Edifici in muratura e sicurezza sismica. I meccanismi di collasso delle pareti di facciata alla luce della normativa vigente.

The paper presents a procedure aimed at the evaluation of seismic safety of masonry historic buildings subjected to earthquakes. The approach chosen is based on a failure analysis of the structures through the identification of the two most ordinary out of plane collapse mechanisms of the façade walls (vertical overturning and overturning with side wings) and calculation of their associated failure factors according to the current legislation in Italy. First mechanism refers to the overturning of the façade without the participation of the party walls and this usually occurs when there is not a connection at the edges of the wall, or this one is rather poor, due to the geometric dimensions of the connecting elements. Second mechanism occurs instead of first one when the level of connection is sufficient to involve respectively one or both the party walls into the overturning. The mechanism develops by the occurrence of a diagonal crack along the party wall and an horizontal hinge on the façade.