Critical path incremental loading procedure for system reliability analysis of offshore structures

A procedure is presented for the ultimate strength system reliability analysis of offshore structure. The structural system reliability model is generated through a so-called Critical Path Incremental Loading Procedure in which incrementation is performed along a failure path reflecting the lowest kinematic energy absorbed by the most significant failure path. This procedure reflects the existence of model dependence in structural system reliability, and environmental dependence due to the high loading roughness to which structural systems are generally subjected. No apriori load incrementation scheme is selected, but incrementation is applied on the most contributive load to fail member with the lowest reliability. the procedure can incorporate various member post-failure behavior models. A semi-probabilistic characterisation of structural system redundancy is described which is suitable for early design situation in which different structural layouts leading to different significant failure paths and system reliabilities are contemplated. The procedure is demonstrated for the system reliability analysis of truss model of jacket structures. Results show that parallelization strategy to proved alternative and multiple failure path is not always effective in attempts to increase the reliability of structural systems.