Degradation and Buckling of I-Beams under Cyclic Pure Bending

Abstract

This paper presents experimental and numerical results of the elasticplastic response and buckling of S3 x 5.7 steel and aluminum I-beams subjected to cyclic pure bending. A special 4-point bending device was designed and built for this purpose. The emphasis of the work is on the description of the response and buckling of the beams. The numerical results were obtained using a commercial finite element program that implements the nonlinear kinematic hardening plasticity model. Results indicate that the beams considered, most of which had length-to-height ratio of 5, buckled first in a global mode involving either twisting or lateral deflections of the beams. The prevailing deflection mode seems to be determined by the nature of the initial geometric imperfections. The deformations induced by the global deflections could induce a local buckle at mid-span. The finite element predictions yield results that qualitatively reproduce the development of most of the aspects of the response of the beams, but generally at a slower rate.