A methodology for deriving analytical fragility curves for masonry buildings based on stochastic nonlinear analyses

A new analytical approach for the derivation of fragility curves for masonry buildings is proposed. The methodology is based on nonlinear stochastic analyses of building prototypes. Since such structures are assumed to be representative of wider typologies, the mechanical properties of the prototypes are considered as random variables, assumed to vary within appropriate ranges of values. Monte Carlo simulations are then used to generate input variables from the probability density functions of mechanical parameters. The model is defined and nonlinear analyses are performed. In particular, nonlinear static (pushover) analyses are used to define the probability distributions of each damage state whilst nonlinear dynamic analyses allow to determine the probability density function of the displacement demand corresponding to different levels of ground motion. Convolution of the complementary cumulative distribution of demand and the probability density function of each damage state allows to derive fragility curves. The advantages of the proposed approach are pointed out, making clear the range of validity of the results, which are based on specific hypotheses. Although the quantitative results obtained in this study are only applicable to structures belonging to the same typology as the prototype building being analyzed, the proposed procedure has a general validity and can be extended to other types of buildings.