## 2 Experimental Overview  
### Speciment Design  
In this study, four groups of group stud specimens were designed, comprising three full-scale specimens and one 1:3 scaled specimen, named Z-40, Z-32, Z-16, and S-13, respectively. The number following the dash represents the total number of studs in a single slot. The size parameters of the scaled specimen were determined by reducing the Z-16 specimen in accordance with the standards outlined in GB/T 50152-2012 (Standard for Test Methods of Concrete Structures) [21]. Each group of specimens consists of a steel loading beam and two prefabricated concrete slabs on either side, which are connected by group studs and cast-in-place concrete to form a composite structure. Figure 2 provides a detailed illustration of the shear studs, with Figure 2a showing the full-scale specimens and Figure 2b showing the scaled specimens. The shear stud dimensions are in strict accordance with the requirements specified in GB/T 10433-2002 (Cheese Head Studs for Arc Stud Welding) [22], and the specimen design adheres to the guidelines outlined in GB/T 50152-2012 (Standard for Test Methods of Concrete Structures) and JGJ 138-2016 (Technical Specification for Steel-Concrete Composite Structures) [23]. This arrangement ensures that the shear studs conform to the design specifications regarding spacing, welding processes, and material properties, thereby facilitating efficient and reliable shear transfer within composite structures. Figure 3 shows the geometric dimensions of the specimens, and the specific dimensions of each component are listed in Table 1. Each prefabricated slab contains two group stud slots, with the studs arranged as follows:  
Figure 2: Detailed stud connector arrangements of full-scale and scaled specimens. (**a**) Full-Scale Specim; (**b**) Scaled Specim. Specimen Z-40: The studs are arranged in a uniform grid of 10 rows and 4 columns. Each side of the concrete slab contains two slots, with studs arranged in a 10-row by 4-column configuration within each slot, as shown in Figure 3a. Specimen Z-32: The studs within each slot are symmetrically divided into two regions, each containing a 4-row by 4-column arrangement. The slot shape and overall layout remain identical to those in Z-40, but the studs are uniformly distributed across the two regions within each slot, as shown in Figure 3b. Specimen Z-16: The studs in each slot are arranged in a diagonal pattern, forming a 4-row by 4-column grid. In all three full-scale specimens, the horizontal spacing between the studs is 50 mm, while the vertical spacing is 100 mm, as shown in Figure 3c. Scaled Specim S-13: The studs are similarly arranged in a diagonal pattern within each slot, with 13 studs distributed in a 6-row by 2-column configuration, plus a central stud. The horizontal and vertical spacings between the studs are 40 mm and 50 mm, respectively, as shown in Figure 3d. \begin{table}
\begin{tabular}{c c c c c c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Stud**} & \multicolumn{3}{c}{**Precast Concrete Slab**} & \multicolumn{3}{c}{**Steel Beam Stud Base Plate**} & \multicolumn{3}{c}{**Steel Beam Web Plate**} \\ \cline{2-13}  & **Diameter** & **Height** & **Height** & **Width** & **Thickness** & **Height** & **Width** & **Thickness** & **Height** & **Width** & **Thickness** \\ \hline Full-scale specimen & 19 & 160 & 1600 & 690 & 320 & 1600 & 670 & 14 & 1600 & 400 & 12 \\ \hline Scaled specimen & 10 & 54 & 1050 & 230 & 107 & 1000 & 224 & 6 & 1000 & 130 & 4 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Component size parameter table (unit: mm). Figure 3: Geometric dimensions of specimens. (**a**) Specimen Z-40; (**b**) Specimen Z-32; (**c**) Specimen Z-16; (**d**) Specimen Z-13. Notably, the slots in specimens Z-40 and Z-32 are relatively large, accommodating a higher number of studs. To enhance the overall mechanical integrity of the structure, a stepped shape is adopted in the casting direction to increase the bonding surface between the new and existing concrete.