New interaction formula for plastic resistance of channel sections under combinations of bending moments My,Ed, Mz,Ed and bimoment BEd

Abstract

The interaction formulae for the plastic resistance of channel sections under combination of 4 internal forces: the bending moment about strong axis My,Ed, the bending moment about weak axis Mz,Ed, the bimoment BEd and the axial force NEd were created and analyzed. The exact interaction curves obtained by the linear programming for 4 internal forces have enabled to create and to verify the proposed approximate interaction formula for 3 internal forces.The approximate interaction formula for the design plastic resistance of channel sections under combination of 3 internal forces: the bending moment about strong axis My,Ed, the bending moment about weak axis Mz,Ed and the bimoment BEd was analyzed and verified. The explicit interaction formula that takes into account these 3 internal forces is missing in Eurocodes. A large parametrical study was performed for the rolled channel profiles within the size range UPE 80 UPE 400. The differences between the results of the approximate interaction formula and the exact interaction curves were analyzed and summarized.Till today nobody presented results of the parametrical study of the channel sections under the combination of 4 internal forces.