## 3 Experimental Analysis of the Bearing Capacity of the Vertical Member
### Experimental Results and Analysis
#### 4.5.1 Establishment of the Numerical Model  
To more closely model the actual stress state of the formwork support and to better simulate the stress state of the vertical pole of the formwork support, the following basic assumptions were made for the vertical pole model of a formwork support: (1) The connection between the vertical pole and the horizontal bar was a semi-rigid connection, and the bending moment was transmitted between the vertical pole and the horizontal bar. (2) The vertical pole was a continuous, complete vertical pole, and the welding system was ignored. (3) The foundation and the formwork support were connected by hinges, and no bending moment was transmitted, which was more consistent with the actual situation. (4) The roles of scissor supports and inclined bars were ignored, and conservative assumptions were made about the support frame. (5) Considering the geometric nonlinearity of the structure, the critical load was determined according to the stress diagram and load-displacement curve. Additionally, the size of the vertical load was changed, and the calculation of the structure was repeated. Finally, the critical load value was obtained.  
According to the size of the formwork support, solid modelling of the single-layer vertical pole of the formwork support was conducted. The vertical pole and horizontal bar with specifications of 1.2 m were used for solid modelling in three working conditions (central, side, and corner poles). Among them, the wheel and vertical pole, the sleeve and vertical pole, and the socket and horizontal bar were considered to be single entities, consistent with the above. The vertical pole, horizontal bar, and sleeve were all set as Q235 steel, and the other components were set as cast steel. The meshing method was set as previously described. The node connection between the vertical pole and the horizontal bar was set up with a surface-to-surface friction connection. The models of the three working conditions are illustrated in Figure 28.  
Figure 26: Failure modes of double-layer vertical poles: (**a**) Central pole; (**b**) side pole; (**c**) corner pole.  
Figure 27: Load—displacement curves of measuring points: (**a**) Single-layer central pole; (**b**) single-layer side pole; (**c**) single-layer corner pole; (**d**) double-layer central pole; (**e**) double-layer side pole; (**f**) double-layer corner pole.  
It was important to keep the boundary conditions of the \(FEA\) and the experimental analysis consistent. Thus, in the \(FEA\) of the stability bearing capacity of single- and double-layer vertical poles in the formwork support, the bottom ends of the other vertical poles that were not affected by the load were fixed. The top ends of the other vertical poles were set as free ends, which limited the out-of-plane translational degree of freedom at the low end and the rotational degree of freedom in the vertical direction, and the load was applied only to the single- and double-layer stressed poles (central, side and corner poles). The displacement control method was adopted in the \(FEA\) of the stability bearing capacity of single- and double-layer vertical poles. The maximum vertical displacement of the stressed vertical pole was set to 50 mm, and a uniform axial load was applied at the upper end of the stressed bar.