Iterative Eigenvalue Analysis for Stability Design of Three-dimensional Frames Considering a Fictitious Axial Force Factor

Abstract

In design of steel frames, it is well known that the Euler buckling equation with eigenvalue analysis may lead to unexpectedly large effective lengths of members that have relatively small axial force. This paper illustrated the use of a fictitious axial force factor to overcome the problem mentioned above. Considering a fictitious axial force factor, the illustrated method determines the elastic and inelastic effective lengths of each member in three-dimensional steel frames based on iterative schemes and the stiffness reduction factors. To verify the validity of the illustrated method, the effective lengths of example frames by the proposed method were compared with those of previously established methods. The results show that the proposed method gives reasonable effective lengths of all members in space frames, and can be a good substitute for previously established methods.