Study On The Axial Compression Performance Of A Steel Tube-concrete-GFRP Tube Combination Column With Built-in T-beam

Fiber Reinforced Polymer（FRP）has many advantages,however,because FRP materials are linearly elastic,the ductility of GFRP pipe restrained concrete assemblies is poor and brittle damage is likely to occur.This problem has been solved by the use of built-in steel sections to increase the restraint effect on the central core concrete,thus maximising the properties of the GFRP pipe.Scholars at home and abroad have studied the mechanical properties of the combined steel-GFRP tube-concrete structure,but there is still a lack of research on the combined long central column.In this study,the steel section is welded to the middle of the built-in steel tube,and the concrete is poured between the two tubes with the built-in steel tube as the inner formwork and the GFRP tube as the outer formwork.Nine long hollow columns of the composite structure were set up for axial compression tests using the number of I-beams,the length to diameter ratio,the thickness of the GFRP pipe and the diameter of the built-in steel pipe as experimental variables.The damage pattern of the composite hollow column was observed,the working mechanism of the members was studied and the effect of each of the four experimental variables on the ultimate load carrying capacity and the corresponding bending deformation of the composite hollow column was analysed.Through the analysis of the force mechanism and material properties of the long column of steel tube-concrete-GFRP pipe composite with built-in steel sections,the ultimate load carrying capacity of the FRP pipe restrained concrete column with reinforced steel sections is calculated by co MParing the calculated values with the experimental values,the influence coefficients of the experimental variables are corrected,and finally the applicability of the coefficients in the equations is determined.The ultimate load capacity calculation formula for the steel tube-concrete-GFRP pipe combination with built-in steel sections is verified and the ultimate load capacity calculation formula for the steel tube-concrete-GFRP pipe combination with built-in steel sections is deriv...