Research On Mechanical Properties Of ECC-PVC Composite Concrete Columns Under Axial Compression And Eccentric Compression

With the advancement of economic and social development and construction,building structures are more complex and diverse,and people’s requirements for building performance are constantly improving.The concept of composite columns is proposed.Compared with traditional reinforced concrete columns,composite columns have better mechanical properties.Concrete-filled steel tube(CFST)column is a composite column formed by filling concrete into the steel tube.Due to its high strength and good ductility,the composite column has been widely studied and is a common form of composite members.However,the surface corrosion and fire resistance of concrete filled steel tube are still under study.In this paper,a new type of ECC-PVC pipe concrete composite column is proposed.Compared with steel pipe,PVC pipe can also provide certain binding force for core concrete.The corrosion resistance and aging resistance of PVC pipe make the composite column can be applied to some special environments,such as marine engineering,and PVC pipe can be used as a template to simplify the construction.ECC has good compressive toughness and fire resistance,and has a certain control effect on cracks.Outsourcing PVC pipes can also avoid direct contact with the outside world,and improve the durability of composite columns.The confinement of stirrups and PVC pipes at the same time improves the defect of limited binding force of PVC pipes to a certain extent.The following research is conducted:(1)Twelve ECC-PVC concrete composite short columns with different parameters were designed for axial compression test,and the influence of parameters on the mechanical properties of composite columns under axial compression was analyzed.The test results show that the ductility of composite columns can be improved by adding PVC pipes,increasing the longitudinal reinforcement ratio,reducing the stirrup spacing and increasing the thickness of PVC pipes.The internal PVC pipe will lead to the decrease of the bearing capacity of the composite column;PVC pipe thickness needs to be reasonably valued;The combination effect of ECC and PVC tube is better under axial compression.(2)Based on the ABAQUS finite element analysis software,a finite element model that is consistent with the test size and parameters is established to analyze the stress of each part of the concrete short column wrapped with ECC-PVC pipe during axial compression.The simulation results are compared with the experimental phenomena and data.It is found that the simulation results have small error with the experimental results,and the simulation has certain accuracy.The stress provided by PVC pipe is small,and it gradually plays a role in the decline of bearing capacity.Some suggestions for improvement are put forward.(3)Ten ECC-PVC concrete composite columns with different parameters were designed for eccentric compression test.The effects of PVC pipe diameter,PVC pipe wall thickness,eccentricity,longitudinal reinforcement ratio,stirrup spacing,and internal and external concrete on the eccentric compression mechanical properties of composite columns were analyzed.With the increase of eccentricity,the specimen changed from large eccentric failure to large eccentric failure.It was found in the test that PVA fiber in ECC delayed the development of cracks,and the ECC specimen remained certain integrity at the end of the test,and the external ECC dropped less.Compared with axial compression,the bonding effect between PVC pipe and concrete is poor under eccentric compression.(4)Based on ABAQUS finite element analysis software,the stress of each part in the eccentric compression process of ECC-PVC pipe concrete composite column was analyzed,and the simulation results were compared with the experimental phenomena and data.Due to the influence of eccentricity,there is a certain error between the simulation results and the experimental data.The stress analysis conforms to the conclusion of the eccentric compression test.The failure of internal and external concrete under eccentric compression is not synchronized,and suggestions for improvement are put forward.