Implementation of buckling in the simplified method of EC4-1-1 for CFT sections

Abstract

Eurocode 4 about composite structures proposes a simplified method to design concrete-filled tube sections subjected to combined compression andbi-axial bending, as an alternative to the general one. This method is based on determining the validity of a section by comparing the acting forceswith the interaction curve N–M. In order to take slenderness into account, a reduction factor χ is defined, leading to a reduction of the compressionand bending strength. This text proposes a new approach based on the simplified method mentioned above, thought to provide designers a fasterand simpler checking and designing method for this typology of sections, including also buckling effects. With this purpose, a polynomial function is proposed depending on five known parameters: χ, χ_d, χ_pm,r and μ_max, for which a new formulation is presented.