一种钢-混组合桁架桥下弦杆节点极限承载力研究

钢-混组合桁架是一种新型铁路桥梁结构，节点受力复杂，通过对3个采用PBL连接件的钢-混组合桁架节点进行水平单调加载试验，研究了外接式节点的受力特性、破坏模式和极限承载力。基于有限元软件ABAQUS对试件进行3D模型分析，计算结果与试验结果较为吻合。研究表明：钢-混组合桁架节点受力性能良好，PBL连接件传力效果明显；钢腹杆为节点薄弱环节，增加腹杆厚度可有效提高节点屈服后强度和节点极限承载力；通过模型分析，提出的腹杆不对称的设计方法，破坏顺序明确，与3个钢-混组合桁架节点的试验结果相比偏于安全，能够满足我国桥梁抗震设计要求。研究成果可为同类节点的应用提供参考。

Study on ultimate bearing capacity of steel-concrete composite truss bridge bottom-chord joints

Steel-concrete composite truss is a new type of railway bridge structure. Performance of joints in bottom chord of steel-concrete composite trusses is complicated. 3 joint models with PBL connectors were tested under horizontal loading to study the mechanical performance, failure modes and load-bearing capacity. Influences of mechanical characteristics, failure models, and the ultimate bearing capacity are investigated. A 3D finite element model is developed to further analyse the horizontally loaded behaviour of the steel-concrete composite truss and the numerical results agree well with the experimental data. The results show that the joints have good mechanical behaviour and the PBL shear connectors transfer force well. The web members are weak links, whose yield strength and ultimate bearing capacity can be obviously improved by increasing the thickness of the steel web member. Based on modeling analysis, a ventral pole asymmetry design rule is proposed, which gives more conservative data than the experimental results. The proposed method can meet the requirements of domestic bridge design and provide reference for the practical engineering application.