Nonlinear dynamic analysis of Italian code-conforming one-storey steel buildings for seismic risk assessment

This papers describes the nonlinear analyses of steel single-storey buildings designed according to the current Italian codes in three cities with increasing seismic hazard (Milan, Naples and L’Aquila) and considering two soil conditions (stiff and deformable) for each site. In the first part, the geometry, material characteristics and main design properties of the buildings, including their elastic dynamic properties, are illustrated. In the second part, the geometric and material nonlinear model used for the nonlinear analyses is presented. Such a structural model includes distributed plasticity models for beams, columns, and concentric braces; lumped plasticity models for the connections and stiffeners of the braces to the columns and beams. The geometric nonlinear corotational formulation is used to include both global instability problems in the buildings as well as local instability effects in effects the braces. Geometric imperfections of the braces are calibrated consistently with the nonlinear analysis format. Collapse criteria are introduced to identify the collapse point and the results of the multi-record nonlinear incremental dynamic analyses are presented to provide information on the structural performance of the designed buildings under seismic input as a basis for collapse risk assessment.