Seismic vulnerability assessment indices for buildings: Proposals, comparisons and methodologies at collapse limit states

Seismic vulnerability assessment of existing buildings is an essential process for earthquake disaster management. It can support decision-makers to estimate critical response parameters and improve them. While several seismic vulnerability assessment techniques have been introduced over the past years, a detailed formulation to measure the vulnerability index of existing buildings along with the operative procedure is still lacking. Current standards and literature worldwide mostly propose simplified approaches (e.g. based on limited engineering analyses, visual inspection) to perform a rapid vulnerability assessment that can be useful when a large number of buildings should be analyzed. This paper presents a methodology to perform the seismic vulnerability assessment of existing buildings at collapse, analyzing a standard vulnerability index, and proposing alternative formulas. The methodology combines field investigations and experimental tests with nonlinear structural analyses. It has been applied to a case study that consists of an existing reinforced concrete school building to analyze and compare the proposed indices with respect to different ground motion selection procedures. Furthermore, a detailed comparison with alternative vulnerability indices from literature has been also performed