Research Of Ice Load On Offshore Structure Based On Strain Data

Ice actions are the dominant forces on offshore structures in ice infested waters. Although lots of research work has been done, including analytical approach and tests performed in laboratories and in-situ, there are still many debates on both static and dynamic ice loading on vertical or conical structures. The difficulty of ice actions study is due to the complicated and scattered mechanical behaviors of sea ice. So far, it is quite challenging to describe the failure process of ice sheet using fracture mechanics or numerical simulations, as a result, the popular formulations of ice loads are empirical which are based on real data. In the case of Bohai Sea, most structures are relatively compliant and suffer from severe ice induced vibrations. Field tests are considered as the best way to obtain first-hand information related to ice actions, response of real structures and ice parameters like ice thickness and ice drifting velocity. In present thesis, the structure's responses are employed to calculate the global ice loads acting on structures, and the main accomplishments are as follows:1) A series of model tests are conducted and the model structure's response including displacement, acceleration and local strain are obtained. FEM model of the model structure is built and the relationship between displacement and local strain are analyzed in detail. Ice loading is calculated based on the strain data. Comparison between response calculated by FEM model and real data indicates that it is reasonable to do so;2) Based on the FEM analysis of the oil platform named Nanpu 12-9, location for strain gauges is determined and ice forces are calculated based on strain data. As a result, the calculated peak ice force is higher than the value by conventional formula, but a little bit lower than the results by SNiP code (formerly Soviet Union code). It is concluded that the dimensionless coefficient for ice force in the sea areas of Nanbao should be in the range 0.7-1.03) Strain data obtained by FBG strain gauge is used herein to calculate ice forces for the first time. FEM analysis and real data including structure's response and ice.parameters are cooperated to achieve the reliable value of ice load. This approach is innovative and useful for the study of ice actions...