基于改进Smith方法的大型集装箱船极限承载能力及可靠性研究

The crash accidents of container ships in recent years unveiled the shortcomings in current methods of ultimate strength evaluations, so it is necessary to further investigate the key techniques in large container ship ultimate strength analysis, and to unveil the mechanical background of the structural behaviors, so that more professional technical support can be supplied for future container ship designs..In this research, the key factors such as modelling extent, boundary conditions, seawater pressure and initial deflection in ultimate strength analysis and corresponding mechanism are studied by Nonlinear Finite Element Method (NFEM), and the modelling settings are validated, and the bending-torsional interaction mechanism is investigated with double-shell structure experimental model test for ultimate torsional strength. By modifying effective breaths of attached plates for stiffened plates, the Smith’s method in ultimate strength analysis is improved to consider the factors such as transverse and horizontal bending, torsion, lateral pressure, residual stress and initial deflection, meanwhile the results can be validated by above NFEM analyses. Finally, the different behaviors and mechanism of ultimate strength under uniform and non-uniform corrosion are studied, and the new method for the reliability problem is also studied considering uncertainties of uniform corrosion and external loads based on the improved Smith’s method and surrogate models..This research will solve the key problems in improving Smith’s method and demonstrating the background mechanism, and propose a new reliability analysis method considering structural corrosion based on above investigations. It will be beneficial to both newly-built and currently operating ships with technical suggestions, and meanwhile provide data support for classification rules modification.

近年来集装箱船断裂事故显示大型集装箱船极限强度分析方法的不足，有必要进一步研究其关键技术和力学机理，为后续船舶设计提供坚实的技术支撑。.本研究将首先采用非线性有限元方法研究并阐释大型集装箱船极限强度的力学机理，包括弯扭极限强度耦合机理及双壳结构扭转模型试验，并通过推导相应加筋板的有效带板宽度改进Smith方法，使其兼容横向和水平弯曲、扭转、侧压、残余应力和初始变形等因素，同时通过非线性有限元方法对其进行验证。最后，阐释均匀和非均匀腐蚀下船体结构极限强度机理差异，并考虑均匀腐蚀和载荷的不确定性，形成基于改进后Smith方法和代理模型的可靠性评估方法。.本研究将解决多种载荷因素下的Smith方法改进等关键问题并诠释其力学机理，并提出结构腐蚀下可靠性分析的方法，研究结果可为船舶设计和运维提供技术建议，并为船级社规范修订提供数据支撑。

近年来集装箱船断裂沉船事故时有发生，显示大型集装箱船极限强度分析方法的不足，为降低此类安全隐患，有必要进一步从力学机理等基础层面对集装箱船结构承载能力开展更加深入细致的分析，掌握其强度分析的关键技术，为后续船舶设计提供坚实的技术支撑。本研究采用理论推导、数值仿真和试验验证相结合的方式，对大型集装箱船结构极限承载能力开展了研究。一方面基于非线性有限元方法，研究并阐释了大型集装箱船极限强度及其失效的力学机理，包括多种关键影响因素的分析，弯扭极限强度耦合机理及双壳结构扭转模型试验设计方法，并通过推导相应加筋板的有效带板宽度、板筋耦合下结构屈曲强度，结合数值仿真研究了侧压下极限强度修正方法和曲面加筋板的极限强度预测公式，在此基础上对Smith方法进行了改进，使其兼容扭转、侧压、水平弯曲等多种因素的影响，并通过非线性有限元方法对其进行了验证。另一方面，阐释了均匀和非均匀腐蚀下船体不同层次结构（船体板、加筋板、船体梁）极限强度及其失效模式的变化，并考虑到载荷和结构本身的不确定性因素，基于可靠性分析的理论框架，形成了基于改进后Smith方法、非线性有限元及其高精度代理模型的可靠性评估方法，并基于多目标协同优化方法，对基于确定性和可靠性的结构优化设计开展了应用研究，为更合理地评估大型集装箱船结构安全性提供了技术基础。本项目的研究结果可为集装箱船结构设计和运营维护安全提供技术建议和参考依据，为船级社规范修订提供数据和理论支撑。