NEW STABILITY EQUATION FOR COLUMNS IN BRACED FRAMES

A new approximate method that overcomes some limitations of the current design procedures for determining effective length factors for columns in braced frames is presented. Generalized stability functions are developed, including a linear model for joint flexibility and the column-strength curve of the Structural Stability Research Council (SSRC) to take into account the inelastic behavior of members subjected to axial compression. Thereafter, a mathematical formulation based on the interaction between the column being analyzed and the adjacent members is presented by considering differentiated stiffness parameters as well as the boundary conditions at the far ends of all the attached elements. A computer program was implemented and an extensive numerical analysis about the influence of the involved variables was performed. It is proved that the use of some current design methods, such as the alignment-chart procedure and related modifications, may provide unconservative results.