大跨度公铁两用斜拉桥正交异性钢桥面板疲劳机理研究

Tests and numerical simulation researches would be carried out to deal with the fatigue problem of orthotropic steel bridge deck in Long-Span Rail-Road Cable-Stay Bridge. Firstly, the characteristic of typical traffic in the Long-Span Rail-Road Cable-Stay Bridge would be investigated. The load spectrum of total bridge could be obtained by numerical simulation while the stress spectrums of local parts in the orthotropic steel deck system could be also obtained. The effect of vehicle load and axial force in deck and girder that caused by horizontal component of Stayed-Cable would be taken into account in the study of fatigue problem. Than fatigue performance of four special typical details that were basic metal detail of U-rib, welding detail in joint of U-rib, basic metal and welding details of cope holes in crossbeam, welding details between U rib and deck in the orthotropic steel bridge deck. Meanwhile the influence of stress-concentration that caused by welding would be discussed in details. Based on the theory of fracture mechanics, full-scale model tests and numerical simulation researches would be carried out to analyze the stress concentration factor, stress intensity factor (include its amplification coefficient) and the cracking toughness of the four special typical details in orthotropic steel deck system in order to analyze effects of fatigue performance that caused by the factors above. Considering the different fatigue cracking lives of the parts of orthotropic steel deck system and the randomness and uncertainty of the parameters, the reliability analysis and safety evaluation of the Long-Span Rail-Road Cable-Stay Bridge could be taken to provide technical support for fatigue design code of the details.

针对大跨度公铁两用斜拉桥中正交异性钢桥面板系统疲劳的问题，开展数值模拟和试验研究。调研大跨度公铁两用斜拉桥的典型疲劳车特点，通过数值模拟提出其荷载谱，研究正交异性钢桥面板系统的局部应力谱。研究由于斜拉索对主梁和桥面板的轴力和车辆疲劳荷载作用下，正交异性钢桥面板中的四类典型母材与焊接细节(U肋母材细节、U肋拼接焊接细节、横隔板U肋开口母材与焊缝细节、U肋与面板焊接细节)的疲劳性能和裂纹发展规律，深入研究应力集中对疲劳性能的影响。基于断裂力学理论，进行数值模拟和足尺模型的疲劳试验研究，研究分析上述四类细节的应力集中系数、应力强度因子放大系数和断裂韧性性能，分析各因素对桥面板结构的疲劳性能的影响。在考虑正交异性钢桥面板系统中各部分不同疲劳开裂寿命的前提下，评估疲劳问题中各参数的随机性和不确定性，对大跨度公铁两用斜拉桥进行可靠度分析和安全性评估，为相应的疲劳细节设计规范的制修订提供技术支撑。

在公路荷载和铁路荷载的共同作用下，公铁两用桥承受了巨大的荷载。作为斜拉桥直接承受车辆荷载的构造，正交异性钢桥面板疲劳问题突出。针对大跨度公铁两用斜拉桥中正交异性钢桥面板系统的疲劳问题，开展了数值模拟和试验研究，主要工作内容概括如下：.（1）基于梁格法理论对正交异性钢桥面板进行划分，得出一种快捷使用的计算斜拉桥正交异性钢桥面板的方法。通过数值模拟得到了具有宽U肋的正交异性钢桥面板的疲劳敏感细节的应力谱。.（2）对板桁斜拉桥的Q500qE正交异性钢桥面板的疲劳性能进行综合研究，分析了正交异性钢桥面板结构的整体失效模式。.（3）对正交异性钢桥面板U肋嵌补段的裂纹扩展过程进行详细分析，分析了U肋嵌补段由于装配误差引起的次内力，并讨论U肋嵌补段的应力集中效应。.（4）提出基于神经网络算法的热点应力外推计算方法，为横隔板支撑托板疲劳细节提出了相对应的疲劳强度设计标准。.（5）对桥面板疲劳裂纹预防措施进行研究，对横隔板支撑托板新构造进行参数分析，同时对比了顶板-U肋构造中传统焊缝、镦边焊缝、双面焊缝的受力特性，讨论了熔透率对双面焊缝的影响。.（6）针对顶板-U肋双面焊及全熔透构造的主导疲劳失效模式进行分析，通过疲劳试验研究全熔透构造的疲劳性能、破坏特征及裂纹特性。详细记录并分析了裂纹参数。.（7）基于U肋焊趾裂纹关键几何参数对疲劳裂纹扩展特性进行研究。基于裂纹的初始尺寸、形状比、裂纹与焊趾的间距及初始角度参数，对U肋焊趾裂纹的应力强度因子、扩展特性及接头的剩余疲劳寿命进行研究。.（8）对U肋焊趾多裂纹扩展进行研究。给出顶板-U肋焊接接头在焊趾多裂纹融合扩展情况下的剩余疲劳寿命经验计算公式。.（9）探索将共面的相邻表面三维裂纹等效为单裂纹进行疲劳寿命评估的方法，提出基于虚拟裂尖接触的VCTC裂纹合并准则。.（10）采用装配式钢板对因嵌补段开裂而失效的试件进行加固，并进行疲劳试验，发现该方法效果良好，显著提升了结构的剩余疲劳寿命。