## 3 Experimental Results and Analysis
### Load-Deflection Curves  
Figure 6A-D show the measured load-deflection curves for different parameters. The point where the secant rigidity of the specimen decreases to a large extent is taken as the yield point of the specimen. The load-deflection curves of the specimens can be divided into two categories according to the different trends as follows.  
Category I: The curves are divided into three stages: elastic stage (specimen not cracked), elastic-plastic stage after cracking to yielding of the reinforcement and yielding to damage of the reinforcement. In the elastic phase of the specimen, the increment of deflection of the specimen changes less with the rising load (as shown in the Figure 6). This is because the tensile force in the lower part of the beam is shared by the reinforcement and the bond between the reinforcement and the concrete interface, and the reinforcement is in the elastic stage at this stage, while the bond between the reinforcement and the concrete  
Figure 5: Curve of maximum crack width of specimen.  
Figure 6: Load–deflection curve.  
interface is intact and also in the elastic rising section, so the specimen as a whole is in the elastic stage.  
In the elastic-plastic stage, that is, after the specimen cracking to the yielding stage of the reinforcement, the incremental deflection of the specimen with the rise of the load becomes larger than the first stage. This is because the reinforcement enters the elastic-plastic phase, and the bond between the reinforcement and the concrete interface appears to be damaged to some extent with the growth of the reinforcement strain. Therefore, the growth of deflection of the specimen is greater than the elastic phase under the same load increment.  
After entering the yielding section of the reinforcement until the damage, the cut-line rigidity of the specimen decreases to a greater extent and the deflection grows while the load increment is relatively small (e.g., specimen SSCB-R6 in Figure 6D). This is because there is no significant increase in the stress of the reinforcement after it enters the yield section, while the strain increases more rapidly. Therefore, the cut-line rigidity of the specimen shows a large degree of decrease. After the yielding section, the reinforcement section is entered and the stress increases slowly, while the strain increased substantially. The crack develops faster and the bond between the reinforcement and concrete interface is further damaged during this process as the crack continues to develop. The deflection of the specimen grows, while the load rises slowly until the reinforcement necking is broken and the load drops abruptly, and the loading ends.  
Category II: The overall trend is basically the same as the first category of curves, the difference lies in the elastic phase without cracking and the elastic-plastic phase after cracking to the yielding of the reinforcement. The increment of deflection in this part of the second category of curves under the same load increment is significantly larger than the first category of curves, the degree of difference mainly depends on the duration of service in tidal environment (as shown in Figure 6D), which can be clearly observed by the comparison of SSCB-R10 to SSCB-R6 specimens.