Analytical Study on Seismic Performance of Switchboard with Hybrid Spring Supports

Abstract

Electrical equipment such as switchboard should be protected from the seismic hazard to enable stable electric power supply even after the earthquake, since its seismic damage results in the severe damage such as social chaos, fire, and explosion. The general method to secure the excellent seismic performance of switchboards is to reduce the inertial forces by introduction of base isolating systems into a switchboard frame. However, the introduction of base isolating systems may cause the increase of installation and manufacturing costs, which is more true for a low-and medium-seismicity zones, such as Korea. In order to solve finance-related problems, this paper evaluates the seismic performance of switchboards supported by the hybrid springs consisting of wire rope elastic mounts with vertical and horizontal direction stiffness and polyurethane that provides additional vertical stiffness and damping. To do this, this study constructs an analytical model that can properly capture the hysteretic behavior of a hybrid spring. Nonlinear time-history analyses were carried out with floor acceleration time-histories taking into account Koreas seismic design quantities. The analysis results show relatively small deformation of switchboard supported by hybrid springs and high resistance against over-turning moments due to additional vertical stiffness of polyurethane.