Simple checks to prevent the collapse of heavy historical structures and residual life prevision through a probabilistic model

A survey on about 60 Italian ancient towers is described, carried out to collect information on the most common symptoms of structural decay, particularly on the crack patterns. A simple procedure is proposed which local institutions might adopt, aimed to achieve a pre-diagnosis of the tower structures and to identify the cases where more detailed investigations have to be designed for defining the safety of the structure. The vulnerability assessment of historic buildings toward the effects of persistent loading and the achievement of a reliable lifetime estimate on a deterministic basis is often very complex. Therefore, an attempt has been made of matching the problem through a probabilistic approach.