风暴状态下自升式平台非线性动力分析模型

NONLINEAR DYNAMIC ANALYSIS MODEL FOR JACK-UPS UNDER EXTREME STORM CONDITION

以风暴状态下的自升式平台为研究对象 ,建立了用于分析平台结构的非线性动力模型。该模型采用改进的NewWave模型描述随机波浪 ,借助非线性弹簧模拟平台结构的桩—土之间的相互作用 ,综合考虑了影响平台结构动力响应的动力敏感性、非线性以及波浪载荷的随机性因素 ;同时以波面极值出现前后的若干载荷循环作用下的结构响应结果作为对平台结构响应的估计 ,大大节省了计算时间。建立了简化的三维有限元结构模型。通过具体实例分析 ,给出了使用该模型进行风暴状态下自升式平台动力响应的计算步骤 ,并对分别采用非线性弹簧模型和传统的铰接模型时的平台结构动力响应进行了对比。计算结果表明 ,风暴状态下自升式平台甲板位移响应极值服从对数正态分布。使用该模型进行自升式平台动力响应分析时 ,能够兼顾模型复杂程度和计算效率 ,这为今后进行自升式平台结构动力可靠性分析奠定了基础。

A finite element model for calculating the nonlinear dynamic response of Jack-ups under extreme storm conditions was proposed. This model is based on the non-linearity between soil and piles, in consideration of dynamic sensitivity and load randomness of wave loading. The computational efficiency can be improved with this model. In this model, the random wave was described by the constrained New Wave theory and the interaction between pile and soil was simulated by means of several nonlinear springs. In addition, the whole platform structure was simplified using a three-dimension finite element model. The steps of dynamic analysis on Jack-ups under storm condition were illustrated with an applied case. The structural response results of the Jack-ups obtained with two foundation models (nonlinear spring model and pin model) were compared and analyzed. It is proven that the extreme response of Jack-ups under extreme storm condition obeys the log-normal distribution, and the computational model can meet the demands of both complexity and the efficiency. So this model can provide a necessary condition for the future research on dynamic reliability of Jack-ups.