Stud shear connectors are a familiar, proven mechanism for steel–concrete composite construction, particularly in bridges. But the way composite bridges are built is changing. In prefabricated bridge construction, many steel and concrete components are prefabricated in the factory and then assembled on the construction site. In such components, studs are no longer always detailed as widely separated single connectors; instead, stud connectors are arranged on the surfaces of steel girders in the form of grouped studs. Current research on the grouped stud effect has been performed using normal concrete, not ultra-high performance concrete. Researchers Wenhao Chai, Meng Wang, Jin Di, Fengjiang Qin, Jie Wang, and Pengfei Men wanted to address this gap and gain a deeper understanding of the shear behavior of grouped stud connectors in steel–UHPC.
In their paper, “Shear Behavior Analysis of Grouped Stud Connectors Embedded in Ultrahigh-Performance Concrete for Composite Bridges,” the authors sought a deeper mechanistic and predictive understanding of the steel–UHPC systems. They conducted two types of push-out tests on seven sets of grouped stud connectors and one set of single-stud connectors. The validated 3D nonlinear finite-element model they developed explores how key construction-driven detailing variables, such as stud longitudinal spacing and number of stud rows, influence load transfer, load–slip behavior, and ultimate capacity. This research helps engineers anticipate how grouped arrangements can change per-stud strength and stiffness. Read their full findings in the Journal of Structural Engineering at https://ascelibrary.org/doi/10.1061/JSENDH.STENG-15025. The abstract is below.
Abstract
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.
Learn more about improving stud placements in steel–ultrahigh-performance concrete composite beams in the ASCE Library: https://ascelibrary.org/doi/10.1061/JSENDH.STENG-15025.
