混凝土层切缝对大跨斜拉桥正交异性钢-混组合桥面板受力性能影响

Effect of concrete layer cutting on stress distribution of orthotropic steel-concrete composite deck of long-span cable-stayed bridge

为分析混凝土层切缝对大跨斜拉桥正交异性钢-混组合桥面板负弯矩区混凝土拉应力消减效果,并比较不同切缝方式(切缝宽度、深度和位置)对桥面板受力的影响,依托川南城际铁路临港长江大桥,采用有限元方法建立了全桥有限元模型和组合桥面板节段有限元模型,模拟了在斜拉桥的辅助墩处桥面混凝土层切缝的方法和受力性能的影响。结果表明:在最不利工况下,辅助墩处桥面混凝土层纵向拉应力可达10MPa,容易开裂。桥面混凝土层切缝对钢桥面受力行为影响不大,可大幅度减小混凝土层的纵向拉应力,降低其开裂风险。以对切缝宽度、深度和位置的参数分析表明:切缝深度须达到混凝土层厚度,切缝宽度(5~20cm)对组合桥面板受力影响不大。综合考虑切缝对混凝土层拉应力的消减效果和切缝构造后期养护维修的不利影响,宜只在辅助墩处切缝,成果可为大跨度斜拉桥正交异性钢-混组合桥面板混凝土层切缝设计提供参考。

In order to analyze the effect of concrete layer cutting on concrete tensile stress reduction in the negative moment zone of orthotropic steel-concrete composite deck of long-span cable-stayed bridge, and compare the effects of different cutting methods(cutting width, depth and location) on the stress of deck, relying on the Lingang Yangtze River Bridge in the Southern Sichuan Intercity Railway, the whole bridge and the sectional finite element model of composite deck are established by using the finite element method. The method of cutting in concrete layer at the auxiliary pier of the cable-stayed bridge and the influence on the mechanical performance are simulated. The results show that under the most unfavorable conditions, the longitudinal tensile stress of the bridge deck concrete layer at the auxiliary pier can reach 10MPa, which is easy to crack. The cutting of bridge deck concrete layer has little effect on the mechanical behavior of steel bridge deck, which can greatly reduce the longitudinal tensile stress of concrete layer and reduce its cracking risk. The parameter analysis of the width, depth and position of the cutting shows that the depth of the cutting must reach the thickness of the concrete layer, and the width of the cutting(5~20cm) has little effect on the stress of the composite bridge deck. Considering the effect of cutting on the tensile stress of concrete layer and the adverse effect of the later maintenance of cutting structure, it is advisable to cutting only at the auxiliary pier. The results can provide a reference for the design of cutting in concrete layer of orthotropic steel-concrete composite deck of long-span cable-stayed bridge.