Design of steel beams affected by local/global coupled instabilities

The present paper investigates the resistance of I and H-shapes subjected to uniform major-axis bending moment and prone to suffer from local/global coupling effects. Numerical parametric studies allowed the determination of local/global coupling functions for hot-rolled and welded sections aiming at correcting the influence of local effects -- which tends to decrease -- when the member slenderness increases. These functions, included into an O.I.C.-type design approach, may be seen as an alternative to the current Eurocode rules in which local/global interactions are roughly accounted for through the global relative slenderness definition and a rather conservative final strength verification. A formulation predicting the strength of beams made of such sections is then eventually suggested. These design proposals were seen to lead to great improvements in accuracy and consistency compared to current European provisions.

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