Study On Axial Bearing Capacity Of Confined Concrete Filled CFRP Steel Tube

Concrete filled CFRP steel tube is a structure derived from concrete-filled steel tube.The composite material structure is based of core concrete,steel tube and CFRP,which use carbon fiber cloth wrapped around the outside of the concrete.Compared with the traditional concrete-filled steel tube,CFRP has a higher load-carrying capacity due to the constraint of CFRP.Considering advantages of concrete-filled steel tube and CFRP,the composite system has advantages of high strength,good ductility,light weight and corrosion resistance.Meanwhile,confined concrete filled CFRP steel tube whose good concrete performance is destined to have a better future in engineering application.The influence of structural mechanics of different load forms is very different,for CFRP steel tubular concrete column structure,load is mostly two forms,namely(A type)axial pressure by the steel tube and the core of the common commitment of concrete or(B type)only load on the core concrete.The research on the former is more,this article focuses on the axial load only acting on the core concrete(B type),because CFRP and steel tube only play a role in the constraints known as "confined concrete filled CFRP steel tube".Based on the existing research work,the axial compression mechanics performance of confined concrete short columns filled CFRP steel tube is deeply studied by experimental test,theoretical analysis and finite element numerical simulation respectively.The main contents of this paper are as follows:(1)This text has done six groups of confined concrete short columns filled CFRP steel tube under B-type axial compression test and two groups of A and B axial compression tests,each group of three specimens.The layer number of wound CFRP is 0,1 and 2,respectively.Through observing and analyzing 24 specimens and failure modes.The failure process of members is analyzed by material parameters,strain analysis and load-axial displacement curves.Thus,I study the effects of three kinds of materials on the axial bearing capacity and ductility coefficient and analyze B-loading mode advantage through A-type,B-type comparative test.(2)Through analysis of test phenomena and failure modes,it is found that CFRP improves the instability of the internal force distribution in the core concrete,compressive strength and overall stiffness of specimens.The influence of concrete,steel tube thickness and CFRP thickness on the ultimate bearing capacity is analyzed by bar chart.Based on the experimental data,confined concrete short columns filled CFRP steel tube are respectively drawn under the B-type axial compression loading models,I draw the relationship curves of the bearing capacity increasing coefficient SI,diameter to thickness radio D/t,steel tube restraint effect coefficient ls,CFRP restraint effect coefficient lf,and ductility coefficient DI-ls,DI-lf.The results of analysis show that increase of bearing capacity depends on lf,and ductility of the structure is affected by both steel tube and CFRP.(3)Through linear regression and multiple regression of experimental data,I can get restraint model between bearing capacity increase coefficient and restraint coefficient,and the calculated expression of confined concrete short column filled CFRP steel tube under different concrete strength conditions.Based on reasonable assumption of CFRP,steel tube and core concrete under ultimate bearing capacity in stress condition.By means of limit equilibrium method to get ultimate load-carrying expression of confined concrete short column filled CFRP steel tube under B-type.(4)In order to make up for the deficiency of number of test components,finite element software ABAQUS is used to simulate all test components and analyze stress cloud,circumferential displacement,global stress cloud,material parameters and load-axial displacement curve.