Use of nonlinear static procedures for irregular URM buildings in literature and codes. 16th European conference on earthquake engineering

The paper presents a study on the nonlinear static procedures (NSPs) proposed in codes and literature and their application to irregular unreinforced masonry (URM) buildings. NSPs were originally developed mainly for the seismic design of regular reinforced concrete buildings, on the contrary existing URM buildings often presents structural irregularities and not rigid diaphragms. As a consequence, the applicability of NSPs on URM buildings is still debated. To assess the reliability of current NSP when applied to this type of buildings, a numerical investigation was undertaken on ten case studies representative of typical URM buildings existing in Italy and, more in general, in European countries. A comparison among codes and various literature proposal was conducted, in particular the following was studied: 1) the load pattern distributions to apply, 2) the performance level (PL) evaluation and 3) the correspondent intensity measure (IM). From the analysis of the results, the main issues of current NSPs were highlighted and refinements were proposed to overcome the drawbacks observed. Nonlinear time-history (dynamic) analyses were adopted as reference solution.