铁路混合梁斜拉桥钢-混结合段传力及疲劳性能试验研究

Study on mechanics behavior and fatigue performance of steel-concrete composite joints of railway hybrid girder cable-stayed bridges

为了解大跨度铁路混合梁斜拉桥钢-混结合段的传力和疲劳性能,根据应力等效原则设计制作了结合段局部足尺模型,进行了疲劳验证加载和疲劳破坏加载,测试了疲劳加载过程中结合段钢箱梁及剪力钉的应力变化情况。同时,通过考虑钢和混凝土之间不同的摩擦系数,对摩擦力在结构剪力传递中的影响进行了研究。试验研究结果表明:利用接触分析,摩擦系数分别取0.1和0.6时,钢梁纵向应力计算值偏差在0.5%以内,说明在疲劳荷载作用下结构弹性受力时,钢和混凝土之间的摩擦力对剪力传递贡献较小;200万次疲劳验证试验过程中,结合段整体应力水平较低,各测点应力基本保持不变,结构传力安全可靠,具有良好的疲劳性能;100万次的疲劳破坏试验后,钢结构和剪力钉部分测点应力明显增大,结合段钢和混凝土出现黏结滑移现象,尤其在顶板位置,但结构整体稳定性良好,仍具有一定的疲劳安全储备。

A partial full-scale model is designed and manufactured by the principle of equivalent stress to investigate the mechanics and fatigue performance of steel-concrete composite joints of long-span railway hybrid girder cable-stayed bridges. Both verification fatigue load and destruction fatigue load are applied to the test model,where the variations of stress on the steel beam and shear stud with loading history are obtained. Meanwhile,the influence of friction force in shear force transmit on the joint section is investigated by considering different friction coefficients. The test results indicate that the friction has little contribution to the transmitting shear force under the fatigue load when the structure is in elastic state. The calculation value difference of the longitudinal stress using contact analysis is less than 0. 5% when the friction coefficient is 0. 1 and 0. 6,respectively. Moreover,the stress of the composite structure is low and the stress of each measure points is stable for the 2 million times verification fatigue test,which demonstrates the reliability and good fatigue performance of structure force transmitting. The stress of steel beam and shear stud increases obviously due to the separation between steel and concrete,especially on the top position after 1million times destruction fatigue loading,but the steel-concrete composite structure still works well with fatigue safety reserves to some extent.