Probabilistic collapse analysis of jackets

For realistic structures the structural behavior near collapse may be very complex to model and the computation time can be exhaustive. This complexity may be due to the non-linear mechanical behavior of the structure, the applied loading and load distribution near failure. The structural behavior beyond the first member-failure, depends not only on the degree of static indeterminacy, but also on the ability of the structure to redistribute the load and on the post-failure behavior, e.g. the ductility of the individual members. In addition, the probability of system failure depends on the uncertainty of the load, uncertainty of the response calculation, uncertainty of the member capacity and the correlation between the uncertain parameters. In a reliability analysis of fixed offshore structures, the problem is generally load driven, i.e. the uncertainties in load are much greater than in the system capacity. A major question is how important is the probabilistic effect as compared to the deterministic effect. The purpose of this paper is to gain insight into the above question by performing studies on randomness of the ultimate capacity of different types of jackets in the North Sea. A state-of-the-art non-linear structural collapse analysis program USFOS are used for the progressivemore » collapse analysis, and a general PROBabilistic ANalysis program, PROBAN, is used for the reliability calculation and to generate outcome of the stochastic parameters in the simulation studies of the ultimate capacity of the structures.« less