钢-UHPC组合桁式拱桥拱肋与腹杆节点性能试验研究

钢-UHPC组合桁式拱桥的提出，有望解决特大跨径拱桥造价高、难以施工等难题。对1000m钢-UHPC组合桁式拱桥拱肋与腹杆关键节点的受力性能进行了研究，计算表明，在荷载基本组合作用下节点拉、压杆的轴力均超过10000kN，为保证节点处钢和UHPC两种材料牢固结合，通过节点受力分析和优化研究，提出了一种带混合连接件钢接头的UHPC箱型拱肋与钢腹杆新型节点连接构造。对最不利受力的节点制作了1∶5缩尺模型，不考虑箱型拱肋底板和腹板对节点受力的贡献，开展了平面三向加载试验和抗拔试验。试验结果表明：平面三向加载试验中节点的破坏模式为UHPC拱肋一侧开裂，另一侧压溃，但节点连接保持完好；抗拔试验中节点的破坏模式为UHPC拱肋沿钢接头的轮廓剪切破坏；平面三向加载试验中，钢腹杆的极限荷载是设计荷载的2.72倍，且UHPC拱肋的名义开裂应力为13.36MPa，是设计应力的1.85倍，表明节点的承载能力和抗裂性能满足设计要求；钢接头与UHPC拱肋结合面的抗剪性能和抗拔性能满足正常使用极限状态和承载能力极限状态的要求。

Experimental study on performance of joints between arch ribs and web members of steel-UHPC composite truss arch bridge

The proposal of the steel-UHPC composite truss arch bridge is expected to solve the problems of high cost and difficult construction of very-long-span arch bridges. The mechanical performance of the key joints between the arch ribs and web members in a 1000m long steel-UHPC composite truss arch bridge was studied. The calculation showed that the axial forces in both the tension and compression web members were over 10,000kN under the fundamental combination of loads. In order to ensure a firm combination of steel and UHPC at the joint, a new specific joint structure with the steel connector which has different shear connectors between the UHPC box arch ribs and steel web members is proposed via structural performance analysis and optimization study for the joint. A 1/5 scale test model was fabricated for the most unfavorable joint, which ignores the contribution of the bottom plate and webs in the box arch rib to the joint’s mechanical performance. Then, a planar three-directional loading test and a pull-out test were carried out. The test results showed that the failure mode of the joint structure in the planar three-directional loading test was characterized by cracking in one side and crushing in the other side while the composite effect was preserved well. Besides, the failure mode of the joint structure in the pull-out test was characterized by the shear failure in the UHPC arch rib along the outline of the steel connector. The ultimate load of the joint in the planar three-directional loading test was 2.72 times the design load, and the nominal cracking strength of the UHPC arch rib was 13.36 MPa, which is 1.85 times the design stress, indicating that the bearing capacity and crack resistance of the joint can meet the design requirements. The shear and pull-out resistance of the joint structure along the interface between the steel connector and UHPC arch rib can meet the requirements under the serviceability limit state and ultimate limit state.