On the response of yielding seismically isolated structures

Abstract

SUMMARYThis paper investigates the seismic response of yielding isolated structures. To establish a general understanding of the nonlinear response of seismically isolated structures, this study first investigates the nonlinear response of isolated structures subjected to steady-state harmonic motion and nonlinear transient ground excitation. The response of both viscously damped and hysteretically damped isolation systems is investigated in three phases. Initially, basic insights are gained through simple nonlinear two degrees of freedom (2-DOF) models subjected to harmonic motion of varying frequencies. Next, the transient response analysis of the nonlinear 2-DOF model is investigated for a wide range of isolation system and superstructure properties. The results obtained from both approaches indicate that the yielding behavior of a structure on an isolation system is significantly different from that of the comparable fixed-base structure. Finally, the response of the nonlinear 2-DOF system model is compared with that of a 15-story, three-dimensional model. Based on the results of these analytical investigations, some important considerations for the design of seismically isolated structures are presented.

Comparative response assessment of minimally compliant low‐rise conventional and base‐isolated steel frames

“…The intuitive assumption that superior performance of an isolated building in a design event naturally leads to superior performance in other earthquake scenarios deserves critical examination. Yielding of the isolated superstructure in extreme events is likely and the associated response trends have been examined by many [7][8][9][10][11][12][13][14].…”

Dynamics of inelastic base‐isolated structures subjected to analytical pulse ground motions

“…, Kikuchi et al . , and Thiravechyan et al . indicate that inelastic deformation of base‐isolated structures, if it occurs, may be much larger than expected.…”

A Probabilistic Approach Towards an Evaluation of Existing Code Provisions for Seismically Isolated Structures

“…Constantinou and Quarshie [4], Ordonez et al [5], Kikuchi et al [6], Thiravechyan et al [7] and Cardone et al [8] investigated the response of inelastic seismically isolated structures and agreed that allowing base-isolated superstructures to yield requires careful consideration because of possible occurrence of large ductility demands. Vassiliou et al [9][10][11] concluded that designing typical seismically isolated structures to behave elastically, as prescribed by current seismic design codes, is not overly conservative but a necessity that emerges from the fundamental dynamics of such structures.…”