Stability of Open Top Cylindrical Steel Storage Tanks: Design of Top Wind Girder

Design of the top wind stiffeners of aboveground storage tanks designed to the requirements of API 650 is investigated. The current design methodology is based on intuition and experience without a sound technical justification. This paper investigates a diameter limit to be used in the design of the top stiffener ring by using finite-element analysis (FEA) in a parametric study. Linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) were performed on cylindrical storage tanks. By modeling tanks with different diameters and limiting the design of top stiffener ring for a diameter of 170-ft (52-m), the buckling loads are investigated. It was found that the 170-ft (52-m) diameter is a suitable upper limit to design the top stiffener rings for larger diameters.