Validation of the line-like nature of ice-induced loads using an inverse method

Throughout the last 50 years, knowledge of ship-ice interaction and the mechanics of the ice breaking process has improved through numerous full-scale studies; however, the understanding of precise ice-induced pressures and load heights requires further refinement to design safer, more efficient ships. During its construction, the hull structure of the oblique icebreaker Baltika was instrumented with strain gauges. The sensor arrangement was designed to allow the measurement of the vertical distribution of ice loads and the ice-induced load patch height. Two years of data have been gathered during operations in the Russian Arctic. An inverse method was developed to study the applied ice-induced loads and the load patch on the ship’s hull. The method utilises an influence coefficient matrix to describe the structural response to an applied load. Using FEM, strain response functions are fitted at each sensor location to generate the terms of the influence coefficient matrix. An optimisation routine solves the inverse equation and determines the magnitude of the applied pressure and the height of the load patch. Using the full-scale measurements recorded on board the Baltika, the development of the ice pressure from first contact to load disengagement was studied for individual ice impact events. The analysis revealed that the structures experienced concentrated, high pressure loads during impact events. The results confirmed that ice-induced loads are line-like in nature.