海洋平台冰激疲劳时域精细评估

为了评估冰区平台在服役期内的安全可靠性，给出了平台冰激疲劳时域精细评估的详细流程。根据海冰漂移方向、冰速和冰厚的概率分布特征，确立冰激振动分析的24个疲劳予工况。考虑平台桩柱的不同结构型式和冰-结构耦合作用．分别采用简化冰力函数模型和Sodhi改进模型对平台中锥体结构和直立桩柱结构进行冰激动态响应分析；建立管节点精细有限元模型计算热点应力集中系数，从而得到管节点的疲劳应力时程，并利用雨流计数法进行统计．计算整个疲劳环境的等效应力幅以及相应的循环次数，最后利用Miner线性累积损伤准则计算疲劳损失和疲劳寿命。结果表明：4根钭撑杆上的支管冰激疲劳损伤最大，应作为今后检测的重点部位。

Fine Assessment on the Time-Field of Ice-induced Fatigue on the Offshore Platform

The detailed process of fine assessment on the time-field of ice-induced fatigue on the offshore platform is presented in order to evaluate the safety reliability of offshore platform in the ice region within the service period. Based on the ice moving direction and the probability distribution of ice velocity and ice thickness, 24 fatigue sub-states are determined in the analysis of ice-induced vibration. In consideration of the interaction between the different types of platform piles and ice structures, the simplified ice force function model and the modified model Sodhi are applied to the analysis of ice-induced dynamic response about conical structures and vertical piles among platforms respectively. Then the hot spots stress concentration factors of tubular joints are calculated by establishing their fine finite element models, and thus obtaining the hot spots stress time histories of tubular joints. Meanwhile, the equivalent stress amplitude of fatigue environment and the recycling frequency are counted by rain-flow counting method. And finally the fatigue damage and fatigue life are computed according to the rule of Miner linear damage accumulation. The result shows that the damages of four sub-tubes of bracing poles on the platform are the biggest, which should be regarded as the critical positions for inspection