Response Analysis of a Novel Combined Seismic Isolation Structure under Long-Period Ground Motions

Abstract

Long-period ground motions may induce pronounced responses in seismically isolated systems with relatively long fundamental periods, thereby increasing displacement demands in the isolation layer. Supplemental energy dissipation devices around isolation bearings effectively restrain isolation-layer displacements yet generally compromise the isolated system's isolation effectiveness under ordinary ground motions. To address this issue, a switchable damper (SD) based on a displacement-threshold triggering mechanism is introduced to replace conventional dampers in existing seismically isolated systems. A MATLAB-based analytical model is established for the steel frame structure equipped with the SD, and its dynamic responses are evaluated. The results show that the SD can effectively reduce the isolation-layer displacement, base shear, and inter-story displacement. Further analysis indicates that a displacement threshold of 100 - 200 mm provides a favorable balance between displacement control and acceleration mitigation.