Behavior of T-shaped embedded-nut bolted shear connectors in prefabricated steel-concrete composite beams

Abstract

Steel–concrete composite beams joined by shear connectors are extensively used in building and bridge engineering owing to their favourable structural performance, ease of construction, and low cost. Recently, owing to the demand for prefabricated structures, research on demountable shear connectors for prefabricated steel–concrete composite beams has become widespread. In this study, innovative T-shaped embedded nut bolted shear connectors (T-ENBCs) with superior mechanical performance and demountability are proposed and investigated. Push-out tests were conducted to evaluate the shear behavior of T-ENBCs in a steel–concrete composite beam, including twenty-one T-ENBC steel–concrete (EN) specimens and three high-strength friction-grip bolt connector (HF) specimens. For the EN specimens, various types of T-ENBCs were examined to ascertain the effect of variables, such as the diameter of the bolt, length of the embedded nut, and embedded nut type. Accordingly, the failure modes, load–slip curves, ultimate shear resistance, and shear stiffness of the specimens were obtained. Finite element (FE) models for T-ENBCs, validated with test data, were employed to analyse the influence of a number of parameters. Using the experimental and FE results, the properties of the connector, such as its shear resistance, stiffness, ductility, and failure modes, are discussed. The study shows that T-ENBCs have larger shear resistance and higher shear stiffness than high-strength friction-grip bolt connectors. Finally, specific design formulae are proposed for predicting the ultimate shear resistance and load–slip relationship for members with T-ENBCs.