纵肋与横隔板交叉构造细节穿透型疲劳裂纹扩展特性及其加固方法研究

纵肋与横隔板交叉构造细节是正交异性钢桥面板最易发生疲劳开裂的构造细节，通过建立有限元数值模型，采用断裂力学方法，研究栓接角钢加固方式对该处疲劳易损细节穿透型裂纹的加固效果。基于疲劳试验足尺节段模型相对应有限元模型，建立了纵肋与横隔板焊接处穿透型疲劳裂纹模型，针对栓接角钢和纵肋外侧栓接钢板两种加固技术的加固效果进行评估。研究结果表明：钢桥面板纵肋与横隔板交叉构造细节的疲劳裂纹扩展至一定长度后将发展成穿透型裂纹，裂纹面受力复杂，纵肋腹板内外侧疲劳裂纹扩展特性表现的不一样，但是随着裂纹扩展的逐步进行，裂纹尖端的开裂模式均以复合型开裂为主；栓接角钢加固方式主要抑制纵肋与横隔板交叉构造细节易损部位疲劳裂纹的I型开裂，因此能很好地抑制短裂纹的扩展，但对于该细节处以复合形式扩展的穿透型疲劳裂纹的加固效果并不显著；在纵肋外侧栓接半U形钢板的加固方法能有效改善穿透型疲劳裂纹的等效应力强度因子，并且加固之后均保持在裂纹扩展阈值以下，表明该加固方式对穿透型疲劳裂纹有良好加固效果。

RESEARCH ON PROPAGATION CHARACTERISTICS AND REINFORCEMENT METHOD OF PENETRATING CRACK AT RIB-TO-DIAPHRAGM WELDED JOINTS IN STEEL BRIDGE DECK

The rib-to-diaphragm welded joints in the deck of an orthotropic steel bridge is most prone to fatigue cracking. A FE model was established and fracture mechanics was used to study the reinforcement effect of angle steel reinforcement methods on the penetrating crack at fatigue vulnerable details. Based on the finite element model corresponding to a full-foot segment fatigue test model, a penetrating fatigue model was established for the cracks in rib-to-diaphragm welded joints, and the reinforcement effect was evaluated on two reinforcement techniques: bolted angle steel and the bolted steel plate beside a longitudinal rib. The results indicate that: the fatigue cracks at the welded joint in the rib-to-diaphragm of a steel bridge deck expand into a certain length and will develop into penetrating cracks, the deformation of the crack surface under stress conditions is complicated, the fatigue crack propagation characteristics of the inner and outer side of longitudinal ribs are not the same, and as the crack propagation progresses, the cracking mode of the crack tip will be dominated by composite cracking. The existing research results show that: the bolted angle steel reinforcement method can well inhibit the longitudinal rib and diaphragm connection details of the vulnerable part with the fatigue crack type I cracking. Therefore, the short crack propagation can be well suppressed. However, the reinforcement effect on penetrating fatigue cracks extended in a composite type in this detail is not as good as the short crack that have not penetrated the web;the reinforcement method of the half U rib steel plates bolted to the outside of longitudinal ribs can effectively reduce the equivalent stress intensity factor of penetrating fatigue cracks, and stay below the crack propagation threshold after reinforcement. It shows that the reinforcement method has a good reinforcement effect on penetrating fatigue cracks.