A probabilistic framework far the preservation of historic masonry towers

A great part of the Italian and European built heritage is constituted of historic masonry towers. Such structures, due to their intrinsic slenderness, are prone to seismic risk and, as every historic structure, exhibit several constructive aspects which are difficult to be properly described from an engineering point of view. In this paper, with the aim to include most of the sources of uncertainties, a probabilistic framework is proposed to assess the seismic risk of historic masonry towers. The probabilistic approach is presented through the discussion of an emblematic case study: the Torre Grossa in San Gimignano (Italy). In a first part of the paper some experimental results (accelerations of monitored levels of the tower under ambient noise), are employed to identify a numerical finite element model. Subsequently the identified model is employed to perform non-linear time history analyses which constitute the basis for the evaluation of the collapse probability of the historic tower.