Local buckling of thin-walled fibre composite beams under transverse loading

Abstract

Plate structures are often subjected to differential compression due to nonuniform bending during their service life. In practice, most beams are subjected to transverse loads that create moment gradient; the resulting loading system for such beams is a combination of longitudinal stress gradient with associated shearing and transverse stresses. This paper presents a theoretical view of elastic local instability of anisotropic composite beams which are treated as assemblies of symmetric angle-ply composite plates buckling under nonlinear varying, uniaxial compressive forces. Uniformly distributed load and central concentrated load are two common loading systems acting on simply supported, wide-flange I-section beams. The Galerkin method is applied to the resulting plate equilibrium equations. The present study shows that the buckling load obtained from the proposed approach for composite flanges is greater than that obtained by existing solutions. Results also show that for beams subjected to the uniformly distributed load loading system, local buckling may be initiated in the web, especially for short-span deep beams. However, under the central concentrated load loading system, the compressive flange limits buckling strength.Key words: local buckling, stress gradient, fibre composite, pultruded beam.