## 2 Experimental Program
### Specim and Experiment Outline  
Figure 6 shows a conceptual diagram of the test specimens. Four specimens were fabricated in total. First, the UBM (Unreinforced Brick Member) specimen consisted of perforated bricks and mortar without any reinforcement, and, in the IRBM (Internally Reinforced Brick Member) specimen, an internal reinforcement of four SI rods was added. From these two specimens, the internal reinforcing effect of the SI rods was examined. Next, in the IRBM--F (Internally Reinforced Brick Member Fixed by nut) specimen, the four SI rods were fixed by nuts after sandwiching both ends of the specimen with steel plates to enhance integrity. As mentioned earlier, according to the previous test results [49], the flexural strength of the specimen increased when the bonding performance between the steel and mortar was sufficiently secured. Therefore, in order to enhance structural performance, fixing work with steel plates and nuts was introduced. It was noted that every hole of the perforated brick was filled with mortar in IRBM--F. On the other hand, the mortar filling work to the holes was omitted in the IRBM--FNM (Internally Reinforced Brick Member Fixed by nuts with No filling Mortar) specimen to further improve workability as well as to save on costs and materials. The internal SI rods were fixed by nuts at both ends of the specimen, and the joint mortar was only employed on each layer between bricks in the IRBM--FNM.  
The specimen dimensions were 210 \(\times\) 430 \(\times\) 970 mm (depth \(\times\) width \(\times\) height), and the cross-sectional details are shown in Figure 7. As was performed in the previous experiment [49], the 3 arrangement patterns shown in Figure 7 were stacked in order for 14 layers to fabricate each specimen since such a combination arrangement was thought to provide more robust resistance against lateral loading. In order to find out the effective reinforcing method as well as to understand fundamental structural behaviors, 3-point bending tests were carried out, where the distance between two supports was set to be 770 mm, as can be seen in Figures 7 and 8. In the 3-point bending test, the vertical deflection of the specimen was measured at three points by displacement transducers (LVDTs). The strains at the crucial points of the SI rods were also measured for the specimens with internal reinforcements. It was noted that B1-B3 and T1-T3 represented the strains of the bottom and top side rods, respectively. From those strains, bond stresses between the mortars and rods were calculated to investigate the bonding performance, as discussed later in Section 3. All the specimens were fabricated by non-experts such as lab students, supposing self-buildable economic housing. In the specimens with SI rods, the rods were fixed vertically in advance, and then the masonry work was carried out by passing the perforated bricks through the rods. The bricks were stacked one-by-one, and mortar works were applied at the same time. The accuracy of the mortar filling work was likely to vary depending on the workers. Hence, it may have affected the bonding performance between the mortars and SI rods, which was the reason why the rods were fixed by steel plates and  
\begin{table}
\begin{tabular}{c c c} \hline \hline
**Yield Strength \(\sigma_{y}\) (MPa) ** & **Yield Strain \(\epsilon_{y}\) (\(\mu\)) ** & **Tensile Strength \(\sigma_{t}\) (MPa)** \\ \hline
446.9 MPa & 3833 \(\mu\) & 537.4 MPa \\ \hline \hline \end{tabular}  
* Strength and strains by 0.2\% offset method.  
\end{table}
Table 3: Material characteristics of screw iron (SI) rod.  
Figure 6: Conceptual diagram of test specimens: (a) UBM; (b) IRBM; (c) IRBM—F; (d) IRBM—FNM.  
nuts in IRBM--F and IRBM--FNM. It was also noted that the ends of the SI rods were lightly tightened with nuts using human power after curing the mortar; thus, the initial prestressing force was little.