SOIL-STRUCTURE INTERACTION, DAMPING AND HIGHER MODE EFFECTS ON THE RESPONSE OF A MID-STORY-ISOLATED STRUCTURE FOUNDED ON MULTIPLE SOIL LAYERS

 

Chong-Shien Tsai
Department of Civil Engineering, Feng Chia University, Taiwan, R. O. C.

Yan-Ming Wang
Ph. D. Program for Civil Engineering, Water Resources Engineering, and Infrastructure Planning, Feng Chia University, Taiwan, R. O. C.
Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Hui-Chen Su
Department of Water Resources Engineering and Conservation, Feng Chia University,
Taiwan, R. O. C.

Abstract

This paper investigates the effects of soil-structure interaction (SSI), higher modes, and damping on the response of a mid-story-isolated structure founded on multiple soil lay-ers overlying bedrock. Closed-form solutions for the entire system which consists of a shear beam type superstructure, seismic isolator, and multiple soil layers overlying bedrock were obtained, while subjected to ground motion. The proposed formulations simplify the problem in terms of well-known frequency and mechanical impedance ra-tios that can consider the effects of SSI, higher modes, and damping in the entire system, and be capable of explicitly interpreting the major dynamic behavior of a mid-story-isolated structure interacting with the multiple soil layers overlying bedrock. The SSI effects on the dynamic response of a mid-story-isolated structure because of multiple soil layers overlying bedrock were extensively investigated through a series of parametric studies and physically explained by derived formulations. In addition, the results of numerical exercises show that higher damping provided by the isolator may provoke higher mode response of the superstructure; that the lower structure below the isolator may have significantly larger deformations compared to those of the upper structure above the isolator; and that isolator displacements may be amplified by the SSI effects while compared to those of mid-story-isolated structures with fixed-base.

Keywords: mid-story isolation; seismic isolation; soil-structure interaction; closed-form solution; higher-mode effects; soil stratum; passive control; damping effects

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