Effects of Shell Thickness on Directional Deformation and Buckling Behaviour Cylindrical Steel Water Tanks Subjected to the Kobe Earthquake

Abstract

Cylindrical steel storage tanks are widely used for the storage of various liquids, industrial chemicals and firefightingwaters. They have also been used for cooling purposes in nuclear power plants in recent years. Liquid-storage tankshave many different configurations; however, in this study, cylindrical ground-supported liquid steel tanks werepreferred because of simplicity in their design and construction as well as their efficiency in resisting appliedhydrostatic and hydrodynamic loads, when compared with other configurations. If liquid steel tanks are damaged inan earthquake, they can also cause great financial loss and environmental damage due to their hazardous chemicalcontents. These tanks may be exposed to several types of failures such as elephant-foot buckling, diamond-shapebuckling, overturning and uplifting during earthquakes. The aim of this study is to compare the deformity states ofcylindrical steel tanks with three different roof shapes. For this reason, dimensions of the cylindrical open-top, flatclosedand torispherical-closed top tanks were determined for 3D-finite element method (FEM) models in an ANSYSworkbench software. This article focuses on the seismic-activity-resistant ground-supported cylindrical (vertical)steel liquid storage tanks. Seismic analyses were conducted under Kobe earthquake loads. The free vibrationfrequency values calculated using API 650 (American Petroleum Institutes) were verified with the FEM results.Directional deformation and buckling were presented for both impulsive and convective regions. According to API650 standard, the tank shell thickness is 6 mm. Analyses were performed for tanks with 4 mm and 8 mm shellthickness. In this study, directional deformation and buckling were observed in models with shell thickness under thestandard (4 mm) and above the standard (8 mm), unlike the earlier studies in the literature. It was also observed thatincreasing shell thickness above the specified code values the deformation in the flat-closed tank. In addition,torispherical dome-shaped tanks were observed to have smaller directional deformation and buckling in all casesconsidered.