Non-linear analysis of unbraced frames of variable geometry

Abstract

A non-linear analysis of unbraced, rigid-jointed, and elastically restrained (against rotation) portal frames of variable geometry is presented. The loading system consists of eccentric concentrated loads and a transverse uniformly distributed load. Among the important conclusions one may list the following: (a) symmetric portal frames, loaded symmetrically, buckle through a stable bifurcation (sway-buckling) from a symmetric bent equilibrium configuration, and (b) nonsymmetric portal frames do not buckle; their behavior is similar to that of imperfect cantilever columns.