An efficient method for computation of effective length factor of columns in a steel gabled frame with tapered members

The concept of effective length is the only available common method for column design without non-linear structural analysis. Researches conducted for determination of effective length of members are mainly related to a constant moment of inertia. In many investigations related to members with variable moment of inertia, finite element and approximation methods are used. In this article, a method for quick calculation of the effective length factor of columns in steel gabled frames with tapered members is proposed. The method is based on two-dimensionless design-oriented charts relating the critical load of columns to frame characteristics and boundary conditions. Since I-sections are usually used for gabled frames members, the variation of moment of inertia along the length of members (beams or columns) is approximated as a parabolic function. As is demonstrated in the Numerical studies, these calculations can yield, in a very efficient way, accurate results for gabled frames consisting of tapered elements.