Investigation on base-isolated structures in the regions of high seismicity

The base isolated buildings are considered high performance structures in seismic design approaches, therefore the proper prediction of their behaviors are noticeable in high seismic zones. In provisions, in seismic design of base-isolated structures several parameters affect the design base shear of superstructure; among them, spectral seismic coefficients ( ) which include the effect of constructions site conditions such as soil profile . seismic hazard level. distance to seismic source and seismic source type are notified. The focus of this paper is to investigate the dominant effect of high intensity of earthquake load caused by high seismic hazard level along with its source features. To achieve this aim, several nonlinear dynamic analysis were conducted to investigate the performance of a base-isolated building designed for a region of low seismicity, but subjected to a near-field characteristics. In this paper, a 2D steel frame building which sits on the LRB isolators is assumed to be located in near-fault regions, in order to take into account the effect of strong ground motion on the isolation system and superstructure.It was observed that storey drift and base shear force superstructures vulnerability index es and displacement of isolation system, isolation system vulnerability index were significantly increased. The basic vulnerable index which should be controlled primarily was displacement demand; afterward mitigating superstructure damage due to excessive story drift. It was concluded that the supplemental passive viscous energy absorbing devices such as viscous damper can be a good choice to limit displacement demand in isolation level to maximum design displacement but it can significantly increase the internal forces and also in some circumstances adding a supplemental viscous damper may lead to more drift in the superstructure.

Keywords:

base isolation , seismic hazard level , supplemental passive viscous dampers