Nonlinear dynamics of above-ground thin-walled tanks under fluctuating pressures

The nonlinear dynamics and stability of an empty above-ground steel tank is analyzed. The tank considered is one of the typical configurations found in the Caribbean Islands and in the United States, constructed with a cylindrical shell with variable thickness, and a conical roof supported by rafters. An assumed space variation of pressures and a simplified deterministic model of time fluctuating pressures due to wind are applied. The response is calculated by a finite element model of the tank using explicit integration of the equations of motion for several pressure levels and period of fluctuations. The dynamic buckling load is evaluated using the criterion due to Budiansky and Roth. The response is analyzed in the time and in the frequency domain in order to recognize the nature of the problem. The results show that pressure fluctuations do not induce resonance of the structure, so that simpler pressure models may be used in practical analysis.