Experimental And Theoretical Study On The Axial Compression Performance Of Renforced Concrete Columns Reinfored By FRP Grid/ECC Composite FRP

The long-term use of reinforced concrete structures is affected by many factors.When the structural performance cannot meet the requirements of the specification,structural reinforcement and repair is the most economical solution.Carrying out research on structural reinforcement is conducive to the renovation and restoration of old buildings.In recent years,the application of fiber woven mesh reinforced ECC composites in the field of structural reinforcement provides a new method for solving structural reinforcement in complex environments.Related research in this area has attracted widespread attention.In order to explore the reinforcement effect of fiber woven mesh reinforced ECC composites to strengthen reinforced concrete columns,this study takes common reinforced concrete square columns as the reinforcement object,and conducts experiments and theoretical studies on the axial compression performance of FRP mesh reinforced ECC reinforced concrete square columns.The research is as follows:(1)Carry out FRP grid reinforced ECC(abbreviation: FRP-ECC)composite material tensile performance test,mainly considering the influence of ECC thickness,grid type,grid layer number,interface treatment and other factors on the tensile performance of FRP-ECC material.The test shows that: FRP mesh and ECC base layer have better adhesion;compared with ECC tensile specimens,the tensile strength of FRP-ECC specimens is greatly improved;in FRP-ECC materials,the thickness of the substrate ECC affects the specimens Cracking load;the increase in the number of grid layers will increase the tensile strength of the specimen,but the increase will gradually decrease;the tensile performance of CFRP-ECC material is better than that of BFRP-ECC material;the interface sand treatment of FRP grid can be Improve the tensile properties of FRP-ECC.(2)Carry out theoretical analysis on the tensile test of FRP-ECC composite material,establish FRP-ECC stress-strain constitutive model and tensile strength calculation model.The comparison between the theoretical value and the experimental value shows that the theoretical stress-strain curve is basically consistent with the experimental stress-strain curve,and the calculated theoretical strength is in good agreement with the experimental value.(3)Conduct the axial compression performance test of FRP-ECC composite reinforced reinforced concrete square columns.Mainly consider the reinforcement effect of FRP grid layers,chamfer radius,slenderness ratio,age and other parameters on concrete square columns.The test shows that,in addition to the accidental brittle failure of the plain concrete column,the other specimens are ductile failure;compared with the control group,the ultimate load and vertical deformation capacity of the reinforced column are significantly improved;with the increase of the FRP grid,the reinforced column The load-bearing capacity is increasing,but the increase is decreasing;the opening of the chamfer radius reinforcement layer has better restraint on the core concrete,and the reinforcement effect is more obvious;this experiment shows that the change of the slenderness ratio has a weak effect on the reinforcement effect;FRP-ECC reinforcement In the range of layer curing age ≤ 28 days,the longer the curing age,the greater the increase in bearing capacity,but the increase gradually decreases.(4)Deduction of the axial compression theory of FRP grid reinforced ECC composite reinforced concrete square columns.Based on the experimental data,the strength model proposed by Richart was revised,the FRP-ECC confined concrete square column axial compression strength prediction model was proposed,and the FRP-ECC reinforced concrete square column ultimate bearing capacity calculation model was established according to the superposition theory.Comparing the calculated value of the proposed theoretical model with the experimental value,the analysis shows that the calculated value of the proposed theoretical model is in good agreement with the experimental value,and can predict the ultimate bearing capacity of FRP-ECC confined reinforced concrete square columns.