On the behaviour, failure and direct strength design of thin-walled steel structural systems

•Elastic buckling behaviour of thin-walled steel continuous beams and simple frames.•Determination and interpretation of the dominant buckling mode nature of structural systems.•Post-buckling, ultimate strength and failure of elastic–plastic thin-walled steel structural systems.•Numerical results for lipped channel continuous beams and simple frames with various cross-sections.•Preliminary development and assessment of a DSM-based approach for thin-walled structural systems.

This paper reports the main results of an ongoing numerical investigation aimed at (i) assessing the buckling, post-buckling, strength and collapse behaviour of thin-walled steel structural systems and (ii) developing an efficient direct approach to estimate the ultimate loading of such structural systems, which may fail in complex modes that combine local, distortional and global features. The results currently available, obtained from Generalised Beam Theory and Ansys shell finite element analyses, concern continuous beams and simple frames subjected to various transverse loadings applied at/along the shear centre axis and causing non-uniform bending. The possibility of developing a design approach, based on the application of the existing Direct Strength Method (DSM) strength curves, is explored for the structural systems under consideration. The quality of the corresponding failure loading estimates is assessed through the comparison with the values yielded by shell finite element simulations.