Abstract
Based on geometrical assumptions and principle of virtual velocity, finite displacement equilibrium equations and their boundary conditions are generally derived for thin-walled members with open section in incremental form which is usefull for elastic-plasitc analysis. And the relations between resultant stress rates and velocities are also derived in both elastic and plastic ranges. The proposed theory is a direct generalization of the elastic buckling theory established by Vlasov and it includes Vlasovs' theory as a special case.
