海洋平台疲劳寿命预测的优化分析

Optimization analysis of fatigue life prediction for offshore platforms

针对目前海洋平台延寿评估过程中频繁出现的谱疲劳分析的计算寿命远小于平台服役年限的现状,从谱疲劳分析和时域疲劳分析的基本原理和求解过程出发,对两者的优劣性进行深入研究。研究结果表明时域疲劳分析方法可以得到较谱疲劳分析方法更精准的疲劳损伤结果,但需要耗费巨量的计算时间。研究进一步阐明了造成节点疲劳寿命计算值偏低的主要原因,指出了优化疲劳寿命的主要措施和途径,并建立了谱分析与时域分析相结合的结构寿命评估方法。该方法通过谱疲劳分析进行疲劳敏感节点的筛选,以热点损伤散布图的方式确定损伤主贡献海况,再利用时域分析方法优化主贡献海况下的损伤结果。该方法解决了谱分析结果过于保守而全时域分析过程过于耗时的问题,可作为平台结构设计或延寿评估时合理挖掘其疲劳强度潜力的重要手段。

Currently,the calculated life of spectral fatigue analysis is far less than the service life of platforms,and this occurs frequently in the life extension evaluation of offshore platforms.Therefore,the advantages and disadvantages of spectral fatigue analysis and time-domain fatigue analysis are deeply studied in terms of the basic principles and solution process.The results reveal that the time-domain fatigue analysis method can obtain more accurate fatigue damage results than the spectral fatigue analysis method,but it requires huge time consumption for calculations.Furthermore,the main reasons for the low calculated value of joint fatigue life are further clarified;the main measures and ways to optimize the fatigue life are pointed out,and the structural fatigue life evaluation method combining spectral analysis and time-domain analysis is proposed.In this method,the fatigue-sensitive joints are selected by spectral fatigue analysis,and the main sea states contributing to damage are determined by scatter plots of hotspot damage,the damage results under which are then optimized by time-domain analysis.This method solves the problem that the spectral analysis results are unduly conservative,and the full-time-domain analysis process is excessively time-consuming.It can be used as an important means to reasonably tap their fatigue strength potential in the structural design of platforms or life extension evaluation.