斜拉桥正交异性钢桥面板疲劳试验研究

Experimental study of fatigue on orthotropic steel deck of cable-stayed bridge

以板桁斜拉桥的Q500qE正交异性钢桥面板作为研究对象,采用足尺节段模型疲劳试验和数值模拟的方法,对具有宽U肋的正交异性钢桥面板关键细节的疲劳性能进行研究.通过施加预应力的方法模拟桥面板的轴压力. 3个试验模型总计进行650万次变幅疲劳循环加载.研究结果表明,嵌补段焊缝初始裂纹以宏观长裂纹的方式出现在腹板下缘,荷载幅越大,初始裂纹越长;宽U肋嵌补段腹板和底板的裂纹扩展可以分为4个阶段,各阶段间有明显的分界点;裂纹扩展速度与裂纹扩展长度正相关;轴压力增大了嵌补段裂纹扩展速度;对设置了焊接垫板的宽U肋嵌补段的焊缝余高进行铲除并磨平处理可以提高焊缝细节的疲劳强度.推荐采用我国公路钢桥结构设计规范(JTG D64-2015)中110类细节疲劳强度设计宽U肋嵌补段对接接头焊缝.

Orthotropic steel (Q500qE) deck of cable-stayed bridge with plate-truss composite structure was taken as the research object. Fatigue test and numerical simulation were done to study full-scale girder segment models with broad U-rib fatigue features of key fatigue details in orthotropic steel deck. Method of pre-stressing force was adopted to simulate the initial axial pressure in deck. The three segment models were loaded by 6.5 million variable amplitude fatigue cycles. Results prove that the initial long macro crack occurs in the bottom of butt-welded splice joints of U-rib-web. The length of initial macro crack is proportional to the stress amplitude. The crack growth stage of broad U-shape-rib can be divided into four parts with clear demarcation point between each part. Crack growth rate is proportional to crack length. Crack growth rate is increased under the effect of axial force. Fatigue strength of welding details can be increased when the excess weld metal of welding seam is eradicated and abraded after welding with back-up member for embedded section of broad U-rib. It is recommended that the butt joint weld of the wide U-rib embedded section can be designed with the fatigue strength of category 110 in China's specification for structural design of highway steel bridge (JTG D64-2015).