## 6 Conclusions  
This paper presents an experimental study on the flexural performance of reinforced sea sand concrete beams exposed to tidal conditions (270 d). Eight specimens were tested under a four-point load. The following main conclusions can be drawn. 1. For specimens with different lengths of service in a tidal environment, the effect of each variation parameter on their crack width development was not significant. The damage process and final damage morphology are similar, and they all exhibit positive section damage in the reinforced suitable beams, which is not much different from that of ordinary reinforced concrete beams. 2. Seawater mixing can improve the peak load and cracking load of the specimen by increasing the concrete strength, but the initial rigidity, peak deflection, energy dissipation index and ductility index of the specimen are reduced to some extent. 3. The reinforcement ratio of longitudinal bars has a significant effect on the peak deflection, energy dissipation index and ductility index of the specimen. The effect on initial rigidity, cracking and peak load is less, and the degree of effect depends on the size and tensile properties of the reinforcement. In engineering, the initial rigidity of the specimen (at the same reinforcement ratio) can be improved by reducing the diameter of the reinforcement and using a higher elongation reinforcement to enhance the peak deflection of the specimen. 4. The sea sand replacement rate was positively correlated with the initial rigidity of the specimen and negatively correlated with the peak load. The peak deflection, energy dissipation index and ductility index of the specimens showed a trend of decreasing and then increasing with the increase in the sea sand replacement rate. 5. In the short-term (270 d) exposure to the tidal environment, the increase in duration of service causes a significant decrease in the initial rigidity, peak deflection, energy \begin{table}
\begin{tabular}{c c c c c c c c} \hline \hline
**Lable** & **Duration of Service** & \(f_{\text{cu}}\)***/Mpa** & **Q** & **\(M\)/kN**-**m** & \(P_{\text{y}}\)/kN** & \(P_{\text{ca}}\)/kN** & \(P_{\text{ca}}\)/\(P_{\text{y}}\) \\ \hline SSCB-R6 & 90 d & 37.3 & 0.946 & 21.794 & 141.2 & 124.54 & 0.882 \\ SSCB-R7 & 180 d & 37.3 & 0.876 & 21.741 & 146.4 & 124.24 & 0.849 \\ SSCB-R8 & 270 d & 41.2 & 0.791 & 21.739 & 146.2 & 124.22 & 0.850 \\ SSCB-R9 & 270 d & 48 & 0.791 & 21.842 & 131.6 & 124.81 & 0.948 \\ SSCB-R10 & 270 d & 37.3 & 0.791 & 21.663 & 139.3 & 123.79 & 0.889 \\ SSCB-R11 & 270 d & 37.3 & 0.791 & 12.434 & 120.9 & 71.05 & 0.588 \\ SSCB-R12 & 270 d & 37.3 & 0.791 & 16.312 & 111.2 & 93.21 & 0.838 \\ SSCB-R13 & 270 d & 47.5 & 0.791 & 21.835 & 152.5 & 124.77 & 0.818 \\ \hline \hline \end{tabular} Note: \(f_{\text{cu}}\)* represents the cube compressive strength of concrete under conventional atmospheric conditions. \(Q\) is the concrete strength correction factor. \(M\) represents the section bending moment of the specimen. \(P_{\text{y}}\) represents the test value of the yield point of the specimen. \(P_{\text{ca}}\) represents the calculated value of the flexural bearing capacity of the specimen.  
\end{table} 
Table 3: Calculated results of the specimen compared with the test results. dissipation index and ductility index of the specimens, but has less effect on the cracking load and peak load of the specimens. 6. Based on the Chinese design standard, the method to calculate the flexural capacity of reinforced marine sand concrete beams after exposure to a tidal environment is proposed by considering the effect of concrete strength variation and combining with experimental data. It provides a reference for the design of reinforced marine sand concrete beams in offshore projects. 7. The bending performance variation of reinforced sea sand concrete beams exposed to a tidal environment (270 d) is revealed. For the specimens with longer duration of service in the tidal environment, further experimental studies are needed to provide more abundant data for engineering applications. Z.C.