Mechanical Behavior Of Rectangular GFRP-tube Confined Recycled Aggregate Concrete Columns Under Axial Compression

To alleviate the pressure of exploiting natural resources and realize the recycling of construction waste,the waste concrete blocks can be broken into recycled coarse aggregates(RCAs)which can be used to produce recycled aggregate concrete(RAC),achieving green sustainable development and environmental protection.However,the existing research shows that the reuse of RCAs could deteriorate the structural performance of members,which limits the application and development of RAC.Fiber-reinforced polymer(FRP)has the advantages of lightweight,high strength,and high fatigue resistance.The combination of FRP and concrete can give full play to their respective advantages.This paper takes the rectangular recycled concrete column confined by a glass fiber reinforced polymer(GFRP)tube as research object.The composite column is composed of GFRP tube and RAC filled in this tube.The GFRP tube provides confinement to core concrete which in turn possesses improved compressive strength and deformation performance.This paper studies and summarizes the mechanical behavior of rectangular GFRP-tube confined RAC columns under axial compression using experimental study,theoretical derivation,and numerical analysis:1.The axial compression test on 16 rectangular GFRP-tube confined recycled aggregate concrete columns was conducted with the effects of layers of GFRP tube,replacement ratio of RCA,section height/width ratio,and loading mode investigated.Besides,standard tests on the material properties GFRP flat plate and RAC with different replacement ratios of RCA were also conducted;2.Based on existing test data,the theoretical calculation model of the load-carrying capacity of rectangular GFRP-tube confined RAC columns was derived,and the theoretical calculation results were compared with the test results to verify its applicability;3.ABAQUS finite element model was established,and the analysis results were compared with the test results to verify such model.Then,the internal stress of said column was analyzed by finite element analysis,and the effect of GFRP tube confinement on the internal stress of core concrete was studied.Finally,parameter analysis was carried out by using the verified finite element model to study the influence of GFRP confining stiffness,chamfer radius,and section height/width ratio.The results show that,compared with unconfined concrete columns,rectangular GFRP-tube confined RAC columns have higher strength and better ductility.Besides,it is found that the replacement ratio of RCA and the section height/width ratio influenced the load-carrying capacity of said columns but the loading mode had little effect on that.