考虑横向预应力效应的钢-混组合梁桥PBL剪力键试验研究

为研究钢-混组合梁桥PBL剪力键的抗剪承载能力及其影响因素,以兰州小砂沟大桥为工程背景,设计3类13组共33个试件,采用推出试验的方法进行试验研究,对比分析了PBL剪力键的破坏形态、破坏机理以及抗剪承载能力的影响因素,提出了考虑横向预应力效应的PBL剪力键抗剪承载能力的计算公式.研究结果表明:贯穿钢筋直径、钢板开孔孔径以及钢板厚度的增加均能有效提高PBL剪力键的抗剪承载能力;横向预拉应力的存在促进了混凝土的开裂,使得混凝土、钢板及贯穿钢筋的强度和刚度无法得到充分发挥,从而降低了PBL剪力键的承载能力,对单孔抗剪承载能力降低可达10%;横向预压应力的约束作用延缓了混凝土的开裂,使得混凝土、钢板及贯穿钢筋的强度和刚度得到充分发挥,提高了PBL剪力键的承载能力,对单孔抗剪承载能力提高可达20%;考虑横向预应力效应的公式计算结果与试验结果吻合较好. 

Experimental Study on PBL Shear Connectors of Steel-Concrete Composite Bridge Considering Transverse Prestressing

In order to study the shear capacity and its influencing factors of PBL shear connectors for steel-concrete composite girder bridges, 33 specimens in 13 groups of three types were designed for push-out tests conducted in Xiaoshagou Bridge in Lanzhou, China. The failure modes, failure mechanisms, and influencing factors of shear capacity of these PBL shear connectors were analyzed comparatively. On this basis, a shear capacity calculation formula for PBL shear connectors considering the transverse prestressing effect was proposed. The results show that the shear capacity of PBL shear connectors could be effectively increased by increase of transverse rebar diameter, perforated rib diameter, and perforated rib thickness. The existence of transverse pretension stress accelerated the cracking of concrete, causing the strength and stiffness of concrete, perforated plate, and reinforcing rebars unable to exert their effect fully. As a result, the shear capacity of PBL shear connectors were reduced by about 10%. In addition, the constraint effect of transverse stress improved the strength and stiffness of concrete and delayed the concrete cracking, bringing the strength and stiffness of concrete, perforated plate, and reinforcing rebars into full play, and resulting in an significant improvement (20%) in the shear capacity of PBL shear connectors. The calculated results from the proposed formula close to the test results verified its effectiveness.