Elastodynamic analysis of damaged open thin-walled beams subjected to axial load

Thin-walled beams are widely used in many areas of engineering. As it is known, the low torsional stiffness and the eventual non-coincidence of the shear centre and centroid of the cross-section, make compressed thin-walled open profiles vulnerable to torsional and flexural-torsional buckling. Moreover, in real-world applications, critical loads are affected by initial imperfections, which generally have a significant influence. In previous studies [1-6], we have investigated numerically and experimentally on the effects of non-trivial equilibrium paths and warping constraints in thin-walled open profiles subjected to axial load. In particular, we compared the results obtained by a numerical in-house code to those found in the lab, for some remarkable cases of beams with two axes of symmetry [5,6]. Indeed, the code is based on a finite difference procedure where a direct one-dimensional model of standard beam is enriched with a coarse descriptor of warping, and stability is analyzed in a dynamic setting, including the geometric nonlinearity of the pre-critical equilibrium path [1-3]. In the present contribution, we extend the previous investigations by including the effects of a localized damage, i.e., a sharp variation of a cross-section, which reduces the global stiffness of the beam, therefore affecting the buckling load and the natural frequencies.