单点系泊海洋导管架平台结构的疲劳寿命可靠性分析

Fatigue life reliability analysis of single point mooring offshore jacket platform structures

为了确保海洋平台结构继续安全可靠地运行,根据BZ28-1 SPM油田海域环境荷载的统计特性,利用Ray-leigh分布对波高和系泊力进行离散化,运用线性波浪理论计算作用在小尺度结构上的波浪力,采用有限元法分别计算在波浪力和系泊力作用下结构构件的名义应力,乘以相应的应力集中系数,得到管节点的热点应力范围.应用疲劳累积损伤理论和S-N曲线对导管架结构的疲劳寿命进行了可靠性评估.分析结果表明,波浪荷载引起的结构疲劳损伤相对于系泊力荷载是非常小的;对由波浪力、高频系泊力和低频系泊力引起的导管架结构的疲劳损伤进行线性累积相加是不合理的,这样得到的疲劳寿命比采用组合方法计算得到的疲劳寿命大很多,会导致过高地估计结构的疲劳寿命.

A software was developed to evaluate the cumulative damage and fatigue life of jacket structures in order to insure the safe service of BZ28-1 SPM platform in succession. Rayleigh distribution model was adopted to discretize wave and mooring forces, and linear Airy wave theory was employed to predict the fluid loading on offshore jacket structures. The nominal stress of structural members was respectively cal- culated under the wave and mooring loading using the finite element method, which was multiplied by the corresponding stress concentration factors to gain the hot stress range of welds at the location connected with relative tubular joint. S-N curves and Miner rule were used for the fatigue damage assessment and prediction of fatigue life. The results showed that the fatigue damage induced by single wave loading was very minor; comparing with the combination approach, the linear addition of fatigue damages respectively coming from wave, high frequency and low frequency mooring loading was not rational and resulted in overestimating the fatigue life of jacket structures.