Analysis Of Post-cast Horizontal Concrete Filled Steel Tubular Compression-bending Members

Concrete filled steel tubular(CFST) is usually defined as the member formed by filling concrete into the steel tubular and taking advatage of two materials. It posesses high bearing capacity, high plasticity and good ductility, convenient construction, good fireproof performance, as well as good economic effect. Therefore they are widely used in engineering structures at home and abroad.As to large-span structures, CFST members are usually used horizontally or at slant,enormous initial stress and intial defleciton have been produced in steel tubular by the weight of liquid concrete and steel tubular before concrete final setting and forming strength because of large span of the CFST member and construction procedure. So the constuction procedure seems to affect later period bearing capacity of the member.Firstly, on the basis of numerous domestic and foreign references, the stress-strain relationships of steel tubular and core concrete is introduced and the bond-slip relationship between steel tubular and core concrete is also discussed. Then select and confirm the stress-strain relationships of steel tubular and core concrete and the bond-slip relationship between steel tubular and core concrete.Secondly, axial compression capability experimentation of vertical CFST members is simulated and analysised by nonlinear finite element method using ABAQUS6.10 whose results compare with experimental values in reference. The accuracy and applicability of the stress-strain relationship and the bond-slip model used in the paper are verified.Thirdly, according to technical specification for concrete-filled steel tubular structures(CECS 28:2012), the effect of construction procedure on bearing capacity of horizontal CFST members is researched by three parameters(L/D, D/t and e/r), and the bearing capacity value considering construction procedure is compared with the bearing capacity without considering construction procedure, then the reduction factors of axial compression and eccentric compression members are figured out and simple calculation formulas of the reduciton factors are educed with mathematics regress analysis using visual graphic data processing software Oringin8.5, afterwards the carrying capacity calculation formula of horizontal CFST compression-bending members considering construction procedure is brought forward to provide reference for actual project.