| 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), following researches were done in this thesis:1) By analysis of test data of 48 beams with accelerated corrosion,the damage mode and feature of crack with different corrosion-rate of beam were obtained and the distributing character of concrete strain in the section in midspan of beam . Analysis of combined reduction coefficient was done. By fitting data, the expression of combined reduct- -ion coefficient was obtained.2) The conclusion has been obtained that the strain of corroded steel bar and concrete no longer fit in with the assumption of plane section through the analysis of the strain data, the strain relation of steel bar and concrete in the mid-span section of variously corroded beams at ultimate has been obtained.3) Through the analysis of the damage mode of corrosion-beams.It is known that the corrosion-beams has different damage mode with different corrosion-rate. At the same time the strain between bar and concrete at the same place with bar is different, all this factors above were considered. The strength of corrosion-beams were analyzed and finally used test data to check the conclusion.4) By the software of Msc.Marc,the strength of corrosion-beam was analyzed by finite element. The method of simulating corrosion-beam was clearly introduced. How corrosion-rate influenced strength, bond stress,strain between concrete and reinforcem- -ent, feature of crack were discussed .5) Through the analysis of test data, the way to calculate the stiffness of corrosion-beam was presented by modifying the formula presented by code.
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