Report - PEER - University of California, Berkeley

SEISMIC FRAGILITY ANALYSIS OF STRUCTURAL SYSTEMSPaolo E. PINTO 1 , Paolo FRANCHIN 1 , Alessio LUPOI 1 , Giorgio LUPOI 2ABSTRACTA method is presented for the evaluation of the seismic fragility function of realistic structuralsystems. The method is based on a preliminary, limited, simulation involving non lineardynamic analyses performed to establish the probabilistic characterisation of the demands onthe structure, followed by the solution of a system reliability problem with correlated demandsand capacities. The results compare favourably well with the fragility obtained by plain MonteCarlo simulation, while the associated computational effort is orders of magnitude lower. Themethod is demonstrated with an application to a 3D RC building structure subjected to bidirectionalexcitation.Keyword: Fragility functions.1. INTRODUCTIONFragility functions can be obtained through a variety of methods that range fromexpert judgment (ATC13,1985), to data analysis on observed damages (Singhal 1998,Shinozuka 2000), to fully analytical approaches, as for example in Cornell 2002,Gardoni 2003, Franchin 2004, Au 2003.A feature common to most of the approaches of the latter category is the use of areduced number of simulations to compare probabilistically the maximum structuralresponses with the corresponding capacities. The difference among them lieessentially in their balance between cost and accuracy, i.e., in their ability to accounteconomically for all the aspects entering the reliability problem. These latter include:• The possibility of the structure reaching collapse in more than one failuremode (system reliability problem)• The degree of dependence among the possible failure modes• The uncertainty in the capacity of the structure (due to the approximatenature of the models)1 Dept. Struct. & Geotech. Eng., University of Rome “La Sapienza”, Rome, Italy2 European School for Advanced Studies in Reduction of Seismic Risk, Pavia, Italy221