On the non-linear rotational response of one-storey asymmetric structures

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 fundamental linear-elastic parameters and the additional non-linear parameters which govern the torsional response of one-storey asymmetric systems have been clearly identified. Second, 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 a) capable of capturing the essence of the torsional behaviour of linear-elastic systems and allowing effective maximum rotational response estimations. Third, preliminary non-linear dynamic simulations are carried out to investigate the rotational trends of asymmetric systems characterised by non-linear behaviour 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) the estimations of the maximum rotation obtained using the a parameter are generally on the safe side, thus providing useful upper bounds for the actual rotation of non-linear systems.