Improved Interaction Formula for the Plastic Resistance of I- and H-Sections under a Combination of Bending Moments My,Ed, Mz,Ed, and Bimoment BEd

Abstract

The resistances of HVH sections (H—horizontal upper flange, V—vertical web, H—horizontal bottom flange) were investigated by the authors in the frame of the large parametrical studies focused on the complete HVH-section categories: channels, Z-sections, I-sections, and H-sections. The three different variants of the approximate formulae for the calculation of the elastic and plastic resistances of I-shaped sections loaded by several internal forces were previously published by the authors. In this paper, the improved approximate formulae are presented for the plastic resistance of I- and H-sections loaded by bending moments My,Ed, Mz,Ed, and bimoment BEd. It is shown in the graphical form that the proposed approximate formulae give almost identical values of relative plastic resistances of I-shaped sections to the exact solution, in which Pattern Search Algorithm, offered by MATLAB, is used. It is proven that the proposed approximate formulae are better then previous authors’ formulae, which are themselves better than the older Greek proposal and the newer German proposals. The approximate formulae may be used in the CEN Technical Specification (TS) or in Non Contradictory Complementary Information (NCCI) for supporting safe and economical design according to metal (steel and aluminum) Eurocodes.