Maximum rotational response of non linear asymmetric systems

Structures characterized by eccentricity in plan between the centre of mass and the centre of stiffness, under seismic excitations, develop coupled lateral-torsional response which may increase the deformation level of the structural elements which are more distant from the centre of stiffness. In this paper, first, the basic findings are briefly recalled of previous research works by the authors which have led to the identification of a synthetic structural parameter (called alpha) capable of capturing the essence of the torsional behaviour of linear-elastic systems and allowing effective maximum rotational response estimations. Second, preliminary non-linear parametric analysis are conducted through one-storey models by varying some key structural parameters which control elastic and inelastic torsional response in order to investigate the rotational trends of inelastic asymmetric systems under seismic excitation. The results indicate that (i) the ratio of the maximum rotation over the maximum displacement for non-linear systems is generally inferior to the corresponding ratio for linear-elastic systems, and that (ii) a useful upper bound and a good estimation for the maximum rotation developed by non-linear asymmetric systems under seismic excitation can be obtained using the alpha parameter.