Thermal buckling behavior of open cylindrical oil storage tanks under fire

Abstract

This paper reports the computational results of an investigation of oil storage tanks with the shape of an open cylindrical shell under thermal loads induced by fire. Interest in this problem has arisen as a consequence of a catastrophic fire that affected an oil storage facility in Puerto Rico in 2009 that caused the failure of 21 large tanks. To identify patterns of deformations that could be expected under various fire conditions, computer modeling has been carried out for one tank geometry. It is assumed that fire occurs outside the tank and induces an increasing temperature field affecting part of the external surface in the circumferential direction. The nonlinear shell response is modeled using finite elements under thermal loads and self-weight. The nonlinear behavior is computed to identify thermal buckling of the shell as a limit point. The response is initially computed for empty tanks, and the influence of various factors is investigated, including the liquid stored, a temperature gradient across the thickness, the circumferential zone affected by fire, and the shell thickness. The results for open tanks show that the location of large out-of-plane displacements attributable to thermal buckling coincides with the heated zone. The importance of thermal gradients in the thickness to the buckling load and mode are shown.