Influence of Plan Irregularity in the Seismic Vulnerability Assessment of Existing Unreinforced Masonry Buildings with RC Slabs

In the seismic vulnerability assessment of buildings, irregular configurations can significantly affect structural performances. Moreover, existing buildings have been often designed without aseismic criteria so that the capacity of the structures is not able to rule the failure mechanisms. The present paper deals with the seismic vulnerability assessment of unreinforced masonry building with RC slabs. Plan configurations are based on regular geometries combined in irregular ways through staggered aggregations of two or three units. The “knowledge path” recommended by the Italian codes has been developed, concerning archive researches and experimental campaigns. Buildings modelling has been made adopting an equivalent frame discretization; the seismic performance of the case studies has been investigated through non-linear static analysis adopting two different load patterns. The capacity of the selected buildings has been compared to the one of the single-unit buildings and the capacity of linear configurations. The procedure aims to determine how the irregular combination of regular units affects the seismic behaviour through torsional effects. The results, expressed through damage patterns and capacity/demand ratios, highlight the role played by the irregular configurations for these typologies of buildings.