Safety Reliability Analysis And Optimization Design Of Moderately Deep Water Jacket Platform

Offshore platforms are main structures for marine petroleum and nature gas exploitation because of advantage of convenient construction.However,in consideration of the adverse working conditions,the safety and economics of deep water jacket platform has been demand.The damage of jacket platforms will lead to serious consequences.As fierce competition of petrochemical industry,Structural optimum design has been received more attention to help lower costs.On the basis of applied basic research project of China Petroleum & Chemical Corporation-“The key technology research of deep water jacket platform”,the main research contents of thesis are as follows.According to the drawings and data,the model is developed by the software of SACS.According to the design environmental conditions,we combine the loads acting on the platform to get some worst combinations and the static analysis has been done,the combined loads include loads in operation condition and loads in extreme condition.The purpose of the analysis is to perform structural strength check and pile foundation bearing capacity check under operation and extreme loading conditions.The results of pile stress check indicate that the piles meet the code requirements.The dynamic wave analysis has been performed to calculate structure natural period and mode shape.The purpose of the analysis is to calculate the dynamic amplification factors(DAFs)for the platform under operating and extreme loading conditions.Seismic analysis has been done for the platform jacket in the ductility and strength level.The purpose of the analysis is to perform structural strength check and pile foundation bearing capacity check under operation and extreme loading conditions.The fragile members have been find out.The purpose of the analysis performed on the platform is to calculate joint fatigue life by using wave spectrum method.Basic S-N Curves for welded joints according to API are used to check the jacket tubular connections.All joints provide adequate fatigue strength with the S-N curve without any weld improvement except four Joints.These joints can provide adequate fatigue strength with the S-N curve with weld profile.The optimum design of jacket platform has been performed to optimize structure.We introduce the classification and characteristics of structural optimization,structural optimization of the main process,and the method of structural optimization.The model is developed by the software of ANSYS.According to the design environmental conditions,we combine the loads acting on the platform to get some worst combinations and the static analysis has been done,The results demonstrate that the weight of the jacket could decrease significantly based on optimum design.