Structure Analysis Modularization And Fatigue And Fracture Research For Jacket Platforms

Structural assessment for a fixed platform involves geometry modeling, environmental loads calculation as well as soil-pile interactive simulation, etc. The preprocess is tedious and time-consuming. There are some specialized software packages for the ocean structural analysis, for example, StruCAD*3D, SUCS, however, their function are always limited. On the contrary, most of general purposed commercial FE software packages have powerful functions but without the specialized modules. It's necessary to develop some special modules for the general purposed FE software packages to satisfy our unique requirements in ocean platform structural analysis. In addition, the tubular joints are the most important but the weakest members of ocean platform. Fatigue and fracture at tubular joints are recognised as the predominant factors which contribute to the fixed platform failures; consequently, it is compelling to further understand the fatigue and fracture mechanism of tubular joints on fixed platforms.The main work of this article includes three aspects: first, wave load module and pile-soil interactive module were developed under the ANSYS environment; meanwhile, the validity of these modules was checked. Second, an FE model of BZ-281 platform was established and stress distributions were obtained under 64 wave load cases according to the long-term wave distribution, then, the fatigue life was assessed in spectrum method. Third, a convenient automatically mesh generation method for the crack model was put forward after studying the mesh characteristic of cracked bodies. Then, the effect of ratio of the element size(L) to the crack length(a) on Stress Intensity Factors were discussed and compared with Newman-Raju formula.The result shows that the developed modules can be applied in practice. And the BZ-281 platform can be reused after fatigue assessment. In addition, the method recommend in this article for meshing cracked bodies , which extends the way to build crack model, brings convenience for stress intensity factors research.