Research On Calculation Of Flexural Stiffness Of Corroded Reinforced Concrete Beam And The Character Of Crack

Concrete durability is one of the world-wide concerned problems in the field of the structure engineering. Corrosion of reinforcement steel bar is already recognized as one of the most important factors effect the durability of reinforced concrete structures, it is particularly important to research the change laws of the mechanical properties of the corroded steel bar. Combining with the National Natural Science Foundation of China(No.50478032), test studies combined with theoretical analyses are used to correlative investigate flexural stiffness and crack problem of the corrosed reinforced concrete beam.Factors affecting flexural stiffness of corroded reinforced concrete beams are investigated firstly, and a conclusion is reached that main factors affecting the establishment of calculation model is steel strain lagging behind concret strain for bond degrading due to steel corrosion. The section stiffness of flexural members with deteriorated bond strength is analyzed by means of stiffness analytic method.A steel strain lagging coeficient is adopted to reflect effects of both steel strain tending to uniformly distributed and lagging behind, and a calculation model of flexural stiffness of reinforced concrete beams with corroded bars established, Through the fitting for the test data ,the relationship between the rate of corrosion and disharmony of the reinforced strain is built; The calculated results coincide wih test results well.Through the comparative analysis of the test beam deflection data and theoretical value at the normal use stage, revision the siffness formula of the reinforced concrete beam by introduction the enlargement coefficient of the deflection, contrast and analyse the two methods of calculation, the paper offers a certain reference for the durability study of reinforced concrete bridges.Finally, compare the measured stress and theoretic stress of the the corroded steel reinforced concrete beams, the relationship between the enlargement coefficient of the crack width and the rate of corrosion is built, then the proposed method of calculation of the crack width of the corroded reinforced concrete beam is advanced.