## 5 Conclusions
The test frame retrofitted with the CFT-MF system exhibited seismic response strength about 1.72 times higher than the reference test frame when the same seismic acceleration was applied at 200 cm/s\({}^{2}\). The difference was even larger when the seismic acceleration was higher: about 2.45 times at 300 cm/s2 and about 3.09 times at 400 cm/s\({}^{2}\). The test frame retrofitted with the CFT-MF system also exhibited smaller seismic response displacements than the reference test frame. The difference was about 0.19 times at 200 cm/s\({}^{2}\), about 0.38 times at 300 cm/s\({}^{2}\), and 0.67 times at 400 cm/s\({}^{2}\). When the same seismic acceleration was applied at 200 cm/s\({}^{2}\), the seismic response displacement was about 81% lower in the test frame retrofitted with the CFT-MF system. These results indicated that the CFT-MF system was able to effectively enhance the ability of the test frame to absorb the applied seismic energy, verifying the effectiveness of the proposed seismic retrofitting method. 4. The non-linear dynamic analysis and pseudo-dynamic testing methods, conducted at input seismic ground motions of 200, 300, and 400 cm/s\({}^{2}\), showed similar results. The deviation was about 10% or less on average. These results confirmed that the non-linear dynamic analysis model and methodology developed in the present study were able to effectively simulate the seismic behavior of the CFT-MF system and RC frames retrofitted with the system. This led to the conclusion that the seismic retrofitting performance of the CFT-MF system developed in the present study could be effectively evaluated via non-linear dynamic analysis based on the established analytical models and methods. 5. This CFT-MF seismic retrofitting method makes the most of the advantages of both concrete and steel pipes, thereby significantly improving constructability and increasing integration between the existing structure and the reinforcement joints. This method falls into the category of typical seismic retrofitting methods that focus on increasing strength, in which the required amount of seismic reinforcement can be easily estimated. Therefore, the method provides a suitable solution to improving the strength of middle- and low-rise RC structures with non-seismic details that are prone to shear failure. The validity of the method was verified through pseudo-dynamic testing and non-linear dynamic analysis. 6. To commercialize the Concrete-filled Tube Modular Frame (CFT-MF) going forward, a method to estimate the required amount of seismic reinforcement, along with seismic reinforcement design methods, needs to be proposed. Furthermore, the practicality of the CFT-MF seismic retrofitting method needs to be thoroughly assessed by conducting non-linear dynamic analysis of RC structures with non-seismic details retrofitted with the CFT-MF system. All authors have contributed to the development of the research and the elaboration of this article. Particularly, [PERSON] contributed to the methodology, the experimental research and conceptualization; [PERSON] and [PERSON] contributed to the methodology, the experimental research and the dynamic analysis; [PERSON] contributed to the methodology and the experimental research; [PERSON] contributed to the methodology and the experimental research, and edited the manuscript. All authors have read and agreed to the published version of the manuscript. This research received no external funding. Not applicable. All datasets are available from the corresponding author on reasonable request. This research was supported by a grant (2020-MOIS31-012) from the Fundamental Technology Development program for Extreme Disaster Response, funded by the Ministry of Interior and Safety, and a grant (21 CTAP-C153033-03) from the Korea Agency for Infrastructure Technology Advancement Grant funded by the Ministry of Land, Infrastructure, and Transport Affairs of the Korean government. The authors declare no competing interests.