Behaviour of asymmetric structures under multi-component earthquake excitations

In this paper, a wide parametric analysis has been conducted in order to evaluate the effects of plastic interaction between bi-directional horizontal forces and axial forces in vertical resisting elements of stiffness eccentric systems, considering two component horizontal earthquake excitations. The influence of level of axial forces due to gravity loads in columns, with respect to their vertical strength, has been also investigated. Results point out that interaction phenomena and the axial forces in column play an important role in seismic behaviour of plan asymmetric building structures. In particular, interaction phenomena induce a reduction in torsional response as represented by floor rotations. Moreover, interaction phenomena and the action of axial forces in columns result in amplifications of ductility demands of resisting elements that may be very high, depending on the level of the axial forces.