EFFECTIVE LENGTH FACTOR OF COLUMNS IN SEMI-RIGID JOINTED AND BRACED FRAMES WITH CONSIDERATION OF SHEAR EFFECTS

In order rationally to evaluate the stability of columns in semi-rigid jointed and braced frames, the equations for determining the effective length factor of columns are derived by considering the effects of the non-linear moment-rotation characteristics of beam-to-column connections and shear deformation. In this study, to derive the equations, a rotation spring with variable stiffness is used to model the flexibility of a beam-column connection and the modified stiffness factor of a semi-rigid connection is introduced. It is shown that the effective length factor of braced semi-rigid steel frames is notably different due to shear-deformation effects in the stability analysis for columns with less slenderness ratios. As a result of the weak restrictions by the semi-rigid connections to the column, there will be some errors in buckling calculations if not considering the effects of shear deformation. And also, the effective length factor (μ-factor) will have an increase of 5.6%―10%. Therefore, the effects of shear deformation should be considered in stability analysis of braced semi-rigid steel frames.