Abstract
Oil storage tanks are usually constructed directly on the earth foundations without anchors. In such a flat-bottom cylindrical tank subjected to seismic excitations, a part of the bottom plate adjacent to the shell will be lifted off the foundation due to overturning moment. Then, it results in a failure of the shell-to-bottom junction when fatigue cracks or defects exist at the toe of the fillet weld.
In this paper, the elastic-plastic fracture analysis code “FRACT-2D” based on the updated Lagrangian formulation of the finite deformation theory has been developed by the author for evaluating the nonlinear fracture parameter J-and J-integral of an axi-symmetric crack problem.
Applying this code to a crack assumed at the toe of the fillet weld joint of a 113, 000kl oil storage tank, the crack opening displacement (COD) and the crack-tip opening displacement (CTOD) are evaluated numerically under the uplift behavior of tank bottom. Then, the J-and J-integral are found to be path-independent except very close to the crack-tip in the region affected by plastic strain concentration.
