## 4 Flexural Loading Test Results and Discussion
### Strain Behavior of Reinforcement and Joint Casting Materials  
#### 4.4.1 Load-Strain Relationship of Reinforcement  
As shown in Figure 5c, strain gauges to the loop reinforcement were attached to the middle position of the loop curve, at the top and bottom reinforcement located at the span center, and to the straight part of the tension-side reinforcement at intervals of 60 mm within the joint. Figure 11 presents the relationship between the applied load and the reinforcement strain of each measurement for the specimen Types A-D. The vertical axes represent the applied load, and the horizontal axes denote the strain. Figure 11 also shows enlarged views (insets) of the initial stage of the loading up to 50 kN. The reinforcement strain is the average value of the two loop reinforcements at each pair of locations. The insets of Figure 11 for all the test specimens show a small strain on both the compressive and tensile sides until the opening of the interface between the PCa slab and the joint. After the opening started at the interface, the strain of the reinforcement on the tensile side increased with the load. As for the reinforcement strain L1 (compressive side), the compressive strain occurred in the initial stage of the loading, but the strain gradually increased to the tensile strain as the load increased. The behavior of the reinforcement strain L2 (middle of the loop curve) was similar to that of L1. Figure 11: Relationship between applied load and strain of loop reinforcement in joint (**a**) Type A; (**b**) Type B; (**c**) Type C; (**d**) Type D (locations of L1 to L6 in Figure 5c). In addition, from Figure 11a, the reinforcement strains L3 and L6 of the Type A specimen increased sharply at around 150 kN due to the yielding of the loop reinforcement. The reinforcement strains L1 and L2 (top and middle positions, respectively) also increased sharply to the tensile strain at around the same load. These increases were due to the increase in the bearing pressure in the loop reinforcement. The slope of the curve at the reinforcement strain L3 was lower in the specimen Types B-D than in the Type A specimen. Larger strain occurred in the specimen Types B to D than in the Type A specimen at the same applied load. The reason was that the bearing pressure in the loop reinforcement of the specimen Types B-D was larger than that of the Type A specimen, as the conventional loop joint (Type A) had a wider joint and longer overlapping of the loop. Similarly, as seen in the result of the reinforcement strain L3 of the specimen Types B and C, the bearing pressure in the Type B loop was larger than that in the Type C specimen because of the shorter overlapping of the loop in the Type B specimen. Moreover, the slope of the curve at the reinforcement strain L3 was lower in the Type D specimen (concrete joint) than in the Type B specimen (PVA-FR mortar joint). Hence, the bearing pressure in the Type D loop was larger than that in the Type B loop. The fiber reinforcement reduced the bearing pressure in the loop reinforcement by resisting the tension stress in the transverse direction--the cross-linking effect of the fiber reinforcement. Figure 12 shows the relationship between the load and the transverse reinforcement strain of the conventional loop joint (Type A). The transverse reinforcement strain was measured in three reinforcements, as shown in Figure 5e1,e2 by attaching two gauges at each location. Almost no strain was observed in the transverse reinforcement until 150 kN, but the strain increased from around 150 kN at all measurement locations. In the load-deflection relationship (Figure 8a), the slope of the curve of the Type A specimen decreased from 150 kN, and the tensile strain in the loop reinforcement (Figure 11a) also increased from 150 kN. The largest strains occurred in the middle transverse reinforcement because of the bearing pressure from loop reinforcements, as shown in Figure 12b.