Experimental and Analytical Investigation on Pull-Out Performance of Multihole Thin-Rib Perfobond Connectors

Abstract

Perfobond connectors are commonly used to transfer the shear force with the transverse bar sheared off as the failure mode in steel–concrete composite structures. However, the perfobond connectors used to prevent the steel–concrete interface from separating in composite structures with load bearing steel bars that cannot be sheared off urgently need to be studied. Experimental and analytical studies were conducted to develop a novel thin-rib perfobond connector used in steel–concrete composite bridge towers. Based on the load characteristics of the Nanjing No. 5 Yangtze River Bridge tower, which is the first double-steel–plate concrete composite cable-stayed bridge tower in the world, the pull-out performance of the perfobond connectors in the large-scale composite tower were studied. Thin ribs were adopted in the connectors to avoid shearing off the longitudinal steel bars during the pull-out process. The coupling pull-out performance between adjacent perfobond connectors was investigated to demonstrate the performance differences between the multihole and the single-hole thin-rib perfobond connectors. The effects of the plate thickness, the distance from hole edge to rib bottom, the distance from hole edge to rib side, the hole diameter, the transverse bar diameter, and the transverse bar position in the connector hole were examined based on the experiments of 24 single-hole specimens and 24 trihole specimens. All stages of the load-displacement curves were calibrated, and the strain history of the steel parts was discussed. The main failure mode observed from the pull-out tests was steel plate fracture. Failure mechanism analysis showed that the position of the transverse bar in the hole affected the bearing capacity, stiffness, and ductility of the connector. Considering the effect of hole numbers, the hole-side part of a multihole thin-rib perfobond connector was relatively strengthened. An analytical model and calculation formulas to predict the pull-out capacity of the thin-rib perfobond connectors were further established, and the proposed method was found to be in good agreement with the experimental results, offering theoretical guidance for engineering practice.