Evaluation and refinement of closely spaced buildings’ performance under near-fault ground motions

Abstract

This paper investigates the seismic behaviour of closely spaced fixed-base and isolated building structures in near-fault (NF) zones. Seismic pounding of fixed-base structures is considered at different heights, being from one or both opposite sides and at different seismic gap width. The response evaluation results of fixed-base buildings drive towards providing limited, but adequate, seismic gaps to perform seismic isolation. This aims at reducing structural responses with no seismic pounding under limited gaps, minimising the possible damage repair and diminishing the needed maintenance works due to strong NF earthquakes. To achieve that untraditionally, the paper presents a recently proposed seismic isolation system, named roll-in-cage (RNC) isolator, as a non-traditional solution to avoid direct seismic pounding of isolated buildings with their surrounding adjacent structures. It was found that the RNC isolator’s buffer mechanism is able to draw down any possible pounding of the isolated superstructure to be within the isolator solid limits. This entirely prevents direct structure-to-structure pounding but on the account of amplifying its acceleration and drift responses. However, such amplified responses might lead to only minor or moderate structural damage under sever NF earthquakes with 1.20g peak ground acceleration. Nevertheless, such damage could be avoided entirely using stiffer RNC isolators to achieve reduction of seismic response up to 69.0% under the same severe loading conditions and limited seismic gaps with no seismic pounding. Consequently, the RNC isolator could be an efficient solution for aseismic design in NF zones considering limited seismic gaps.