A seismic index method for vulnerability assessment of existing frames: application to RC structures with wide beams in spain

Abstract

A method for assessing the vulnerability of existing frames in terms of an energy-based seismic index is proposed. The ground motion is characterized by the so-called Seismic Hazard Energy Factor AEI, and the susceptibility of the frame to damage is a function of two counterpart energy factors, AEIS and AEIU. AEIS represents the level of the “maximum earthquake” that the frame can sustain within the elastic range. AEIU characterizes the level of the “ultimate earthquake” associated with the collapse of the structure. The procedure takes into account the relation between the dynamic properties of the existing frame and the spectral shape of the ground motion expected at the site. The seismic index used by the method has a transparent and direct physical meaning; thus, it is useful not only for screening existing buildings but also to design a seismic retrofit solution, if needed. The method is applied to reinforced concrete frames with wide beam-column connections built in the southern part of Spain during the 1970’s, 1980’s and 1990’s.