Optimization Method Of Mooring Line Clump Parameters In Semi-submersible Platform

With the increasing use of semi-submersible drilling platforms in deep water areas,the overall mooring capacity of the platform needs special attention.In order to improve the mooring capacity,we can set clumps on the mooring lines.The position and weight of each clump are usually determined by empirical formulas and actual engineering needs.With the change of factors such as the working environment,the range of optimal clump parameters is also changing.Therefore,this paper proposes a method which can quickly find the optimal clump parameters,and provides a reference for the preliminary design of the mooring system.Taking the semi-submersible platform as an example,this paper firstly calculates various environmental loads on the platform under operating conditions and survival conditions.Then we calculate the response amplitude operator of the platform,the tension of eight mooring lines,the length of the mooring lines lying on the bottom and the displacement of the platform under various conditions.The results show that the safety factor of the mooring line does not meet the requirements of the specification under the survival conditions.After setting clumps on mooring lines,the tension has significantly reduced.In order to find the optimal clump parameters,we build a PSO-BP neural network.Since the selection range of the weight parameters is too large,the orthogonal experiment method is selected to optimize the sample database,and finally an optimized PSO-BP neural network is formed.Combined with the genetic algorithm,the optimal parameters under the optimization objective are found within the range of the weight parameters.In this process,the predicted value of the neural network is used to approximate the actual finite element calculation value,which not only greatly reduces the calculation time,but also obtains reliable results.The results of clump parameters provide calculation basis for subsequent mooring system design.