Fatigue Life Prediction And Optimization Design Of Minimum Offshore Platform Loaded Random Ice Force

With the rapid development of the offshore oil industy, the exploitation of ocean marginal oil field is attained more and more attention to many countries. The minimum offshore platform is the main style of engineering structure used in exploiting oil and gas in marginal offshore for its simpleness, low investment and high economic benefit. However, large response caused by repeat dynamic load will reduce the safety and applicability of the minimum offshore platform. It's very valuable in practice engineering to exactly predict the fatigue life and decrease the vibration response of offshore platform. The minimum offshore platform has been used and developed oversea for several decades but few in our country. The minimum offshore platform will have a good application future in our country which has broad marginal oil field.The thesis introdues a new method to exactly predict the fatigue life of minimum offshore platform loaded random ice force. This method is also applied to wave and current force. Firstly, the hot-spots'stress respone is calculated by numerical method. Secondly, the hot-spots'stress respone is counted by rain-flow method. Finally, the fatigue life using S-N curve method is obtained. In addition, a method of decrease the vibration response by optimizing the style of the minimum offshore platform is introduced. Hot-spot stress method in predicting fatigue life and optimization design method are efficient and feasible shown in an engineering project.