Experimental verification and performance evaluation of an inertia-type bidirectional isolation system

Abstract

Both horizontal and vertical ground motion can cause damage to vibration-sensitive equipment. However, most mature seismic isolation devices only isolate horizontal ground acceleration; few devices isolate both vertical and horizontal ground acceleration. In this paper, a novel inertia-type bidirectional isolation system (IBIS) is proposed that comprises independent vertical and horizontal seismic isolators. The IBIS’s vertical isolator comprises leverage apparatus with a counterweight, which provides a vertical lifting force in the static state to balance the self-weight of the isolated object, and an additional inertial force in the dynamic state, resulting in higher static but lower dynamic effective vertical stiffness. The horizontal isolator is a conventional sliding-type system comprising a sliding platform and pair of springs. The IBIS’s equations of motion are derived by using Lagrange’s equation, and the theoretical model is verified through shaking-table test results. Numerical simulation and experimental results show that the IBIS has an anti-resonance property in the vertical direction, leading to higher isolation performance under both near-fault and far-field ground acceleration. The conventional sliding-type horizontal isolator component performs well under far-field ground acceleration but may perform unsatisfactorily under near-fault ground acceleration.

Keywords:

• Equipment isolation
• vertical isolation
• bidirectional isolation
• vertical ground motion
• anti-resonance

Acknowledgments

The authors thank the National Center for Research on Earthquake Engineering (NCREE, Taiwan) for their technical support on the shaking table test.

Disclosure statement

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

Additional information

Funding

This research was partly sponsored by the National Science and Technology Council of R.O.C. (Taiwan), through [Grant No. NSTC 111-2625-M-006-011, and NSTC 111-2625-M-992-002].