## 4 Results
### Suggestion of Nonlinear Rotational Stiffness  
The rotation angle as a function of the load was calculated using the measured displacement and Equation (1). Figure 14 shows the moment-rotation curve of each specimen. As the slope of the moment-rotation curve represents the rotational stiffness, the Figure shows that the specimens with new members exhibited the highest initial rotational stiffness and that they generally exhibited higher moment-rotation curves than the reused specimens. As the reuse period increased, the moment-rotation curves were found to be lower. However, the moment-rotation curves of the specimens with a seven-year reuse period showed that these specimens exhibited higher stiffness than the specimens with a four-year reuse period. It is noted that the results of the specimens with seven-year reuse period shows considerable variability among the specimens. It was assumed that the moment-rotation curves in Figure 14 could be described by a trilinear model (see Figure 4), and the stiffness values (K\({}_{1}\), K\({}_{2}\), and K\({}_{3}\)) and rotation angles (\(\beta_{1}\), \(\beta_{2}\), and \(\beta_{3}\)) of the trilinear model were estimated by interval for each specimen, as summarized in Table 7. Each moment-rotation curve was simplified by the third interval where the first interval means the \begin{table}
\begin{tabular}{c c c c} \hline \hline  & **Mean** & & **1.036 kNm** \\ \hline
95\% confidence interval for mean & \
\begin{tabular}{c} Upper bound \\ Lower bound \\ \end{tabular} &
\begin{tabular}{c} 1.074 kNm \\ 0.997 kNm \\ \end{tabular} \\ \hline \hline \end{tabular}
\end{table} 
Table 6: Probabilistic bending capacity of wedge joint. Figure 14: Moment–rotation curves of all specimens. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multicolumn{2}{c}{**Kolmogorov–Smirnov**} & \multicolumn{2}{c}{**Shapiro–Wilk**} \\ \cline{2-6}  & **Statistic** & **df** & **Sig.** & **Statistic** & **df** & **Sig.** \\ \hline Maximum moment & 0.125 & 44 & 0.083 & 0.978 & 44 & 0.560 \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Tests of normality of maximum moment. initial linear behavior and the second interval includes the moment increase immediately after yielding. For the third interval, the overall behavior after yielding was assumed as a linear by excluding the moment increase after yielding, even though the additional moment increment was shown in all specimens with a seven-year reuse period and some specimens with a four-year reuse period. In the case of Reused-4-5, however, the experimental data obtained until the LVDTs broke away from the horizontal member were only sufficient to evaluate the initial rotational stiffness. Therefore, only the initial rotational stiffness according the trilinear model was evaluated for this specimen. For the wedge joints with new materials, the initial rotational stiffness (K\({}_{1}\)) ranged from 14.375 to 35.725 kNm/rad, the rotational stiffness of the second interval (K\({}_{2}\)) ranged from 5.501 to 8.206 kNm/rad, and the rotational stiffness of the third interval (K\({}_{3}\)) ranged from 1.302 to 3.885 kNm/rad. For the specimens with a one-year reuse period, K\({}_{1}\) ranged from 18.443 to 27.71 kNm/rad, K\({}_{2}\) ranged from 3.166 to 6.481 kNm/rad, and K\({}_{3}\) ranged from 0.289 to 2.570 kNm/rad. For the specimens with a four-year reuse period, the ranges of K\({}_{1}\), K\({}_{2}\), and K\({}_{3}\) were 12.783-27.618 kNm/rad, 3.093-6.509 kNm/rad, and 0.510-1.812 kNm/rad, respectively. For the specimens with a seven-year reuse period, the ranges of K\({}_{1}\), K\({}_{2}\), and K\({}_{3}\) were 10.428-25.424 kNm/rad, 2.715-7.041 kNm/rad, and 0.821-2.150 kNm/rad, respectively.