Experimental Investigation Of The Cfrp-super Thin-wall Round Steel Tube Concrete Axial Compression Short Column

CFRP-concrete filled round steel tubular column, derived from concrete filled round steel tubular column, is a kind of composite structure combined by three materials by using the CFRP past on the peripheral of the concrete filled round steel tubular column.The concrete filled steel tubular column possesses good performance on mechanical and construction. The CFRP possesses the characters of high strength, light weight and tensile. Composed the advantages of the concrete filled round steel tubular column and CFRP, the carbon fiber concrete filled steel tube formed by pasting the CFRP on the surface of the steel tubular, possesses the characters of high strength, low steel consumption and light weight, and can partly solve the problem of corrosion of steel pipe and FRP tube plastic is poorer. In recent years, as the component with circular crosses section possesses good mechanical property, research on the CFRP-concrete filled round steel tubular column is becoming in-depth; the application prospect is very vast.The diameter-thick ratio of steel tubular is an important factor which affects the mechanical and economic performance of the concrete filled steel tubular column. The standard CECS28:2012, AIJ-1997, ACI318-05, CECS159-2004, DBJ13-51-2010all set a max diameter-thick ratio design value for the steel tubular. The diameter-thick ratio of steel tubular is also an important factor for the bearing capacity of the CFRP-concrete filled steel tubular column, but there is no project standard and discipline for the CFRP-concrete filled steel tubular column at present. Relevant scholars always set the diameter-thick ratio as30-120when researching the mechanical properties of the CFRP-concrete filled round steel tubular column, it is extremely necessary to research for the CFRP-concrete filled steel tubular column which with the diameter-thick ratio of steel tubular on120. Except that, on the angle of the ferrule index, the test specimens’ferrule index on present mostly dominated by the steel tubular, the CFRP work as auxiliary. The test specimens’ferrule index dominated by the CFRP is rare. Based on the two aspects above, to seek for the practical and integrity of the research on this subject, this paper have had the static test of9axial compression short columns which with the diameter-thick ratio span from124to185, research on the axial compression performance of the CFRP- concrete filled round steel tubular column which with the ferrule index dominated by the CFRP, and big diameter-thick ratio of steel tubular.This paper carried out the following several aspects:(1) Through the axial compression test of the9CFRP-concrete filled round steel tubular columns, which involve3groups differentiate by the diameter-thick ratio of the steel pipe as124,158and185, each group contains3specimens with the CFRP layers differentiate by0,1, and2, we observe and analysis the difference between the failure model of the specimens, analysis the failure process of the specimens by the load-displacement curve of short column and the load-strain curve of the steel pipe and CFRP, research the different effect on ductility and bearing capacity of the short columns from the two kinds of materials.(2) Through multiple regressions of experimental data, we get the plane relational model of the coefficient of concrete strength increase and confinement index of the short column, and deduce the calculation formula for the bearing capacity of CFRP-super thin-wall round steel tube concrete short columns on axis pressure; Base on a reasonable assumption of stress state of the CFRP tube, steel tube and core concrete on ultimate load, deduce the calculation formula for the bearing capacity of CFRP-super thin-wall round steel tube concrete short columns through limit equilibrium method.(3) On the basis of test data, we draw the curve of coefficient of axial compression bearing capacity increase SI between diameter-thick ratios D/t, ferrule indicators of steel pipe (ξs) and CFRP (ξf), and the curve of ductility coefficient DI between ξs and ξf· Ana lysis result indicates that the bearing capacity increase mainly depends on factor ξf· The ductility of the specimens dual effected by the CFRP and the steel pipe, the ductility coefficient range a parabola relationship with the ξs in0.24-0.37, range a linear relationship with the ξf in0-1.0; the ductility of the specimens is the best when the D/t is about160(235/fy).(4) In order to make up for the drawback of insufficient of the test specimens, this paper simulates all the test specimens through the ANSYS program, analysis the mechanical process and state of stress and strain, the simulation result can match well with the test result.