Tensile behavior of stud connectors in high strength concrete

Stud connectors are commonly used in steel-concrete composite structures. As high strength concrete (HSC) will be applied in the construction of a composite structure, it is needed to study the performance of stud connectors in HSC. In this study, tension (pull-out) tests were conducted on the studs with different combinations of diameters-d(13, 16, and 19 mm) and effective embedment depths-h( ef ) (40, 60, and 80 mm) in HSC with a 28-day compressive strength of 88 MPa. Based on the experimental results, the concrete breakout failure mode dominates and only the scenario with the smallest diameter and largest h( ef ) is controlled by steel failure mode. Because of high strength, the steel failure occurs at smaller h( ef )/d in HSC than normal concrete. In the concrete breakout failure mode, brittle load-displacement behaviors are presented and the angle of the breakout cone ranges from 30 similar to 35 degrees, which is close to the concrete capacity design (CCD) method. Also, the ultimate tensile strength (N- u ), stiffness, and pre-peak ductility are dependent on h( ef ) and diameter. The existing prediction models (CCD method and variable angle cone method) both overestimate the N- u in HSC, which is due to its lower ratio tensile/compressive strength than normal concrete. Considering the mechanism of how the breakout cone is formed, a modified reduced_CCD method is proposed for predicting N- u of studs in HSC.