Assessment of K factor formulas

Abstract

The effective length (K) concept is considered an essential part of many analysis procedures and it can handle several cases which can occur practically in all structures. The concept is valid for ideal structures, but its implementations involves several assumptions. A number of methods have been suggested for the calculation of K factors and they are based on different assumptions and types of modeling the frame behavior. Alignment charts, for example, have been prepared assuming the buckling of an idealized subassemblage in a frame and that all columns in a story buckle simultaneously. LeMessurier's formula offers some correction to the alignment chart assuming the stronger columns in a story brace the weaker ones in that story. Liu's proposed method appears simple and more effective in evaluating the K factor for framed columns in sway frames. K factor values obtained by using the overall system buckling analysis are, however, considered to be exact solutions.