## 3 Analysis of Test Results  
### Load-Displacement Curves  
The load-displacement curves of the reinforced steel angle and unreinforced steel angle are shown in Figure 8. For comparison purposes, the load-displacement curves of components with the same steel angle specifications and the same slenderness ratio are plotted in the same figure. For components that experience instability and failure, the load-displacement curve can be divided into three stages: in the first stage, starting from  
Figure 6: Flexural–torsional buckling failure mode.  
Figure 7: Local buckling failure mode.  
the origin, the curve approximately grows in a straight line until the slope of the curve changes. This stage is a linear stage, and the material plasticity has not yet developed. The specimen has no obvious lateral bending deformation, and the material is in an elastic state; in the second stage, the slope changes between the peak points of the curve, indicating a significant lateral displacement of the specimen. The second-order effect begins to become apparent, and the specimen has already buckled, but the material has not yet yielded. Therefore, the load can still rise slightly until the steel yields; in the third stage, namely the descending section after the peak, when the limit equilibrium state is exceeded, the lateral deflection of the specimen rapidly develops, and the deformation is too large to continue bearing the load, indicating the failure of the specimen.  
Figure 8: _Cont_.  
The increase in bearing capacity of the reinforced steel angle is shown in Table 3, with an increase in bearing capacity of approximately 39% to 174%, indicating a significant strengthening effect. After analysis, it is not difficult to find that the bearing capacity conforms to the following rules: Firstly, for steel angle specimens of the same specification, under the same slenderness ratio, the influence of fixture spacing and fixture form on the bearing capacity is not significant. For example, the difference in load-bearing capacity among the three groups of specimens LR1-2-1, LR1-2-2, and LR1-2-3 is within 10%, and there is no obvious distribution pattern, indicating that the fixtures used in the experiment can provide strong constraint capacity and still have optimization space. The second is that the initial aspect ratio when the steel angle is not reinforced has a significant impact on the reinforcement effect. For example, LR1-1-1, LR1-2-1, and LR1-3-1 specimens that  
Figure 8: Axial load–displacement curves. (**a**) Curves of LR1-1 group; (**b**) Curves of LR1-2 group; (**c**) Curves of LR1-3 group; (**d**) Curves of LR2-1 group; (**e**) Curves of LR2-2 group; (**f**) Curves of LR2-3 group; (**g**) Curves of LR3-1 group; (**h**) Curves of LR3-2 group; (**i**) Curves of LR4-1 group; (**j**) Curves of LR4-2 group; (**k**) Curves of LR5-1 group; (**l**) Curves of LR5-2 group.  
have slenderness ratios of 50, 90, and 110, respectively, behave with an increase in bearing capacity of 39.19% and 153.19% and 174.66%, reflecting a positive correlation between the increment in bearing capacity and the slenderness ratio. In order to better demonstrate the reinforcement effect, Table 3 calculates the critical bearing capacity of steel angle specimens under weak and strong axial instability based on AISC360-16 \"American Code for Design of Steel Structures\" for reference.