## 4 Analysis of Test Variation Parameters
### Longitudinal Reinforcement Ratio  
Figure 9 shows the effects of different longitudinal reinforcement rates (0.64%, 0.93% and 1.27%) on the initial rigidity, cracking and peak load, peak deflection, energy dissipation index and ductility index of reinforced sea sand concrete beam specimens.  
As seen in Figure 9A, the initial rigidity of the specimen was 61.35 kN\(\cdot\)mm\({}^{-1}\), 46.19 kN\(\cdot\)mm\({}^{-1}\) and 53.35 kN\(\cdot\)mm\({}^{-1}\), which decreased by 24.7% and then increased by 15.5% with the increase in the longitudinal reinforcement rate.  
As seen in Figure 9B, the cracking loads of the specimens were 40.1 kN, 30.5 kN and 30.4 kN in order with the increase in the longitudinal reinforcement rate, which showed a  
Figure 9: The performance index changes with the ratio of reinforcement.  
decreasing trend with a decrease of 23.9% and 0.4%, respectively. The peak loads of the specimens were 150.7 kN, 148.7 kN and 161.3 kN in order, with an overall small increase. The peak loads of specimens with reinforcement rates of 0.64% and 0.93% were close to each other, and the difference was only 1.3%. The peak loads of specimens with a reinforcement rate of 1.27% were raised by 8.5%.  
As seen in Figure 9C-E, with the increase in the longitudinal reinforcement rate, the peak deflection of the specimens (peak deflection of 14.69 mm at 0.64% reinforcement rate) first increased by 57.7% and then decreased by 36.7%, the energy consumption index first increased by 80.5% and then decreased by 33.4% and the ductility coefficient first increased by 11.5% and then decreased by 30.7%, all of which showed a trend of increasing and then decreasing, with large fluctuations.  
The above shows that the reinforcement rate of longitudinal bars has different effects on the initial rigidity, cracking and peak load, peak deflection, energy consumption index and ductility index of the specimens. The peak deflection, energy consumption index and ductility index were significantly affected, and the peak deflection of the specimen reached 23.17 for the reinforcement rate of 0.93% (12 mm diameter), while the peak deflection of the specimens with reinforcement rates of 0.64% and 1.27% was close to that of the former, which was about 63%. The peak loads of the three specimens are not very different, so the energy dissipation index and ductility index also show similar trends. The reason for this is that the difference in the diameter and tensile properties of the longitudinal reinforcement makes the difference in the bonding performance between the reinforcement and the concrete interface. Therefore, the performance indexes of the specimens do not show a linear increase with the rise of the reinforcement rate, but with the difference in the diameter and performance of the reinforcement to show different work performance (as shown in Table 1 and Section 2.2.1). Therefore, in the engineering design, it is recommended that the contact area between the reinforcement and concrete interface can be increased by reducing the diameter of the reinforcement at the same reinforcement rate, which is conducive to improving the initial rigidity of the specimen. At the same time, considering the elongation of the reinforcement, the use of reinforcement with higher elongation can effectively improve the peak deflection of the specimen, thus improving the energy dissipation index and ductility of the specimen.  
In summary, the reinforcement rate of longitudinal bars has a significant effect on the peak deflection, energy dissipation index and ductility index of sea sand concrete beams. The effects on initial rigidity, cracking and peak load are small, and the degree of influence depends on the size and tensile properties of the reinforcement.