Numerical Model and Seismic Vulnerability of Infilled Industrial Steel Structures

A numerical framework for the seismic vulnerability assessment of industrial steel structures with masonry infills is presented. This peculiar structural typology has been extensively observed in many industrial areas in the Italian territory and is commonly characterized by the absence of bracings or any anti-seismic design criteria. As such, masonry infills represent the main seismic resistant structural component which, then, cannot be neglected in the vulnerability analyses. An efficient finite element model is adopted to simulate the structural nonlinear behaviour, considering both geometrical and constitutive nonlinearities. Epistemic uncertainties related to the geometric data and the mechanical characteristics of steel and masonry are considered. The approach is tested for infilled steel structures in the industrial area of Spezzano Albanese, in southern Italy. Fragility curves are constructed considering or not considering the presence of infills and the results show that the seismic behaviour is drastically different in the two cases. In particular, it turns out that if the mechanical contribution of the infill is neglected, the structures exhibit high damage even for low intensities of the seismic action.