钢-超薄UHPC组合构件新型界面连接的抗剪性能

Shear resistant performance of novel interfacial connection in steel-UHPC lightweight composite structures

摘要:

为实现预制UHPC薄板与钢构件的装配式连接、后期可拆卸等目标,以及针对钢-超薄超高性能混凝土（ultra high performance concrete, UHPC）组合桥面体系中UHPC层过薄而无法采用常规抗剪连接件的问题,提出一种由预埋带垫加长套筒、高强螺栓连接组成的新型抗剪连接方式。开展了6组新型螺栓连接件的推出试验,包括5组高强螺栓和1组负泊松比螺栓连接件,分析了新型连接件的破坏形态及荷载-滑移曲线特征,研究了螺栓直径、螺栓长径比、螺栓种类等参数对极限滑移、抗剪刚度等力学性能的影响,研究结果表明:新型螺栓连接件的破坏形态均为螺栓杆被剪断,预埋带垫加长套筒底部的UHPC无损坏压溃现象；新型高强螺栓连接件的抗剪承载力、界面相对滑移随高强螺栓的直径增大而增大；高强螺栓连接件的抗剪承载力约为螺栓抗拉强度的55.8%,故建议在钢-UHPC组合构件中采用较大直径的高强螺栓连接件,有效减少抗剪连接件的数量；而负泊松比螺栓的抗剪承载力和抗剪刚度明显较小,但极限滑移却明显增大,表现出良好的延性,建议将负泊松比螺栓应用于钢-UHPC组合构件的负弯矩区段,避免负弯矩区段出现开裂。

Abstract:

Considering that conventional shear connectors cannot be applied to steel-ultra-high performance concrete (UHPC) composite deck systems as the UHPC layer is too thin, a novel shear connector consisting of specified designed pre-embedded sleeve and high-strength bolt was proposed, which can realize the rapid assembly and disassembly of prefabricated UHPC and steel member. Push-out tests on six groups of specimens were conducted, including five sets of high-strength bolt connectors and a set of negative Poisson’s ratio bolt connector. The failure pattern and load-slip curve characteristics of the novel shear connectors were analyzed. The effects of different parameters (diameter, aspect ratio, and type) of bolts on the mechanical properties (ultimate slip and shear stiffness) of the novel shear connector were discussed. Results show that the failure mode of the novel shear connectors was the shear-off failure of the bolt shank, and there was no apparent local collapse of UHPC under the pre-embedded sleeves. The shear capacity and the relative slip of the high-strength bolt connector increased with the increase in the diameter of the high-strength bolt. The shear capacity of the novel high-strength bolt connector was approximately 55.8% of the tensile strength of the bolt. Thus, bolt connectors with larger diameters are recommended in steel-UHPC composite structures to effectively reduce the number of shear connectors. The shear capacity and shear stiffness of the negative Poisson’s ratio bolt connector were significantly smaller, but the ultimate slip was significantly increased, showing good ductility. Therefore, it is suggested to apply negative Poisson’s ratio bolt to the negative moment section of steel-UHPC composite structure, so as to avoid cracking in the negative moment section.