Fatigue of headed studs welded with improved ferrules under rotating shear force

• Improved headed studs showed higher fatigue strength than conventional headed studs.
• Two failure modes were observed as well as in wheel running fatigue tests.
• Concrete strength was a crucial factor affecting fatigue strength of headed studs.
• Average S–N curves were obtained by the probabilistic treatment.

This paper presents an evaluation of the fatigue strength of headed studs welded with improved ferrules under rotating shear force. In steel–concrete composite structures, shear connectors are essential components to transfer shear forces at the interface between steel and concrete. Particularly, headed studs in steel–concrete composite decks for highway bridges are subjected to rotating shear force when vehicle loads pass through the steel–concrete composite decks. The authors have developed welding ferrules for headed studs with higher fatigue duration than conventional headed studs. In this study, the rotating shear force was applied to the improved headed studs by using a specially developed testing machine in order to determine the fatigue strength in association with the concrete strength. The fatigue strength of the headed studs increased with the higher concrete strength and two failure modes were observed. Finally, the average S–N curves in correspondence with concrete strengths were determined for the improved headed studs.