Targeted energy transfer using nonlinear energy sinks for the attenuation of transient loads on building structures

Nonlinear energy sinks (NESs) have been proposed as a practical and robust means of passively protecting buildings structures subjected to extreme transient loads. NESs are a type of passive attachment that differentiate themselves from tradition linear attachments through the exploitation of essentially nonlinear stiffness elements. The essentially nonlinear restoring force provided by these elements allows the NES to interact with any mode of the primary structure to which the NES is attached and participate in targeted energy transfer (TET), the broadband transfer of energy from the primary structure to the NES where it can be rapidly dissipated. Additionally, this nonlinear restoring force allows the linear modes of the primary structure to become coupled and energy to be transferred from the lower modes of vibration to the higher modes where it is dissipated at a faster rate. Previous experimental investigations of the effectiveness of NESs have used table-top sized specimens; however, little, if any, work has been done using larger-scale models that allow practical implementation issues to be considered. In addition, the existing body of work with NESs is far from complete, with limited work presented on the use of systems of multiple NESs, the experimental realization of several different NES types, or their response to realistic loads. The primary objective of this research is to explore the potential for nonlinear energy sinks to be a practical and robust means of passively protecting buildings structures subjected to extreme transient loads. In this research, experimental testing and numerical simulations will be used to perform this investigation. The two types of transient loads focused on are impulsive loads, such as blasts, and broadband random loads, such as seismic ground motions. As a part of this investigation, small-, medium-, and large-scale primary structures and several types of NESs were designed and fabricated. With these structures and NESs, the experimental investigation of the performance of these different types of NESs was carried out using impulse-like shake-tableproduced ground motion. Additionally, large-scale investigation of a non-parasitic (no net added mass) system NESs was performed with explosive blast loading and seismic loading. Furthermore, numerical simulations were performed to validate experimentally identified NES models and to investigate the robustness of NES systems. The results of this research show that NESs can significantly attenuate the response of building structures subjected to a variety of different transient load types, as well as reduce the peak demand on a structure. Furthermore, the synergistic effects realized by the simultaneous use of the different types of NESs allows for consistent performance to be maintained across a broad range of load amplitudes. CONTENTS Page CHAPTER 1 INTRODUCTION . 1 CHAPTER 2 LITERATURE REVIEW . 7 CHAPTER 3 BACKGROUND. 20 CHAPTER 4 DEVELOPMENT OF EXPERIMENTAL BLAST SIMULATION TECHNIQUE USING SHAKE-TABLE-PRODUCED GROUND MOTION . 32 CHAPTER 5 DEVELOPMENT AND EXPERIMENTAL INVESTIGATION OF SMALLAND MEDIUM-SCALE NESS . 54 CHAPTER 6 DEVELOPMENT OF LARGE-SCALE BASE STRUCTURE AND SYSTEM OF NESS . 102 CHAPTER 7 EXPERIMENTAL INVESTIGATION OF NES PERFORMANCE USING LARGE-SCALEBASE STRUCTURE SUBJECTED TO REAL AND SIMULATED BLAST LOADING . 114 CHAPTER 8 NUMERICAL AND EXPERIMENTAL STUDIES OF THE EFFECTIVENESS OF NESS AT MITIGATING SEISMIC RESPONSE . 148 CHAPTER 9 CONCLUSIONS AND FUTURE STUDIES . 167 REFERENCES . 171 APPENDIX A DESIGN DRAWINGS FOR BASE STRUCTURES AND NONLINEAR ENERGY SINKS. 178 APPENDIX B ADDITIONAL EXPERIMENTAL RESPONSES OF THE SMALL-SCALE TYPE I NES AND BASE STRUCTURE . 264 APPENDIX C ADDITIONAL EXPERIMENTAL RESPONSES OF THE SMALL-SCALE TYPE III NES AND BASE STRUCTURE . 279 APPENDIX D ADDITIONAL EXPERIMENTAL RESPONSES FOR THE LARGE-SCALE TEST STRUCTURE AND SYSTEM OF NESS . 328 1 Chapter