Seismic Performance of Low-Ductility Precast Wall Structure with Base Isolation

It is impractical and uneconomic to design a structure that remains elastic throughout severe ground motions. The main design philosophy is that minor structural damages are acceptable as long as the structure does not collapse. Hence, seismic base isolation of structures provides a better alternative in constructing seismic resistant structures. A fixed-base structure designed in accordance to seismic code provisions would be more prone to damage than their seismic isolation counterparts. This paper presents finite element analyses carried out to investigate the feasibility of applying locally produced elastomeric rubber bearing base isolators in seismically isolating non-ductile precast concrete structures from earthquake excitations. The precast wall structures were analyzed in terms of in-plane and out-of-plane isolation effects due to dynamic lateral loads. Ground excitations from three classifications of acceleration history based on different a/v ratios were used in dynamic analyses of the structures. The results showed that although the base isolator had successfully reduced most of the critical structural responses, it also compromised some other less crucial seismic behaviour of the structures. Current design philosophy for seismic base isolation should be urgently revisited. Imperative discussion and review of the feasibility in utilizing base isolators as seismic mitigation plan for seismic prone areas are presented.