Study Of Flexural Bearing Capacity Of Normal Section Of Frost Reinforced Concrete Beams

Study on the damage mechanism and the structural performance of existing concrete structures under freezing and thawing environment is an important aspect of durability of concrete structures. The long-term environmental effects caused by freezing and thawing is not only resulting in degradation of the mechanical properties of the concrete itself, but also causing degradation of bond performance between steel and concrete, which will undoubtedly lead to the changes in the bearing performance of concrete structure. It can reveal potential dangers of existing concrete structures and provide decision on both the safety control and maintenance and reinforcement of existing concrete structures to carry out the research on the deterioration of existing concrete structural performance under freezing and thawing environment.Based on the previous test results of the mechanical properties of freezing concrete and statistical analysis, this paper regarded the relative compressive strength as the basic parameters and gives the relationship between the changes of mechanical properties of freezing concrete and the relative compressive strength,such as peak compressive strain,ultimate tensile stress, peak tensile strain. And on this basis, a suggestion of the freezing concrete compressive stress- strain curve equation and tensile stress- strain curve equation is gived. Based on the experimental study on the bond property between the freezing concrete and deformed bars, the paper analysis the effect of freeze-thaw on the bond behavior between the reinforcement and concrete, and gives the bond-slip curve equation between reinforcement and concrete.Considering the degradation of mechanical properties of concrete and deterioration of bond properties between reinforcement and concrete, this paper analyzed the frostreinforced concrete simply supported beam. The results of finite element analysis show that strain of reinforcement and strain of concrete in the mid-span section of frost reinforced concrete beam can still meet the plane section assumption; and with the increasing damage of frost beam, the stiffness and load capacity of frost RC beam decreases. The effect of the degradation of bond properties between between reinforcement and concrete on flexural bearing capacity and stiffness of frost reinforced concrete simply supported beams is small.Based on the mechanical model of freezing concrete and the finite element analysis,the paper gives the relationship between the limit of relative compression zone height and the maximum reinforcement ratio of frost RC beam and the degree of freezing damage, and finally establishes a theoretical formula of flexural bearing capacity of normal section of the frost reinforced concrete beams.