Control of Secondary Systems Response in a Base-Isolated Building under Tridirectional Ground Motion

The studies on the seismic control of a secondary system (S-system) in the base-isolated primary system under multicomponent earthquake is scanty. In this study, an S-system response mounted on a floor of a three-dimensional (3D) base-isolated building is investigated under three component earthquake. The main objective of the study is to examine the response reductions of the S-system in all three directions, including the vertical direction, in which the building is not isolated. For the purpose of the study, two 6-story 3D building models, one base isolated and the other nonisolated, are analyzed. The S-system consists of a single portal frame with a mass at its center. The nonlinear time history analysis of both building models is carried out for three component ground motion, using commercial software SAP 2000, in order to study the control of response of the S-system. The nature, peak ground acceleration (PGA), and component ratios of the earthquake are varied to perform the parametric study. The findings of the study show that significant reduction in the lateral displacement and acceleration of the S-system is achieved by base isolating the building. In addition, the S-system's vertical responses are reduced despite the isolation being ineffective in the vertical direction. (C) 2021 American Society of Civil Engineers.