Study On The Axial Compression Performance Of GFRP Tube Concrete Composite Columns Subjected To Freezing And Thawing

With the development of major infrastructure such as municipal engineering,water conservancy,ecology,transportation and pipelines in the engineering field,the durability of concrete has become a factor that needs to be considered in engineering constru ction.GFRP pipes have good durability and can play a role in concrete structures.To better protection.Facing cold regions such as the northwest and northeast,the structural performance of GFRP pipe concrete is greatly affected by temperature changes.Temperature has direct and indirect freeze-thaw effects on GFRP and concrete,resulting in huge changes in the overall structural performance.Therefore,considering the effect of freeze-thaw on GFRP The influence of tube-concrete structure and the study of static performance of GFRP tube-concrete compression members under freeze-thaw action are of great significance to project construction and maintenance.This article is to study the effect of freeze-thaw cycles on the static performance of GFRP pipe concrete compression members.Through static axial compression tests,50 indoor freeze-thaw cycle tests and finite element simulation analysis methods are used to analyze the static performance of GFRP pipe concrete compression members.Based on the influence o f GFRP pipe concrete components,the axial compression bearing capacity formula after freeze-thaw cycle deterioration is modified based on theory.The main work is as follows:1.Indoor test of GFRP pipe concrete components.The experimental design of 6 GFRP pipe concrete compression members,through 50 freeze-thaw cycle degradation tests on 3 of them,and carry out corresponding axial pressure tests on them,compare with the members under standard curing conditions,and provide experimental data Form verification with finite element simulation;2.Establish a finite element model of 48 GFRP pipe concrete compression members,one of which comes from the experiment of others,two from the experiment of this article,and the other 45 are used to analyze the effects of different freeze-thaw cycles of 0,25,50,75,and100.The influence of different concrete strength,GFRP pipe thickness,fiber layer angle and reinforcement ratio on the axial compression performance of structural members;3.Combining the results of finite element analysis,analyze the variation law of the axial compression bearing capacity of the GFRP tube concrete compression member,and introduce the attenuation coefficient to modify the axial compression bearing capacity formula of the member after the freeze-thaw cycle deterioration.Research indicates:1.After 50 indoor freeze-thaw cycle tests,the axial load bearing capacity of structural members is reduced by 4.92%,the axial displacement is increased by 1.93,and the hoop and axial peak strains are reduced by 18.2%and 6.27%,respectively.2.The ultimate bearing capacity of concrete members of different strength grades after100 freeze-thaw deterioration decreased by 19.43%,18.67%and 15.85%;the ultimate bearing capacity of different GFRP pipe thickness members after 100 freeze-thaw deterioration decreased by 18.67%,18.38%and 18.14%;the ultimate bearing capacity of components with different fiber layer angles after 100 freeze-thaw deterioration decreased by 18.67%,21.00%,and 21.76%;the ultimate bearing capacity of members with different reinforcement ratios after 100 freeze-thaw deterioration Reduced by 19.03%,18.67%and 16.10%.3.Analyze the influence of the change of the ultimate bearing capacity of the component under the action of multiple factors,from large to small,in order of GFRP pipe thickness,concrete strength,fiber layer angle,reinforcement ratio,and freeze-thaw cycle times.It can be seen that GFRP has better protection for structural components.effect.Through the finite element analysis value,because different parameters have different influences on the attenuation coefficient K_us of freezing and thawing,the attenuation coefficient K_us is introduced to modify the bearing capacity formula after freezing and thawing,and the theoretical value is in good agreement with the analysis value.