Response of Sliding Structure with Restoring Force Device to Earthquake Support Motion

Seismic performance of a symmetrical space frame structure resting on sliding bearing with restoring force device is studied considering all the six degrees of freedom. The sliding support is modeled as a fictitious spring with two horizontal degrees of freedom. In non-sliding phase the horizontal stiffness of sliding bearing is considered as very large whereas it is equal to zero during sliding phase. The El Centro, Turkey and Mexico earthquakes are adopted as the input motion. The response quantities obtained from the analysis are the acceleration, base shear, bending moment and displacement. In this study, the response of the isolated structure is compared with the response of the structure fixed at the base. Response of the isolation system with restoring force device is also compared with the response of the isolation system without restoring force device. In addition, the effects of coefficient of friction of sliding material, time period of the superstructure and the number of storeys on response of structure are also investigated. It is concluded from the study that the sliding bearing with restoring force device reduces the earthquake response of the structure. The restoring force device reduces the sliding and residual displacements without transmitting additional forces into the structure. Response of the isolated structure varies with the coefficient of friction of sliding material, time period of superstructure and number of storeys. Also, there exists an optimum coefficient of friction of sliding material for acceleration, base shear and bending moment at which acceleration, base shear and bending moment attains a minimum value.