Experimental Study on the Biaxial Loading Effect on Group Stud Shear Connectors of Steel-Concrete Composite Bridges

Abstract

Clustering stud shear connectors with minimized spacing based on specifications to form group studs are useful for concrete slab prefabrication and prestress installation efficiency in steel-concrete composite bridges. To date, many long-span composite bridge girders have been designed with wide transverse cantilevers and web spacing, and most of these girders use group studs. The concrete’s self-weight and the weight of moving loads result in a significant transverse bending-induced effect generally consisting of bending stresses and tensile concrete cracks. In this sense, the studs are actually under longitudinal interlayer shear force that is influenced by the transverse bending-induced effect. This biaxial loading effect has not been investigated experimentally. Thus, standard and newly designed push-out tests and corresponding analyses were carried out. In addition, the stud arrangement effect also was of concern. In this study, the ratio of stud height to shank diameter was approximately 6.2. This study found that steel-concrete interlayer friction and biaxial concrete compression around the stud roots contribute to a favorable effect of biaxial loading on stud performance. However, the residual tensile concrete cracks are unfavorable. Engineers should note the tendency toward mechanical degradation of studs when such a situation occurs. Moreover, arranging studs in clusters to form group studs may lead to comparatively more severe concrete damage at the ultimate stage. The specification-based evaluations of stud strength were found to be more or less conservative based on related test results.