Dynamic Response Analysis And Safety Reliability Research Of Ice-resistant Platform

Ice load is the dominant load of offshore platform in the Bohai Sea, severe ice-induced vibration directly threatened the platform's safety. Research shows that ice breaking cone can effectively reduce horizontal ice force, and the ice-induced resonance still happens on conical structures, so it is necessary to study the dynamic characteristics and safety performance for offshore platform which has been installed the ice breaking cone. In this paper, the natural vibration characteristics of ice-resistant platform, dynamic response and safety reliability of platform in dynamic ice force were systematically analyzed and researched by means of theoretical guidance and numerical simulation.The main research contents of this thesis are as follows:(1)Based on sea ice environment monitoring information, the ice thickness, ice velocity, ice drifting direction and ice compression strength of sea area were determined. For the target offshore platform, finite element analysis model was established with CAE technology, and get main vibration model of the platform through modal analysis, then evaluate the dynamic behavior of platform structure system.(2)Finite element modal of platform which is installed ice breaking cone was established. On the basis of study of the interaction mechanism between sea ice and platform, the dynamic respones analysis of conical ice-resistant platform was carried out. Have studied the influence law of conical structure to offshore platform suffered ice force and to reducing ice-induced vibration of platform, and also have analyzed the effect of ice-induced vibration on the upper working personnel and key equipment.(3)Aiming at huge thrust produced by sea ice motion, the carrying capacity of platform under extrame load is analyzed. With nonlinear analyses, considering pile-soil-structure non-linearity interaction, the calculation model of offshore platform under extreme ice load is established, and the collapsing procedure of platform is studied.(4)Based on reliability theory, have respectively established the dynamic reliability analysis model for offshore platform in ultimate limit state and serviceability limit state. With the Monte Carlo method and Latin Hypercube Sampling technology, a random samping of ice parameter and design parameters is made. On the foundation of dynamic finite element analysis, the ice-induced vibration reliability analysis of offshore platform is completed.