钢桥面板U肋与横隔板焊缝疲劳强度分析

Fatigue strength analysis of weld seam between U-rib and diaphram on steel bridge deck

针对钢桥面板U肋与横隔板连接焊缝的疲劳强度,建立钢箱梁的整体有限元模型和局部子模型.首先提取不同工况下U肋焊趾与横隔板焊趾处应力,分析其受力特征,并在最不利工况下获取应力梯度,研究不同的应力路径、应力类型和外推方法下的热点应力.然后利用热点应力和参考应力对U肋焊趾与横隔板焊趾进行疲劳强度评估,验证IIW提供的S-N曲线的适用性.最后用整车模型按实际车辆行驶情况进行加载,对U肋与横隔板焊缝进行疲劳寿命分析.研究结果表明:U肋与横隔板焊缝面内外应力特征显著,且受局部变形、纵向弯曲和横向扭转等因素影响;距焊趾2 mm可以作为参考应力取值点;运用IIW提供的S-N曲线进行疲劳强度评估,参考应力和热点应力获得了相近的疲劳寿命评估结果,可为钢桥面板疲劳性能研究提供参考.

The whole finite element model and local submodel of the steel box girder are established to evaluate the fatigue strength of the weld seam between U-rib and diaphram on steel bridge deck.First,the stress at the U-rib weld toe and the diaphragm weld toe are extracted under different working conditions to analyze the mechanical characteristics.After the stress gradient is obtained under the most unfavorable conditions,and the hot spot stress under varying stress paths,stress types and extrapolation methods are studied.Then,the hot spot stress and reference stress are used to evaluate the fatigue strength of U-rib welded toe and diaphragm welded toe to verify the applicability of the S-N curve provided by IIW.Finally,the whole vehicle model is loaded according to the actual driving condition of the vehicle,and the fatigue life of the weld seam of U-rib and diaphragm are analyzed.The results show that the internal and external stress on the weld surface of the U-rib and diaphragm are significant,and the weld seam is affected by local deformation,longitudinal bending and transverse torsion;the place that is 2 mm away from the weld toe can be used as the point to determine the reference stress value;the S-N curve provided by IIW is used to evaluate fatigue strength,and similar results of fatigue life are obtained for reference stress and hot spot stress,which can provide reference for the study of fatigue performance of steel bridge deck.