A computational method for determining combined ductility demands on steel structures subject to multi-hazards

This paper presents a computational method for investigating the ductility demands induced by thunderstorm downbursts to steel building structures that have been previously damaged during a strong hazard event of any nature (earthquakes, strong winds). The proposed computational method synchronizes the finite element (FE) analysis software ABAQUS and MATLAB reverse optimization subroutines. A nonlinear static pushover analysis is initially performed to induce the ductility demands of the first hazard event and identify the relationship between the base shear force and lateral roof drift up to a target plastic deformation. The method uses the pushover analysis in order to bring the structure at a pre-defined ductility level, including the descending branch of the load-deformation curve, thus allowing for a direct control of the initially imposed damage. The transient non-stationary wind loads are then subsequently applied as an externally applied dynamic loading and the revised displacement ductility demand is directly determined. The method is applied on a tall steel building subject to several initial damage stages and three subsequent thunderstorm downburst synthetic records. The results demonstrate the non-negligible effects of such wind events on the total ductility demands. The method can successfully quantify the increased ductility demands on structures subjected to multi-hazards.