基于环境包络线法的深水浮式平台极值响应长期预报

海上结构设计包括对荷载和响应的可靠性评估。对结构进行全面长期响应分析繁琐且费时,故将基于逆一阶可靠性方法的环境包络线进行海上结构概率可靠性分析,对结构的长期响应进行近似估计。在二维标准正态空间中画出与重现期相对应的圆,将圆离散为点后通过Rosenblatt变换转化为环境参数空间中的点来形成闭合的环境包络线。描述海洋环境条件的模型对绘制环境包络线极为重要,基于我国南海荔湾海域40年波浪模拟数据,建立了描述南海波浪的Weibull-Gev条件分布模型,进而绘制南海有效波高—谱峰周期包络线,并与张力腿平台(TLP)系泊张力的长期响应预报结果对比,给出南海海域在波浪作用下应用环境包络线法预报TLP系泊张力的分位数,为未来南海TLP设计中系泊张力预报提供快速估算方法。

Long-term prediction of extreme response of deepwater floating platform based on environmental contour method

Offshore structure design includes reliability assessment of load and response. A full long term analysis is cumbersome and time consuming. Environmental contours based on inverse first order reliability method is usually used for probabilistic reliability analysis of offshore structures to estimate the long-term response of structures. This paper establishes such an environmental contour by drawing a circle corresponding to the radius of the return period in a standard two-dimensional normal space, then discretizing the circle into points and drawing the points in the original data space to form a closed contour by Rosenblatt transform. The model describing marine environment is very important to draw the environmental contours. Based on 40-year wave simulation data in the Liwan sea area of the South China Sea, the Weibull-Gev conditional distribution model describing waves in the South China Sea is established, and the contours of significant wave height-peak spectral period in the South China Sea are drawn. Compared with the long-term response prediction results of a TLP mooring tension, the quantile of applying environmental contour method to TLP tension leg tension in the South China Sea under beam waves is given. This paper provides an approximate estimate for the mooring tension prediction in the future TLP design in the South China Sea.