Shear Behavior Analysis of Grouped Stud Connectors Embedded in Ultrahigh-Performance Concrete for Composite Bridges

In this study, push-out tests were conducted on two types of stud connectors (seven sets of grouped studs and one set of single studs) to study the shear behavior of grouped stud connectors in steel–ultrahigh-performance concrete (UHPC) composite beams. The experimental results demonstrate that the presence of the grouped stud effect leads to grouped stud connectors having lower shear strength and shear stiffness compared to single-stud connectors. When the stud longitudinal spacing increased from 4d (d = the diameter of studs) to 10d, the average shear strength and the average shear stiffness for an individual stud of the grouped stud connectors increased by 8.9% and 7%, respectively. A three-dimensional nonlinear FEM was established to examine the influence of stud longitudinal spacing and number of stud rows on the grouped stud effect of these connectors. Finally, the prediction formulas for load–slip behavior and shear strength of grouped stud connectors in steel–UHPC composite beams are proposed.