## 4 Validation of Model of Interior Joint
\begin{table}
\begin{tabular}{c c c c c c c c c c c c c c c c c c c} \hline \hline
**Test ID** & \(k_{c}\) & \(k_{c}\) & \(\sigma_{c}\) & \(\sigma_{bappy}\) & \(\theta\) & \(\theta\) & \(\theta\) & \(E_{f}\) & \(E_{f}\) & \(C_{LL}\) & \(C_{LL}\) & \(f_{b}\) & \(f^{\rm 2000}\) & \(\sigma_{b}\) & \(P_{Uc}\) & \(P_{Uf}\) & \(\varphi_{b}\) & \(p_{b}/p_{bappy}\) \\ \hline - & **mm** & **mm** & **MPa** & **MPa** & **rad** & (\(\gamma\)) & **mm\({}^{2}\)** & **GPa** & **MPa** & **-** & **MPa** & **-** & **mm** & **MPa** & **MPa** & **MPa** & **-** \\ \hline PRO(d,b) & 200 & 200 & 1.6 & 11.68 & 0.9 & 48.8 & 44 & 264.0 & 264,000 & 1 & 1 & 36.5 & 11.00 & 0.0289 & 1.75 & 5.32 & 7.83 & NA \\ PRO(d,b) & 200 & 200 & 3.1 & 14.55 & 0.9 & 51.1 & 42 & 264.000 & 1 & 1 & 39.8 & 11.66 & 0.0020 & 1.83 & 5.56 & 8.80 & NA \\ \hline AL-SA(H) & 160 & 300 & 3 & 6.46 & 1.0 & 57.5 & 588 & 61.5 & 61.500 & 0.8 & 1 & 30 & 9.65 & 0.0071 & 1.59 & 3.65 & 6.85 & 1.09 \\ AL-SA(Si) & 160 & 300 & 3 & 8.56 & 1.0 & 547 & 567 & 61.5 & 61.500 & 1 & 1 & 30 & 9.65 & 0.0088 & 1.9 & 4.53 & 7.47 & 0.92 \\ AL-SA(H2) & 160 & 300 & 1.6 & 6.73 & 0.9 & 51.6 & 546 & 61.5 & 61.500 & 0.8 & 1.5 & 25 & 8.55 & 0.0006 & 1.45 & 4.94 & 7.15 & 1.09 \\ AL-SA(H2) & 160 & 300 & 2.5 & 6.35 & 1.0 & 55.8 & 574 & 61.5 & 61.500 & 1 & 1.5 & 25 & 8.55 & 0.0120 & 1.45 & 6.18 & 8.59 & 1.49 \\ PAN(20,3) & 406 & 406 & 2.2 & 7.10 & 0.9 & 53.4 & 203.4 & 40.0 & 1 & 1 & 43 & 12.27 & 0.0038 & 1.90 & 2.26 & 5.14 & 0.71 \\ PAN(20,24) & 406 & 406 & 2.2 & 6.58 & 0.9 & 54.1 & 1973 & 106.0 & 106.000 & 1 & 1 & 43 & 12.27 & 0 For further verification and confirmation of the validity and accuracy of the equation, the joint shear stresses of the specimens calculated by using the proposed analytical model are compared with that of the experimentally determined joint shear stresses, as demonstrated in Figure 4.  
A better coherence is shown with high similarity among the experimental and predicted results. The joint stresses were determined using the proposed analytical model for two different directions, i.e., varying and constant of the principal compressive stresses. A moderate R factor (R\({}^{2}\)) of equal to or more than 0.70 is noted for both directions of the principal compressive stress, verifying the model's precision. Similarly, the mean of ratios of the predicated and experimental joint shear stresses is found to be 0.98, with a low coefficient of variation (COV) of 0.24 for the varying direction of principal stress and 0.92 with 0.22 of COV for the constant direction of principal stress. The decent average (near to one) of the ratios also supports the satisfactory accuracy of the proposed equation in assessing the joint shear stress. Similarly, the contribution of FRP to the interior joint's compression strength is compared with that of the experimentally calculated to check the accuracy of the analytical model in assessing the contribution of the FRP. The contribution of the FRP is calculated by using both directions (varying and constant) of the principal compressive stress of the joint. The comparison of the experimentally and analytically calculated FRP contributions is shown in Figure 5.  
Figure 4: Comparison of experimental and predicted results in terms of joint shear stress. Figure 5: Comparison of experimental and predicted results in terms of FRP contribution. Such as the substantial similarity between the predicated and experimental joint shear stresses, better coherence is noted between the predicated and experimental contribution of the FRP to the shear strength of the joint. In addition, the coefficient of regression is more than 60% for both directions of the principal compressive stresses of the joint. Similarly, the averages of the ratios of the experimentally and analytically calculated contribution of the FRP to joint shear strength are 0.94 and 1.05 for varying and constant directions of principal stress, respectively.