## 1 Introduction  
With the continuous advancement of marine engineering, the durability of concrete structures has received more and more attention [1, 2, 3]. It is well recognized that steel corrosion is the main reason for the shortened service life of marine structures [4, 5]. Offshore engineering structures are in a complex corrosive environment where the corrosion of steel reinforcement by chloride ions in seawater will not only reduce its effective cross-sectional area, but the generation of rust will also cause cracking and spalling of the concrete protective layer [6, 7, 8], resulting in the deterioration of the force performance of the structure [9, 10]. This degradation effect may be further exacerbated by seawater scourage and wet and dry cycles [11, 12, 13]. Therefore, clarifying the time-varying performance of the structure under a corrosive environment is a guarantee to promote the safe construction of offshore projects. In addition, adopting local materials and using marine sand as aggregate to prepare concrete can greatly reduce the cost of offshore engineering and time [14; 15; 16] and realize the efficiency of offshore engineering construction. The durability of reinforced concrete beams has been studied by many authors [17; 18; 19; 20; 21; 22; 23; 24; 25; 26]. [PERSON] et al. [17] investigated the mechanical performance of reinforced concrete beams under simultaneous loading and corrosion and experimental results showed that the ultimate load capacity and deformation capacity of the beams significantly decreased with corrosion cycles at higher sustained load levels. [PERSON] et al. [18] investigated the degradation of the seismic performance of corroded RC columns and proposed an empirical model to predict the residual load capacity of corroded columns. [PERSON] et al. [19] analyzed the effect of reinforcement corrosion on the buckling behavior of corroded RC beams and further predicted the residual buckling strength of concrete beams. [PERSON] et al. [20] proposed a method considering many effects to predict the residual bearing capacity of corroded RC columns under different degradation conditions, such as reinforcement buckling and deformation incompatibility between the reinforcement and the surrounding concrete. [PERSON] et al. [21] developed an empirical model to predict the structural behavior of corroded RC columns based on the experimental results of full-size RC columns. [PERSON] et al. [22] studied the effect of different concrete cover thicknesses on the performance of building structures and proposed solutions for the corrosion of reinforcement. [PERSON] et al. [23] proposed a new method to improve the carbonation resistance of calcium sulfate aluminate cements, which led to further improvement in the durability performance of concrete. [PERSON] et al. [24] studied the effect of marine environmental exposure on sea sand seawater concrete beams and revealed the mechanisms causing structural performance changes through analysis and calculations. [PERSON] et al. [25] found the law of the effect of random arrangement of steel fibers on the fracture and ductility properties of concrete beams through an experimental study. [PERSON] et al. [26] studied the effect of reinforcement configuration and continuous loading on the performance of reinforced concrete beams affected by reinforcement corrosion, giving the evolution of reinforcement corrosion and central deflection under simultaneous loading and corrosion. Most of the studies on the mechanical performance of members in a marine environment have been conducted by artificially simulating dry and wet cycles and seawater scouring, which still have some differences from the real marine environment. In the existing studies on the mechanical properties of reinforced concrete beams in real marine environments [27; 28], there is a lack of relevant research information on the time-varying mechanical properties of reinforced marine sand concrete beams in tidal environments, which need to be investigated through experiments.