| The tubular joints are the most important but the weakest members of ocean Platform.It has been found that tubular joints fatigue cracks are a dominating type of damage in ocean platform.Kinds of methods included theoretical research, model test and numerical simulation were used to research the fatigue properties of tubular KK-joints of leg structure.The main research contents of the thesis include:(1) Using the model test and numerical simulation methods, the fatigue properties of tubular KK-joints which are the typical joint type in the truss legs of the jack-up platform was carried. The main tasks of experiment study are:testing the fatigue properties of KK-joints model under axial loading, obtaining the hot spot stress (HSS) distribution and the stress concentration factors(SCF) along the weld toe in the HSS region, finding the initial fatigue crack position and crack propagation law, etc.. Based on ANSYS software, the simulation models of the multi-planar tubular KK-joints were established to analyze the fatigue properties, and some geometric parameters which influence the fatigue properties of KK-joints were investigated. The proposals improved the fatigue properties of KK-joints were given.(2) The jack-up platform structure strength analysis model were established by the finite element analysis software ANSYS as well as related marine platform design rules and construction rules.The structure strength was analyzed under the conditions of normal operation and cheeked under the platform construction rules.(3) Based on the results of platform structure strength analysis,the KK-joints model was picked out and remeshed,Then, the fatigue strength analysis of KK-joints was carried out. This method can exactly obtain the hot spot stress (HSS) of tubular KK-joints of leg structure.The result provided a reference for the jack-up platform leg structure optimization. |
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