The coupled acoustic-structural analysis strategy in ABAQUS is frequently employed to perform UNDEX resistance performance evaluation of structures to date. Proper consideration of the shock loading on the structure is vitally important for a coupled acoustic-structural UNDEX analysis. The authors carried out a numerical simulation of a partially submerged circular RC column undergoing an UNDEX shock loading. The study focuses on two factors that might affect the shock loading implementation: (a) the duration of an UNDEX shock front (the rise time), and (b) the employed acoustic-wave formulation type (scattered or total). With the total wave formulation, the calculated kick-off displacements of the column in the rise time = 30 and 40 μs cases are reasonably consistent with the experimental one (Zhuang et al., 2020). The simulation shows that the predicted structural response of the column is sensitive to the rise time. The findings suggest that a period of time of 30–40 μs could be reasonable and practical for small-explosion-equivalent scenarios. Note that the present conclusion is limited to small explosive charges but invalid for large UNDEX loadings (usually having much “higher” frequencies). The study also shows that the scattered wave formulation is not applicable for the current case due to the simulated negative pressure loading on the column. The total wave formulation should be used for low-stiffness structures to properly simulate possible local cavitation. The most important limitation lies in the planar incident wave assumption that makes the current findings less generalizable to other structures with larger lengths/heights or stiffnesses.