Abstract: The authors rationally evaluate the impact of local concrete voids on the shear performance of stud connectors and investigate the effectiveness of void repair measures in restoring connector performance. Ultrahigh-performance concrete (UHPC) grouting is used in the experiments, with void depth and void ratio as parameters representing void defects. The influence of UHPC voids and their repair on the mechanical properties of stud connectors is examined experimentally. The following findings are obtained: (1) All specimens are mainly characterized by stud shear failure, without noticeable cracking in the UHPC slabs; voids and repairs have minimal impact on the final failure mode of the specimens. (2) Voids cause a substantial decrease in the shear capacity and shear stiffness of the studs. With increasing void depth, the shear performance declines, with the impact on shear stiffness being more pronounced than that on shear capacity. (3) The void ratio does not influence the shear performance of the studs. (4) The use of UHPC grouting to repair 20-mm-deep voids enhances the shear capacity and shear stiffness of specimens, with a greater enhancement effect on shear stiffness than on shear capacity. However, the shear performance of the studs after repair does not recover to the level of void-free specimens: shear capacity and shear stiffness are 22.7% and 10.2% lower, respectively, than those of the void-free specimens. A calculation formula for shear capacity of stud connectors considering UHPC voids is proposed based on the experimental data.

Key words: stud connector, ultrahigh-performance concrete, shear resistance, push-out test, concrete voiding, void repairing