地震荷载作用下海洋平台结构物动力可靠度分析

Analysis of dynamic reliability of offshore jacket platforms subjected to seismic action

主要针对地震荷载作用下的海洋平台结构动力可靠性问题进行研究 .海洋平台动力可靠性实质上是综合应用动力响应理论和概率理论 ,先对平台结构响应特性起主要影响作用的随机变量进行抽样 ,然后进行平台结构随机响应分析 ,并对响应结果进行概率统计分析 ,进而求得平台结构动力可靠性 .本文分析过程中 ,考虑了地震烈度、地震输入方向、不同地震波等因素对结构响应的影响 .应用本文所提出的海洋平台结构物动力可靠度分析方法 ,结合工程应用 ,进行南海某三腿海洋平台动力可靠性评估 .分析结果表明 ,考虑了桩 -土共同作用后 ,平台结构刚度降低 ,系统结构更为柔软 ,因此考虑桩 -土共同作用后的结构响应比考虑六倍桩径处固定时的结构响应小 ;南海某三腿海洋平台体系动力可靠指标小于目标可靠指标 ,该平台在实际工程应用中是安全、合理和可行的 .

This work applied the structural dynamic response theory and the stochastic theory to develop a method for dynamic reliability analysis of offshore jacket platforms subjected to seismic action. In this method, the random variables that mainly affect the response characteristics of offshore platforms were selected and sampled. The stochastic responses of offshore platforms to these random variables and subjected to seismic action were analyzed. Statistical analysis of the response parameters yielded a probabilistic function describing the response of the platform to seismic action. Finally dynamic reliability of offshore platforms can be achieved by proper application of the limit state function of the integrated platform structure under dynamic conditions. By means of the method proposed in this paper, the dynamic reliability of the Weizhou 11-4C offshore platform subjected to seismic action was evaluated. The Weizhou 11-4C platform is a tripod-legs simple jacket platform located at the Gulf of Weizhou, South China Sea. In the dynamic reliability analysis, the influences of earthquake intensity, direction and occurrence frequency were considered. The analysis results showed that the responses of the Wei114-4C platform considering the pile-soil-structure mutual interaction were less than those of a fixed platform with 6 times the diameter, and that the dynamic reliability index of Weizhou 11-4C offshore platforms was high and the failure probability was very low. So the Wei11-4C platform subjected to seismic action is safe.