Performance of sliding systems under near-fault motions

Response of structures supported on the sliding systems under near-fault earthquake ground motion is investigated. The fault normal and parallel components are applied in two horizontal direction of the system. The superstructure is considered to be rigid and the frictional forces mobilized at the interface of the sliding system are assumed to be velocity dependent. The interaction between frictional forces of sliding system in two horizontal directions is duly considered and coupled differential equations of motion of the system are solved in the incremental form using step-by-step method with iterations. The iterations are required due to dependence of the frictional forces on the response of the system. The response of the system is analyzed to investigate the performance of sliding systems under near-fault motion. In addition, the effects of velocity dependence and bi-directional interaction of frictional forces on the response of isolated system are also investigated. The response of sliding system due to fault normal and parallel components is found to be more or less uncorrelated and the resultant sliding base displacement is mainly contributed by the fault normal component. It is also observed that the dependence of friction coefficient on relative velocity of system does not have noticeable effects on the peak response of the isolated system. However, if the effects of bi-directional interaction of frictional forces are neglected then the sliding base displacements under near-fault motion will be underestimated which can be crucial from design point of view. (C) 2001 Published by Elsevier Science B.V. All rights reserved.