## 5 Conclusions  
The moment capacity and nonlinear rotational stiffness of wedge joints, which are the predominant type of joint used for the connection of the vertical and horizontal members of assembled support systems, were evaluated by examining the characteristics of new and reused members. Loading tests were conducted with new and reused specimens, and the behavior, moment capacity, and initial rotational stiffness of the joints were probabilistically analyzed by reuse period (new versus one, four, or seven years). The conclusions drawn from the results of this study are as follows. The failure of joint system was mainly contributed by the strength of the vertical member since the end of the horizontal member contacted and gradually deformed the vertical member, leading to a failure. In addition, the specimens with little space in the grove where the joint ring passed showed the additional resistance occurred by the contact between the joint ring and grove surface at the horizontal member after joint yielding. The average maximum moment of the specimens with new members was 1.16 times higher than that of the specimens with a one-year reuse period, 1.15 times higher than that of the specimens with a four-year reuse period, and 1.06 times higher than that of the specimens with a seven-year reuse period. The correlation between the increase in the reuse period and the average maximum moment of the joint was not clear due to the moment increment in all specimens with seven-year reuse period and some specimens with four-year reuse period, resulting from the little groove surface. However, it was clear that the variation in the moment-displacement curves of the specimens increased as the reuse period increased, indicating that an increase in the reuse period lowered the moment capacity and increased the quality variation. In particular, as the increase in variation of the joint resistance performance reflects an increase in the probability of member failure, it appears that the increasingly  
Figure 16: Frequency distribution and normal distribution curve of initial rotational stiffness data. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Mean Value** & **22.475 kNm/rad** \\ \hline
95\% Confidence Interval for Mean & Upper bound & 24.262 kNm/rad \\  & Lower bound & 20.688 kNm/rad \\ \hline \hline \end{tabular}
\end{table} 
Table 10: Probabilistic initial rotational stiffness of wedge joint. inconsistent performance of wedge joints with increasing reuse period is a potential cause of the collapse of support systems. As a result of probabilistically estimating the moment capacity of wedge joints using the maximum moment values of the new and reused specimens tested, the maximum moments obtained from the experiments were confirmed to be normally distributed. The lower and upper limits of the 95% confidence interval of the maximum moment were 0.997 kNm and 1.074 kNm, respectively. As a result of estimating the joint stiffness by assuming that the rotational stiffness of the joint could be described by a trilinear model, the average rotational stiffnesses (for both new and reused specimens) were found to be 22.475 kNm/rad (rotation angle limit value: 0.022 rad) for the first interval, 4.705 kNm/rad (rotation angle limit value: 0.080 rad) for the second interval, and 1.577 kNm/rad (rotation angle limit value: 0.178 rad) for the third interval. The specimens with a one-, four- and seven-year reuse periods exhibited initial rotational stiffnesses that were 89.5%, 80.7%, and 68% of the initial rotational stiffness of new specimens, respectively. A probabilistic analysis of the initial rotational stiffness for all of the specimens showed that, the lower and upper limits of the 95% confidence interval of the initial rotational stiffness were 20.688 kNm/rad and 24.262 kNm/rad, respectively. [PERSON] designed experiments and analyzed results. [PERSON] and [PERSON] performed experimental tests. [PERSON] analyzed experimental results, and [PERSON] and [PERSON] performed the statistical program.