Torsional instability of open thin-walled beams: Numerical and experimental investigation

The present thesis deals with the structural instability of axially compressed thin-walled beams with open cross-section. Experimental and numerical (FEM) results will be shown for cruciform section beams with stiffeners placed in different positions. Such stiffeners are represented by longitudinal plates, which connect the flanges on a beam portion, thus providing intermediate warping restrictions. This work is structured into five chapters. Chapter 1 is an introductory chapter in which the problem is framed and early studies are mentioned. Chapter 2 gives some remarks on the instability of thin-walled beams subject to compressive axial load. Chapter 3 presents the experimental set-up and the instrumentation used to investigate buckling, as well as the programs used for data acquisition and processing. Furthermore, this chapter describes the experimental campaign and the results obtained under two end warping constraint conditions, i.e. free and (partially) restrained warping. Chapter 4 is devoted to the numerical analyses. The numerical simulations were implemented in Lusas finite element code, and the results were compared with the experimental ones. Finally, chapter 5 presents some conclusive considerations regarding the results obtained.