中国南海极端风暴海况下固定式平台结构可靠性分析

Structural reliability analysis for fixed offshore platforms in South China Sea under extreme storm conditions

基于中国南海海域风暴环境条件,研究分析南海海域固定式导管架平台结构整体性和可靠性,以及新建固定式平台结构设计准则。采用海洋环境数据后报方法,得到南海海域1972~2011共40年的风、浪、流联合数据,从中抽取风暴环境条件;利用通用荷载模型,将40年间的风暴环境数据转变成结构的荷载数据,即基底剪力或倾覆力矩;并计算得到风暴环境荷载的短期及长期分布,以及任意风暴下荷载的概率分布;根据结构可靠性模型,结合荷载的长期分布,研究基于结构暴露等级及失效概率的固定式平台结构强度储备比。根据计算,得到了不同暴露等级下中国南海平台的强度储备比,并与墨西哥湾及北海海域进行了比较,为新建平台提供设计参考。

This paper presents a reliability based methodology to develop the design acceptance criteria for fixed offshore platforms under extreme storm conditions in South China Sea. Four achievements have been presented in this paper. Firstly, winds, waves and currents of 40 years between 1972 and 2011 are hindcasted in South China Sea and the extreme storm conditions extracted. Secondly, generic load model is used to transfer the data of storm waves, winds and currents into load. Thirdly, load statistics model is adopted to investigate the short and long term distributions of the extreme environmental load, as well as the load distribution of random storm. Finally, a structural reliability model is proposed to give the relationship between the structure failure rate and reserve strength ratio. Reserve strength ratios for four different exposure categories are listed in the paper, which may provide some guidance for newly built platforms in South China Sea, and comparison has been made of the reserve strength ratios for Gulf of Mexico, South China Sea and North Sea.