Axial Compression Test And Bearing Capacity Calculation Of GFRP-tube Confined Concrete Columns

Glass fiber reinforced polymer(GFRP)tube is a new type of tube which is made of multiple strands of continuous fiber at a certain angle.It has the advantages of light weight,high strength,corrosion resistance,high temperature resistance,creep resistance and simple construction.In recent years,the research on recycled concrete has become a hot issue in the academic and engineering circles,the application of recycled concrete also greatly reduces the exploitation of natural aggregate,improves the utilization rate of resources,and has good economic and environmental benefits.GFRP-tube confined concrete column can not only effectively play the green environmental protection characteristics of recycled concrete,but also give full play to the mechanical properties of high-strength ordinary concrete.At the same time,the advantages of GFRP tube are fully utilized to improve the strength and durability of components.In order to investigate the axial compression behavior of GFRP-tube confined concrete columns,13 circular section specimens were designed,the main work is as follows:(1)The axial repeated compression tests were carried out on 6 specimens of high strength ordinary concrete columns with GFRP tubes,6 recycled concrete columns with GFRP tubes and 1 empty GFRP tube.The failure modes and failure processes,load displacement curves,characteristic loads and displacements,skeleton and stiffness degradation curves,load strain curves and load residual displacement curves were analyzed the variation law of axial bearing capacity and stiffness.(2)On the basis of experimental study,the axial bearing capacity is deduced according to the mechanical equilibrium condition by using the method of limit equilibrium theory,and the influence of recycled aggregate replacement rate on the axial compressive strength is considered,and the calculation formula of axial compressive bearing capacity is established.(3)The ABAQUS finite element analysis model is established to simulate the mechanical behavior of GFRP-tube confined concrete columns.The accuracy of the numerical model is verified by the coincidence between the simulation results and the test results.The damage characteristics and load displacement curves obtained from the simulation are in good agreement with the test results,which can provide theoretical support for similar analysis.Main conclusions:(1)Under repeated axial compression,the failure process and failure mode,load displacement curve,skeleton and stiffness degradation curve,load strain curve and load residual displacement curve of GFRP tube high-strength ordinary concrete column and GFRP tube recycled concrete column are similar.With the increase of specimen diameter,the axial compression bearing capacity and stiffness of each specimen gradually increase,and the ductility is better.(2)The axial bearing capacity of GFRP high-strength ordinary concrete column and GFRP recycled concrete column is 11.29 times and 7.39 times higher than that of GFRP empty tube under the same diameter,respectively.It shows that the internal concrete supports the external GFRP tube and prevents its instability.The two reinforce each other,which greatly improves the overall strength of the component.(3)Under the mutual restraint and support between GFRP tube and concrete,GFRP-tube confined concrete column has good elastic-plastic deformation ability,which makes the structure more safe and reliable.(4)The calculated value of the formula of bearing capacity of GFRP tube confined concrete column is about 0.6% variance with small dispersion and high consistency.The simulated value is in good agreement with the experimental value,and ABAQUS can simulate the mechanical behavior of GFRP tube concrete column more accurately.