Research On Calculation Methods Of Normal Section Bearing Capacity Of Reinforced Concrete Under Freeze-thaw Cycles

As the dominant structure for the basic infrastructure construction in China, concrete structure has been extensively used in many fields. For our country has a vast territory, as well as the development of times, the service environment of concrete structures has become increasingly complex, and the damaging effects on concrete durability is also increasingly complex. Among these damages, the most common one is freeze-thaw damage. Therefore, the study of mechanical properties and deformation performance of concrete in freeze-thaw environment has very important significance to make full use of material strength, enhance the level of design and reduce project cost.As the sequential part of National Natural Science Foundation Project (grant number: 50978224) "Research about Mechanical Performance of Reinforced Concrete and Prestressed Concrete under Freeze-thaw Cycles", this paper carries out test study on the examining the tensile behavior and the compression performance of concrete under freeze-thaw cycles. The main contents of the work are as follows:1. Analyzed the stress-strain curve in compression under freeze-thaw cycles, established the empirical formula with stress and strain in compression and the strength grades of concrete and cycle time of freeze-thaw, and then compared with the measured results. The calculation results show good agreement with the experiments;2. Analyzed the stress-strain curve in tension under freeze-thaw cycles, established the empirical formula with stress and strain in tension and the strength grades of concrete and cycle time of freeze-thaw, and then compared with the measured results. The calculation results show good agreement with the experiments;3. Based on these, considering the establish method for equivalent rectangular stress block of concrete, obtain the modified formula about stress coefficient, which takes into account cycle time of freeze-thaw. Then calculate normal section bending bearing capacity M of beams and normal section compressive bearing capacity Nof columns using the calculation method of normal section bearing capacity of "Concrete Structure Design Code" (GB/T 50010-2010). Compared and analyzed with the experimental results, the calculation results show good agreement with them.The results show that the calculated results using the analysis methods above agree well with experimental results. The calculation formula of normal section bearing capacity considering cycle time of freeze-thaw can effectively forecast the failure in normal cross section.