This paper reports on double shear push-out tests conducted on steel-to-ultra-high-performance concrete (UHPC) connections based on studs of 30- or 22-mm diameter in slabs of 35, 55, or 150 mm thickness. The results show that with an increase in stud diameter, the longitudinal shear strength has improved by 25% and 94% for ultra-short and long studs (of aspect ratios below and equal to 4.0), respectively. For short studs, both the aspect ratio and concrete cover greatly influenced failure by partial stud fracture or UHPC pryout, while the diameter governed failure behavior for long studs. Decreases in aspect ratio and cover thickness caused shear resistance to drop by 40% and 7%, respectively, for 30- and 22-mm diameter studs. Regression analyses show that the shear strength, slip stiffness, and ductility of the connections are exponential, sinusoidal, and polynomial functions, respectively, of the stud aspect ratio. The ultra-short stud–UHPC connections are 62% stiffer in slip than their normal concrete counterparts. Future work should entail fatigue testing of the connections
