Shear behavior and design of headed studs embedded in steel-UHPC composite structures

Headed studs are key connectors to transfer the interfacial shear force between the steel and concrete component in steel ultra-high performance concrete (UHPC) composite structures. This paper presented a systematic study on the shear behavior of headed studs embedded in UHPC. A total of 30 push-out tests, categorized into 10 groups, were conducted to investigate the effects of length-to-diameter ratio of stud, fiber content, compressive strength of concrete, and diameter of studs. The load-slip curve, shear strength, shear stiffness, and ductility of studs were analyzed. The test results showed that: (i) the shear strength and stiffness of studs embedded in UHPC were higher than those in normal concrete (NC), while the ductility was lower; (ii) the shear strength increased with increasing diameter of studs; and (iii) the length-to-diameter ratio of studs (3.75-10.0) and fiber content (0%-2%) had a limited effect on the shear strength and stiffness. Results from the tests were used to evaluate the existing design methods, which were found to be relatively conservative for estimating the shear strength of headed studs embedded in UHPC. New equations were then proposed to estimate the load-slip curve and shear strength of headed studs embedded in UHPC.