某桁式组合拱桥新拱脚结点局部应力分析

Local Stress Analysis of Joint of New Arch Spring of a Composite Truss Arch Bridge

桁式组合拱桥的新拱脚支撑着中部桁架拱,新拱脚结点构造和受力复杂。以某桁式组合拱桥为例,借助通用有限元程序ANSYS,建立其新拱脚结点局部三维有限元模型,通过提取新拱脚结点处各杆件断面轴向应力沿各条路径的变化图,分析该部位的应力分布特征。分析结果表明:在最不利荷载组合工况下,新拱脚截面上缘、新拱脚处各杆件与新拱脚连接处以及各杆件间连接的圆弧段拉应力均较大,这些位置都容易出现横向裂缝。理论分析结果与实桥病害情况吻合。提出新拱脚结点局部设计的改进思路和方向。

The new arch spring of composite truss arch bridge is used to support the middle truss arch of the bridge and the structural formation and force conditions of the joint of the spring are complicated. By way of example of a composite truss arch bridge, the three-dimensional finite element model for the locality of the joint of the new arch spring is established by the universal finite element program ANSYS. In accordance with the diagrams of the sectional axial stress of all members at the joint varying along different paths, the characteristics of the stress distribution therein are analyzed. The results of the analysis show that under the most unfavorable load combination, the tensile stress in the upper edge of the cross section of the arch spring, in the connection of the members with the spring and the arc section of the connections among the members is fairly great and these parts are all prone to transverse cracks. The results of the theoretic analysis are consistent with those of the inspection of the actual deterioration of the bridge and the idea and way of improvement for the locality design of the joint of the arch spring are hence proposed.