薄开孔板连接件抗拔性能试验及理论研究

在试验研究基础上，对组合结构索塔中开孔板连接件的抗拔性能进行理论分析。组合索塔中连接件设计主要考虑抗拔性能。为避免剪坏纵向承重钢筋，需要采用薄板。设计了一批34个单孔薄开孔板连接件抗拔试验，通过反力架上方的穿心千斤顶顶升丝杠实现对连接件的拉拔作用，同时千斤顶的反作用也可以将反力架固定在混凝土基体之上。考察了板厚、开孔位置、钢筋在钢板孔中的相对位置、开孔直径、钢筋直径等参数对其抗拔性能的影响；通过对钢筋应变的检测，记录钢筋在薄开孔板连接件受力过程中的应力分布情况。总结薄开孔板连接件拔出过程和破坏形态规律，发现其表现为钢板破坏为主，钢筋在孔中位置对其承载力、刚度、延性等均有一定影响；得到了钢筋在连接件受力过程中的应力分布，发现钢筋在距中心7 cm的位置应力不超过50 MPa，推知并排放置的连接件之间互相影响很小。连接件初始及弹性加载阶段荷载-位移曲线特征研究表明，该连接件具有足够的初始刚度，为其工程应用提供了理论指导。最后，总结薄开孔板连接件受力机理，建立预测其抗拔承载力的计算公式，适用于开孔板连接件钢板部分的抗拔承载力，计算结果与试验符合良好。

Experimental and Theoretical Study on Pullout Resistance of Single-hole Thin-rib Perfobond Connectors

This work aimed to investigate the pullout performance of perfobond connectors in steel-concrete composite bridge towers based on experimental results. The first steel-concrete composite large-span cable-stayed bridge tower has been applied in the Nanjing No. 5 Bridge. Pullout performance is most important for the perfobond connectors in the bridge tower. Specifically, thin-rib perfobond connectors are needed to avoid cutting off the longitudinal steel bar. In this study, 34 specimens were tested to determine the effects of plate thickness, hole side distance, hole bottom distance, position of the steel bar in the plate hole, hole diameter, rebar diameter, and some other parameters on the pullout bearing capacity of thin-rib perfobond connectors. Pullout force was applied by a center hole jack pushing the screw, whereas the reaction of the jack to the steel frame fixed it to the concrete base. During loading, the stress distribution of the rebar in the thin-rib perfobond connectors was revealed by detecting the steel strain of the transverse bar. This paper summarizes the mechanism of the uplifting process and the failure mode of the thin-rib perfobond connectors. The main failure mode occurs when the steel plate is pulled off. The position of the transverse bar in the hole exerts some influence on the bearing capacity, stiffness, and ductility of the connectors. It was found that the stress of rebar 7 cm away from the center does not exceed 50 MPa, leading to the conclusion that connectors placed side by side have little influence on each other. The characteristics of the load-displacement curves during the initial elastic loading stage were also studied, providing theoretical guidance for its engineering application. Finally, this paper establishes a formula for predicting the pullout bearing capacity of the connectors that also applies to the steel rib of all perfobond connectors. The calculated results are in good agreement with the tests.