The categorized literature review of retrofitting and strengthening methods of reinforced concrete (RC) beam-column joints clarified that non-disruptiveness; practical implementation, ductility and perseverance of lateral resistance as well as economical issues still remain the most challenging aspects of seismically retrofitting the vulnerable existing RC beam-column joints. Current research attempted to observe the seismic design principals of RC frame structures in seismic retrofitting of the vulnerable frames as a strategy of retrofitting based on the capacity design concept. Accordingly, the beam sidesway mechanism was redefined for seismic retrofitting by relocating the beam plastic hinges far enough away from the joints. Consequently, with introducing innovative energy dissipation devices such as Multi Functional Corbels (HMFC) and Harmonica Damper Plates (HHDP), the innovative Retrofitting Techniques 1 and 2 (RT1 and RT2) were proposed. The introduced devices of HMFC and HHDP as a passive energy dissipation system absorb energy through inelastic deformations. The proposed RT1 and RT2 were experimentally evaluated through a series of 3/4-scale beam-column joint specimens under an extremely severe loading history. The excellent performance of retrofitted specimens through the experimental study confirmed that the proposed retrofitting techniques (RT1 and RT2) are able to retain structural integrity with the minimum strength and stiffness degradation. As intended, the energy dissipation capacity was dramatically increased and beam sidesway mechanism was actually formed. Furthermore, a series of non-linear finite element analysis using ATENA was carried out on all reference and retrofitted specimens. The FEM models were validated with experimental outcomes. Subsequently, the validated models were utilized to develop a new simplified method for upgrading based on the advantages of RT1 and RT2. In the new proposed innovative Retrofitting Technique 3 (RT3), HHDP was replaced by Frictional-Bending Damper Plate (HFBDP) which dissipates energy based on friction and bending. The effectiveness and reliability of the proposed RT3 was investigated through a numerical analysis. As confirmed through experimental and numerical investigation, all acceptance criteria of ACI Committee 374 [ACI 374.1-05] were effectively satisfied by the proposed retrofitting techniques.

Abstract

Kurzzusammenfassung

Acknowledgments

Table of contents

List of figures

List of tables

Notation

1 Introduction

1.1 Introduction

1.2 Motivation of the research

1.3 Objectives

1.4 Organization of the research

2 Background and State of the Art

2.1 Introduction

2.2 Seismic behaviour of substandard RC beam-column Joints

2.2.1 Summary of results

2.3 Retrofitting and strengthening techniques of beam-column joints

2.3.1 Epoxy repair procedures

2.3.2 Jacketing and other mechanical retrofitting techniques

2.3.3 Utilization of fiber-reinforced polymer composites, FRP

2.3.4 The summary of the results and discussion

2.4 Design approaches by codes of practice

2.4.1 The bond and shear requirements within the beam-column joints

2.4.2 Summary and conclusions of the codes comparison

3 Seismic Retrofitting by Developing the Beam Sidesway Mechanism

3.1 Introduction

3.2 Seismic design principals of structures and joints

3.3 Performance-based retrofitting through developing the beam plastic hinges

3.3.1 Strategy of seismic retrofitting through the capacity design concept

3.3.2 Forces acting on an exterior beam-column joint

3.3.3 Strength and Failure Sequence Diagram (SFSD)

3.4 Innovative Multi Functional Corbels (HMFC)

3.4.1 General description

3.4.2 Hysteretic behaviour

3.5 Innovative Harmonica Damper Plates (HHDP)

3.5.1 General description

3.5.2 Hysteretic behaviour

3.6 An Innovative strengthening and retrofitting technique through Multi Functional Corbels (HMFC), Retrofitting Technique 1 (RT1)

3.6.1 Approach and modified SFSD

3.6.2 Upgrading the resistance to bond-slip of the beam bottom bars

3.6.3 Procedure for designing and developing

3.7 An Innovative strengthening and retrofitting technique through HMFC and Harmonica Damper Plates (HHDP), Retrofitting Technique 2 (RT2)

3.7.1 Approach and modified SFSD

3.7.1 Upgrading the resistance to bond-slip of the beam bottom bars

3.7.2 Procedure for designing and developing

4 Experimental Program and Development

4.1 Introduction

4.2 Test specimens, energy dissipation devices and retrofitting

4.2.1 RC beam-column joint specimens

4.2.2 Multi Functional Corbels, HMFC

4.2.3 Harmonica Damper Plates, HHDP

4.2.4 Retrofitted specimens

4.3 Loading setup

4.3.1 General specifications

4.3.2 Details and fabrication of the loading setup

4.3.3 Testing procedure and loading history

4.4 Instrumentation

4.5 Experimental tests and results

4.5.1 Tests of reference units

4.5.2 Tests of retrofitted units

4.6 Test results and summary of findings

4.6.1 Strength

4.6.2 Energy dissipation

4.6.3 Damage mechanisms

4.6.4 Hierarchy of strength

4.6.5 Joint behaviour

4.6.6 Decomposition of lateral displacement

5 Numerical Analysis and Simulations

5.1 Introduction

5.2 Implemented constitutive models in ATENA

5.2.1 Constitutive modelling of concrete

5.2.2 Constitutive modelling for reinforcement

5.2.3 Constitutive modelling for reinforcement bond

5.2.3 Constitutive modelling for Von Mises plasticity

5.2.4 Constitutive modelling for interface

5.3 Element types

5.4 Solutions of nonlinear equations

5.5 Numerical models for reference units

5.6 Sensitivity study

5.6.1 Sensitivity of element size

5.6.2 Sensitivity of fracture energy

5.6.3 Sensitivity of cyclic reinforcement

5.6.4 Sensitivity of tension stiffening

5.6.5 Sensitivity of cracking model

5.7 Numerical models for retrofitted specimens

5.8 Comparison the results of FE analysis and experimental test

5.8.1 Reference unit BD-B

5.8.2 Reference unit SD-B

5.8.3 Retrofitted specimen BD-H1

5.8.4 Retrofitted specimen SD-H2-D

5.8.5 Retrofitted specimen BD-H3-D

5.9 Developing a new upgrading method, Retrofitting Technique 3 (RT3)

6 Conclusions and Recommendations

6.1 Conclusions

6.1.1 Conclusions of experimental study

6.1.2 Conclusions of numerical study

6.1.3 General conclusion

6.2 Recommendations for further research

References

Appendix A: Supplementary Reviews of Laboratory Activities

Appendix B: Scheme and Details of Loading Setup

Appendix C: Installation of Specimens into the Loading Setup

Appendix D: Decomposition of Specimen Deformation

Appendix E: Concept of Relative Energy Dissipation Ratio