An objective seismic damage index for the evaluation of the performace of RC buildings

Abstract

In modern earthquake-resistant design codes, structural elements have a non-linear behavior during an earthquake, similar to what is considered in the design process, which implies that elements are damaged and it is interesting for designers to be able to estimate structure expected global damage and correlate it to design ductility, as well as to ductility demand. Damage indexes calculated when applying the finite element method have values not reflecting deterioration in case of buildings designed for low ductility; this feature being contrary to damage indexes calculated for ductile buildings. Therefore, an objective damage index is proposed, based on ductility and elastic and ultimate stiffness values, independent to selected structural typology. The procedure is illustrated by means of an index assessment from damage caused to three buildings, two designed for low ductility (buildings with waffle slabs and framed buildings with wide beams) and a framed building, designed for high ductility. For the three buildings static non-linear response has been determined by means of a force-based procedure. Results obtained demonstrate that the proposed objective damage index provides values which describe properly the damage suffered by the buildings at the instant of collapse.