Shaking table investigation of inelastic deformation demand for a structure isolated using friction-pendulum sliding bearings

Anastasios Tsiavos,Tomislav Markic,David Schlatter,Bozidar Stojadinovic

doi:10.1016/j.istruc.2021.02.040

Abstract

This study aims at investigating experimentally if seismically isolated structures can manifest inelastic behavior when they are subjected to strong earthquake ground motion excitation. A steel structure is seismically isolated with four friction pendulum bearings and subjected to an ensemble of recorded earthquake ground motion excitations using the shaking table of ETH Zurich Laboratory. The structure is designed to concentrate its inelastic behavior on a mechanical clevis connection comprising two hinges and a pair of replaceable steel coupons. The use of this configuration enables the adjustment of the strength of the structure and thus the parametric investigation of its displacement ductility demand µ for a wide range of earthquake ground motion excitations. The experimentally derived values of the ductility demand µ for the seismically isolated structure are compared with the analytically determined values obtained through the use of Ry-μ-Tn relations for fixed-based structures and the corresponding relations developed for seismically isolated structures.

Highlights

The favorable role of seismic isolation on the decoupling of the seismic response of a structure from the motion of the ground through the use of frictional or elastomeric devices has been elucidated by many researchers in the past [1,2,3]
This study aims at investigating experimentally if seismically isolated structures can manifest inelastic behavior when they are subjected to strong earthquake ground motion excitation
The experimentally derived values of the ductility demand μ for the seismically isolated structure are compared with the analytically determined values obtained through the use of Ry-μ-Tn relations for fixed-based structures and the corresponding relations developed for seismically isolated structures

Summary

Introduction

The favorable role of seismic isolation on the decoupling of the seismic response of a structure from the motion of the ground through the use of frictional or elastomeric devices has been elucidated by many researchers in the past [1,2,3] This decoupling reduces substantially the acceleration response of the seismically isolated structure, enabling the decrease of the seismic damage in the structure compared to fixedbased, conventional structures. Current codes prescribe designing the isolated structure to base shear force that is equal or up to two times smaller than that required for the structure to remain elastic in a designbasis event. Within this frame, most of the existing studies investigating the dynamic response of seismically isolated structures assume an elastic response of the isolated structure. The investigation of the inelastic behavior of existing seismically isolated structures can facilitate their seismic eval uation, retrofit, and the determination of their reliability and robustness compared to conventional structures, as defined by Castaldo et al [5,6], Tsang [7] and Takewaki [8]

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