# Experimental and Parametric Study on the Pull-Out Resistance of a Notched Perfobond Shear Connector
## 1 Introduction  
In recent decades, steel and concrete composite structures have been increasingly used in bridge engineering due to their great structural performance and favorable construction cost. The shear connection between steel and concrete is critical for the design of composite structures. Among the various types of shear connectors in the literature [1; 2; 3; 4; 5; 6; 7; 8], the perfobond shear connector is one of the most competitive shear connectors in practice, having a great shear resistance, shear stiffness, and fatigue strength [9; 10]. The conventional perfobond shear connector is a flat steel plate which makes circular holes. Concrete dowels will form in these circular holes to resist shear forces and prevent separation between steel and concrete. With the merits of easier installation, no obvious fatigue problems, higher stiffness, and greater shear resistance, the perfobond shear connectors have been increasingly used in many types of innovative composite structures [11; 12].  
When perfobond shear connectors were installed with multi-ribs, it was time-consuming to perforate the reinforcing bars through many holes on these ribs. To increase the construction efficiency, a new type of notched perfobond shear connector was developed by cutting out the hole edge of the perfobond rib, which enabled the reinforcing bars to be directly put into many holes at the same time, as shown in Figure 1. Extensive research has been performed to study the shear behavior of the conventional perfobond shear connectors [13; 14; 15; 16; 17]. The influences of the specimen dimension,the number and size of the hole, the configuration of the rebar in the hole, and the material properties were investigated. Based on experimental and numerical analysis results, several equations were proposed to estimate the shear resistance of perfobond shear connectors [13; 14; 15; 16; 17]. In comparison, little research has been done to reveal the shear behavior of notched-type perfobond shear connectors. The reference was made to the analysis work by [PERSON] and [PERSON] [18].  
Shear connectors are usually used to transfer the shear forces between the concrete slab and steel beams when composite beams are subjected to longitudinal bending moments. In recent years, some newly built steel and concrete composite bridges have been designed to bear more lanes by using steel beams of wide distances and a concrete slab with long cantilevers. In this circumstance, local transverse bending moments are induced by the wheel load and balanced by contact with the steel top flange and the pull-out force of shear connectors. A large pull-out force may cause vertical separation between the steel beam and the concrete slab, which should be prevented to ensure the structural performance of composite bridges, referring to the study of [PERSON] et al. [19]. However, little research has been reported on the pull-out behaviors of conventional and notched perfobond shear connectors [20; 21].  
In this study, a total of six pull-out tests were performed to compare the failure modes and the load-separation behaviors of conventional and notched perfobond shear connectors. Moreover, 33 nonlinear finite element models of notched perfobond shear connectors were built to further study the effects of several parameters, including the hole diameter, the cut width, the perfobond thickness, the concrete strength, the rebar diameter, the rebar strength, and the steel strength. The parametric results were generated to evaluate the pull-out behavior of perfobond shear connectors. Finally, an analytical model was proposed to predict the pull-out resistance of notched perfobond shear connectors in steel and concrete composite structures.