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AEM SIMULATION OF SEISMIC RETROFITTING METHODS OF UNREINFORCED MASONRY RAILWAY STRUCTURES రಕͶ͕͜Ζໃ۔͹ૌ੷ߑଆ෼͹ଳਔึک๏๑ by PHAN Thanh Ngoc Student ID number: 17RB903 A Dissertation submit

AEM SIMULATION OF SEISMIC

RETROFITTING METHODS OF

UNREINFORCED MASONRY RAILWAY

STRUCTURES

రಕͶ͕͜Ζໃ۔͹ૌ੷ߑଆ෼͹ଳਔึک๏๑

by

PHAN Thanh Ngoc

Student ID number: 17RB903

A Dissertation submitted to Yokohama National University

In partial fulfillment of the requirements for the degree of

Master of Engineering

Supervisor

Professor Akira HOSODA

Graduate school of Urban Innovation Yokohama National University

Yokohama, Japan January 2019

ACKNOWLEDGEMENT

The author would like to express his great appreciation to his research supervisor, Prof Dr Akira Hosoda for his patient guidance, invaluable suggestions, enthusiastic encouragement and useful critiques at every stage of this research work

The author is equally grateful to Prof Dr Hamed Mohamed Mahmoud Salem, Structural Engineering Department, Cairo University, Egypt for his consistent guidance and supports the author in doing numerical analysis using Extreme Loading for Structures which follows Applied Element Method

The author’s grateful thanks are also extended to Mss Sakiko Takahashi, Assistant Manager, Structural Engineering Center, East Japan railway company for her kind help in doing data analysis of experimental results

The author extends his thanks to project 599 of Vietnam International Education Development of the Ministry of Education and Training of Vietnam which gave a good scholarship for supporting his study

Finally, the author wishes to thank his parent and older brother for their encouragement and support throughout his study

ABSTRACT AEM SIMULATION OF SEISMIC RETROFITTING METHODS OF UNREINFORCED MASONRY RAILWAY STRUCTURES

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According to previous surveys on railway structures in the metropolitan area of Japan, it has been reported that there are some old unreinforced masonry structures made of bricks or stones or plain concrete while are in service In order to enhance the performance of unreinforced masonry piers in very limited spaces under severe seismic actions, many kinds of strengthening techniques have been planned by JR EAST company in Japan such as vertical-prestressed steel, grid-steel plate and Concrete Filled Tubes (CFT) methods The basic concept of the methods is to prevent the large horizontal sliding and residual displacement at the mortar joints between bricklayers which may cause catastrophic failure of structures or difficulty of early resuming railway service after the earthquake In this study, an attempt is made to apply the Applied Element Method (AEM) which is highly developed for simulating the experimental results in the case of Grid-steel plate retrofitting method Two separated low strength concrete column was retrofitted by gird-steel plate method A Polyvinyl Chloride (PVC) sheet was inserted between the joint of two column blocks to expect the reduction of the sliding friction when horizontal displacement was applied to the specimen The Grid-steel plates were arranged on the two side surfaces of the column and joined with the penetrating reinforced bars The investigated cases include the alteration of the dimensions, the thickness and the arrangements of the steel plates in the vertical direction to assess the sensitivity of the related influencing factors on the performance of the testing specimens The grid-steel plate retrofitting method showed good contribution to mitigate the sliding behavior of the retrofitted column at the joint and caused rocking behavior at the base The numerical monotonic and cyclic analysis results showed that the crack occurrences, crack propagation, load-displacement relation and failure pattern of the experimental specimens are quite comparable and highly validated In addition, some possible techniques for the next stage of the research is also demonstrated

