## 4 Results  
### Failure Mode  
Figure 5 shows the shape of the vertical and horizontal member joint system at failure. As seen from the figure, the joint ring was deformed in the loading direction for both the new and reused specimens. It was found that the end of the horizontal member contacted and gradually deformed the vertical member, leading to a failure. Thus, the moment capacity of joints can be increased by reinforcing the contact surface or attaching the plate at the end of the horizontal members, as shown in [PERSON] et al. [27]. The deformation of the vertical member was relatively larger when the reuse period of the members of the specimen was longer. The detailed failure mode showed slightly different results according to the grove size at the end of the horizontal member, as shown in Figure 6. In the case of sufficient space in the grove as mentioned in Figure 3b, the failure was mainly contributed by the strength of the vertical member where the horizontal member was contacted (Figure 6a-c). However, the system with the seven-year reused members, which had little space in the grove (see Figure 3c), showed that the additional resistance occurred by the contact between the joint ring and grove surface at the horizontal member (Figure 6d). After the end of the horizontal member was contacted to the vertical member, the joint ring was also contacted to the grove surface as a loading increased due to the little space in the grove, resulting in occurring the additional resistance in joint and increasing the vertical displacement of the joint ring. Moreover, the connection pin was destroyed in a specimen with a reuse period of seven years, as shown in Figure 7 (Reused-7-2 specimen), indicating that the strength of the connection pin of a product with a long reuse period may not be sufficient. This phenomenon is undesirable since wedges are usually made of steel with higher strength than the other elements of the node. Among all specimens, only one specimen in seven years reused member showed destruction of the connection pin. It was thought that the quality control system had a problem at that time. To prevent accident from this destruction in the experimental test, the prevention device should be installed as shown in Figure 3a. The strains in the joint ring and the horizontal member were analyzed as a function of the load. The strain analysis results for New-S-9, Reused-1-7, Reused-4-5, and Reused-7-10 are shown in Figure 8. As the Figure shows, the maximum horizontal member strain values (from S.G.1 and S.G.2) were small for all of the specimens, and the strains were linear and did not exceed the yield strain. In the case of the joint ring, however, nonlinear behavior was observed after yielding for all of the specimens (based on measurements from S.G.3 and S.G.4). This indicates that the failure of the joint system is caused by the ultimate behavior of the joint ring, regardless of the reuse period. In the case of little space in  
Figure 4: Trilinear moment–rotation model. grooves, the moment in joint rings were additionally increased after yielding due to the contribution of the contact between the joint ring and the grove surface at the end of the horizontal member as explained in failure mode (Figure 8c,d). Figure 5: Failure configuration: (**a**) System with new products (New-S-9); (**b**) system with members used for one year (Reused-1-11); (**c**) system with members used for four years (Reused-4-11); (**d**) system with members used for seven years (Reused-7-2). Figure 8: Strain curves of joint ring and horizontal member: (**a**) New-S-9 (new product); (**b**) reused-1-7 (one year of use); (**c**) reused-4-5 (four years of use); (**d**) reused-7-10 (seven years of use). Figure 6: Detailed failure configuration at joint: (**a**) System with new products (New-S-9); (**b**) system with members used for one year (Reused-1-11); (**c**) system with members used for four years (Reused-4-11); (**d**) system with members used for seven years (Reused-7-2). Figure 7: Pin failure caused in Reused-7-2 specimen.