ETUDE DE L’INFLUENCE DES PARAMETRES GEOMETRIQUES SUR LE COMPORTEMENT STRUCTUREL DES TUBES EN ACIER FORMES A FROID SOUMIS A DES SOLLICITATIONS MECANIQUES

Abstract

This work focuses on the study of the local buckling behavior of cold-formed thin profiles with irregular octagonal tubular cross-sections (IOctHS). Thanks to their unique geometric characteristics, these sections represent a promising alternative to conventional profiles due to their potential for improving structural performance. However, their complex geometry significantly influences their behavior with respect to local instability phenomena. The study involves the analysis of 124 sections subjected to various types of loading. Particular attention is paid to evaluating the local buckling coefficients associated with each loading case in order to: (i) better understand the influence of geometric parameters on the local buckling behavior of the studied sections; and (ii) propose analytical expressions for determining the critical local load, an essential parameter for evaluating the strength of cold-formed profiles using the direct strength method. Given the geometric complexity of IOctHS sections, conventional analytical formulations do not allow for sufficiently accurate estimation of the local buckling coefficients. A numerical approach was therefore adopted, based on calculating the critical loads of the cross-section using the CUFSM software. This tool relies on the classical finite strip method as well as the constrained finite strip method, allowing for the identification and differentiation of the various instability modes, particularly the local mode. It also offers a detailed evaluation of the elastic stability behavior of thin profiles, explicitly taking into account the interaction between the section geometry and the constituent walls. The results obtained highlight the influence of different loading conditions on the local buckling behavior of IOctHS sections and contribute to a better understanding of their structural response. They also provide a practical basis for the design of this new generation of cold-formed profiles.