钢板梁桥主梁腹板焊缝疲劳成因与构造优化分析

Fatigue Causes and Structural Optimization of Web Weld of Main Girder in Steel Plate Girder Bridge

针对钢板组合梁桥钢主梁腹板焊缝的疲劳开裂问题,建立四跨连续钢板组合梁桥全局模型与带小横梁的钢主梁节段模型。针对典型开裂部位腹板间隙,分析其面外变形特征,对比不同构造形式下腹板与竖向加劲肋焊缝的应力特征,明确疲劳开裂成因与面外变形作用机理。基于上述成因分析,提出一种提升抗疲劳性能的构造优化方法。结果表明:横向加劲肋对主梁腹板产生向主梁内侧、竖直向下的“拉拽”作用,其为导致腹板间隙出现面外变形的直接原因;切削横向加劲肋底部的方法可将局部应力峰值下降80%以上,有效缓解应力集中,降低外荷载导致的疲劳损伤。

In view of the fatigue cracking problem of the web weld of the steel girder of the steel plate composite beam bridge,the global model of four-span continuous steel plate composite girder bridge and the segment model of steel girder with small cross beam were established.The out-of-plane deformation characteristics of the typical cracked web gap were analyzed,and the stress characteristics of the welds between the web plate and the vertical stiffener under different structural forms were compared to identify the cause of fatigue cracking and the mechanism of out-of-plane deformation.Based on the above cause analysis,a structural optimization method to improve the fatigue resistance were proposed.The results show that the transverse stiffeners have a“pull”effect on the web of the main beam towards the inner side of the main beam and vertically downward,which is the direct cause of the out-of-plane deformation of the web gap.The method of cutting the bottom of transverse stiffener could reduce the local peak stress by more than 80%,which can effectively relieve stress concentration and reduce fatigue damage caused by external load.