弯扭条件下正交异性钢桥面板疲劳性能试验研究

Experimental Study on Fatigue Performance of Orthotropic Steel Bridge Deck under Flexural-torsional Condition

为研究弯扭条件下正交异性钢桥面板的疲劳性能,根据某实际桥梁图纸制作了6个足尺试件模型,模型由盖板、U肋和横隔板3部分组成,模型间各部分通过焊接连接。首先,采用有限元软件ANSYS对试件受力情况进行数值模拟,获得静力荷载作用下试件的内力分布,确定疲劳试验所要加载的疲劳荷载大小以及要观测热点应力的位置。然后,对6个盖板-U肋-横隔板试件进行高周疲劳加载,观察并记录了试验过程中试件开裂位置、试件的裂缝发展情况和试件开裂过程中竖向位移的变化,分析了复杂应力下桥面板疲劳裂缝扩展、刚度退化和疲劳寿命等。结果表明:弯扭条件下盖板-U肋-横隔板焊接连接试件疲劳开裂出现在焊缝焊趾处,且盖板上靠近U肋处裂缝扩展路线呈弧形;弯扭条件下裂纹扩展可大致分为裂纹萌生阶段、稳定扩展阶段、贯穿板厚阶段和疲劳断裂阶段;加载前期试件刚度退化不明显,接近疲劳破坏时刚度大幅下降,并建立了盖板-U肋-横隔板连接节点竖向位移变化值与疲劳特性参数之间的大致关系;裂缝扩展阶段疲劳寿命较短,其他3个阶段寿命大致相同;给出了测点热点应力突变和肉眼可见裂缝两种准则下的S-N曲线,试验所得盖板-横隔板焊接连接细节疲劳强度均高于国际焊接协会标准IIW和欧洲规范3推荐的FAT 90,FAT 100,FAT 112以及FAT 125的细节疲劳强度。

In order to study the fatigue performance of orthotropic steel bridge deck under flexural-torsional condition,6 specimens of full scale model are made according to the data drawing of a certain bridge.The model consists of decks,U-ribs and diaphragms,and the components of the model are joined by welding.First,the numerical simulation of the specimen is carried out using the FE software ANSYS to obtain the internal force distribution of the specimen under static load,and the fatigue load to be loaded test and the position at which the hot spot stress is to be observed in the fatigue test are determined.Then,the high cycle fatigue loading on the 6 deck-U rib-diaphragm specimens is carried out,the cracking positions,the crack development and the vertical displacements of the specimens during the test are observed and recorded,and the fatigue crack propagation,stiffness degradation and fatigue life of bridge deck under complex stress are analyzed.The result shows that(1)the fatigue cracking of the specimens under flexural-torsional condition occurs at weld toe,and the crack propagation path on the deck near U-rib is arc-shaped;(2)under flexural-torsional condition,the crack propagation can be roughly divided into 4 stages:initiation,stable propagation,running through plate thickness,and fatigue fracture failure;(3)the stiffness degradation of the specimens is not obvious at the early stage of loading,while it decreases sharply when nearing fatigue failure,and the relationship between the vertical displacement change value of deck-U rib-diaphragm joint and the fatigue characteristic parameter is established;(4)except for the fatigue life at the crack propagation stage,which is smaller,the fatigue lives of the other 3 stages are basically equal;(5)the S-N curves under the criteria of the sudden change of the stress at the hot point and the visible cracks by naked eyes are given,and the tested fatigue strength of the deck-diaphragm weld joint details is higher than those recommended by the IIW standard of International Welding Association and FAT 90,FAT 100,FAT 112 and FAT 125 of the European Eurocode 3 respectively.