寿命期内FPSO船体梁的崩溃机理及其抗力概率模型研究

FPSO would be moored in the harsh environment as the most offshore production platform in the world, which will result in cracks and corrosions in the structures. In case the structures fail, the accident as oil spill will result in the loss and environment pollution. It is important to study the safety of the FPSO in life cycle. The collapse mechanics and the resistance probability model will be studied for the FPSO subjected to cracks and corrosions in life cycle. The ultimate strength of stiffened plate subjected to fatigue cracks and corrosion damage is derived using theoretical analysis, numerical simulation and experimental modeling approach considering the true status of the damage. And the influences of crack and corrosion on ultimate strength and failure model are also analyzed. The progressive collapse mechanics in life cycle will be studied for the FPSO subjected to cracks and corrosions and the ultimate strength calculation will be performed. The stochastic analysis models of the ultimate strength of damaged stiffened plate and FPSO hull are established using simulation experiment. Finally, the random time-varying model of ultimate strength of FPSO hull under cracks and corrosions is given. The progressive collapse mechanics of FPSO hull girder in life cycle and the influence of cracks and corrosions and the resistance uncertainty are revealed through the study of this project. The result can provide the accurate resistance model in the FPSO structure reliability analysis. It could provide a theoretical basis for the assessment of ship operating in service and design of the hull structure.

FPSO作为目前主要的油气生产平台，需长期固定于恶劣海域。因此，其结构不可避免产生疲劳裂纹和腐蚀。结构一旦失效，将造成漏油的重大损失和环境污染，因此寿命周期内结构的安全性评估意义重大。本项目开展FPSO寿命期内裂纹、腐蚀损伤下结构的崩溃机理及其抗力概率模型的研究。结合理论、数值模拟以及试验的方法，考虑真实损伤模型，建立疲劳裂纹、腐蚀损伤情况下加筋板极限强度较为准确的计算方法，分析初始缺陷、损伤等对加筋板极限强度及失效模式的影响；在此基础上，探讨裂纹、腐蚀损伤下FPSO船体梁寿命期内的渐进崩溃机理，建立损伤下船体梁极限强度的计算方法。采用数值试验的方法，建立加筋板结构及FPSO船体梁极限强度的随机时变概率模型。通过研究，揭示寿命期内FPSO渐进崩溃机理、受裂纹、腐蚀的影响机制及其统计规律，为FPSO结构的可靠性研究提供准确抗力概率模型，并为其结构的安全营运评估及设计奠定基础。

FPSO作为目前主要的油气生产平台，需长期固定于恶劣海域，其结构不可避免产生疲劳裂纹和腐蚀。结构一旦失效，将造成漏油的重大损失和环境污染，因此寿命周期内裂纹、腐蚀损伤下结构的安全性评估将意义重大。首先采用试验、数值模拟以及理论方法，针对裂纹、腐蚀损伤下海洋工程典型加筋板结构的极限承载能力开展研究，建立疲劳裂纹、腐蚀损伤情况下加筋板极限强度的较为准确的计算方法，发现裂纹的存在将会改变加筋板的屈曲模式，初始变形同样会降低结构的极限强度，点蚀对于加筋板极限强度的主要影响为DOP、腐蚀体积以及最小截面面积，揭示了裂纹、腐蚀下加筋板的崩溃机理，最终给出了基于板格柔度和加筋板柔度折减的裂纹、腐蚀下加筋板极限强度预报公式，误差在15%以内。基于加筋板的研究成果，开展了裂纹、腐蚀作用下FPSO船体梁极限强度的研究，给出了不同裂纹长度、腐蚀程度以及损伤位置对于船体梁极限强度的影响，揭示了寿命期内FPSO渐进崩溃机理。在此基础上，综合有限元和逐步破坏法的优点，建立了裂纹、腐蚀损伤下船体梁极限强度计算的简化方法，其误差在10%以内。考虑裂纹、腐蚀损伤的随机性，计入材料参数、结构尺寸的不确定性，采用拟合技术，建立了寿命周期内FPSO船体梁概率抗力模型。本项目提出的计算方法和结果可为寿命期内FPSO结构的可靠性研究提供准确抗力概率模型，并其结构的安全营运评估及设计奠定基础。