正交异性钢桥面板结构体系的疲劳破坏模式和抗力评估

正交异性钢桥面板的疲劳问题属于包含多疲劳破坏模式的结构体系疲劳问题。基于这一本质特性，以典型的正交异性钢桥面板结构体系为研究对象，由结构体系的主导疲劳破坏模式出发，提出正交异性钢桥面板结构体系疲劳抗力评估的新方法。以纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节为主要研究对象，设计8个足尺节段模型，主要包括传统纵肋与顶板焊接细节、新型镦边纵肋与顶板焊接细节和纵肋与横隔板交叉构造细节，通过模型试验研究了两类重要构造细节的主导疲劳破坏模式和实际疲劳抗力，在此基础上结合切口应力评估方法探讨正交异性钢桥面板构造细节切口应力S-N曲线方程、结构体系的主导疲劳破坏模式等关键问题。研究结果表明：传统纵肋与顶板焊接细节和新型镦边纵肋与顶板焊接细节的主导疲劳破坏模式均为疲劳裂纹萌生于焊根并沿顶板厚度方向扩展，二者的实际疲劳抗力基本相同；纵肋与横隔板交叉构造细节的疲劳破坏模式为焊趾开裂沿纵肋腹板方向扩展；对于研究对象而言，萌生于纵肋与顶板焊接细节焊根并沿顶板厚度方向扩展的疲劳破坏模式为控制结构体系疲劳抗力的主导疲劳破坏模式。

Fatigue failure modes and resistance evaluation of orthotropic steel bridge deck structural system

The fatigue problem of orthotropic steel bridge deck can be viewed as the fatigue problem with multiple fatigue failure modes of structure system. In view of the intrinsic characteristics, with the typical structural system of orthotropic steel bridge deck taken as the research subject, a new evaluation method of the fatigue resistance of orthotropic steel bridge deck was proposed based on the dominant fatigue failure modes of structural system. Furthermore, with the rib-to-deck welded joints and the longitudinal rib-to-diaphragm welded joints taken as the main research subject, eight full-scale girder segment models, including traditional rib-to-deck welded joints, new upsetting edge rib-to deck welded joints and longitudinal rib-to-diaphragm welded joints, were designed, the dominant fatigue failure modes and the actual fatigue resistance for the two types of structural details were investigated by the fatigue test, and then the key issues such as the notch stress S-N curve equation of structural details and the dominant fatigue failure modes of orthotropic steel bridge deck structural system were discussed based on the notch stress method. The results showed that the fatigue cracks of traditional rib-to-deck welded joints and the new upsetting edge rib-to-deck welded joints initiated from weld root and propagated along the deck thickness direction, the actual fatigue resistances of two welded joints were basically the same; As for the rib-to-diaphragm welded joints, its fatigue failure mode that the fatigue cracks initiated from the weld toe and propagated along the web of rib. The mode with fatigue cracks initiating from weld root of rib-to-deck welded joints and propagating along deck thickness was the dominant fatigue failure mode of orthotropic steel bridge deck structural system.