ANALYSIS OF COMPRESSIVE ELASITIC MODULUS OF HOLLOW COMPOSITE CFST COLUMN

A hollow composite CFST (concrete-filled steel tube) is divided into three parts: a concrete core, an inner steel tube and an outer steel tube. As a pseudo planar problem, it was analyzed by an elastic axisymmetrical method. By means of the theorem of the stationary value of potential energy, the elasticity theory analysis of an infinitesimal deformation was performed for the hollow composite CFST column. The theoretical formulas of confinement coefficients, and the composite compressive elastic modulus were gained, and the formulas can actually and reliably describe the elasticity behaviors and the confinement mechanism of the composite column. Analytical results indicate that the composite axial elastic modulus is influenced by the Poisson’s ratio not only of the concrete core but also of the steel tube, and it is also changed with the confinement force between the concrete and steel tube. The composite axial elastic modulus increased linearly as the steel ratio improves. The stress distribution ratios of the concrete core, inner steel tube and outer steel tube were discussed, which was not determined by uniaxial elastic modulus.