## 3 Experimental Analysis of the Bearing Capacity of the Vertical Member
### Experimental Results and Analysis
#### 4.5.2 Finite Element Comparative Analysis  
A finite element analysis was performed on the stability bearing capacity of the single- and double-layer vertical poles (central, side, and corner poles) of the new type of wheel coupler formwork support. The vertical pole deformation and stress cloud diagrams for the three working conditions were obtained, as shown in Figure 29.  
The \(FEA\) results for deformation diagrams and stress cloud diagrams showed that single- and double-layer vertical poles in the new wheel coupler formwork supported under axial compression for three working conditions (central, side, and corner poles), and the \(FEA\) results were basically consistent with the experimental results. According to the results of ABAQUS calculations, the following conclusions were drawn:  
1. Regarding the stress analysis, the stress concentration of the single- and double-layer vertical poles occurred in the middle of the longest free end of the vertical pole, i.e., the stress concentration was in the buckled section.
2. Regarding the failure mode, according to the simulated results for the failure of the single-layer vertical poles (central, side, and corner poles), all the single-layer vertical poles of the formwork that provided support under three working conditions were unstable and damaged due to buckling of the pole, which was consistent with the failure mode of the axial compression member. However, it was still slightly different from the axial compression member. The reason was that when the pole bent, the loading point was not entirely under axial compression, therefore, a bias developed, that is, the pole underwent vertical and also horizontal displacement.  
Figure 28: Finite element model of single-layer vertical pole for calculations of stability bearing capacity: (a) Central pole; (b) side pole; (c) corner pole.  
3. Regarding buckling deformation, in the numerical simulation and experiment, the deformation displacement of the buckling section of the double-layer vertical pole of the new wheel coupler formwork support under three working conditions (central, side, and corner poles) was larger than that of the single-layer vertical pole. The free end was longer than the single-layer vertical pole. However, the free length included the vertical pole connecting the sleeve. When the vertical pole was connected to the sleeve, there was a gap between the sleeve and the vertical pole so that the lower vertical pole could rotate under the force. When the height of the formwork support increased, the number of connections between the vertical pole and the sleeve increased, and the accumulated deformation increased, which may have been one of the reasons that it was not conducive to the overall stability of the formwork support.  
The experimental and \(FEA\) results for the stability bearing capacity of the single- and double-layer formwork supports are compared in Table 6. The predictions of the buckling capacity of the double-layer formwork support vertical pole were very accurate, and the error was basically within 5%. Therefore, the numerical model accurately predicted the buckling capacity of the wheel coupler formwork support in a large range. With a reduction in the number of horizontal bars connected to the vertical pole wheel disk, the stability bearing capacity showed a significant downward trend, especially with increasing layers; the stability bearing capacity decreased the most for the corner pole condition. The failure of a single-layer vertical pole was typical for lateral displacement buckling, while the double-layer vertical pole did not undergo lateral displacement buckling.  
Figure 29: Deformation diagrams of single- and double-layer vertical pole structures: (**a**) Central pole of a single-layer structure; (**b**) side pole of a single-layer structure; (**c**) corner pole of a single-layer structure; (**d**) central pole of a double-layer structure; (**e**) side pole of a double-layer structure; (**f**) corner pole of a single-layer structure.