Ring stability of underground toroidal tanks

• Main Authors: Lubis, Asnawi, Su’udi, Ahmad
• Format: Conference Proceeding
• Language: English
• Subjects: Buckling; Cross-sections; Cylindrical shells; Cylindrical tanks; External pressure; Finite element method; Internal pressure; Mathematical analysis; Nonlinear analysis; Pressure vessel design; Pressure vessels; Shells; Stability; Toroidal shells; Vessels
• ISSN: 0094-243X; 1551-7616
• DOI: 10.1063/1.4985499

The design of pressure vessels subjected to internal pressure is governed by its strength, while the design of pressure vessels subjected to external pressure is governed by its stability, which is for circular cross-section is called the ring stability. This paper presented the results of finite element study of ring stability of circular toroidal tank without stiffener under external pressure. The tank was placed underground and external pressure load from soil was simulated as pressure at the top of the vessel along 30° circumferentially. One might ask the reason for choosing toroidal rather than cylindrical tank. Preliminary finite element studies showed that toroidal shells can withstand higher external pressure than cylindrical shells. In this study, the volume of the tank was fixed for 15,000 litters. The buckling external pressure (p L) was calculated for radius ratio (R/r) of 2, 3, and 4. The corresponding cross-section radiuses were 724.3 mm, 632.7 mm, and 574.9 mm, respectively. The selected element type was SHELL 281 from the ANSYS element library. To obtain the buckling load, the arc-length method was used in the nonlinear analysis. Both material and geometric nonlinearities were activated during the analysis. The conclusion of this study is that short-radius and thin-walled toroidal shell produces higher buckling load.