Caculation Model Of Reinforced Concrete Bending Members Under Freeze-Thaw Enviroment

This research is an important part of"Behavior and calculation model of concrete structures under freeze-thaw environment"which is sponsored by National Natural Science Foundation of China (item approved number: 50278025).By comparison of the simply-supported RC-beams which had received N=0, N=100, N=200, N=300 times freezing-thawing cycles, the paper based on material's properties of frost-resistant concrete structure and the calculation's method of the code for design of concrete structures has analyzed the influence of recycled freeze-thaw environment on simply-supported RC-beams. At the same time, the paper gives the formula of the ultimate bearing capacity's formula and the short term rigidity's formula which reflect the freeze-thaw parameters of concrete member.Also, the paper has got various performance indices of simply-supported RC-beams under recycle of freeze-thaw environment, including strength indices and stiffness indices such as maximum compression stress, maximum tensile stress as well as ultimate bear capacity, maximum central crosswise-displacement of the beam. The paper confirms reliability of the formula of the ultimate the flexural capacity of right section and the short term rigidity's formula which reflect the freeze-thaw parameters of concrete member.By analysis and comparison of the simply-supported RC-beams which had received N=0, N=100, N=200, N=300 times freeze-thaw cycles, we could bring the following conclusions: with the numerical increase of the freeze-thaw cycles, the ultimate flexural capacity of right section of the RC-member will slightly decline, the short term rigidity of the member will decrease under the same bending moment; since the compression strength will decline, the maximum reinforcement ration decline as well, so this paper gives a new definition of the range of the maximum percentage of steel of flexural RC-member under recycled freeze-thaw environment .This paper also gives some advice on the design of the flexural RC-member under recycled freeze-thaw environment.