## 6 Conclusions  
To control the damage caused by debris flow, a net protection system was developed in this study, which is equipped with a new energy absorption device called a brake frame. Deducing the important design parameters was necessary while analyzing the systematic relationship of all elements comprising the net protection system. The quasi-static load tests were performed in order to analyze the performance of brake frames. Using a three-dimensional FE model, the numerical analysis was performed to investigate the behavior of steel rings causing large deformation and the verification of the numerical model was also conducted accordingly. Based on the numerical approach, the effect of the brake frame in reducing the impact load in specific cases was estimated using a proposed equivalent model.  
1. The developed brake frames were based on the absorption mechanism of the impact energy through three elements: rings, wire ropes, and U-clips, with six phases of behavioral characteristics. The brake frames could deform up to 1.5 m, thereby absorbing 53 kJ of impact energy. The field application of the net protection system is possible only when the arrangement as well as the number of brake frames is designed in specific cases according to the impact energy.
2. The steel rings in the brake frame were capable of absorbing the impact energy through the mechanisms of elastic and local buckling, as well as metallic fracture. When the equivalent model based on the one-dimensional axial connector having seven linear force-displacement relationships is utilized, an accurate simulation is performed and an increase in efficiency of the analysis can be expected, as compared to the use of three-dimensional FE model.
3. The anchor capacity was observed to be depending on the performance of the energy absorption devices. The effectiveness of using brake frame in the net protection system was clearly observed because the impact load on the anchor positions (the connection between the wire rope and the ground) was recorded to be about 75% less than that in the case when the brake frames were not installed. The anchor capacity observed for the specific cases can be used as a reference for the anchor design while using the brake frames in the net protection system.  
Extending the observations and conclusions of this study in the future, the relationship between the impact energy and anchor capacity will be developed, and the tensile forces and load distribution in the anchors will be analyzed for various cases of the impact energy based on the full-scale tests.  
Figure 16: Comparison of the development of tensile forces and load distribution in each wire rope with and without using a brake frame.  
**Author Contributions:** [PERSON] supervised the overall process in this study. [PERSON] designed the net protection system using the brake frame, as well as performed quasi-static load tests. [PERSON] performed the numerical simulation and proposed the equivalent model. [PERSON] analyzed the performance and effects of using brake frames, as well as prepared the manuscript by combining the observations of the physical experiments and numerical analysis.  
**Acknowledgments:** This work was supported by the Technology Development Program (S2401940) funded by the Ministry of SMEs and Startups (MSS, Korea).  
**Conflicts of Interest:** The authors declare no conflict of interest.