Headed stud shear connector for thin ultrahigh-performance concrete bridge deck

• Stud shear connectors provide sufficient shear strength for UHPC deck.
• Aspect ratio of stud can be as low as 3.1 without a loss of strength for UHPC deck.
• Cover thickness over the stud can be as low as 25 mm without causing a splitting crack.
• Stud shear connectors do not satisfy ductility demands for UHPC deck.
• Stud shear connectors in a UHPC deck should be used as per elastic design concept.

Ultrahigh-performance concrete (UHPC) provides much higher compressive and tensile strength than conventional concrete. UHPC is advantageous for use as a bridge slab deck owing to its higher strength, stiffness, and durability. One drawback, however, is the fact that the joint region connecting the deck and girder generally has a thicker cross-section to ensure proper shear connection, which hinders making the overall UHPC deck thinner and lighter. In addition, the shear strength of stud shear connectors embedded in UHPC slab has not been verified to be the same as that in a conventional concrete deck. This study investigates a stud shear connector embedded in a UHPC deck through 15 push-out tests. The ultimate strength of the stud and relative slips are measured. The test parameters were chosen to prove the feasibility of a thinner slab. The stud aspect ratio, overall height-to-diameter, and cover thickness on top of the stud head requirement are also examined to verify the existing geometrical constraints specified in the AASHTO LRFD and Eurocode-4 design codes for UHPC decks. It was shown that the aspect ratio can be reduced from 4 to 3.1 without loss of shear strength of the stud, and the cover could be reduced from 50 mm to 25 mm without causing a splitting crack at the UHPC slab. However, the required ductility demand, 6 mm, was not realized in all cases. Therefore, the stud shear connectors in a UHPC deck should be designed according to the elastic criterion.