Experimental study of the effects of interface and core constraints on the shear performance of prefabricated shear studs connectors

For a novel prefabricated composite shear studs (PCSS) connectors, there are two kinds of effects, one is the steel plates-concrete interface effect, and the other is the combined effect of the U-shaped groove formed by steel plates and the horizontal stud pull-out action, which together constitute the core concrete confinement. To study these two effects on the shear performance of PCSS, two sets of 6 parameterized push-out tests conducted to reveal the influencing rules and mechanisms. The results show that both the two effects can enhance the shear performance of PCSS, delaying the cracking and debonding time between the vertical steel plate and concrete. Compared to specimens with natural interfaces and those with interface treatment, the peak load, ultimate load, and shear stiffness of the former increased. The core concrete confinement mainly enhances the shear stiffness. The interface effect and core constraint synergy mechanism of PCSS was proposed: The U-shaped steel groove provides a hoop effect, which works in conjunction with the uplift resistance of the horizontal studs to generate a core restraint on the inner concrete. Then the interface effect and the restraint effect complement each other, enabling the steel plate and the concrete to jointly bear the forces. This combined action extends the effective working time between the stud and the concrete, enhancing overall shear resistance performance. Furthermore, the core constraint variation laws of PCSS were identified: full section constraint occurs during the elastic stage, half-section constraint occurs during the plastic stage, and only the pull-out effect of the horizontal bolts remains during the platform and failure stages.