Recent construction practice has seen a rise in the use of structural hollow sections, due to their appealing aesthetics as well as an increased awareness for the advantages in terms of strength and stiffness of this type of section. At the same time, in order to meet increasing demands for more effcient and economic construction typologies and methods, the European steel industry, and particularly the producers of structural hollow sections, are aiming for a reduction of weight through the use of more thin-walled sections and/or higher-strength steel grades (with yield strength fy>460MPa). These innovations increase the economy and sustainability of construction projects through the reduction of weld volumes, erection timesand foundation costs. However, the introduction of more slender construction typologies for hollow sections leads to a number of scientific and engineering challenges. In particular, higher material, with different constitutive laws (shorter or inexistent plastic plateau, diminished ultimate strain) combined with thinner plates leads to an increased significance of instability phenomena, especially of local buckling phenomena and their interaction with the "global" instability mode of flexural buckling. This thesis addresses the strength and stability of slender, mild- and high-strength-steel hollow sections with at faces and different cross-sectional geometries and develops a new methodology to be used in structural design and for performance predictions for such elements. The problem of buckling is treated for local, global and interactive local-global buckling phenomena. Most of the described results were developed in the framework of the European (Research Fund for Coal and Steel - RFCS) research project HOLLOSSTAB (grant Nr. RFCS-2015-709892), using a novel design method, called the Generalised Slendernessbased Resistance Method (GSRM), which was developed { in its application to square (SHS) and rectangular (RHS) hollow sections - as part of this thesis work. The new, GSRM design rules cover the cross-sectional and member design checks of hollow sections with various shapes and slenderness ratios. This thesis summarises the experimental and numerical campaign carried out within HOLLOSSTAB and describes the development, validation and application of the new GSRM for the case of the cross-sectional and member resistance of SHS and RHS. It furthermore shows some initial work on an extension of the scope of application of the GSRM. It could be shown that, with the proposed GSRM method, significant gains in accuracy and economy in the design of at-faced hollow sections can be achieved.    «

Recent construction practice has seen a rise in the use of structural hollow sections, due to their appealing aesthetics as well as an increased awareness for the advantages in terms of strength and stiffness of this type of section. At the same time, in order to meet increasing demands for more effcient and economic construction typologies and methods, the European steel industry, and particularly the producers of structural hollow sections, are aiming for a reduction of weight through the use...    »