Seismic Performance Assessment of Soft-Story RC Frame Buildings

Abstract

Soft-story buildings are characterized by an inadequate stiffness or flexibility of the ground floor, which is less resistant to horizontal seismic forces than the upper storys. On the other hand, such inadequate stiffness causes disproportional displacement focused on that story. As a result, the ground floor becomes weak and susceptible to partial or complete damage to its structural elements, which in turn, results in collapse of the entire building. The results obtained from the performed linear and nonlinear push-over analyses show that the flexible story may result in a drastic change of the period of vibrations, which will further lead to a change of the seismic design force, the maximal relative story drifts and ductility of the considered structure. Within this paper, the effect of the flexible story on seismic performance of building has been explored through comparison between a structure with regular story heights and a structure with a flexible story. The effects of upgrading the critical story by appropriate structural interventions like enlargement of the base columns cross-section and/or insertion of RC walls are also investigated.

Keywords

• soft-story,seismic resistance,relative displacement,story stiffness,“pushover” analysis,strengthening,upgrading

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