# The Bearing Performance and Sectional Design Method of Yielding U-Shaped Steel Support
## 4 Analysis of the Influence Mechanism on the Bearing Performance of Yielding U-Shaped Steel Support
### Analysis of the Influence Mechanism on Bearing Performance
#### 4.2.2 Analysis of the Influence of Section Forms  
Under the action of a uniform load, the internal forces, deformation, and bearing capacity-displacement curves of support with different sectional forms are analyzed. 1. Analysis of Support Deformation  
The typical deformation patterns of support with different sectional forms are shown in Figure 16.  
It can be known through the analysis of the support deformation diagrams that:  
In the A45-H5 and A55-H5 schemes, the maximum deformation of the support appears in the middle of the straight leg. The straight leg bends inward and the deformation at the top position is not obvious. In the A54-H5 scheme, the maximum deformation of the support appears at the top. The top bends downward, showing an \"M\"-shaped failure state and the deformation of the straight leg is not obvious. Figure 15: Bearing capacity–displacement curve. The main reasons for the analysis are as follows: Under the action of the same uniform load, when the height of the straight leg is greater than that of the top, the bending moment generated at the straight leg is greater than that at the top, resulting in the straight legs on both sides first generating deformation and forming a failure pattern with inward concavities on both sides. On the contrary, when the length of the top is greater than that of the straight leg, the bending moment at the top is greater than that at the straight leg. Under the action of the downward bending moment, the top presents an obvious \"M\"-shaped failure pattern. 2. Analysis of Support Internal Forces  
The internal force distributions of support with different sectional forms are shown in Figure 17.  
It can be known through the analysis of the internal force diagrams of the support that:  
The internal force distribution patterns of support with different sectional forms are basically the same. In the A45-H5, A54-H5, and A55-H5 schemes, the maximum axial forces of the support are all at the bottom foot positions, which are 192.4 kN, 128.7 kN, and 141.5 kN, respectively, and the positions where the axial forces are zero are all in the middle of the straight legs. In the A45-H5 and A55-H5 schemes, the maximum bending moments are at the bottom foot positions, which are 68.4 kN\(\cdot\)m and 62.1 kN\(\cdot\)m, respectively. In the A54-H5 scheme, the maximum bending moment is at the support shoulder position, which is 49.6 kN\(\cdot\)m, and the positions where the bending moments are zero all appear at the straight legs. All three types of support are subjected to uniform pressure, and the magnitudes and distribution patterns of the axial forces and bending moments within the support are basically the same. The maximum axial forces all appear at the bottom foot positions and the maximum bending moments appear at the support shoulder positions. Figure 16: Deformation of steel support under different section forms (mm). Figure 17: Distribution of axial forces and bending moment under different section forms. Analysis of Bearing Capacity-Displacement  
Taking the middle of the straight legs in the A45-H5 and A55-H5 schemes and the middle of the top in the A54-H5 scheme, which are the positions with significant deformation, as examples, the relationship between the section forms of the support and the bearing capacity is analyzed. The bearing capacity-displacement curves of the support are shown in Figure 18.  
It can be known through the analysis of the bearing capacity-displacement curves of the support that:  
The failure of the support goes through three stages: linear elasticity (OA)--plasticity (AB)--yielding (BC). In the OA stage, the displacement of the top has a linear relationship with the load. With the increase in the load, the support deforms uniformly and slowly. When reaching point A, the support enters the plastic deformation stage. When reaching point B, the support starts to yield, the rising speed of the load decreases significantly, and the deformation speed of the support increases rapidly.