Stability of Tubular Steel Structures

This subject becomes topical following a rapid evolution of design procedures for slender structures used widely in the temporary installations, where their stability lie in the internal stiffness of their members. This work concerns the study of buckling and lateral torsional buckling, taking into account, different types of imperfections. New buckling curves and associated imperfection factors are proposed. These curves are obtained by imposing an initial deformed representing the geometrical and mechanical defects. The experimental results showed that the values of the imperfections in the literature are extremely exaggerated. The values advocated in this work could be of interest for a possible adjustment of the European buckling curves for this type of structure. Regarding the lateral instability, an original methodology in real scale tests of trusses consist of tubular elements was also developed. The developed loading system of "free wheels" allows releasing the point of application of the force from the beginning of instability. This technique permit to record more accurate measurement of critical moments that make the lateral torsional buckling.