基于非高斯域转换修正系数法的船体极限强度可靠性评估方法研究

The present assessment methods of ultimate strength and structural reliability for arctic navigation ship do not account for the influence of the arctic environment, which can not integral transformation for non-Gaussian domain to satisfy the requirement of accuracy and efficiency. The formulae of residual stress and initial imperfection considering low temperature will be induced base on experiment and multiphysics coupling method. Using the deflection function considering the interaction of the plate and stiffener, the formula of average stress-average strain relationship including strain and temperature parameter will be developed base on the total potential energy function. The influence of the low temperature on the buckling failure modes and the load carrying capacity of ship structures will be studied as well. The surrogate model of assessment method of wave load will be proposed base on the Monte Carlo method and statistical regression, whose results will compare with that of most likely response wave method to investigate the significance level of the nonlinear of wave moment. .Using the 'ideal' and 'real' models of the resisting force and wave load, the non-Gaussian domain is transformed to standard Gaussion domain by the iterative process of second order reliability method (SORM) and unique pointwise affinity. The 'real' model can be transformed to 'ideal' model by auto-correction coefficient function. This method can avoid the full integral problem due to the gradient calculation of the random variable. Base on the proposed model factor correction method (MFCM), the influence of the low temperature and nonlinear wave moment on the ultimate strength, probability distribution and reliability index will be investigated, which gives the efficient and accurate theoretical method for the safety assessment for the arctic navigation ship.

针对现有的船体极限强度及可靠性方法没有考虑极地环境的影响，不能进行非高斯域积分而无法同时满足计算精度和效率的问题，拟基于实验和多场耦合法，推导低温度下加筋板的应力和几何初始缺陷公式，提出总势能泛函导出包含应变和温度控制的本构关系，揭示低温度对船体结构屈曲失效模式和极限强度的影响规律。提出一种融合Monte Carlo法和统计回归获得波浪载荷预报代理模型的方法,并结合MLRW法研究非线性波浪弯矩的影响。在获得结构抗力和外载荷的理想和复杂模型后，通过SORM迭代过程进行逐点近似把非高斯域转换成标准高斯域，采用关联函数进行极限状态空间域的变换，解决随机变量的梯度计算而无法积分问题，基于修正系数法提出可以考虑非高斯域的船体极限强度可靠性安全评估物理模型。进一步揭示低温度和波浪弯矩非线性对船体极限强度及其概率分布和可靠性指标的影响规律，为极地航行船舶的安全评估提供高效、准确的理论方法。

根据北极航道的温度环境，采用理论方法研究了船体加筋板结构在低温环境下的屈曲失效模式。基于总势能泛函推导了考虑温度和初始缺陷的加筋板结构应力-应变本构关系，并分析了低温度对船体结构屈曲失效模式和极限强度的影响规律。采用多场耦合法分析了船体梁在温度环境下的屈曲失效，并基于逐步崩溃分析方法推导了船体梁极限承载能力评估方法。提出了一种融合Monte Carlo法和统计回归获得波浪载荷预报代理模型的方法,并结合MLRW法研究了非线性波浪弯矩的影响。. 在获得结构抗力和外载荷的理想和复杂模型后，通过SORM迭代过程进行逐点近似把非高斯域转换成标准高斯域，采用关联函数进行极限状态空间域的变换，解决随机变量的梯度计算而无法积分问题。最终，基于修正系数法提出了可以考虑非高斯域的船体极限强度可靠性安全评估物理模型。并采用该模型研究了低温度和波浪弯矩非线性对船体极限强度及其概率分布和可靠性指标的影响规律，为极地航行船舶的安全评估提供高效、准确的理论方法。