The Effect of the Corrosion Degree of Prestressed Steel Reinforcements on the Strain of Concrete Box Girders: An Experimental Fatigue Study

In order to investigate the relationship between the strain of prestressed concrete girders under fatigue loading and the corrosion degree of prestressed steel reinforcements, four 12.4-m-long large-size post-tensioned prestressed concrete box girders were designed and fabricated in this study, and prestressed steel reinforcements were corroded at different degrees by the Electric Accelerated Corrosion Method. The same equal-amplitude loads were used during fatigue loading. The relationship between the strain of different materials (strains of the plain reinforcements and prestressed steel reinforcements, as well as concrete strains in compression zones) and the corrosion degree was investigated. Then, the calculation method for the cumulative residual strain of concrete in the compression zone of the test beam was obtained. The test results show the following: the strains of the test beams under different corrosion degrees all show a three-stage development law; the ratio of the strain amplitude of the prestressed steel reinforcement to that of the regular steel reinforcement during fatigue loading basically stays in the range of 0.65–0.75, and the ratio rises with the corrosion degree of the prestressed steel reinforcement; the increase in strain of the compressed concrete is due to the accumulation of the residual strain of the concrete, and the increase in material strain is almost directly proportional to the growth of corrosion degree under the same fatigue load; the calculated values of the accumulated residual strain of the concrete agree well with the test values and satisfy the accuracy requirements of engineering.