Seismic resistance capacity on pipe braced supporting frame of spherical tank

Abstract

A significant fire and explosion accident on spherical tanks for Liquefied Petroleum Gas (LPG) storage at Chiba prefecture in Japan were induced by the strong ground motion of the 2011 Great East Japan Earthquake and its aftershock. The braces made by steel pipe, of which ends were connected to support legs of one spherical tank filled with water, were broken due to the strong seismic inertia force, and then buckling of support legs were caused. To clarify the failure mechanism of the pipe braced supporting frame of a spherical tank, we performed the elastic and elastic-plastic finite element analysis. From FEA results, it was concluded the fracture mechanism of the pipe braced supporting frame of a spherical tank as follows; (1) high stress was generated in the cross point of two braces due to the structural discontinuities, (2) the generated high stress triggered for the failure initiation of the supporting frame damage, (3) resulting the spherical tank overturn during the aftershock of predominant earthquake. In this paper, the fracture mechanism of the spherical storage tank was clarified for heading off the same type accident, and the effective reinforcement of spherical tanks were proposed for securing safety.