Flexural and lateral-torsional buckling of steel sandwich panels and their imperfections using mechanically consistent buckling curves

• A novel approach is presented combining flexural and lateral-torsional buckling via an extended AYRTON–PERRY formulation for sandwich panels. • Validation through experimental investigations of flexural buckling - including the determination of imperfections - and through comprehensive finite element analyses. • Unified buckling curves describe full load spectrum seamlessly and consistently. Sandwich panels are very often used for building envelopes of industrial and commercial buildings. They also provide time- and cost-effective solutions when used in modular and cold room constructions with a minimum of load-bearing substructures. In these cases, sandwich panels often act as load-bearing wall components, transferring forces parallel to the longitudinal axis. However, with increasing building heights, and consequently, the increasing slenderness of the sandwich panels, stability problems prevail in the structural design. In such scenario, a particular attention need to be paid to the eccentricities of the load application in relation to the longitudinal axis in and out of the plane at top and bottom of the panel. Thus, beyond flexural buckling due to centric and eccentric loads, the combined effects of flexural and lateral-torsional buckling also become significant. So far, there is no consistent analytical approach for a verification that treats both, flexural buckling and lateral torsional buckling of sandwich panels, also for combined cases. Therefore, this paper presents a consistent approach for the buckling curves of axially loaded sandwich panels. Firstly, the mechanical principles underlying an extended buckling curve for combined loading of flexural buckling and lateral-torsional buckling are outlined. Subsequently, these principles are adapted to the sandwich cross-section, enabling the derivation of buckling curves. The mechanical approaches and the buckling curves are validated through comprehensive experimental and numerical investigations.