## 3 Test of Masonry Prisms Strengthened with SFRM Overlay
### Result of Tests for Masonry Prisms
#### 3.2.3. Diagonal Tension Test Result  
The result of the diagonal tension test for masonry prisms made of red clay and concrete bricks are summarized in Tables 9 and 10, respectively. The average shear strength of unreinforced concrete brick prism CP is about 1.6 times higher than that of unreinforced red clay brick prisms RP, but the average shear modulus for CP is only 1.2 times higher than that of RP. The increase rate of shear strength by mortar overlay for RS1.3, RB0 and RB1.0 is from 51 to 69%, and those for CS1.3, CB0 and CB1.0 are between 39 and 56%. The strengthening efficiency for red clay brick masonry is slightly higher than for concrete brick masonry. The maximum enhancements of shear strength are 138% and 67% for RB1.3 and CB1.3, respectively, to which the highest fiber volume fraction is applied. One of the reasons for the higher strengthening efficiency in red clay brick masonry is supposed to be the lower strength of the masonry itself, considering that SFRM with the same mixing ratios and fiber volume fractions was applied to both types of masonry materials. A similar tendency was observed by [PERSON] et al. (2011) [38], in which masonry walls strengthened using high-strength steel wires and mortar were tested and the unreinforced test specimens with higher strength and stiffness obtained less strengthening effects. Therefore, the efficiency of the strengthening method proposed by this study is expected to be more prominent when applied to masonry in poor condition. Regarding the shear modulus, red clay brick masonry and concrete brick masonry obtained an increase of 32% for RB1.3 and 20% for CB1.3, respectively, using SFRM with a fiber volume fraction of 1.3% on both sides. However, the increase rates of the shear modulus are relatively small compared to the increase in shear strength and the shear modulus even decreases for a number of specimen types. The increase rate of shear modulus for red clay brick masonry is slightly better than for concrete brick masonry regarding the shear strength. The stress-strain curves obtained from the unreinforced masonry without strengthening and masonry strengthened on both sides are plotted in Figures 15 and 16 for red clay brick masonry and \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Specimens**} & \multicolumn{3}{c}{**Average**} & \multicolumn{3}{c}{**Rate of Increase (\%)**} \\ \cline{2-6}  & **Load (kN)** & \begin{tabular}{c} **Shear Strength** \\ **(MPa)** \\ \end{tabular} & \begin{tabular}{c} **\(G_{m}\) (MPa)** \\ \end{tabular} & \
\begin{tabular}{c} **Shear Strength** \\ \end{tabular} &
\begin{tabular}{c} **\(G_{m}\)** \\ \end{tabular} \\ \hline CP & 120.2 & 2.4 & 810.3 & - & - \\ \hline CS1.0 & 137.1 & 2.8 & 631.7 & 14\% & \(-\)22\% \\ \hline CS1.3 & 167.2 & 3.4 & 843.1 & 39\% & 4\% \\ \hline CB0 & 170.0 & 3.4 & 746.0 & 41\% & \(-\)8\% \\ \hline CB1.0 & 187.1 & 3.8 & 892.6 & 56\% & 10\% \\ \hline CB1.3 & 201.2 & 4.0 & 969.5 & 67\% & 20\% \\ \hline \hline \end{tabular}
\end{table} 
Table 10. Diagonal tension test results for masonry prisms in concrete brick. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Specimens**} & \multicolumn{3}{c}{**Average**} & \multicolumn{3}{c}{**Rate of Increase (\%)**} \\ \cline{2-6}  & **Load (kN)** & \begin{tabular}{c} **Shear Strength** \\ **(MPa)** \\ \end{tabular}  & \begin{tabular}{c} **\(G_{m}\) (MPa)** \\ \end{tabular}  & \ \begin{tabular}{c} **Shear Strength** \\ \end{tabular}  & \begin{tabular}{c} **\(G_{m}\) \\ \end{tabular}  \\ \hline RP & 60.4 & 1.5 & 671.5 & - & - \\ \hline RS1.0 & 101.4 & 2.4 & 621.7 & 68\% & \(-\)7\% \\ \hline RS1.3 & 91 & 2.2 & 633.3 & 51\% & \(-\)6\% \\ \hline RB0 & 100.2 & 2.4 & 699.1 & 66\% & 4\% \\ \hline RB1.0 & 101.9 & 2.5 & 748.3 & 69\% &concrete brick masonry, respectively. In the initial loading stage, difference between unreinforced and strengthened masonry is not significant, but the strengthening effects become more obvious as the strain increases.