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进行了3榀钢管混凝土桁梁试件四分点对称加载静力试验,研究腹杆布置形式对整体受力性能的影响,并探讨了有限元法和节点承载力验算方法。试验研究结果表明,3榀桁梁试件的整体极限承载力和极限变形能力从大到小的腹杆布置形式为修正的Warren式、Pratt式和Warren式。不同腹杆布置形式的桁梁节点失效模式不同,修正的Warren桁梁和Pratt桁梁的节点失效模式为弦杆钢管扯裂失效,而Warren桁梁为受压腹杆接头局部屈曲。通过对比荷载-变形关系实测曲线与计算曲线,对有限元梁单元模型计算钢管混凝土桁梁整体受力性能的精度进行了分析。在不考虑节点处弦杆钢管与管内混凝土界面非线性的影响时,有限元刚接梁单元模型和铰接梁单元模型计算的整体极限承载力均大于实测值,而计算变形值均小于实测值。与铰接梁单元模型比较,刚接梁单元模型计算的弹塑性阶段整体抗弯刚度及整体极限承载力的精度更高。刚接梁单元模型计算的腹杆轴力与实测值吻合良好。当忽略腹杆弯矩影响时,桁梁节点承载力可以采用钢管K型节点弦杆钢管扯裂失效承载力公式进行计算,节点理论承载力略小于实测腹杆轴力。
The 4-point symmetrical static loading test of 3 × CFST truss specimens was carried out to study the influence of the web layout on the overall mechanical performance. The finite element method and checking method of node bearing capacity were also discussed. The experimental results show that the truss girder specimens with the whole ultimate bearing capacity and ultimate deformation capacity are in the modified Warren, Pratt and Warren formulas. The failure modes of the truss nodes with different web layouts are different. The failure modes of the modified Warren truss and Pratt truss are failure of the chord steel tube, while the Warren truss is partially buckled by the compression web joint. By comparing the measured curve and the calculated curve of the load - deformation relationship, the accuracy of calculating the overall mechanical performance of CFST truss girder is analyzed. Without considering the influence of the nonlinearity of the chord steel pipe and the concrete interface in the pipe, the ultimate bearing capacity of the element model of the rigid element and the element of the articulated beam is larger than the actual value, but the calculated deformation values are less than the actual value. Compared with the hinge beam element model, the accuracy of the overall flexural rigidity and the overall ultimate bearing capacity of the elastic-plastic phase calculated by the rigid beam element model is higher. The web axial force calculated by the element model of just-connected beam is in good agreement with the measured value. When the influence of web bending moment is neglected, the bearing capacity of the truss girder can be calculated by the failure failure bearing capacity formula of the steel pipe K-type chord steel pipe. The theoretical bearing capacity of the node is slightly less than the measured web axial force.