabrics of Glass FRP

L2-REFE L2-GRID-G-F

+ Grids of Glass FRP

Figure 2.6: Overview of the Tested Long Specimens


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S1-REFE S1-LAMI-C-X

+ Plates of CarbonFRP

S1-WRAP-G-F

S2-REFE S2-WRAP-A-F

+ Fabrics of AramidFRP

Figure 2.7: Overview of the Tested Short Specimens

- Plates of Carbon FRP+Fabrics of Glass FRP

Figure 2.8: Dimensions of Half- Scale Clay

Brick Unit [mm]

Figure 2.9: Original (under) and Half-Scale

(above) Clay Brick Units


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2.4.3 Foundation

The pre-cast concrete foundation had an inverted T shape. The nominal length of the foundation was

1.600 m. The flange thickness was 0.30 m and 0.360 m width. The web height was 0.350 m and

0.075 m wide (see Appendix O for concrete dimensions and reinforcements).

The reinforced concrete foundation served the following functions:

To post attach rigidly to the shaking table platform.

To distribute the prestressing force uniformly.

The web provided an anchorage surface for the composite material.

To provide a lifting element for transportation of the wall via the overhead crane.

The foundation was built with two types of holes: 16 mm diameter holes in its web and 25 mm

diameter holes in its flange. The foundation was clamped to the shaking table platform via 20 steel

bars, each of diameter 16 mm. These bars prevented foundation motion relative to the shaking table

during the dynamic tests. The web holes were used to fix the different types of upgrading materials to

the web through screw bolts and steel plates.

The same foundation, as for the long walls was used for the short walls. As in the test set-up the

position of the mass gave the lateral force level, modifications of the height of the foundation web was

required. At this point, a decision was made to cut about 0.190 m from the foundation web and to use

the modified foundation for the short walls (see Appendix O).

2.4.4 Construction procedure

As mentioned previously the bricks were half-scale, and both the head beam and foundation had been

pre-cast and had delivered after curing. Both the head beam and the foundation were reused for several

specimens. Skilled workers built the walls. Prior to use, the bricks were soaked in water. The required

number of half bricks was prepared and lightly scrubbing to adjust the edge. Then the upper face of the

foundation was roughed to increase the bond with the base mortar joint. Then, the walls had been built

in a running bond pattern.Figure 2.10 shows the construction procedure.

A few days (between 3-7 days) after wall construction, the head beam was lifted by crane and adjusted

on the wall specimen. A strong mortar type 0 (except for specimen S2-REFE and L2-REFE) had been

prepared. Then, the mortar was applied to the masonry wall. The head beam was being lowered slowly

till it rested on the masonry wall. A metal balance was used to adjust the level in plane and out-of-

plane through a metal column (Figure 2.10(d)). These metal columns adjusted the beam level and

ensured the stability of the head beam.

2.4.5 Upgrading materials

Fiber reinforced plastic (FRP)

Different types of FRP were used in the experimental program. Mainly, there were two families: the

first family consisted of unidirectional fiber structure and the second family consisted of bi-directional

fiber structures. The unidirectional fiber structure included two types of carbon fiber plates. The bi-

directional family included two different types of glass fibers, and one type of aramid fiber (Figure

2.11). Table 2.4 summarizes the material properties of these commercial products.


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(a) (b)

(c) (d)

Figure 2.10: Typical Construction Procedure: (a) Foundation Grinding, (b) BrickAdjustment, (c) Built in a Running Bond Pattern, and (d) Head Beam Fixation.

