Biaxial bending–axial force elastic interaction diagrams in hollow steel sections

Interaction diagrams are extensively used as a practical tool for designing prismatic members subjected to several combined stresses. For a long time, sets of these graphs have been available in building technologies such as reinforced concrete, steel and composite sections, under di€erent combinations of loadings. This paper will present the general formulation for obtaining the diagrams corresponding to biaxial bending with axial force on hollow steel sections; with circular, rectangular and square shape, with or without rounded edges. In particular, a detailed general analysis of the elastic interaction surface is made for these stresses over the above-cited sections. Ó