基于考虑闭口肋扭转应变能的高强度钢材加劲板稳定性能研究

As long span bridge developed, high-strength steel with higher strength and better mechanical performance is required. However, the application of high-strength steel would decrease the anti-instability capability of stiffened plate with closed ribs which often used as the main board of the steel girder, with reducing component size. In addition, because of the properties and defect sensitivity of high-strength steel is different from ordinary steel, normative clauses about plate stiffened with closed ribs in domestic and foreign design codes are no longer applicable. Although the design theory of ordinary steel stiffened plate with closed ribs is mainly formed, the torsion rigidity of ribs couldn’t be considered by using the formula on American or Japanese specification to design the stiffness of stiffener which is based on Timoshenko theory. In view of the above questions, the research on stability behavior of high-strength steel stiffened plate will be carried out systematically by adopting the theory and model test method in this project. It will be obtained that simplifying distribution patterns of the initial geometrical imperfections and welding residual stress on the high-strength steel closed stiffened plates, formula for predicting critical stress considering the torsion strain energy, the stiffness ratio, and formula for predicting ultimate load considering the initial defects. The effect of the initial defects on critical stress and ultimate load will be revealed in this research. The research result will provide a theoretical basis for designing the stiffened plate with closed ribs.

桥梁跨径的日益增大，要求采用强度更高、力学性能更好的高强度钢材。但高强度钢材的应用在减小构件尺寸的同时，也使钢主梁中的主要板件——闭口肋加劲板的抗失稳能力下降；另外由于高强度钢材的各项性能及其对缺陷的敏感度与普通钢材有别，国内外规范关于闭口肋加劲板的设计条文不再适用。普通钢材闭口肋加劲板的设计理论基本成熟，但以Timoshenko理论为基础的美国、日本等规范在关于加劲肋刚度设计的公式中，未考虑闭口肋的扭转刚度。针对上述问题，本项目拟采用理论与试验研究相结合的方法，对高强度钢材闭口肋加劲板的稳定性能进行深入的研究。预期得到高强度钢材闭口肋加劲板初始几何缺陷和焊接残余应力的简化分布图式、考虑加劲肋扭转应变能的屈曲临界应力和合理刚度比、考虑初始几何缺陷与残余应力的稳定极限承载力公式；揭示初始几何缺陷和残余应力对稳定极限承载力的影响规律。研究成果可为高强度钢材闭口肋加劲板的设计提供理论依据。

桥梁跨径的日益增大，要求采用强度更高、力学性能更好的高强度钢材。普通钢材闭口肋加劲板的设计理论基本成熟，但以Timoshenko理论为基础的美国、日本等规范在关于加劲肋刚度设计的公式中，未考虑闭口肋的扭转刚度。在总结前人研究成果和各国相关规范设计方法的基础上，结合我国大跨度钢箱梁斜拉桥建设实践，采用理论推导、有限元分析和模型试验的方法，较为系统地研究了高强度钢材闭口肋加劲板的屈曲稳定性能，主要完成了以下工作：.在考虑闭口肋扭转应变能和采用加劲板整体截面形心位置计算弯曲应变能的基础上，基于能量法和比拟正交异性板法分别推导了四边简支加劲板在各种荷载条件下屈曲临界应力计算公式。通过与Timoshenko方法、小西一郎方法和比拟正交异性板法进行比较，结果表明能量法公式计算结果与有限元结果最为接近。.基于推导的能量法计算公式，对影响两对边均匀受压四边简支加劲板屈曲临界应力的重要影响因素如母板宽厚比、加劲板长宽比、加劲肋与母板面积比、加劲肋与母板抗弯刚度比、加劲板扭转刚度与抗弯刚度比进行了参数分析。分别推导了加劲肋的合理抗弯刚度比和加劲肋腹板的最大高厚比。.对焊接热源模型进行了研究，选用双椭球热源模型及热生成率热源模型对高强度钢材加劲板进行焊接温度场模拟。在此基础上进行了普通强度与高强度钢材加劲板热-固耦合分析及参数影响分析，得出影响闭口肋加劲板残余应力主要因素为母板、加劲肋板厚度。.对常用钢结构构件截面和闭口肋加劲板的初始几何缺陷与残余应力分布研究成果以及国内外规范的相关规定进行了总结。采用板壳单元对斜拉桥常用的有代表性的闭口肋加劲板改变其材料屈服强度、母板宽厚比和初始几何缺陷后进行稳定极限承载力参数分析。.拟定了高强度钢材残余应力试验方案和稳定极限承载能力试验方案，待试验完成后与有限元结果进行比较分析和必要的修正。进一步拓展有限元分析模型的参数分析数量，最后得到高强度钢材闭口肋加劲板的残余应力分布模型和稳定承载力计算方法。