Inelastic Response of Column Segments under Biaxial Loads

An analytical formulation of the generalized stress-strain relationships for biaxially loaded column segments is presented. The generalized stresses are an axial force, two bending moments about the principal axes, and a bimoment. The corresponding generalized strains are an axial strain at the centroid, two bending curvatures, and a warping curvature. The material characteristics are assumed to be trilinear, i.e., elastic, plastic, and linear strain hardening. Elastic unloading of yielded fibers and Bauschinger effects are included in the analysis. Based upon the equations formulated, a computer program was developed to provide numerical results. The element of the tangent stiffness matrix was evaluated numerically by dividing the wide flange section into finite element.