Research On Analysis Method Of Ice Resistance For Jack Up Platform

This dissertation is supported by one part of China industry and information technology project named "The Brand Engineering of Jack-up Platform(Type II)",which is called "Optimum Design of Platform Structure and Analysis of Operational Adaptability".In order to solve the core theory and key technical problems for the structural strength analysis of jack-up platforms in Bohai Sea,this paper focuses on the operation status of jack-up platforms under ice loads.Interaction between sea ice and pile leg structure of jack-up platform is identified.Evaluation method of strength,fatigue life and time-dependent reliability are determined.The main research contents as follows.(1)Experimental study of Ice-induced vibration on pile legs structureAccording to the structural characteristics of jack-up platform,a scale model of platform truss leg is established.The model ice force test is carried out to obtain the structural response under different ice loads.By studying the interaction mode between sea ice and structure,the ice breaking mode and ice force time history characteristics are analyzed,and the corresponding dynamic ice force model is determined.The influence of ice parameters on the structural response is clarified.(2)Structural strength analysis of jack-up platform under ice loadBased on the study of the interaction between ice and platform,the combined working conditions of environmental loads are determined.The static strength and dynamic strength of jack-up platform under ice load are analyzed.The influence of different working conditions on the structural stress of jack-up platform is studied.By checking the stress of the platform structure,the strength of the platform structure can be reasonably evaluated.(3)Study on ice-induced fatigue life of jack-up platformConsidering the influence of different factors on the fatigue strength of platform,a fatigue damage assessment method for jack-up drilling platform in ice zone is proposed.The fatigue strength of platform structure under different environmental loads is analyzed.The linear and non-linear cumulative fatigue damage accumulation theory are used to evaluate the fatigue life of jack-up platform.(4)Time-dependent reliability analysis of jack-up platform in ice regionConsidering random ice load and resistance attenuation,the environmental load effect of jack-up drilling platform is studied,and the time-dependent reliability model of jack-up platform in ice region is established.The time-dependent reliability of the platform is analyzed by the time discrete method.The influence of resistance attenuation on the reliability and failure rate of jack-up platform is revealed.(5)Design of ice resistance structure for jack-up platformThe ice resistance strategy of jack-up platform is studied,and the ice resistance structure design scheme of jack-up platform is proposed.Through static and dynamic analysis of the structure under this scheme,the role of the ice resistance device in reducing static ice force and restraining ice-induced vibration is clarified,so as to determine the feasibility of the scheme.