Study On Numerical Simulation Method Of Structure Damage Of Jacket Platform In Service

Jacket platform is the most common structure for the exploration of offshore oil and gas in China.Despite its significant numbers,most of the jacket platforms have entered the final stage of service.The jacket structures are subjected to harsh marine environments all the time during service,as well as earthquakes or ship collisions,thereby leading to the potential damages of the structure.To insure the safety and the endurance of the platform,the real-time structure health monitoring(SHM)has been the most promising technique.In the study of the SHM,the prior dynamic response database of the structure under complicate environmental interactions and various damage pattern is needed.Because of the uncertainty of the field measurement and the scaling problem of the model test,numerical simulation of the structural damage has been the key method for the SHM prior database establishment.Considering the cracks of tube joints are deeply hidden in the structure and extremely harmful,this paper focuses on the simulation of crack propagation in tube joint with high computational efficiency and less resource requirements.Based on the method of dynamically controlling the stiffness matrix by changing the constraint of degrees of freedom between elements,this paper propose a method to simulate the crack by establishing the constraint equation at the tube joint,solving the coupling coefficient of the constraint equation according to the solid model.Based on the idea of multi-scale modeling,a multi-scale solid model is established and the MPC(Multipoint Constraint)method is proved to be the optimal method for connecting different types of elements.Through the analysis of the coupling coefficient,the variation of the coupling coefficient with the degree of damage is obtained,and the equivalent simulation of tube joint crack with corresponding degree of damage is achieved.Based on dynamic analysis and application analysis on damage identification,it is concluded that the crack simulation method with constraint equations can be used in nonlinear dynamic response analysis of structure health monitoring.