Study on the shear performance of new high-strength bolted connections of prefabricated steel-concrete composite beams

Abstract

A new type of high-strength (HS) bolt shear connectors was proposed to address the issue of insufficient installation accuracy in prefabricated steel-concrete composite beams (SCCBs). Push-out tests were conducted on three groups of six specimens to study the static mechanical performance and failure modes of such connectors, considering the parameters of bolt depth and assembly status. Load-slip curves, failure modes, and crack development of the specimens were obtained. A refined finite element model was established to conduct the parametric study, where the effects of bolt diameter, bolt strength, and concrete compressive strength on the shear bearing capacity of specimens were investigated. Based on the experimental results and bearing capacity theory, a new formula for calculating the shear capacity of HS bolt connections was proposed and compared with various traditional formulas. The study results indicate that the failure mode of cast-in-place (CIP) specimens is stud shear-off, while the prefabricated specimens exhibit both stud shear-off and local concrete compression failures. The ultimate bearing capacity of prefabricated HS bolt specimens is higher than that of CIP stud connection specimens, demonstrating better mechanical performance. Prefabricated HS bolt specimens also show greater relative slip than CIP stud connection specimens, indicating better ductility. The embedded depth of HS bolts significantly affects the failure mode of specimens, with deeper embedment offering better mechanical performance. The shear capacity of bolts is positively correlated with bolt diameter, concrete strength, and bolt tensile strength, but virtually not affected by the bolt pretension. The proposed shear capacity formula correlates well with the experimental results and shows higher accuracy compared to other available formulas, providing a good practical design of SCCBs.