Determination of ultimate load for centrally compressed concrete filled steel tubular columns based on the deformation theory of concrete plasticity
The article presents the derivation of the resolving equations for calculating centrally compressed concrete filled steel tubular columns of circular cross-section taking into account the effect of lateral compression and physical nonlinearity. When deriving the resolving equations, forced deformations are also taken into account, which may include creep deformations, shrinkage, and temperature deformations. Finally, the problem is reduced to a system of three equations with three unknowns for the contact pressure between the shell and the concrete core p and stresses along z in concrete and steel. As equations establishing the relationship between stresses and instantaneous deformations, the relations of the deformation theory of concrete plasticity by G.A. Geniev are used, in which dilatational deformations of concrete are taken into account. The developed technique is implemented in the Matlab environment and tested on the experimental data of A.I. Sagadatov. The agreement between experiment and theory is good enough. The constructed model is based on the most general relations of solid mechanics and is free of empirical coefficients.