Nonlinear deformation model in the analysis of eccentri-cally compressed concrete-filled steel tube elements

This paper discusses the applicability of a nonlinear deformation model for determining the parameters of the stress-strain state of eccentrically compressed concrete-filled steel tube elements. Adjustments to the deformation diagrams of the concrete core and the steel tube were introduced to account for the complex stress state of the materials. The cross-section of the concretefilled steel tube element is considered as a collection of elementary areas. As the criterion for calculating compressive resistance at the ultimate strength stage, it is proposed to use the maximum force calculated based on the compatibility condition of steel and concrete deformations. The advantage of this criterion is that it eliminates the need to normalize the ultimate compressibility of concrete and accounts for the high degree of force redistribution in cross-sections. The method was verified by comparing the calculated and experimentally obtained ultimate forces on a sample of experimental data. The applicability of the nonlinear deformation model based on deformation diagrams, considering the multiaxial stress state of concrete and the steel tube, was confirmed for the analysis of eccentrically compressed concrete-filled steel tube elements.