Loading issues in coupled acoustic-structural analysis of dynamic responses of dams in underwater explosion events: A gravity-dam case study

Abstract

The coupled acoustic-structural analysis is an efficient and practical approach to underwater explosion (UNDEX) resistance evaluation of various underwater structures, including dams. It features its simple manner of implementing UNDEX shock loadings on structures in a direct way without in detail considering the detonation physics and shock wave propagation processes. The loading implementation is thus believed to be the most critical step in determining the reliability of coupled acoustic-structural analyses of structures in UNDEX events. The present paper aims to clarify two important loading issues frequently confronting the coupled acoustic-structural analysis of UNDEX responses of dams, i.e. the reservoir water thickness and the rise time in a typical UNDEX loading pulse. The ABAQUS code is used for the present numerical implementation. The centrifuge-based physical UNDEX test on a gravity dam performed by Wang (2020) is numerically simulated with the coupled acoustic-structural analysis strategy. The simulation results are found to be in reasonable agreement with the corresponding test ones under the planar-wave assumption for the shock loading implementation. The water thickness is found to have little effect on the simulation results. This validates the reliability of the present simulation strategy and indicates the feasibility of using a relatively thin water domain with the planar-wave assumption in UNDEX analyses of gravity dams. However, it is indicated that the predicted response of the dam is significantly stronger than the measured one when the spherical-wave assumption is made with the total wave formulation. This is due to the insufficient water thickness modeled that leads to wave reflection at the fluid boundaries. After that, a parameter analysis is carried out concerning the rise time period in the loading pulse. The comparison results show that the effect of the rising duration on the UNDEX response of the dam is limited. It is thus suggested that a rise time period of around 30–50 μs should be reasonable in most UNDEX resistance evaluation scenarios for general dams. The current findings should be of interest to practitioners who are engaged in the UNDEX resistance evaluation of dams.