Effective buckling length of frames with tapered columns and partially tapered beams

Abstract

This paper presents stability analysis of steel frames composed of linearly tapered columns and partially tapered restraining beams. In the first part of the stability analysis, closed-form equations for the bending stiffness of the symmetrical and unsymmetrical partially tapered restraining beam are derived and presented in form of design charts. Subsequently, slope deflection equations of linearly tapered column subjected to axial compressive load are then assembled along with the bending stiffness equations of partially tapered beams to determine the elastic critical load and the effective buckling length factor for non-sway and sway steel frames. Numerical examples and efficient design charts are presented for several braced and unbraced steel frames. Moreover, the effect of gravity loads acting on leaning columns connected to sway frames is investigated. Based on this investigation it is concluded that correction of effective buckling length factor based on story buckling concept can be extended to cover steel frames with tapered column as well.