CONTENTS

ACKNOWLEDGEMENT i

ABSTRACT ii

TABLES v

FIGURES vi

CHAPTER 1 1

INTRODUCTION 1

1.1 Background 1

1.2 Objectives and scope 2

1.3 Brief outline of the study 2

1.3 Methodology and verification process in the study 3

1.4 Justification of the research 3

1.5 Organization of the Thesis 4

CHAPTER 2 5

LITERATURE REVIEW 5

2.1 Previous studies on the seismic failure mode of unreinforced masonry railway structures 5

2.2 Previous studies on seismic retrofitting methods of unreinforced masonry railway structures 6

2.3 Previous studies on seismic retrofitting methods of unreinforced stone masonry bridge piers 7

2.4 Numerical simulation of masonry 8

2.5 Conclusion 9

CHAPTER 3 10

CONCEPT OF THE RETROFITTING METHOD 10

3.1 Working condition of the existing unreinforced masonry railway bridges 10

3.2 Basic concept of the retrofitting methods 10

3.3 Main seismic retrofitting methods 11

3.3.1 The Grid-steel plate retrofitting method 11

3.3.2 The Vertical-prestressed steel retrofitting method 12

CHAPTER 4 13

AEM SIMULATION AND METHOD OF VERIFICATION 13

4.1 Applied Element Method (AEM) 13

4.2 AEM and FEM in comparison 13

4.3 Software used for the Analysis following AEM 14

4.4 AEM material models in the study 14

4.4.1 Concrete model 14

4.4.2 Reinforcing bars model 15

4.4.3 Bearing material model 16

4.4.4 Elastic material model 16

4.5 Justification of using AEM as a numerical analysis method for the research 17

4.6 Basic assumptions in AEM simulation 18

CHAPTER 5 19

AEM ANALYSIS OF GRID-STEEL PLATE RETROFITTING METHOD FOR MASONRY PIERS OF RAILWAY BRIDGES 19

5.1 Experimental program 19

5.1.1 General 19

5.1.2 Specimen’s details 19

5.1.3 Materials 22

5.1.4 Testing procedures 22

5.1.5 Testing results 23

5.2 Verification of AEM simulation Case 1 26

5.2.1 Interface material between concrete blocks and PVC sheet 28

5.2.2 Interface material between concrete columns and steel plates 29

5.2.3 Verification of simulation 29

5.3 Verification of AEM simulation Case 2 30

5.3.1 Interface material between concrete blocks and PVC sheet 32

5.3.2 Verification of simulation 33

5.4 Verification of AEM simulation Case 3 33

5.4.1 Interface material between concrete blocks and PVC sheet 35

5.4.2 Verification of simulation 35

5.5 Conclusions and future study 36

5.5.1 Conclusions 36

5.5.2 Future study 36

CHAPTER 6 37

AEM ANALYSIS OF VERTICAL-PRESTRESSED STEEL RETROFITTING METHOD 37

6.1 Experimental program 37

6.1.1 General 37

6.1.2 Specimen details 37

6.1.3 Materials 39

6.1.4 Testing procedures 39

6.1.5 Testing results 40

6.2 Verification of AEM simulation Case 2 46

6.2.1 Material properties used in AEM models 46

6.2.2 The use of square section instead of round section when simulating a steel bar 48

6.2.3 Modeling prestressed steel bars in AEM model 49

6.2.4 Monotonic analysis 51

5.5 Conclusions and future study 52

5.5.1 Conclusions 52

5.5.2 Future study 52

CHAPTER 7 53

CONCLUSIONS 53

7.1 General 53

7.2 Conclusions and recommendations regarding Grid-steel plate retrofitting method 53

7.2 Conclusions and recommendations regarding verification model of AEM simulation using in the research 53

7.4 Future works 54

TABLES

Table 5 1 Details of steel plates, steel anchors, sheath tubes and steel bars 20

Table 5 2 Details of columns and PVC sheet 20

Table 5 3 Characteristics of concrete 22

Table 5 4 Characteristics of steel 22

Table 5 5 Material properties of concrete and steel in ELS models 27

Table 5 6 Properties of bearing material in ELS models 27

Table 5 7 Properties of interface material in ELS models 27

Table 5 8 Properties of elastic material in ELS models 27

Table 5 9 Interface material assignment 28

Table 5 10 Material properties of concrete and steel in ELS models 31

Table 5 11 Properties of bearing material in ELS models 31

Table 5 12 Properties of interface material in ELS models 31

Table 5 13 Properties of elastic material in ELS models 31

