Inelastic response of one-storey asymmetric-plan systems subjected to bi-directional earthquake motions

The inelastic response of one-storey systems with one axis of asymmetry sub jected to bi-directional base motion is studied in this paper. The effect o f the system parameters on response is also evaluated: uncoupled torsional- to-lateral frequency ratio, stiffness eccentricity, and yield strength of t he lateral resisting elements. The ensemble of earthquake records used cons ists of 15 two-component strong ground motions. The response to uni-directi onal excitation is considered first to examine the influence of the system parameters and to serve as a basis to examine the results of the bi-directi onal case, which are presented in terms of average spectra for bi- over uni -directional lateral-deformation ratios. It is shown that the effect of ine lastic behaviour is, on the average, noteworthy for stiff structures, in tu rn, the same structures are the most affected by the action of bi-direction al ground motions. The effect of the relative intensity of the two orthogon al ground motion components is also studied. Copyright (C) 1999 John Wiley & Sons, Ltd.