Strength Evaluation of LNG Containment System Considering Fluid-Structure Interaction Under Sloshing Impact Pressure

As LNG carriers become larger and new operating conditions are being designed, it is essential to develop a new procedure for the strength evaluation of a membrane-type LNG containment system under sloshing loads. The conventional comparative method based on existing service experiences and previous damage cases is currently used in most cases, but this method is only valid for designing new LNG carriers with similar size and type of existing ones. In this study, an analytical solution of acoustic-solid interaction has been derived and a simple 2D coupled acoustic-solid model has been simulated to investigate hydro-elastic effects for the verification purpose. After validation of FE modeling, a coupled model considering the fluid-structure interaction between LNG and containment system has been developed for structural analysis of LNG Mark III containment system. For LNG Mark III containment system, nonlinear dynamic FE analysis under sloshing impact pressure has been conducted using the fluid-structure coupling model. In FE simulations, the hydro-elastic effect in structural response has been studied through considering LNG as an acoustic medium, foam as a visco-elastic material, plywood as an orthotropic material, and mastic as an isotropic material. Parametric study has also been done to investigate the effects of material properties and loading patterns on hydro-elastic response in the coupled fluid-structure model. Based on FE results and experimental data, the strength of LNG Mark III containment system has been evaluated in terms of acceptance criteria. Finally, the new procedure has been developed for the strength evaluation of membrane-type LNG containment systems.