## 1 Introduction
This parametric study investigated the effects of concrete strength, stud diameter, and the height-to-diameter (h/d) ratio on the load-displacement performance of steel-concrete composite connections. The findings revealed that concrete strength plays a critical role in the behavior of the connection. Specifically, for concrete with a compressive strength of 160 MPa, the study emphasized the significant impact of stud diameter on connection performance, while the height-to-diameter (h/d) ratio was found to have a negligible effect under these concrete strength conditions. In the literature, it is observed that different modeling approaches are adopted, such as how materials are considered. Advanced numerical models take into account numerous parameters that influence the actual behavior of the connection [21]. Variations or refinements of a single parameter can lead to different outcomes. For instance, the study [20] does not address the descending stage of concrete's post-load capacity due to its difficult modeling. However, other studies [22; 23] emphasize the significant role of accurately modeling the real mechanical behavior of concrete. [PERSON] et al. [24] carried out static push-out tests on headed study embedded in UHPC and observed that the aspect ratio could be reduced from 4 to 3.1 without compromising the shear strength. The absence of splitting cracks in the UHPC slab indicated that the connection functioned efficiently. The stud shear connectors primarily exhibited shearing behavior instead of bending, which can be ascribed to the enhanced stiffness and strength of the surrounding concrete. [PERSON] et al. [25] and [PERSON] et al. [26] have established that, within the context of UHPC, stud connectors with height-to-diameter (h/d) ratios between 2 and 6 exhibit similar behavior. Consequently, short shear studs are capable of developing full strength in UHPC slabs. [PERSON] and [PERSON] [27] examined different stud diameters (d) and heights (h) alongside various compressive strengths of concrete (30, 40, 50 MPa) and highlighted that lower concrete strength could result in more noticeable bending deformation alongside shear deformation. Using finite-element numerical simulations, [PERSON] et al. [28] analyzed studs with diameters exceeding 22 mm. Their findings indicated that both the size of the studs and the strength of the concrete are critical factors influencing the load capacity of the connection. [PERSON] et al. [29] used finite element simulations to investigate the shear performance of grouped-stud connectors and examined how longitudinal spacing affects the connection. A validated numerical parameter analysis was conducted, considering different longitudinal spacings and concrete strengths. The maximum load was observed when the stud spacing was 13d. At lower concrete compressive strengths (e.g., C25/30), variations in shear strength were significantly greater, whereas at higher compressive strengths (e.g., C50/60), these variations were considerably reduced, particularly when analyzed concerning longitudinal spacing. This observation highlights the dependency of shear performance on both material properties and stud configuration, warranting further investigation to optimize structural design parameters. [PERSON] et al. [30] studied the longitudinal spacing and provided the work of [PERSON] et al. [29], especially regarding the reduction factor. [PERSON] et al. [31] conducted a parametrical FEM analysis incorporating damage plasticity. The analysis assessed lateral bending moments leading to maximum concrete crack widths of 0.1 mm and 0.2 mm, with shank diameters varying from 13 mm to 22 mm and stud heights of 80 mm and 100 mm. The study found that larger shank diameters reduced the impact of biaxial effects, while concrete cracks caused by initial bending negatively affected shear stiffness. Furthermore, push-out tests were conducted to examine the decrease in shear stiffness and shear capacity of grouped studs. [PERSON] et al.