钢桥面板竖向加劲肋围焊端部止裂技术有限元分析

Finite Element Analysis of Crack Arrest Technology on Weld end of the Vertical Rib in the Steel Bridge

建立竖向加劲肋围焊端部有限元模型,研究钻孔止裂、碳纤维补强以及两种止裂技术的共同作用对该细节疲劳裂纹的止裂效果。分析裂纹断面疲劳应力分布规律,考虑不同工况对止裂效果的影响,并参照实桥裂纹开裂路径建立裂纹扩展模型,分析止裂后疲劳裂纹扩展规律。研究结果表明,钻孔止裂去除了裂纹尖端的应力集中,同时在孔边创造了一个新的应力集中点,新的裂纹可能会在此处萌生;当碳纤维完全覆盖裂纹表面后,增大碳纤维横向粘贴宽度对降低应力强度因子KI的效果不明显;在裂纹开展前期,叠加使用钻孔止裂与碳纤维补强两种止裂技术可以显著降低裂纹尖端的应力集中系数,在开裂后期其降低应力集中的效果与仅采用碳纤维补强技术的效果相近。

The finite element analysis of crack arrest technology was carried out on weld end of the vertical rib in the steel bridge.Three kinds of finite element models,namely stop-hole,CFRP(Carbon Fiber Reinforced Plastics)reinforcement and stop-hole+CFRP reinforcement were established.The stress distribution of the crack section was analyzed and then the effects of crack arrest technology under various working conditions on fatigue performance of this detail were studied.Besides,the crack propagation of the weld end after crack arrest processing was researched based on the crack models established according to the crack path on real bridges.The result shows that the stress concentration on the crack tip is got rid of by the stop-hole technology while a new stress concentration point is created on the hole edge where the new crack may initiate;the lateral width increasing of the CFRP has little influence on the decline of SIF(Strength Intensity Factor)KI if the crack has been fully covered by the CFRP;at the early stage of crack propagation,the joint action of stop-hole and CFRP reinforcement technology can dramatically decline the stress concentration coefficient of the crack tip,but it shares the similar crack arrest effects with that by using only CFRP reinforcement technology at the later stage.