采用支点位移法施工的斜拉桥钢-UHPC组合梁受力分析

Analysis of Mechanical Property of Steel-UHPC Composite Girder Cable-Stayed Bridge When Raising Elevation of Auxiliary Piers to Improve Loading Condition at Negative Bending Moment Zone

为了解采用支点位移法施工对大跨度斜拉桥钢-UHPC组合梁负弯矩区力学性能的改善情况,以主跨442 m的沾临高速公路黄河特大桥主桥为背景,采用MIDAS Civil软件建立主桥三维有限元模型进行受力分析。计算无应力索长及成桥状态钢-UHPC组合梁线形,并在二者保持不变的基础上,分别对采用、未采用支点位移法施工的钢-UHPC组合梁成桥及运营状态下的弯矩、梁底应力、UHPC桥面板顶(底)缘应力进行对比分析。结果表明:相比于未采用支点位移法,采用支点位移法施工的钢-UHPC组合梁斜拉桥可减小或者消除辅助墩处组合梁的负弯矩,显著增加辅助墩处负弯矩区UHPC桥面板的压应力储备,达到施加预应力的效果,显著改善了负弯矩区钢-UHPC组合梁的力学性能,应用效果良好。

This paper studies the approach to alleviate the negative bending moments in the long-span steel-UHPC composite girder cable-stayed bridge.The main bridge of Huanghe River Bridge carrying a section of the Zhanhua-Linyi Expressway that has a main span of 442 m is used as a case.The 3D finite element model of the bridge was developed in MIDAS Civil to calculate the stay cable lengths in stress-free state and the alignment of the steel-UHPC composite girder after the completion of the bridge.Based on the calculations,the variations of the parameters,including bending moment,stresses in girder soffit,and stresses in the top(bottom)edges of the UHPC panels,were checked when the auxiliary piers were raised during construction.It is shown that raising the auxiliary piers can alleviate or eliminate the negative bending moments in the composite girder at the auxiliary piers,and significantly enlarge the compressive stress margin of the UHPC panels in the negative bending moment zone,which achieves the similar effect of adding prestressing tendons,as a result,the mechanical property of the steel-UHPC composite girder in the negative bending moment zone is remarkably improved.