The St. Silvestro belfry in l'aquila: From the rehabilitation works to the actual performance in terms of dynamic properties and fragility functions estimation

Masonry towers are widespread ancient constructions, located even in seismic zone. The assessment of their seismic capacity is a required task owing to the vulnerability and predisposition to suffer damage. Slender structures are also involved in peculiar dynamic behavior, like torsional mode shapes and acceleration amplification at height. The accuracy of the seismic response prediction depends by the knowledge of geometry, masonry properties and constraint boundary conditions, frequently uncertain. The authors investigated the seismic behavior of a tower, the St.Silvestro belfry in L'Aquila (Italy). The St.Silvestro complex was hit by the 2009 earthquake. The rehabilitation works was finalized to mitigate the vulnerabilities of the masonry complex. The results of operational modal lead to the updating of a finite element model, in terms of dynamic properties. The seismic performance of the belfry are assessed in terms of probability of collapse and revealed through fragility curves.