## 7 Conclusions  
This study proposed a novel V-bracing system equipped with an LLFD, which could supplement the shortcomings of conventional vibration control systems and is applicable to existing R/C buildings. The material performance and energy dissipation capacity of the LLFD were evaluated using a material test. A pseudo-dynamic test was conducted on two-story frame specimens based on an existing R/C building with non-seismic details to verify the seismic retrofitting effect of applying the LLFD V-bracing system to existing R/C buildings. Based on the pseudo-dynamic test results, restoring force characteristics were proposed for the non-linear dynamic analysis of a building (frame specimen) retrofitted with the LLFD V-bracing system. This non-linear dynamic analysis was conducted based on the proposed restoring force characteristics, with the results obtained compared with the pseudo-dynamic test results. Finally, for evaluating the commercialization potential of the LLFD V-bracing system, a non-linear dynamic analysis was conducted on the existing R/C building with non-seismic details retrofitted with the system. The seismic retrofitting effect was verified by examining the seismic response load and displacement characteristics, energy dissipation capacity, and damper load and displacement response before and after seismic retrofitting. The study results can be summarized as follows. A cyclic loading test was conducted based on the test method for displacement-dependent vibration control devices presented in KDS 41 [23] to verify the seismic performance of the LLFD V-bracing system. The results suggested that the LLFD specimens exhibited suitable performance as displacement-dependent vibration control devices. 1. When the pseudo-dynamic test was conducted at a DBE scale of 200 cm/s\({}^{2}\), the two-story R/C frame specimen without reinforcement showed shear failure; however, light seismic damage was expected for the frame specimen retrofitted with the LLFD V-bracing system. When a MCE scale of 300 cm/s\({}^{2}\) was assumed, insignificant seismic damage was also expected. Under 400 and 500 cm/s\({}^{2}\)--assumed for large earthquakes--moderate seismic damage corresponding to the life safety level was also expected. Compared to the non-reinforced frame that showed the shear failure mode, the failure mode changed from shear failure to bending failure for the specimen retrofitted with the developed LLFD V-bracing system, confirming that the system had an excellent seismic energy dissipation capacity. 2. Compared to the reference specimen, the LLFD method increased the seismic response strength by approximately 1.74 times under the input ground motion of 200 cm/s\({}^{2}\), 2.42 times under 300 cm/s\({}^{2}\), 3.00 times under 400 cm/s\({}^{2}\), and 3.51 times under 500 cm/s\({}^{2}\). The LLFD method also increased the displacement response ratio by approximately 0.14 times for 200 cm/s\({}^{2}\), 0.23 times for 300 cm/s\({}^{2}\), 0.40 times for 400 cm/s\({}^{2}\), and 0.54 times for 500 cm/s\({}^{2}\) compared to the reference specimen. The seismic response displacement for the same seismic load (200 cm/s\({}^{2}\)) was suppressed by approximately 86%, confirming that the proposed LLFD method has an excellent seismic energy absorption capacity. 3. Based on the LLFD member test and pseudo-dynamic test results, the restoring force characteristics of the beams, columns, and reinforcement (LLFD) were proposed for the non-linear dynamic analysis of a two-story frame specimen retrofitted with the LLFD method. Based on the proposed restoring force characteristics, a non-linear dynamic analysis was conducted on the pseudo-dynamic test specimens, with the results obtained compared with the pseudo-dynamic test results.