Shear Performance of Precast SHCC Infill Walls for Seismic Retrofitting of Non-Ductile Frames

다국어 초록 (Multilingual Abstract)

A large number of these buildings were designed and constructed during 1970’s and 80’s and do not possess the deformation capacity required for the level of lateral strength provided. Particularly, some buildings were constructed before seismic code had been enacted.
In this case, new building may be constructed to satisfy the seismic design required by current code. But, this scheme that replace existing buildings by new buildings is non-economic, and even environmental pollution may occur. Because of these problems, many researches have been tried and performed to improve seismic performance of buildings by retrofitting methods. However, current codes as ACI and Eurocode 8 do not have appropriate design procedure although the required factors should be considered in designing infill wall-frame.
Therefore, evaluation on a single infill wall is needed to obtain a better understanding of the cyclic behavior of this infill wall-frame system. The objectives of this research are 1) to investigate the cyclic behavior of infill wall-frames and single infill walls by performing cyclic static loading tests, 2) to establish simple but rational design guidelines and suggestions for analysis modeling for this system based on the experimental results, and 3) to provide data for the validation and calibration of computational models of this structural system, such as nonlinear, cyclic finite element analysis.
Tests on the mechanical characteristics of SHCC were conducted to bring up the basic source datum to develop material constitutive models for the analysis method to predict the behavior characteristics of seismic devices made of SHCC. The variables were hybrid conditions and water-cement ratio. The tests results showed that SHCCs with only synthetic fibers are more profitable to improve tensile strength and strain. However, because it is difficult to increase fiber-reinforcing index and the coefficient of strain by reinforcing with only synthetic fibers, hybrid technique and careful selection of the reinforcing fiber based on workability and economical efficiency were needed when fiber-reinforcing index is over 3.0.
The experimental phase was conducted in two phases. The specimens were one-third scale models. In the two phase, four specimens were fabricated and tested, respectively. The experimental results in the first phase showed that a method to control the shear stress effectively, such as the use of a diagonal reinforcing steel bar in the infill wall, should be devised in order to improve the seismic performance of the existing frame reinforced with an infill wall. Moreover, a method to improve the reinforcement effect on existing frames through the use of fiber-reinforced cement composite, such as SHCC, should be considered while, at the same time, simplifying the steel bar arrangement details for economic reasons. The experimental results in the second phase showed that due to bridge action of reinforcing fiber, notched SHCC infill wall specimen showed similar energy dissipation capacity to normal concrete infill wall specimen.
The analysis procedure was performed to assess the validity of modeling techniques for simulating the cyclic behavior of these SHCC infill walls. The specimens were modeled using 8-noded quadrilateral, isoparametric plane stress elements with a 2×2 Gauss integration scheme. All nodes along the bottom edge of the model were constrained in the X and Y directions to represent the base fixity of the specimen. To model the roller supports on the top boundary of wall, spring element were used, which provided stiffness in the vertical direction while providing none in the horizontal direction. In constitutive model, parabolic model in compression and brittle model in tension were used for concrete model, and the SHCC was modeled with a total strain-based rotating crack model developed by Han et al., and Von Mises method was applied to model reinforcement. The analytical results showed that improvements in the finite element model could lead to improvements in the simulation results. However, it was thought that parameter studies have to be performed to determine the effects of varying the tensile characteristics of the SHCC and varying the boundary conditions on the behavior of the SHCC infill wall.

목차 (Table of Contents)

• CHAPTER 1 INTRODUCTION 1
• 1.1 Background 1
• 1.2 Objectives and Scope 5
• 1.3 Organization of Thesis 6
• CHAPTER 2 REVIEW ON THE PREVIOUS RESEARCH AND CURRENT CODES 9
• 2.1 General 9
• 2.2 SHCC 9
• 2.3 Infilled Frames 15
• 2.4 Current Codes 22
• 2.4.1 ACI 318-08 22
• 2.4.2 Eurocode 8 23
• 2.4.3 GBRC 24
• 2.5 General Evaluation of Previous Research 24
• 2.5.1 SHCC 24
• 2.5.2 Infilled frame 25
• 2.6 Complementary Approaches 25
• CHAPTER 3 EFFECT OF REINFORCING FIBER TYPES ON THE BEHAVIOR CHARACTERISTICS OF SHCCS 27
• 3.1 Introduction 27
• 3.2 Testing Program 29
• 3.2.1 Materials 30
• 3.2.2 Mixing procedure, specimen preparation and curing 31
• 3.2.3 Testing procedure 33
• 3.3 Test Results 34
• 3.3.1 Compressive behavior 35
• 3.3.2 Flexural behavior 37
• 3.3.3 Direct tensile behavior 41
• 3.4 Evaluation on the Tensile Performance in SHCC 44
• 3.5 Summary 51
• CHAPTER 4 SHEAR STRENGTH OF INFILLED FRAMES 53
• 4.1 Introduction 53
• 4.2 Experimental Program 56
• 4.2.1 Test specimen 56
• 4.2.2 Material properties 59
• 4.2.3 Testing method 61
• 4.3 Experimental Results 63
• 4.3.1 Crack pattern and general failure mode 63
• 4.3.2 Load vs. Displacement 66
• 4.3.3 Comparison with GBRP for the strength of the RC Infill-wall frame 74
• 4.3.4 Analysis for the previous study on the seismic performance of RC infill-wall frame 76
• 4.3.5 Evaluation of the seismic performance of the RC infill wall-frame 78
• 4.4 Summary 83
• CHAPTER 5 SHEAR BEHAVIOR OF PRECAST SHCC INFILL WALLS 85
• 5.1 Introduction 85
• 5.2 Experimental Program 88
• 5.2.1 Test specimens 88
• 5.2.2 Material properties 90
• 5.2.3 Testing method 94
• 5.3 Experimental Results 95
• 5.3.1 Crack pattern and general failure mode 95
• 5.3.2 Crack width 101
• 5.3.3 Load-displacement relationship 103
• 5.3.4 Energy dissipation capacity 109
• 5.4 Assessment of influencing factor on shear strength of wall 112
• 5.5 Summary 119
• CHAPTER 6 FINITE ELEMENT ANALYSIS ON THE INFILL WALLS 121
• 6.1 Introduction 121
• 6.2 Finite Element Model 122
• 6.2.1 Idealization of specimen 125
• 6.2.2 Constitutive model 127
• 6.2.3 Input data 132
• 6.3 Simulation Results 133
• 6.3.1 Load-displacement response 133
• 6.3.2 Crack pattern and stress distribution 136
• 6.4 Summary 141
• CHAPTER 7 CONCLUSIONS 143
• 7.1 Conclusion from Material Tests on the SHCC 143
• 7.2 Conclusion from Tests on the Infilled Frames 144
• 7.3 Conclusion from Tests on the Infill Walls 145
• 7.4 Conclusion from Analytical Study 145
• REFERENCES 147
• ABSTRACT 165