Impulsive hydrodynamic pressures in ground-based cylindrical structures

The earthquake induced vibration of a ground-based cylindrical structure containing or surrounded by liquid produces hydrodynamic forces in the liquid which should be considered in aseismic design. In evaluating these pressures most current design codes assume the structure to be rigid and ignore the pressures due to its flexible response. In this paper the results of a number of experiments are presented which investigate the pattern and magnitude of the different types of impulsive hydrodynamic pressures in three steel cylindrical models. Extensive forced-vibration, simulated earthquake and impulse tests carried out on the models when water-filled, as well as when surrounded by water show high discrepancies between the overall hydrodynamic pressures and the pressures obtained when the cylinder is assumed rigid. Based on the experimental findings, a method is proposed which enables evaluation of the hydrodynamic pressures due to flexible response in the fundamental mode. Also, improvements are proposed on approximate design methods.