高速铁路大跨度钢桁架-混凝土板组合梁斜拉桥稳定性研究

Study on the Stability of the High-speed Railway Long-span Steel Truss-concrete Plate Composite Girder Cable-stayed Bridge

为研究高速铁路大跨度钢桁架-混凝土板组合梁斜拉桥的稳定性,依托主跨300 m深茂铁路虎跳门水道特大桥,采用有限元软件ANSYS建立以梁单元为主的空间杆系有限元模型,对铁路钢桁架-混凝土板组合梁斜拉桥开展线弹性稳定分析,并进行考虑几何初始变形及材料弹塑性的非线性稳定性分析。结果表明:在弹性稳定分析下,该桥梁的一阶失稳形式为主梁整体纵飘及塔纵弯失稳,二~四阶均为桥塔处的主梁下弦杆首先出现横向偏位而局部失稳;在运营阶段弹性稳定系数最小为7.639,第二、三阶和第四、五阶稳定系数分别相同且失稳形式为对称失稳;考虑最大几何初始变形(k=L/1 000)后,一阶稳定系数减小6.39%;考虑非线性因素影响后稳定系数降低明显,仅考虑几何非线性因素的影响后一阶、二阶和四阶稳定系数分别降低11.23%、9.01%和10.13%,而考虑几何及材料双重非线性因素影响后,一阶、二阶和四阶稳定系数分别降低67.78%、60.63%和52.56%,表明材料非线性对铁路钢桁架-混凝土板组合梁斜拉桥的稳定系数影响更为显著;考虑最大几何初始变形(k=L/1 000)以及双重非线性因素影响后,铁路钢桁架-混凝土板组合梁斜拉桥的稳定系数为1.985,大于规范1.7的要求。

To study the stability of the high-speed railway long-span steel truss-concrete plate composite girder cable-stayed bridge,based on the Hutiaomen Waterway Long-span Bridge of Shenzhen-Maoming Railway with the main span of 300 m,the spatial bar system finite element model mainly composted of beam elements was established using the finite element software ANSYS,the elastic stability analysis of the bridge was carried out,and the nonlinear stability analysis considering geometric initial deformation and material elastic-plastic was conducted.The results show that under elastic stability analysis the first-order instability form of the bridge is the overall longitudinal drift of the main girder and the longitudinal bending instability of the pylon.The second to fourth orders of instability forms of the bridge are the lateral displacement of the lower chords of the steel truss near the bridge pylons.In the service stage,the minimum elastic stability coefficient is 7.639,the second-order and third-order stability coefficients are the same and the instability form is symmetric instability,and the fourth-order and fifth-order stability coefficients are the same,and the instability form is still symmetric instability.Considering the maximum initial geometric deformation(k=L/1 000),the stability coefficient decreases by 6.39%.The nonlinear factors significantly reduces the overall stability coefficient of the bridge structure.Only considering the influence of geometric nonlinear factors,the first-order,second-order and fourth-order stability coefficients decrease by 11.23%,9.01% and 10.13% respectively,while considering the influence of geometric and material double nonlinear factors the first-order,second-order and fourth-order stability coefficients decrease by 67.78%,60.63% and 52.56% respectively,which illustrates the more significant influence of material nonlinear on the stability of the railway steel truss-concrete plate composite girder cable-stayed bridge.Considering the maximum initial deformation(k=L/1 000) and the influence of double nonlinear factors,the stability coefficient of railway steel truss-concrete plate composite girder cable-stayed bridge is 1.985,still larger than the code permitted value 1.7.