Study On Mechanical Behavior Of Concrete-Filled Square Steel Middle-long And Long Columns With Inner CFRP I-shaped Profiles Under Axial Compression

In recent years,with the rapid development of economy and technology in China,has been the biggest civil engineering construction and development,the height of the building,the top and large span buildings full of beautiful things in eyes.Supplement four structure,composite structure arises at the historic moment.In FRP and combination of CFST column structure at home and abroad,on the basis of professor Guochang L first put forward the new type of structural form,built-in i-section CFRP material of square concrete filled steel tube composite column.This paper mainly studies the built-in i-section CFRP material repaired concrete-filled rectangular steel tubular long columns and long columns axial compression mechanical properties.In the concrete filled square steel tubes in placing i-section CFRP material,through,concrete filled square steel tubes and the synergy of CFRP I-section profiles,to reach the bearing capacity and ductility of the columns,to decrease the size of the cross section of pillars.Based on nonlinear finite element software ABAQUS,the use of reasonable steel,concrete,I-section CFRP material constitutive relation model,in 17 built-in I-section CFRP material of square concrete filled steel tube long column axial compression artifacts on finite element analysis of the load-displacement curve of typical components are analyzed,the working mechanism of the stress of the typical long columns and long columns,studied at the different stages of the load,concrete filled square steel tubes and the ratio of CFRP I-section profile bear vertical load,as well as the cross section in the distribution of stress and strain of different parts are analyzed.With ordinary concrete filled steel tubular short column do contrast research for reference,analysis of component failure mode and after joining CFRP I-section profiles on the mechanical behavior of components.And the combination of the column of steel tube and core concrete stress and strain in the whole process of analysis,and analysis of the damage of CFRP I-section profile in the whole loading process failure.Also analysis the different steel yield strength and concrete strength,steel ratio,CFRP reinforcement ratio and slenderness ratio on the load-displacement curve and ultimate bearing capacity of the medium long column.According to the calculation result shows that the higher the concrete strength,ultimate bearing capacity,the more obvious increase.CFRP profile reinforcement ratio improve significantly raise the bearing capacity of components,and make the strengthening component load-displacement curve phenomenon more and more obvious.Steel content change influence on the ultimate bearing capacity and ductility is relatively obvious,the bigger the steel ratio,the bearing capacity of components increase,the more obvious,and the ductility is a trend of increase.Steel yield strength for little effects on the initial stiffness and ductility of the composite column,for the ultimate bearing capacity and greater influence on the residual bearing capacity,with the improvement of steel strength,bearing capacity increases gradually,but the growth rate is reduced.Built-in i-section CFRP ultimate load profile of the medium long concrete filled steel tube column force decreases with the increase of slenderness ratio is obvious,and so on.Based on nonlinear finite element software ABAQUS,the use of reasonable steel,concrete,I-section CFRP material constitutive relation model,for 18 built-in I-section CFRP material of square concrete filled steel tube long column axial compression artifacts in finite element analysis and calculation of the typical long column load-span deflection curves and analysis of the working mechanism of long column.By different CFRP reinforcement ratio effect on mechanical properties of axial compression column structure analysis,get the corresponding component of the load-contrast midspan deflection curve,analysis the built-in I-section CFRP profiles of the ultimate bearing capacity of the repaired concrete-filled rectangular steel tubular axial compression column with CFRP reinforcement ratio increases,the load of different slenderness ratio components-span deflection contrast curve,analyses the influences on the mechanical behavior of components,it is concluded that with the increase of slenderness ratio components limited bearing capacity of a downward trend.Slenderness ratio on fracture load of the specimens has more obvious effect.Analysis based on the finite element calculation of N-?,it is concluded that the built-in I-section CFRP material of square steel tube long column of the elastic buckling of concrete axial compression bounds slenderness ratio,and compared with the theoretical calculation value,and explains its availability.Through a large number of finite element calculation data regression analysis,it is concluded that the built-in I-section CFRP material of square concrete-filled steel tube the stability factor of axially compressed medium long column with long column,the built-in i-section CFRP material of square concrete filled steel tubular axial compression short column on the basis of the calculation formula of bearing capacity,with I-section CFRP profiles of axially compressed medium long concrete-filled steel tube column and the stability of the long column bearing capacity calculation formula,and apply theory verification.