The fatigue design of offshore structures normally uses wave and wind fatigue loading. Currently, fatigue analyses for fatigue damage accumulation assessments of this type of structure are based on signal–noise (S–N) curves for welded structural components, the hot-spot stress approach and the Palmgren–Miner law – according to design codes. Fatigue analyses in design codes and/or recommended practices are supported by global structural analysis. In this paper, a global–local fatigue methodology applied to an offshore jacket-type platform using a local approach through the notch strain damage parameter is proposed. The local approach is based on Neuber's rule combined with the Ramberg–Osgood description. Then, the Coffin–Manson strain–life relation together with the Palmgren–Miner linear damage rule are used to evaluate the fatigue damage accumulation for the critical tubular welded joint. For application of Neuber's rule, the stress concentration factor values are calculated, according to Efthymiou's analytical equations, for the connection under consideration. The proposed methodology is compared with the simplified fatigue analysis presented in the Det Norske Veritas (Norway) and Germanischer Lloyd (Germany) DNVGL-RP-C203 recommendations. These analyses were performed using wave loads from the scatter diagram collected in the North Sea, which were computed through the fifth-order Stokes wave theory and the Morrison formula.

中文翻译：

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使用局部损伤参数评估海上结构的疲劳损伤

海洋结构的疲劳设计通常使用波浪和风的疲劳载荷。目前，针对这种结构的疲劳损伤累积评估的疲劳分析基于信号噪声（S – N）根据设计规范，焊接结构部件的曲线，热点应力法和Palmgren-Miner定律。整体结构分析支持设计规范和/或推荐实践中的疲劳分析。在本文中，提出了一种通过缺口应变损伤参数通过局部方法应用于海上护套型平台的整体局部疲劳方法。局部方法基于Neuber规则与Ramberg–Osgood描述相结合。然后，将Coffin-Manson应变-寿命关系与Palmgren-Miner线性损伤规则一起用于评估关键管状焊接接头的疲劳损伤累积。为了应用Neuber规则，根据Efthymiou的解析方程计算了应力集中系数值，对于正在考虑的连接。将建议的方法与Det Norske Veritas（挪威）和Germanischer Lloyd（德国）DNVGL-RP-C203建议中提供的简化疲劳分析进行了比较。这些分析是使用北海收集的散点图中的波浪载荷进行的，这些载荷是通过五阶斯托克斯波浪理论和莫里森公式计算的。