## 7 Conclusions  
In the present study, a window-type seismic control system (WSCS) using non-buckling slit dampers (NBSDs) was proposed and developed. Materials testing was also conducted to examine the material performance and energy dissipation capacity of the steel NBSD system. A full-scale two-story frame structure modeled from existing RC structures with non-seismic details was subjected to pseudo-dynamic testing. The seismic retrofitting performance of NBSD-WSCS, when applied to existing RC structures, was examined and verified, and based on the pseudo-dynamic testing results, a restoring force characteristics model was proposed. Further, based on the proposed restoring force characteristics, nonlinear dynamic analysis was conducted, and the results were compared with those obtained by the pseudo-dynamic tests. Finally, nonlinear dynamic analysis was conducted on the entire RC building with non-seismic details retrofitted with NBSD-WSCS. The major findings of the present study are as follows. 1. Cyclic loading tests were conducted according to the test method for displacement-controlled seismic control systems provided in KDS 41 [12] to check NBSD-WSCS for conformity with the seismic performance requirements. The results confirmed that the NBSD-based test specimen provided adequate performance as a displacement-controlled seismic control system. 2. Pseudo-dynamic testing was conducted at seismic intensity of 200 cm/s2. The results showed that the full-size two-story RC test frame with no reinforcement applied underwent shear failure, while only minor seismic damage was expected for the test frame retrofitted with NBSD-WSCS. Even when the seismic intensity was set to 300 cm/s2, only small or moderate seismic damage was expected. These results confirmed that, given that the test frame with no reinforcement applied underwent shear failure, the reinforcement using NBSD led to a failure mode shift from shear to flexural failure, demonstrating the significantly improved energy dissipation capacity of NBSD-WSCS developed in the present study. 3. In addition, based on material testing and pseudo-dynamic test results obtained from NBSD members, the characteristics of beams, columns, and reinforcing members (NBSD) with respect to restoring force were proposed to implement the nonlinear dynamic analysis of the full-size two-story test frame retrofitted with NBSD-WSCS. Figure 33: Shear ductility of all column members determined via nonlinear dynamic analysis of the building retrofitted with NBSD-WSCS. Further, based on the proposed restoring force characteristics, nonlinear dynamic analysis was conducted, and the results were compared with those obtained by the pseudo-dynamic tests. It was then found that the average deviation ratios in seismic response load and displacement were within 10%, i.e., the two methods provided similar results. This further confirmed that the nonlinear dynamic analysis model and methodology developed in the present study were able to effectively simulate and evaluate the seismic retrofitting performance of this novel NBSD-based WSCS via nonlinear dynamic analysis. 4. In an attempt to commercialize this NBSD-based WSCS, nonlinear dynamic analysis was conducted on the entire RC building with non-seismic details retrofitted with NBSD-WSCS to examine the effect of seismic reinforcement. The results showed that the reference RC building with non-seismic details underwent shear collapse at seismic intensity of 200 cm/s\({}^{2}\). In the RC building with non-seismic details retrofitted with NBSD-WSCS, however, NBSD-WSCS with excellent energy dissipation capacity was able to accommodate about 42% of the total energy exerted on the test building. Thus, only minor seismic damage was expected. The major findings of the present study clearly indicated that this novel seismic retrofitting method using the NBSD-based WSCS has a high potential for commercialization. This research received no external funding. Not applicable.