Table 2.4: FRP Used in the Experimental Program

Commercial nameFRP[Fiber]

WarpW[g/m2]

WeftW[g/m2]

ft[GPa]

E[Gpa]

[%]

SikaWrap-400A 0/90 Aramid 205 205 2880 100 2.8

SikaWrap-300G 0/90 Glass 145 145 2400 70 3.0

MeC Grid G4000 Glass 139 119 3450 72 4.0

Sika CarboDur S512 Carbon 93 - 2800*

165**

1.7

Sika CarboDur T1.214 Carbon 26 - 2400* 135** 1.6

Warpw and Weftw: Weight of fiber in the warp and weft directions respectivelyft and E: Fibers nominal tensile strength and E-modulus respectively

: Ultimate strain

: Composite tensile strength**: Composite E-modulus


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(a) (b)

(C)

Figure 2.11: Upgrading Bi-Directional Materials, (a) SikaWrap-300G 0/90, (b) MeC Grid

G4000, and (c) SikaWrap-400A 0/90

Bonding adhesive

Two types of adhesive were used in this experimental program: Sikadur-30 and Sikadur-330. Both of

the epoxy resins consist of two components A and B. The two components were mixed in a ratio of

3:1 (Sikadur-30) and 4:1 (Sikadur-330) by weight. The Sika CarboDur S512 and Sika CarboDur

T1.214 plates were bonded to the specimens using Sikadur-30 epoxy structural adhesive, while the

fabrics and the grids were bonded to the specimens using Sikadur-330 epoxy impregnating resin.

2.4.6 Composites application

The upgrading of the reference specimens consisted in the application of a layer of FRP compositematerial on one face of the masonry specimen (Figures 2.12 to 2.18). This was a particularly easy

operation. The main steps may be summarized as follows:

The specimen surface was roughened by grinding.

The dust and any loose particles were removed with vacuum cleaner.

The composites were cut to the desired dimensions by metal saw or disk cutter.

The two-component epoxy was homogeneously mixed.

A thin layer of the epoxy adhesive resin was applied to the masonry substrate by means of a steel

trowel and leveled by scraping. This completely filled and wetted the rough surface of the masonry

specimen.


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This step was a special step for CFRP plates: the surface was cleaned by rubbing it with white

cotton soaked with solvent. The cleaning was continued until the white cotton remains white. The

completely cleaned and dried composites were coated with epoxy adhesive. The adhesive layer

was 2-mm average thickness.

The FRP composites was applied to the specimen face by hand and impregnated with an

impregnation roller until homogeneous color was obtained.

To prevent anchorage failure, steel plates were used at specimens corners to anchor the FRP to

specimens foundations and head beams using steel bolts.

2.5 Loading system

In the test specimens, an axial load of 30 kN was applied via two external post-tensioning bars to

apply a structural concept similar to the building ofFigure 2.3. This was in addition of 12 kN of self-

weight from steel elements at wall top (due to the test set-up), reinforced concrete head beam, and

masonry panel weight. This normal force corresponded to a stress of 0.35 MPa. In one referencespecimen L2-REFE, in the second half of the test, we increased the prestressing force up to 60 kN (see

Appendix J).

During testing of the first four specimens, (L1-REFE, L1-WRAP-G-F, L1-LAMI-C-I, and L1-WRAP-

G-X) the prestressing force increased many times due to the increase of the wall height consecutive to

flexural cracks; in the next specimens four railcar springs were used with the post-tensioning bars in

order to minimize the increase of the post-tensioning force.

For the lateral loads, the concrete head beam was connected to the movable mass to transit and

distribute the horizontal lateral forces to the masonry test specimens. The concrete foundation was

clamped to the shaking table platform and dynamic excitations were applied. Therefore, the test

specimens had boundary conditions similar to a cantilever wall with an effective moment/shear ratioequal to 1.4 for the slender walls and 0.7 for the short walls. From dynamic response standpoint the

test specimen was a single degree of freedom system (SDF).


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Figure 2.12: Roughening of the Masonry

Surface

Figure 2.13: Dust Removing

Figure 2.14: Impregnate Epoxy Resin to

Masonry Substrate

Figure 2.15: Fixation of the Fabric onto Masonry

Surface by Light Finger Pressure

Figure 2.16: Impregnating the Fabric by

Means of a Plastic Impregnation

Roller.

Figure 2.17: CFRP Plates Surface Cleaning by

Rubbing It with White Cotton

Soaked with Solvent


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Figure 2.18: Coating CFRP Plate with Epoxy Resin

2.6 Dynamic Excitations

Spectrum

C9-EPFL SIKA Report VersionSika

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