## 2 Experimental Analysis of the Bearing Capacity of the Horizontal Bar
### Eccentric Tensile Properties of the Socket on the Horizontal Bar
#### 2.1.3 Experimental Results and Analysis  
At the beginning of the loading experiment, the specimen had no noticeable deformation, and the displacement increased linearly. With increasing load, the deformation of the specimen increased, and there was a slight audible sound of metal failure. As the specimen was loaded to the ultimate load, the deformation of the specimen increased rapidly. When the sound of metal fracture was audible and the load could not continue to increase, the specimen was destroyed, and the loading was stopped immediately. After unloading, observations showed that all the specimens were damaged at the weld seam, i.e., the connection between the socket and the horizontal bar; the horizontal bar was not damaged. The failure morphology of the specimens in this group of experiments is shown in Figure 3.  
Figure 1: Geometrical size of connection joints. Figure 2: Experimental device of socket tension and loading diagram. Graphs of the eccentric tensile bearing capacity of the socket on the horizontal bar are shown in Figure 4. The displacement change of horizontal bar socket under tensile force are shown in Table 1. When the socket on the horizontal bar was subjected to eccentric tension, the displacement basically increased linearly. The greater the tension of the socket was, the more obviously the displacement increased. When the load increased gradually, a slight crack formed in the weld at the connection between the socket and the horizontal bar, the tensile bearing capacity of the socket decreased, and the displacement growth rate increased significantly. In summary, according to the experimental observations and data analysis, the failure mode of the socket specimen on the horizontal bar was weld failure, and the failure property was buckling failure. When the bending deformation of the vertical pole of the formwork support caused the sockets at both ends of the horizontal bar to be subjected to eccentric tension (pressure), the bearing capacity of the weld at the connection between the socket and the horizontal bar was low and prone to damage. Therefore, the control of weld quality at horizontal bar connections is key to ensuring safe construction of the formwork support. \begin{table}
\begin{tabular}{c c c c c c c c c} \hline \hline
**Tensile** & **5** & **10** & **15** & **20** & **25** & **28** & **25** & **20** \\
**Capacity/kN** & & & & & & & & \\ \hline SJ-1 & 3.71 & 5.83 & 7.8 & 9.78 & 11.36 & 14.18 & 16.57 & 17.74 \\ SJ-2 & 3.09 & 4.86 & 6.37 & 8.54 & 10.78 & 12.69 & 14.21 & 14.88 \\ SJ-3 & 3.19 & 4.98 & 6.27 & 8.1 & 10.02 & 12.29 & 13.25 & 13.6 \\ SJ-4 & 2.37 & 4.24 & 6.59 & 8.68 & 10.57 & 13.37 & 14.42 & 14.79 \\ SJ-5 & 3.64 & 5.39 & 7.33 & 9.57 & 11.83 & 14.71 & 16.3 & 16.95 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Displacement changes of the horizontal bar socket under tensile force. Figure 4: Graphs of the eccentric tensile capacity of sockets on horizontal bars. Figure 3: Failure mode of sockets on horizontal bars: (a) SJ-1; (b) SJ-2. 1.4 Finite Element Comparative Analysis of Eccentric Tensile Properties of the Socket on the Horizontal Bar  
According to the actual size of the socket, a solid model of the socket on the horizontal bar was established using the ABAQUS 6.14. The horizontal bar and the socket were considered as a whole entity, and the weld unit system was ignored. The horizontal bar and the socket, connected with a tie connection, were made of _Q235_ steel and cast steel, respectively. Due to the complex structure, the socket and the horizontal bar grids were automatically divided. Finer grids were set for the parts prone to stress concentration on the socket. The numerical model is shown in Figure 5. During the construction, with the vertical load increasing, the vertical pole is bent and deformed, such that the sockets at both ends of the horizontal bar are subjected to tension (pressure) and shear force, and the welds at the connection between the horizontal bar and the socket are subjected to tension (pressure).