Study on Reinforcement for Fatigue Cracking of Rib-to-Diaphragm Welded Joints of Steel Bridge Deck
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摘要: 为研究钢桥面板疲劳开裂部位栓接角钢的加固方法，采用足尺模型试验对纵肋与横隔板焊接细节疲劳裂纹的加固效果进行研究，采用ANSYS建立了含有疲劳裂纹的有限元模型，并基于断裂力学理论对比研究疲劳裂纹不同长度条件下的加固效果. 研究结果表明：纵肋与横隔板焊接细节的疲劳裂纹起裂于焊趾并沿纵肋腹板扩展，采用栓接角钢加固后可以使开裂部位关键测点的主拉应力和裂尖各测点的应变分别降低56%和80%，能够有效抑制疲劳裂纹的扩展；栓接角钢加固后裂尖的应力强度因子幅值最少降低80%，裂纹扩展速率显著降低；对贯穿纵肋腹板前不同长度的疲劳裂纹进行加固，裂尖应力强度因子幅值均降低60%～90%，但随着疲劳裂纹长度的增加，栓接角钢的加固方法对裂纹扩展的抑制效果不断降低，加固时机的合理选取是影响加固效果的关键因素之一.Abstract: In order to study the reinforcement effects of bolted angle steel on fatigue cracking of the orthotropic steel bridge deck, the full-scale test model was used to study the reinforcement effect of fatigue cracks on the rib-to-diaphragm welded joints. A finite element model with fatigue cracks was established using ANSYS, and to study the reinforcement effects under different length of fatigue cracks conditions based on the fracture mechanics theory. The results indicate that the fatigue cracks initiate from the toe of longitudinal rib-to-diaphragm welded joints and expand along the longitudinal web, the reinforcement method with bolted angle steel can reduce the main tensile stress of the key measure points at the cracking details and the strain of measure points at crack tips by 56% and 80%, respectively. The stress intensity factor of the crack tip is reduced by more than 80% after bolting angle steel reinforcement, and crack propagation rate is reduced significantly. For the different lengths of fatigue cracks before the longitudinal rib webs, the amplitude of the crack tip stress intensity factor is reduced by 60%−90% using the reinforcement method, but with the increase of the fatigue cracks length, the reinforcement effects are reduced continuously, the reasonable selection of the reinforcement time is one of the key factors in the reinforcement effects.
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图 1 纵肋与横隔板焊接细节处疲劳开裂模式
Figure 1. Fatigue cracking mode for structural details of rib-to-diaphragm
图 6 有限元模型与试验模型关键测点应力对比
Figure 6. Comparisons of tensile stresses of principal measure points in FE model and physical model
图 11 加固前后关键测点主拉应力与循环次数间的关系
Figure 11. Relationship between principal tensile stresses and loading cycles before and after strengthening
图 12 加固前后裂尖应变与循环次数间的关系
Figure 12. Relationship between strain of crack tip and loading cycles before and after strengthening
图 14 不同裂纹长度加固前后裂尖应力强度因子幅值
Figure 14. The stress intensity factors amplitude of the crack tips before and after the reinforcement in different crack lengths
表 1 加固前后有效应力强度因子的变化
Table 1. Stress intensity factors before and after strengthening
裂纹位置 ΔKeff/（MPa•mm1/2） 降幅/% ΔKth/（MPa•mm1/2） 加固前 加固后 内侧裂纹 495 75 85 63 外侧裂纹 522 78 85 63 中裂纹 324 43 87 63 
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