Studies For Impact Of Corrosion On The Performance Of Cracks And Deflection Of Post-tensioned Concrete Beams

At present,the prestressed concrete structure in our country is widely applied in construction,water conservancy,transportation,railway etc.And it has a large fraction of concrete structures because of its particular advantages.In process of construction and operation,the erosion of external environment leads to the loss of prestress,which will directly affect the security,durability and service life of the structure.Considering this background,some the prestressed concrete beams were designed and subjected to accelerated corrosion to obtain different corrosion levels.The flexural test was employed to investigate the effect of strand corrosion on the stiffness of beams.The main contents can be drawn as follows:(1)Eight post-tensioned concrete beams including 7 corrosion beams were designed to investigate the effect of corrosion on the flexural behavior of PC beams.(2)Analysis of the crack distribution,type,quantity,width and other characteristics,Test result shows that the corrosion of prestressed reinforcement has no significant impact on the distribution and type of crack.The corrosion will not affect the quantity and width of crack when corrosion rate is within a certain range.When the corrosion rate is large,the quantity of crack decreases with the corrosion rate increasing while the crack width increases.(3)Under the study of the influence of corrosion on the crack performance degradation and on the basis of composite theory of crack width,the average crack width calculation formula of prestressed concrete beam after the prestressed reinforcement corroded was established.Some parameters of the formula were obtained by regression fitting the test data.After the formula verified by the experimental data of other researchers,the verification results showed the high calculation accuracy of the formula.(4)The analytical method is proposed to calculate flexural rigidity after corrosion by the measured data of load-deflection curve.Test result shows that the stiffness degradation of prestressed concrete beam could be divided into two stages with the corrosion rate of prestressed reinforcement increasing.Before cracking,the stiffness of all test beams are almost the same and the influence of the corrosion of prestressed reinforcement on the stiffness of beams is little.While after cracking,the corrosion of prestressed reinforcement leads to the decrease of the stiffness of test beams.(5)As the load-deflection curve(bending moment-curvature curve)of test beams met the double broken line rule,the short-term stiffness calculation model of prestressed concrete beam after prestressed reinforcement corroded was established by using the direct bilinear method.The parameters of the model involving the influence of the prestressed reinforcement corrosion were determined and the model was verified by the test data of other researchers.The verification results showed the high calculation accuracy of the model.