Experimental Study And Finite Element Analysis On Bending Properties Of Reinforced Concrete Beams At Cryogenic Temperatures

This dissertation is the sub-project of the Natural Science Foundation project（51078260）‘Material Properties of Reinforced Concrete at Cryogenic Temperature’.In this paper, experimental study and finite element analysis on the flexuralperformance of reinforced concrete beam under cryogenic environment had beenresearched.The experiments shall be conducted at cryogenic temperatures. According to thisrequirement, the specimens were cooled down by cryogenic temperature cold storageand tested in a self-design cryogenic environment box. In addition, the finite elementanalysis was carried out on the basis of material constitutive relation at lowtemperature. Relevant researches are as follows:1. On the data of cooling equipment, cryogenic temperature cold storage,self-design cryogenic environment box and loading equipment in Structure TestingLaboratory of Tianjin University were chosen for the testing.2. Considering the influence of different parameters such as temperature andreinforcement ratio,12reinforced concrete beam specimens in3groups divided ondifferent reinforcement ratios were tested at0℃,-40℃,-70℃and-100℃toanalysis the different failure characteristics and flexural performances. In addition,another test on the reinforced concrete beam after freezing and thawing twice at-100℃was carried out, and corresponding suggestions had been advised.3. Analyzed the material constitutive relations, established a reasonable finiteelement model, and made reasonable adjustments to fit test results. Finite elementanalysis with variable parameters was take out to find the regularity of test results.The following are the conclusions obtained from this research:1. The cracking space of beams with low reinforcement ratio is getting biggeras the temperature decreases, while the beams with high reinforcement ratio have asmaller cracking space. And the appropriate reinforcement range of beams is gettinghigher at low temperatures.2. The cracking load, yield load and ultimate load increase at low temperatures,the yield load increases more than ultimate load, and the beams getting more brittle.The improvements of bearing capacity have a small difference with different concreteand reinforcement ratios.3. The rigidity and brittleness of beams with low grade of concrete improvemore at low temperature. At cryogenic temperature, the brittleness of beams withdifferent grades of concrete is almost the same. And the improvement of yield loadand ultimate load are determined by the strength of steel in low temperature.4. At low temperature, the plane cross-section assumption still sets up. And thecracking load and yield load can also be calculated by the standard formula afterconsidering the temperature effect of material. Though the brittleness of beams at lowtemperature has certain fluctuations, the result of deflection still has certain referencesignificance.5. The results of finite element analysis on the basis of material constitutive relation at low temperature have good fitting with the experimental results, but theresearch about material constitutive relation should be more deeply to provide morereasonable parameters.