Re-examination of YLinen and Other Column Equations

Abstract

In 1991, Ylinen’s column equation was adopted for the design of wood columns in the United States. Ylinen originally derived this equation as a plasticbuckling criterion, using a nonlinear compressive stress-strain law as the startingpoint. The stress-strain law contained a parameter c ≤ 1, which controlled the degree of nonlinearity. Linearity was achieved at c = 1. This same parameterappeared in the final column equation. At c = 1. the column equation reduced to elementary theory, i.e., to a perfectly plastic-perfectly elastic failure criterion. Column design equations are viewed in this paper as interaction equations between two modes of failure: crushing and buckling. Ylinen’s column equation is found to result from the addition of a cross-product term to the linear interaction equation.This enables us to view c as measuring the degree of departure from the assumptionsof elementary theory, including such phenomena as inhomogeneity of material. imperfections of shape, and accidental eccentricity of loading. in addition to nonlinearity of the stress-strain law. Column design equations from wood design codes in Europe and Canada are compared and discussed from this point of view.

Citation

Zahn, John J. 1992 Re-examination of YLinen and Other Column Equations. Journal of Structural Engineering, Volume 118, Number 10, October 1992; pp. 2716-2728.