Seismic damage on merlons in masonry fortified buildings: A parametric analysis for overturning mechanism

The present paper analyses both merlons on towers and on walls, in clay brick masonry or in stone masonry, and describes, through a parametric analysis, their behavior as the features change. A simple linear elastic model was adopted to identify the activation of the out of plane mechanisms, while the subsequent collapse was analyzed with a non-linear kinematic model. Moreover, appropriate filtering equations were chosen to modify the response spectrum at the ground, thus taking into consideration the seismic filtering effect exerted by the supporting wall or tower. The proposed procedure is discussed and validated by means of three different case studies: the San Felice sul Panaro Fortress (damaged in the Emilia 2012 earthquake), the Arquata del Tronto Fortress, and the Rancia Castle (both damaged in the 2016 Central Italy earthquake). By changing the parameters (geometries, materials, soil) between extreme but realistic values, the curves that relate the slenderness of the merlons to the PGA that leads to the activation of the mechanism (or collapse) are plotted. These graphs supply ranges of vulnerable conditions, representing a straightforward and reliable instrument, also for practitioners and public bodies in charge of heritage preservation, useful to define priority lists for interventions and to optimize the resources for the prevention of future damage.