Study On Axial Bearing Capacity Calculation Method And Axial Compression Performance Of FRP-CFST Composite Column

FRP-concrete filled steel tube(FRP-CFST)composite column is fabricated by pasting Fiber Reinforced Plastic(FRP)on the surface of concrete-filled steel tube(CFST).As a new kind of composite structure,FRP-CFST composite column has fully combined the capacity of both FRP tube and steel tube in confining the inner concrete,which makes it more likely to have high bearing capacity and be used as heavy-load column in high-rise/mega-high-rise buildings and long-span bridge structures.Besides,because of the characteristics of high strength-mass ratio,corrosion resistance,durability as well as convenient construction process,FRP can also be used to protect the damaged CFST columns and prolong their service life.Based on the comprehensive investigation on the related research status,This paper carries out the study and discussions on the axial bearing capacity calculation method and the axial compression performance of FRP-CFST composite column.The research methods and main work in this paper are as follows:(1)According to the existing experimental phenomena and analysis,a series of reasonable assumptions were firstly adopted,further,a unified formula calculating the axial bearing capacity of FRP-CFST was deduced by introducing the lateral pressure as a basic parameter.The unified formula equips a simple calculation procedure and a definite physical meaning,moreover,its applicability range is superior to those existing calculation methods.Comparisons between the calculation results and a total of 61 experimental data showed that the unified formula exhibits a higher calculation precision,which provides a reliable guidance for the design and theoretical analysis of FRP-CFST composite column.(2)By means of software ABAQUS,18 finite element(FEM)models were set up.The ultimate axial bearing capacity,the load-displacement curves as well as the failure modes were then compared between the models and the tests reported in literature.The comparisons showed that the modeling method proposed in this paper could simulate the bucking deformation of steel tube and the fracture distribution of FRP,also,the total of 18 load-displacement curves fit well with those in the experiments,which means that the modeling method mentioned in the paper can be applied to evaluating and analyzing the axial compression performance of FRP-CFST composite column.(3)The FEM modeling method verified above was employed to establish a total of 78 FRP-CFST composite column model.Firstly,the parameter influence on the axial compression performance of composite column were studied and the parameters include FRP layer,FRP type,concrete strength,steel yield strength and steel thickness;Secondly,in order to investigate the similarities and differences of the axial compression performance between the circular composite column and the square composite column,two typical composite columns were selected and stress analysis of each component were conducted during the whole loading process;Lastly,a simplified four-stage model for describing the whole loading process was put forward and the mechanical mechanism of each stage was expounded in detail,which will lay the foundation for elastic-plastic analysis for FRP-CFST composite structures.