Table 5 14 Interface material assignment 32

Table 5 15 Material properties of concrete and steel in ELS models 34

Table 5 16 Properties of bearing material in ELS models 34

Table 5 17 Properties of interface material in ELS models 34

Table 5 18 Properties of elastic material in ELS models 34

Table 5 19 Interface material assignment 35

Table 6 1 Prestressed force used in the test ……….38

Table 6 2 Characteristics of concrete 39

Table 6 3 Characteristics of steel 39

Table 6 4 Material properties of concrete and steel in ELS models 47

Table 6 5 Properties of interface material in ELS models 47

Table 6 6 Properties of elastic material in ELS models 47

Table 6 7 Interface material assignment 48

FIGURES

Fig.1 1 Unreinforced masonry railway bridges in Kantou area 1

Fig.1 2 Damage of Unreinforced masonry railway structures under earthquakes 1

Fig.1 3 Brief outline of the study 3

Fig.1 4 Verification process of AEM simulation 4

Fig.2 1 The Great Kantou Earthquake’s damage to Minatogawa bridge……… ………5

Fig.2 2 Loading test on brick masonry wall Fig.2 3 The degree of seismic resistance 6

Fig.2 4Partial steel plate retrofitting method 6

Fig.2 5Horizontal loading test 7

Fig.2 6Typical Elevation Views of Rest Piers with Proposed Mini-piles as Strengthening Reinforcement 8

Fig.2 7 State of stresses in a masonry prism subjected to vertical compression 9

Fig.3 1 Rocking behavior after retrofitting………10

Fig.3 2 The use of brackets to prevent falling and overturning 11

Fig.3 3 The grid-steel plate retrofitting method 11

Fig.3 4 The Vertical-prestressed retrofitting method 12

Fig.4 1 Connectivity matrix spring ………13

Fig.4 2 Analysis domain of AEM compared to FEM 14

Fig.4 3 Partial element connectivity 14

Fig.4 4 Concrete material model 15

Fig.4 5 Reinforcing bars model 16

Fig.4 6 Bearing material model 16

Fig.4 7 Elastic material model 17

Fig.4 8 8-node hexahedron elements 17

Fig.5 1 The three reinforced concrete specimens ………20

Fig.5 2 The main components of the specimen 21

Fig.5 3 Construction joint between lower block and footing 21

Fig.5 4 Spongy pads were inserted to prevent local failure 21

Fig.5 5 Compressive strength test and splitting test 22

Fig.5 6 Experimental results Case 1 23

Fig.5 7 Diagonal cracks in Case 1 24

Fig.5 8 Experimental results Case 2 25

Fig.5 9 Experimental results Case 3 26

Fig.5 10 The interface material in model case 1 29

Fig.5 11 The elastic interface model 29

Fig.5 12 Monotonic analysis Fig.5 13 Cyclic analysis 30

Fig.5 14 Cracks and failure patterns 30

Fig.5 15 The interface material in model Case 2 32

Fig.5 16Monotonic analysis Fig.5 17 Cyclic analysis 33

Fig.5 18 Cracks and failure patterns 33

Fig.5 19 Monotonic analysis Fig.5 20 Cyclic analysis 35

Fig.5 21 The crack patterns 36

Fig.6 1 The main components of the specimen……….……… 37

Fig.6 5 Experimental results Case 3 46

Fig.6 6 Summation of experimental results 46

Fig.6 7 Components in ELS model 48

Fig.6 8 The corresponding square section of steel bar in AEM model 49

Fig.6 9 Spring controller setting in ELS 49

Fig.6 10 Internal force in the PC steel bar 50

Fig.6 11 Construct scenario option in ELS 50

Fig.6 12 Loading scenario in ELS 51

Fig.6 13 Applying prestressed force using construct scenario in ELS 51

Fig.6 14 Monotonic analysis of Case 2 52

Fig.6 15 Failure mode of the ELS model Case 2 52

3.3 Main seismic retrofitting methods 11

3.3.1 The Grid-steel plate retrofitting method 11

3.3.2 The Vertical-prestressed steel retrofitting method 12

CHAPTER... retrofitting………10

Fig.3 The use of brackets to prevent falling and overturning 11

Fig.3 The grid-steel plate retrofitting method 11

Fig.3 The Vertical-prestressed retrofitting...

2.2 Previous studies on seismic retrofitting methods of unreinforced masonry railway structures

2.3 Previous studies on seismic retrofitting methods of unreinforced stone masonry