University of Pavia, Department of Structural Mechanics, Pavia
European Centre for Training and Research in Earthquake Engineering (EUCENTRE), Pavia
University of Pavia, Department of Structural Mechanics and EUCENTRE, Pavia

The evaluation of the seismic behaviour of masonry structures is affected by different sources of uncertainty, related to definition of seismic input, modelling assumptions, uncertain and incomplete knowledge of structural details and material properties. Moreover material properties can vary significantly from element to element even within the same structure. In order to account for the effect of such uncertainties on structural response, thousands of nonlinear stochastic analyses have been carried out. In particular the uncertainty involved in the definition of structural capacity is evaluated through stochastic pushover analyses, based on experimental distributions of mechanical properties. From the results of such analyses the probability distribution functions of selected damage thresholds are obtained. The uncertainty in the definition of seismic demand is instead considered by performing nonlinear dynamic analyses to derive the probability distributions of drift maxima as a function of ground motion parameters. To this aim an extended set of natural strong motion records has been used. The convolution of capacity and demand distributions allows to compute analytical fragility curves taking explicitly into account all sources of uncertainty for the considered damage states.

Key words
Stochastic analysis, seismic assessment, URM buildings, fragility