极端海洋环境对海洋平台疲劳寿命的影响

Study on the method of the fatigue design of offshore platforms considering extreme sea states

基于渤海和南海的海洋平台设计环境条件,分析了近年来我国近海极端海洋环境条件的发生规律及其对海洋平台疲劳设计条件的冲击。采用Miner’s线性累积疲劳损伤准则和疲劳可靠性理论,研究了极端海况引起的疲劳损伤对海洋平台疲劳寿命的影响,提出了考虑极端海洋环境条件的海洋平台疲劳设计方法。研究表明,由于近年来全球气候变换带来的极端气象条件频发,导致海洋工程结构经历传统意义上的多年一遇海洋环境条件的概率大大增加,使得现行的海洋平台疲劳设计条件偏离了实际的海洋环境条件。数值算例表明,极端海况引起的疲劳损伤在总的疲劳损伤的比例大大增加,甚至成为疲劳损伤的主要部分。因此,这些极端海况引起的疲劳损伤对结构疲劳寿命的影响不容忽略,考虑极端海洋环境条件的海洋平台疲劳设计符合近年来的灾害性海况频发的现状。

Based on the design data for the offshore platforms to serve in Bohai bay and South China Sea, the trends of extreme sea states in China offshore and its impact on the fatigue design conditions of offshore platforms have been analyzed. The effect of the fa- tigue damage induced by extreme sea states on the fatigue life of offshore platforms has been studied based on the Miner＇ s linear cumu- lation rule of fatigue damage and the theory of fatigue reliability. The results show that the probability of offshore platforms experiencing years-return sea states has risen largely because the extreme weather happens frequently due to the global warming and it makes the cur- rent conditions for the fatigue design of offshore platforms less reasonable. The numerical example shows that the proportion of the fa- tigue damages induced by extreme sea states to total fatigue damages rises sharply with the extreme sea states happening frequently, e- ven being main fatigue damage. Therefore, the effect of the fatigue damages induced by extreme sea states on the fatigue life of offshore platforms should not be neglected. The fatigue design of offshore platforms considering extreme sea states is in accordance with the changing trend of environmental conditions in recent years.