The Research Of Global And Local Finite Element Models For Jack-up Structures

Jack-up structures are the main facilities of offshore petroleum drilling operation, so the structural safety performance is widely focused on. And with the increasing operating depth, the accurate verification of its elevating system in leg well area becomes an urgent requirement. Limited by the development of computer hardware nowadays, building local refined finite element model of leg well area turns out to be the best way to solve this problem, and moreover how to simulate the force condition of local leg well area factually becomes the key to solve the problem.In this paper, the global and local finite element models of a jack-up for a hundred meters water depth are built by applying ANSYS. Plate and beam parameters of the global model are set and all loads are loaded according to the data, and from the calculation result the force between legs and jacking structures are extracted and loaded on the local model to simulate the force condition of it.According to China Classification Society, Rules for the Construction and Classification of Mobile Offshore (2005), the yield stress of shell and beam elements and the buckling stress of all the shell elements are checked.The influence scope of boundary effect can be judged intuitively from the comparative analysis of stress nephogram of local model's different cabin conditions. The quantitative conclusion of boundary effect can be obtained from the comparative analysis of stress data of fourteen plate samples in different positions.The check analysis of global and local models proves that it is feasible to do the effective strength analysis of sophisticated jack-up for a hundred meters water depth in this way at the computer hardware level nowadays. The comparative analysis of stress nephogram and data of leg well area is of guiding significance to the research on how to avoid boundary effect during the calculation of jack-up's leg well area.