Development and Performance of Innovative Steel Wedge Block–Crossed Inclined Stud–UHPC Connections for Composite Bridge

This paper reports the shear performances of steel wedge block–crossed inclined stud–ultrahigh performance concrete (UHPC) connections for application to steel-concrete composite bridges. The study entailed 36 pushout tests based on the studs with 1.0, 1.5, and 2.0 aspect ratios, inclined 0°, 30°, 45°, and 60° from vertical. The test results show that in studs with aspect ratio less than 1.5 (ultrashort studs) and inclined at either 30° or 45°, shear strength increases 12% with initial slip increase of 47% and 110%, respectively, relative to the 0° connection. Also, the specimen comprising studs at 45° inclination showed a 1%–91% increase in secant shear stiffness at the elasto-plastic stage, implying less nonlinear sectional flexural stiffness response for such inclined connections. As the stud aspect ratio increased from 1.0 to 1.5, the shear strength increased by 13%, 25%, and 18% for studs inclined 30°, 45°, and 60°, respectively. Increased stud aspect ratio from 1.5 to 2.0 had only a minor influence on shear strength. During the test, the local embedment (UHPC over the stud head top) and UHPC slab shear failure with many subtle cracks showed pronounced ductility (continuous clear snapping sounds from steel fibers and major cracks observed approaching failure) for a stud aspect ratio less than 1.5. Furthermore, the reduced rigidity method, used in a given section under the service load, showed 10% lower deflection than 0° stud connections and a within-5% increase of the rigid connections for ultrashort studs. These results show that this type of shear connector exhibits good stiffness and strength performance, especially for ultrashort studs. In future research, low cyclic loading and high cycle fatigue tests should be performed on these connections.