The uplift effect of bottom plate of aboveground storage tanks subjected to wind loading

Because aboveground storage tanks are usually empty during construction, inspection and repair periods, they are more vulnerable to buckling due to wind loading than they are in use filled with liquid product. The uplift effect of the bottom plate of empty storage tanks due to wind pressure is investigated in this work. The buckling behavior of two sets of tanks were studied using finite element analysis (FEA): (1) tanks with bottom plate modeled directly in the analysis and (2) tanks without bottom plate but suitable boundary conditions applied in the analysis. Linear bifurcation analysis (LBA) and geometrically nonlinear analysis including imperfections (GNIA) are performed to obtain the deformation shapes and buckling capacities of tanks. The soil supporting the with-bottom tanks were modeled using nonlinear compression only springs connected to each node of the bottom plate. The buckling modes and the results from GNIA show that when a bottom is included into a tank FEA simulation, instead of fixed, the buckling pressure load will be substantially reduced for slender tanks having height to diameter ratio greater than 1/3. However, the broad tanks having height to diameter ratio less than 1/3 experience relatively small reduction in budding load.