Derivation of fragility curves for URM school buildings in Nepal

In recent years there has been an increasing interest from governmental authorities and Non-Governmental Organizations (NGOs) in the seismic safety enhancement of school buildings in developing countries. Schools represent a reference point for local communities and can be used as primary facilities for emergency and recovery activities after an earthquake. Focusing on the Nepal case, the last 2015 seismic events have shown that Nepalese school buildings are characterized by a high level of vulnerability. According to post-disaster surveys, more than the 20 percent of the country’s classrooms experienced damage or collapse during the earthquake. Nepal’s building stock is mainly constituted by non-engineered constructions realized without seismic detailing and material quality controls. Particularly, unreinforced masonry (URM) structures, representing the majority of the total building inventory, are characterized by numerous construction deficiencies such as inadequate wall-to-wall or wall-to-floor connections which have led to frequent out-of-plane collapses. Herein, a spectral-based methodology to derive fragility curves for Nepalese unreinforced masonry school buildings subjected to out-of-plane damage is discussed. The technique is applied to the case of typical mud-mortar URM Nepalese structures, by taking into account regional variations in construction practice, material properties and recurrent failure modes detected after the 2015 seismic events.