耳板式钢—混凝土组合桁架节点力学性能试验研究

Experimental Research on the Mechanical Properties of the Steel-Concrete Composite Truss Joint with Ear Plate

钢—混凝土组合桁架梁上弦端节点受力复杂,是组合桁架结构受力的关键部位。以西平铁路桥梁钢—混凝土组合桁架节点为原型,设计制作了3个耳板式节点的1∶2缩尺模型,进行水平静力性能试验和有限元分析,研究钢—混凝土组合桁架节点的应变发展规律、极限承载力、破坏模式和荷载-位移曲线等力学性能。研究表明:耳板式钢—混凝土组合桁架节点极限承载力和刚度满足设计要求;PBL连接件具有较好的抗剪能力;节点的薄弱部位为弦杆核心区混凝土;节点的破坏模式主要有弦杆混凝土开裂破坏、腹杆屈曲破坏、腹杆与耳板连接处屈服等,因此提高混凝土强度和节点配筋率,增加腹杆厚度有助于提高整个节点的承载力。

The mechanical force of the joint on the top chord of the steel-concrete composite truss beam is complicated,and is the key part of the composite truss structure.As the prototype of steel-concrete composite truss joint used in Xi＇an—Pingliang railway bridges,three joint specimens of ear plate form at 1∶2 scale model are designed and made.The tests under monotonic horizontal load and finite element analysis are carried out to study the mechanical properties of the steel-concrete composite truss joint,such as the development law of strain,the ultimate bearing capacity,the failure mode and the load-displacement curves,etc.The results indicate that the ultimate bearing capacity and stiffness of the steel-concrete composite truss joint with ear plate meet the design requirements.The PBL connectors have better shear capacity.The weak part of the joint is the concrete in the core area of the chords.The failure modes of the joint mainly include the cracking failure in chord concrete,the buckling failure of web member and the yielding in the connectors between the web member and the ear plate.Hence,the ultimate bearing capacity of the joint can be increased by improving concrete strength and reinforcement ratio of the joint as well as increasing the thickness of web member.