The sloshing effects on the crack instability of the spherical tank under the simultaneous effect of internal pressure and earthquake

Abstract

Spherical tanks have an important function in the industry due to the internal pressure of their contents. Also, the supporting structure of the spherical tank controls stability and damage to the tank One of the damages that can lead to a critical situation is an unstable crack in the column-vessel joint. In this study, the sloshing effects on the instability of 10 mm and 20 mm long semi-elliptical cracks with three aspect ratios in the connection zones of the supporting structure under the effect of internal pressure and eleven earthquakes have been investigated. Furthermore, using the finite element sub-modeling method around the crack area and part of the structure, the effect of fluid–structure interaction has been considered for three liquid levels to calculate the stress intensity factors along the crack front. Since the tank is under the simultaneous effect of internal pressure, earthquake, and sloshing motion, a three-dimensional mixed-mode stress intensity factor needed to be considered to study the crack instability. The results show that earthquakes and sloshing motions can have various effects on the equivalent stress intensity factors. For almost two-thirds of the studied cases, the equivalent stress intensity factor for the 50% filled vessel was 10%–70% greater than the 98% filled vessel. This finding shows that the crack located in the connection zones of the supporting structure under the simultaneous effect of internal pressure, earthquake, and sloshing motion, could lead to failure.