The article discusses a method for taking into account the compression of concrete using standard formulas when calculating using an inverse numerical-analytical method, taking into account the actual rigidity of concrete filled steel tube elements. The inverse numerical-analytical method makes it possible to calculate concrete filled steel tube elements for strength and stability under eccentric compression. Dependencies are presented showing the possibility of taking compression into account at various eccentricities and flexibility.

Keywords: concrete filled steel tube elements, CFST, inverse numerical analytical method, nonlinear deformation model, concrete compression,concrete filled steel tube column, eccentric compression

A step-by-step finite element method calculation algorithm of concrete filled steel tubes is provided with an example. A comparison of the finite element calculation results with experimental data, calculations according to Russian (SP266.13 25800.2016) and European standards (Eurocode 4) and the “inverse” numerical-analytical method, which takes into account the actual rigidity of sections, is given as well. The study shows an accuracy of the proposed finite element model using Drucker-Prager model for concrete and the “inverse” numerical-analytical method in comparison with standard calculation methods.

Keywords: finite element method, concrete filled steel tubes, Drucker-Prager model, “inverse” numerical-analytical method, eccentric load