| Abstract: | Corrosion and fatigue cracks are major threats to the structural integrity of aging offshore platforms.For the rational estimation of the safety levels of aging platforms,a global reliability assessment approach for aging offshore platforms with corrosion and fatigue cracks is presented in this paper.The base shear capacity is taken as the global ultimate strength of the offshore plaffoms,it is modeled as a random process that decreases with time in the presence of corrosion and fatigue crack propagation.And the corrosion and fatigue crack growth rates in the main members and key joints are modeled as random variables.A simulation method of the extreme wave loads which are applied to the structures of offshore platforms is proposed too.Furthermore,the statistics of global base shear capacity and extreme wave loads are obtained by Monte Carlo simulation method.On the basis of the limit state equation of global failure mode,the instantaneous reliability and time dependent reliability assessment methods are both presented in this paper.Finally the instantaueous reliability index and time dependent failure probability of a jacket platform are estimated with different ages in the demonstration example. |
