部分斜拉桥混凝土脊骨梁受力机理与结构优化

长山大桥为主跨260m的双索面预应力混凝土部分斜拉桥,跨度为同类型桥梁之最.为保证双索面布置的主梁受力可靠,基于索梁传力机理提出了一种具有稳定三角边箱室的主梁结构形式——脊骨梁,并优化分析确定了多向混合预应力配束尤其是主梁下缘"弓形"预应力束的布置方案,以及在三角边箱室设置加劲肋以替代横隔板的横向传力构造.通过建立全桥有限元模型进行数值模拟分析计算,结果表明,在最不利状态下全桥应力、挠度远低于规范限值,剪力滞现象得到明显改善,横向受力更为均匀、合理.

Stress Mechanism of Concrete Spine Girder of Extra Dosed Cable Stayed Bridges and Structure Optimization

Changshan Bridge is an extra dosed cable stayed prestressed concrete bridge with two cable planes. Its 260m main span is the longest among the same type of bridges. In order to ensure the reliable force resistance of its main girder, a new beam type, i.e. spine beam, was proposed firstly based on the force transmission mechanism between the cables and girder. Furthermore, the layout scheme of the multi directional mixed internal and external prestressing tendons was determined through optimization analysis, especially the bow prestressing tendons arranged at the bottom flange of the main girder. The stiffeners installed in the triangular side boxes rather than diaphragm were used to transfer lateral forces. The full bridge finite element model was established for numerical analysis. The calculation results show that the stress and deflection of the full bridge are far below the specification limits under the most unfavorable condition. The shear lag of the main girder is significantly improved. The lateral force of the main girder is more uniform and reasonable.