Assessment Of Structural Safety And Design Optimization For Jacket Offshore Platform

With the continuous exploitation of marine oil and gas resources,the number of offshore platforms in service is also increasing year by year.Because of the special service environment of offshore platforms,accidents of offshore platforms occur frequently at home and abroad,resulting in huge economic losses.Therefore,it is of great significance to study the applicability of the offshore platform to ensure their safe service.At present,it is generally believed that a structural integrity management(SIM)system that achieve monitoring and assessment during their service life is an effective way to ensure the safe operation of the platform.Based on the offshore engineering recommended practices and finite element software,this paper designs the interface of SIM system for steel offshore platforms,and further carries out deterministic assessment and reliability risk assessment for two offshore platforms in the South China Sea and North China Sea.Finally,considering the reliability of platform structure,the optimization model of offshore platform structure is established,and the optimization solution is completed based on the optimization theory of agent model.The optimization results can provide theoretical guidance for the reconstruction of offshore platform structure.The main contents of this paper are as follows:First,the interface of structural integrity management system for Jacket Offshore platform is designed.On the basis of SACS software and domestic and foreign recommended practices,through the study of the four elements of SIM: data,evaluation,strategy and program,the human interaction interface of four modules of SIM system is designed.Each module is interrelated,which realizes the continuous updating of data,dynamic evaluation of platform and targeted detection.With the help of interface software developers,the development of the interface of the jacket offshore platform SIM system has been completed.At the same time,through the linkage of database and finite element model,the user's management of the platform has been facilitated.Then,the structural reliability analysis and risk assessment for Jacket offshore platform are carried out.In the core evaluation part of SIM,this paper introduces the deterministic evaluation technology based on SACS software,including the analysis principle and process of static,fatigue and collapse evaluation.Considering the randomness of the environmental loads on offshore platforms,according to the reliability analysis theory and the safety evaluation criteria of offshore platform components,the limit state equation is constructed.The distribution of random variables in the state equation is determined,and the reliability analysis of offshore platform components is carried out based on the statistical law of the environmental loads and structural resistance at home and abroad.By introducing the concept of risk,the risk matrix of component evaluation is established,and the component of jacket platform is evaluated.Taking South China Sea and North China Sea as examples,the feasibility and rationality of the above assessment methods are illustrated.Finally,the jacket offshore platform structure is optimized in terms of platform reliability evaluation criteria.Based on Kriging model,the response function between platform evaluation criterion and component size is constructed.Under the constraints of platform evaluation criterion,the platform weight is minimized,and the optimal design model of offshore platform structure is established.Simulated Annealing Algorithm is used to solve the optimization problem,and the optimal design within the platform safety evaluation range is obtained,which provides a theoretical basis for the transformation of the aged offshore platform.