江阴长江大桥钢箱梁疲劳应力特征分析

Analysis of Fatigue Stress Property of Steel Box Girder of Jiangyin Changjiang River Bridge

为准确评估钢桥结构的疲劳损伤状态和剩余疲劳寿命,以江阴长江大桥为背景,对该桥钢箱梁疲劳裂纹产生位置进行连续疲劳应变监测,获取应变时程数据,结合雨流计数法技术建立日疲劳应力谱;分析应力幅~循环次数分布规律;研究累积损伤度分布特征,建立损伤度分布模型,计算不同车道构造细节疲劳损伤度和剩余寿命。研究结果表明:钢箱梁顶板测点、U肋与横隔板焊接末端处、弧形缺口有效截面最小处均以压应力为主,U肋以拉应力为主;应力幅累积循环次数分布服从Weibull函数分布;疲劳累积损伤度分布服从Boltzman函数分布,顶板与U肋连接处U肋腹板沿横桥向慢车道疲劳损伤较快车道损伤大,下游车道较上游车道损伤大,其中下游慢车道U肋腹板细节疲劳损伤最大。

To accurately evaluate the fatigue damaging condition and remaining fatigue life of steel bridge structure,the Jiangyin Changjiang River Bridge was cited as an example.Continuous fatigue strain monitoring was conducted at the locations where fatigue cracks were found on the steel box girder to gain real-time strain data.The monitoring data,combined with the rain flow counting method,were used to set up the daily fatigue stress spectrum to analyze the distribution law of S^N curve.The distribution law of fatigue accumulating damage was studied.The model of damage distribution was set up,to calculate the fatigue damages and remaining life of different structural details of the traffic lane.The results of the study demonstrate that compressive stress was dominant at the testing locations in the steel box girder,ends of U-rib and diaphragm welds and least effective cross section of the arc notches,whereas tensile stress was found primarily on U ribs.The distribution of the accumulated stress cycle follows the way of Weibull function distribution.The distribution of accumulated fatigue damage obeys to Boltzman function distribution.At connections of the top plate and U ribs,the fatigue damage of U rib webs carrying slow traffic lanes along the bridge width is more severe than that of U rib carrying the fast traffic lanes.The damage of the downstream traffic lanes is more serious than that of the upstream traffic lanes,among which the U rib web details of the downstream traffic lanes suffer the severest fatigue damage.