Shaking-table tests on super long-period seismic isolation systems for near-source earthquakes

摘要

This paper discusses part of experimental results conducted on a new type of seismic isolation system called Suspended Pendulum Isolation (SPI) to examine applicability of long-period seismic isolation system against strong near-field motions. The versatility of both the SPI system and its multi-layer lead damper allowed to carry out several periods for isolator ranging from 2 sec to 6 sec along with variety of yield strengths for lead damper. Several numbers of near-source ground motions recorded in the 1994 Northridge and the 1995 Hyogoken-Nanbu earthquakes as well as other secific areas are used in shaking-table tests. Results indicate that near-source earthquakes of low-frequency contents can be very destructive to relatively short-period isolation system such as 2 sec (frequently applied in current isolation design of LRB system), however, longer periods of isolator can improve the effectiveness of seismic isolation system through significant acceleration reduction factor. Moreover, peak base displacements of the SPI system stay at tolerable range of practice.