SEISMIC FRAGILITY ASSESSMENT OF UNREINFORCED MASONRY AGGREGATE BUILDINGS IN ROW

Masonry buildings in Italy represent the majority of the historical and cultural heritage and they very often represent the
\nresult of an unbridled urban growth, due to the need to fill all the possible urban spaces. For this reason, aggregate
\nmasonry buildings have been generated over the years, allowing the aggregation of different inhomogeneous structural
\nunits, interacting under seismic action. The present work is focused on the study of unreinforced masonry aggregates in
\nrow, considering structural units along the aggregate with geometrical differences each other, generated starting from
\nthe medium values of the variables used to study masonry aggregates with identical structural units in row. Once some
\ndistributions of those variables were defined, a set of aggregations of different structural units in row is generated,
\nfollowing the rules of the Response Surface (RS) statistical method, based on the definition of a statistical model
\nexpressing a response parameter (for instance the spectral acceleration corresponding to the attainment of the Life
\nSafety Limit State) as a function of a set of variables. The RS model is calibrated through numerical data obtained by
\nnon-linear static analyses, with reference to buildings whose geometrical and mechanical properties are varied in
\nprescribed distributions. A group of registered accelerograms was used to consider the variability of the seismic action,
\nfor defined ranges of magnitude and epicenter distances referred to the considered earthquakes. Finally, the data
\nobtained from the simulations were used to plot the fragility curves, by applying full Monte Carlo simulations, in order
\nto obtain the conditional probability of failure for different values of the peak ground accelerations (PGAC). The results
\nshowed considerable differences in the fragility if different directions of the seismic action are considered, due to the
\ngeometrical properties and the arrangement of the resisting masonry walls of the aggregate and to the torsional effects
\nderiving from the aggregation of structural units in row. Moreover, the various structural units along the aggregate
\nexhibit different seismic fragility, according to their position in the masonry aggregate in row.