# Flexural Behavior of Corroded High-Speed Railway Simply Supported Prestressed Concrete Box Grider  
[PERSON]  
1 School of Civil Engineering, Central South University, Changsha 410075, China;
degree of strand corrosion is assessed by comparing the mass loss before and after corrosion. However, [PERSON] et al. [5] observed that prestressing strands mainly exhibited inhomogeneous corrosion in a chloride salt environment and usually suffered fracture in the most corroded areas. In references [6; 7; 8], a nonuniform chloride-induced corrosion model was used to estimate the residual area of steel bars, which in turn provided new insights into the seismic response and seismic fragility estimates of aging highway concrete structures. [PERSON] et al. [9; 10] acquired corroded strands from actual structures, and they classified the corrosion pit configuration into three types. By analyzing the reduction in tensile strength and ductility of the corroded strands, they proposed an equivalent stress-strain constitutive model. Furthermore, [PERSON] et al. [11] conducted a 3D laser scan of 24 strands within a 10-year-old naturally corroded prestressing beam. They found that the majority of the corrosion pits belonged to Types I and III, with only a very small number belonging to Type II. [PERSON] et al. [12] adopted the constant current accelerated corrosion method to investigate the effect of different mass losses on the degradation of strand mechanical properties. Then, a bilinear constitutive model for corroded prestressing strands was proposed.  
However, there is excellent scope for exploring flexural behavior such as the flexural stiffness, cracking moment, and ultimate bearing capacity of corroded PC beams. Strand corrosion could decrease the flexural stiffness of PC beams because it induces prestress [13; 14; 15]. [PERSON] et al. [16] tested the flexural bearing capacity of two concrete box girders serviced for 42 years. They found that strand corrosion could cause reduced flexural bearing capacity. [PERSON] et al. [17] experimentally investigated the flexural properties of nine pretensioned PC beams with different mass losses. They observed that when the strand mass loss was higher than 7%, the failure mode of the PC beams changed. The test beams had two different failure modes: concrete crushing and wire rupture. Through 10 specimens with different strand mass losses, [PERSON] et al. [18] found that the degree of bond degradation and the mass loss were not simply linear. In addition, considering the cross-section reduction and mechanical property degradation of the corroded strand, some empirical models [19; 20; 21] were proposed to predict the flexural behavior of corroded PC beams.  
The above-mentioned flexural experiments have achieved some research results, but specific investigation of the flexural behavior of corroded high-speed railway simply supported PC box girders is limited. In addition, there are fewer empirical models for cracking moment prediction, and the above empirical models cannot predict the failure mode of corroded PC beams. In the present study, six T-shaped scaled beams were designed and fabricated according to the specifications for a high-speed railway PC box girder. The corrosion process of the prestressing strands in scaled beams was simulated by using the constant current accelerated corrosion method. The flexural behavior of scaled beams was revealed through four-point bending tests. Afterward, an analytical model including the effects of strand cross-section reduction, strand property deterioration, and concrete cracking was proposed and verified by comparison with the experimental results. This study can provide some useful suggestions for assessing the flexural behavior of the high-speed railway simply supported PC box girder subjected to complex climatic environments.