Explicit Nonlinear Dynamic Analysis of Cylindrical Water Storage Tanks Concerning Coupled Vibration Between Fluid and Structure

This study describes a nonlinear vibration analysis for a cylindrical water storage tank considering oval-type vibration, which is a higher-order vibration mode (axial wave number m ≥ 1 and circumferential wave number n ≥ 2). Oval-type vibration occurs in the side wall of cylindrical tanks when a coupled vibration system forms between the sidewall and the contained liquid. Recently, it was found that oval-type vibration causes the nonlinear vibration response of the tanks. Hence, it would be useful for future seismic design methods to conduct a nonlinear dynamic analysis of water storage tanks considering the influence of oval-type vibration. This study proposes a nonlinear dynamic analysis method concerning the coupled vibration between fluid and structure using an explicit method. The proposed method uses a shell element which can take into account the geometric nonlinearity characteristics and a solid element which follows Euler’s equation. The ALE method is applied to the coupling analysis between fluid and structure, and the explicit time integration method is used for the time-history response analysis. Next, the proposed method is used to conduct a numerical simulation of the dynamic response of oval-type vibration and the nonlinear vibration behavior of the tank, and the analytical results are compared with the experimental ones. Both results are in good agreement concerning the occurrence and modes of oval-type vibration in addition to the nonlinear vibration response of the tank. Regarding the dynamic fluid pressure, the local pressure by oval-type vibration as well as the main pressure by beam-type vibration can be calculated accurately. These results confirm that the proposed method achieves a more accurate analysis for the nonlinear vibration response of the tank considering the influence of oval-type vibration.