联合载荷作用下受损船舶极限状态方程研究

The limit state function is the basis for strength criteria formulation and structural strength assessment. In order to evaluate the residual strength reasonably and investigate the effect of combined wave loads on residual performance for damaged ship, limit state function (LSF) of damaged ships subjected to combined wave loads is studied..Firstly, improved analysis methods of residual bearing capacity are studied. An improved Smith method is presented by considering translation and rotation of neutral axis of damaged transverse section. Simplified material models of common ship-built materials and equivalent simplified modeling methods for initial imperfections are studied for non-linear finite element analysis. On the basis above, the residual bearing capacities of damaged ship subjected to combined wave loads are estimated..Secondly, the fitting techniques of LSF of damaged ship subjected to combined wave loads are studied. According to the two-parameter LSF, an explicit expression of LSF of damaged ship subjected to combined wave loads is derived and the least square method is applied to determine parameters. Then, neural network response surface method is adopted to fit LSF of damaged ship subjected to combined wave loads, and the network topology, mapping function and activation function is selected responsibly. After data learning and training, the LSF of damaged ship subjected to combined wave loads is presented in mapping function expression..Finally, the limit state functions of damaged ship subjected to combined wave loads are applied to evaluate residual strength. On the basis of the evaluation results, the explicit limit state function is optimized.

极限状态方程是制定强度评估标准并进行结构强度评估的基础。为合理地评估受损船舶的剩余强度并考察船体梁载荷耦合作用对剩余强度的影响，课题将开展联合载荷作用下受损船舶极限状态方程的研究。.首先，开展现有剩余承载能力分析方法的改进研究。考虑受损剖面中和轴偏转，改进Smith法；研究非线性有限元分析中常用船用材料的简化模型和结构初始缺陷的等效简化模拟方法。在此基础上，开展联合载荷作用下剩余承载能力分析。.其次，开展联合载荷作用下受损船舶极限状态方程拟合方法研究。基于二元极限状态方程，推导联合载荷作用下极限状态方程的显式表达式并拟合显式方程。在此基础上，开展基于神经网络响应面法的极限状态方程拟合方法研究，选择合理的网络拓扑形式、映射函数和激活函数，并通过样本学习建立网络映射函数表达的极限状态方程。.最后，开展极限状态方程在剩余强度评估中的应用研究，并根据评估结果进一步优化显式极限状态方程以提高其精度。

为了合理地评估受损船舶的剩余强度，课题开展了联合载荷作用下受损船舶极限状态方程的研究，分别基于线性搜索方法和粒子群算法提出了非对称受损剖面中和轴确定方法，并建立了考虑中和轴偏转的剩余承载能力计算的改进Smith法；同时，对非线性有限元分析中常用船用材料的材料简化模型和初始缺陷的等效简化模拟方法开展了研究；在此基础上，开展联合载荷作用下受损船舶极限状态方程拟合方法研究，首先推导了联合载荷作用下受损船舶的显式极限状态方程，误差较大，其次基于改进的响应面法研究建立了联合载荷作用下受损船舶隐式极限状态方程的构造方法，拟合优度R2>0.9999；最后，基于可靠性原理对联合载荷作用下受损船舶的剩余强度评估开展了初步研究。