# Shear Resistance Assessment of the Y-Type Perfobond Rib Shear Connector under Repeated Loadings
## 1 Introduction  
As the steel-concrete composite structures are applied widely to various structures, many studies have been performed to investigate the behaviors of the shear connectors in various design conditions such as shear connector types, material properties, load conditions, etc. The shear connectors between steel and concrete parts may experience either one-directional repeated cyclic loadings or fully reversed cyclic loadings depending on the structural functions and acting loads. Many studies related to the performance of shear connectors under cyclic loads have been conducted. If the shear connectors may experience the cyclic loads during the service life, the shear resistance capacity may deteriorate. Therefore, it is essential that the energy dissipation and residual performance related to cyclic behavior of structures have to be evaluated to secure the target performance of the structures. Many studies have been performed with different types of shear connectors under different loading types: the fully reversed cyclic loading and one-directional cyclic loading(repeated loading). [PERSON] and [PERSON] [1] conducted monotonic loading tests and fully reversed cyclic loading tests with stud shear connectors to evaluate the hysteretic performance of composite beams. [PERSON] and [PERSON] [2] conducted low cyclic tests depending on the diameters of stud shear connectors. They considered the effects of varying the degree of shear connection to evaluate shear strength and ductility of stud shear connections under low cyclic loads. [PERSON] et al. [3] conducted fully reversed cyclic loading tests to evaluate the effects of load condition on the shear strength and fatigue strength of stud shear connections. [PERSON] and [PERSON] [4] analyzed the behavior of shear connections composed of channel shear connectors. Reversed cyclic loading tests and monotonic loading tests were conducted for different types of concrete. Studies by [PERSON] et al. [5; 6; 7] evaluated shear strength reduction and ductility of channel and angle shear connections under fully reversed cyclic loads, compared with design codes, and analyzed the failure modes of shear connections. [PERSON] et al. [8; 9; 10] conducted fully reversed cyclic loading tests to evaluate the effect of load condition and transverse rebar size, and to compare the shear connection of stud and Y-type perfobond rib shear connectors. [PERSON] et al. [11] conducted fatigue tests on one-direction of Y-type perfobond rib shear connector, which consider service load intensities. [PERSON] et al. analyzed the ultimate shear strength by the fully reversed cyclic loads with studs [12] and perfobond rib shear connectors [13]. They suggested that the ultimate shear strength in cyclic loads might be lower than the estimation suggested by design specifications. Thus, the more detailed evaluation formulae for the ultimate shear strengths were proposed. [PERSON] et al. [14] proposed the model to estimate the cyclic response of perfobond rib shear connectors. The unloading-reloading process with push-out specimens was performed, and the model was based on the load-slip relations with empirical data. [PERSON] et al. [15; 16; 17] performed repeated and monotonic loading tests to define the shear strength for steel block shear connectors, plate perfobond rib shear connectors with notched holes, and groups of studs. [PERSON] et al. [18] tried to define the scope for the use of shear connectors by repeated loading. They dealt with different types of shear connectors such as I, channel, stud, and Z sections. In the previous studies [8; 9; 10; 11], the stubby Y-type perfobond rib shear connectors were tested to be adopted for the steel beam-RC slab composite system in the multi-bay, multi-story frame. The stubby Y-type perfobond rib height is very short and 50 mm high (the total height is 85 mm including the root and dowel hole) to be embedded in the shallow depth RC slab (150 mm deep slab specimens) and the concrete compressive strength is designed to be around 30 MPa.