Pull-out tests on handcrafted headed studs

The aim of this paper is to contribute towards better understanding of the behaviour of site-welded headed studs embedded in normal-weight concrete. The axial failure loads of these studs estimated by design codes and other calculation methods are conservative and inaccurate for concrete cone detachment. The concrete tensile strength and embedded length of the steel shank are believed to be the most influential factors on the final pull-out resistance of headed studs. In an experimental programme, ten headed studs with varying head thickness were pulled out from concrete blocks of strength 25 MPa or 35 MPa. The failure loads, failure modes and steel yield loads were used as parameters to verify the efficiency of the studs and to evaluate which design methodology gave estimated final resistances closest to the experimental values. Two collapse types were observed: one was located along the shank when the applied load exceeded the steel tensile failure load while the other was in the concrete and occurred when the applied load exceeded the concrete ultimate tensile strength, creating a conical failure surface. The two head thicknesses were found to be satisfactory and the theoretical loads underestimated the concrete tensile strength.