Static assessment of load capacity at collapse of open cross-section thin-walled beams

The work presents an analytical method, which enables static assessment of load capacity at collapse of thin-walled beams with open cross-section. The foundation of considered approach makes the assumption of the diagrams of normal and shear stresses in plastic hinge, which are consistent with the distribution of sectorial co-ordinate and sectorial static moment. The computer-aided analysis (Abaqus 2004), based on shell elements is helpful in search for suitable stress distributions. The results of used procedure are interaction formulae between cross-sectional forces (stress resultants), including specific for thin-walled beam theory: bimoment, Vlasov torsional moment and Saint-Venant torsional moment. These formulae can be applied in practice, in the case of steel structures, designed beyond linear elastic state. The method is illustrated by numerical example of Z-section thin-walled beam under tensile forces.