高疲劳抗力钢桥面板的疲劳问题Ⅰ：模型试验

正交异性钢桥面板的疲劳开裂问题是制约桥梁工程可持续发展的关键难题，亟需发展具有高疲劳抗力的正交异性钢桥面板。同时引入纵肋与顶板新型双面焊构造细节和纵肋与横隔板新型交叉构造细节2类构造细节，提出了一种高疲劳抗力钢桥面板，设计了2个足尺节段模型，通过模型试验确定了纵肋与顶板传统单面焊构造细节和新型双面焊构造细节的疲劳开裂模式和疲劳性能，采用扫描电子显微镜（SEM）确定了单面焊构造细节焊根和双面焊构造细节焊趾的初始微裂纹尺度；研究了纵肋与横隔板传统交叉构造细节和新型交叉构造细节的疲劳开裂模式。研究结果表明：纵肋与顶板传统单面焊构造细节的疲劳裂纹起裂于顶板焊根并沿顶板厚度方向扩展，其疲劳强度为98.7 MPa，新型双面焊构造细节的疲劳裂纹起裂于顶板内侧焊趾并沿顶板厚度方向扩展，其疲劳强度为123.2 MPa；传统单面焊构造细节焊根的初始微裂纹尺度显著大于新型双面焊构造细节焊趾的初始微裂纹尺度，初始微裂纹尺度的差异是2种开裂模式的疲劳抗力存在显著差异的主要原因；纵肋与横隔板传统交叉构造细节的疲劳裂纹起裂于纵肋腹板焊缝端部焊趾并沿纵肋腹板扩展，新型交叉构造细节的疲劳裂纹起裂于纵肋底板焊缝端部焊趾并沿纵肋底板扩展，2类构造细节的起裂次数基本一致，但新型交叉构造细节的疲劳裂纹扩展速率远低于传统构造细节；相同加载条件下，高疲劳抗力钢桥面板结构体系的疲劳寿命显著优于传统钢桥面板结构体系。

Fatigue Performance of High Fatigue Resistance Orthotropic Steel Bridge Deck Ⅰ: Model Test

Fatigue cracks in traditional orthotropic steel bridge decks (OSDs) are a major problem that restricts the sustainable development of bridge engineering. Innovative both-side welded rib-to-deck and rib-to-diaphragm welded joints can improve the fatigue resistance of an OSD. Accordingly, taking both rib-to-deck and rib-to-diaphragm welded joints as research objects, this study designed two full-scale segment models. The fatigue cracking modes and fatigue performances of traditional one-sided and innovative both-side welding of a rib-to-deck welded joint were determined. The initial microcrack scales of one- and both-side welding were studied using scanning electron microscope (SEM), and the fatigue cracking modes of the traditional and innovative rib-to-diaphragm welded joints were studied. The results show that the fatigue cracks of the one-sided welding originate from the weld root and propagate in the deck thickness direction, and its fatigue strength reaches 98.7 MPa. The fatigue cracks of the innovative both-side welding originate from the inner weld toe and propagate in the deck thickness direction, and its fatigue strength is 123.2 MPa. Results also show that the initial microcrack scale of the one-sided welding root is noticeably greater than that of the both-side welding toe, leading to a notable difference in the fatigue properties of the two cracking modes. Thus, the weld root is more prone to fatigue cracking under the same load. The fatigue cracks of the traditional rib-to-diaphragm welded joint initiate from the weld toe of the rib-to-diaphragm welded joint and extend along the rib. By contrast, the fatigue cracks of the innovative joint initiate from the weld toe of the rib bottom and then propagate along the bottom plate. The crack initiation times of the two structures are basically the same, but the propagation rate of the traditional OSD is remarkably higher than that of the innovative one. Under the same loading conditions, the fatigue life of the high fatigue resistance OSD is significantly better than that of the traditional OSD.