Ry-μ-Tn relations for seismically isolated structures

Abstract

The relations between the strength reduction factor Ry, the displacement ductility μ and the vibration period of the structure Tn have been extensively studied for fixed-base structures by numerous researchers in the past. This project aims at identifying similar relations for base-isolated structures. The investigation is conducted using a two-degree-offreedom model of a base-isolated structure. The hysteretic behavior of the base isolation devices and the isolated superstructure is simulated in Matlab and OpenSees using a Bouc-Wen model. The results of the observed response are verified through the excitation of the isolated structure by a large number of recorded ground motions. These motions cover a wide range of ground motion types, magnitudes and distances. The effects of base isolation and superstructure design parameters, such as stiffness and strength, are quantified through parametric studies. The resulting Ry-μ-Tn relationship for inelastic seismically isolated structures is based on the statistical processing of the inelastic response data of the isolated superstructure.