Response of pure-friction sliding structures to bi-directional harmonic ground motion

The response of structures with sliding support to bi-directional (i.e. two horizontal components) harmonic ground motion is investigated. The frictional forces mobilized at the sliding support are assumed to have the ideal coulomb-friction characteristics. The coupled differential equations of motion of the sliding structure in two orthogonal directions are solved in the incremental form using Newmark's method with iterations. The iterations are required due to dependence of the frictional forces on the response of the system. The responses of the system with bi-directional interaction are compared with those without interaction (2D idealization in two orthogonal directions) in order to investigate the effects of bi-directional interaction of frictional forces at the sliding supports. It has been shown that effects of bi-directional interaction are significant and should be included for the effective design of sliding structures. Further, if the effects of bi-directional interaction of frictional forces are neglected then the sliding base displacement will be underestimated which is crucial from the design point of view. In addition to harmonic ground motion the significant effects of bi-directional interaction are also observed for selected real earthquake ground excitations. Copyright (C) 1996 Elsevier Science Ltd.