Investigating the behavior of cracks in welded zones of supporting structure of spherical pressure vessel under seismic loading

Abstract

In this paper, the numerical studies on the semi-elliptical crack behavior in different locations of welded zones in the supporting structure of a spherical pressure vessel under an earthquake are presented. The cracks in the welded zones of supporting structures under earthquake effects may jeopardize the safety of spherical pressure vessels and result in catastrophic failure. A detailed finite element sub-modeling technique is carried out to compute the mixed-mode stress intensity factors along the crack front. Furthermore, crack behavior with different aspect ratios a/c: 0.25, 0.5, and 0.75 at the weld and the heat-affected zone of the supporting structure is evaluated. The fluid-structure interaction for three liquid levels: 0%, 50%, and 98% filled vessels of a spherical pressure vessel is considered. The results show that seismic loading can have different effects on the mixed-mode stress intensity factors at multiple liquid levels. As an example, for 50% filled vessel, the semi-elliptical crack behavior located at the heat-affected zone of column-vessel joint intersection is more critical than 0%, and 98% filled vessels and is susceptible to crack growth. This finding shows that the safety margin of the structure can be significantly influenced by the presence of cracks under seismic loading.