Sloshing load inversion and stress monitoring of LNG carrier cargo containment system based on improved impulse-space superposition method

Abstract：Objectives The sloshing load is one of the most important and complicated loads in the cargo containment system, but it is difficult to calculate or measure accurately due to the simplification of numerical simulation and model experiments. To obtain accurate time history characteristics of the sloshing load and realize real-time health monitoring of the cargo containment system, the inverse impulse-space superposition method was used to measure the local response of the structure and deduce the sloshing load and the response of the high-stress region (hotspot). Methods The inverse mathematical model of measuring point position and sloshing load position is established to predict multi-region load. The response prediction mathematical model of sloshing load positions and hotspot positions is established to predict the multi-hotspot stress. Load inversion is carried out according to the Duhame integral and the Tikhonov regularization method, and then the L-curve method is used to select regularization parameters. The step length for load prediction is studied. Results The prediction accuracy of sloshing load decreases with the increase of load complexity and increases with the decrease of load prediction step size. The time history curve of load and hotspot stress under all cases is consistent with the real value. By controlling the load prediction step size, the peak error of sloshing load and hotspot stress can be kept below 10% and 1%, respectively. Conclusions Compared with the positive method of experimental measurement and numerical simulation, the method of load inversion provides a new way to obtain the sloshing load of the cargo containment system. The improved inverse impulse-space superposition method has been successfully applied to the inversion of the sloshing load and the prediction of the hotspot stress of the cargo containment system of the LNG carrier, which verifies the feasibility of applying this method to the composite structure, and provides a reference for the application of this method to other ships and marine structures.