The effects of imposing initial imperfections on a thin-walled cold-formed channel section

Abstract

The axial strength of a strut is liable to decrease with the imposition of initial imperfections. The object of this dissertation is to investigate the effect of initial imperfections on a cold-formed thin-walled channel under axial load. Initial imperfections are to be imposed of three principal types: 1. A lateral out-of-plane deformation along the major x-axis, 2. A lateral out-of-plane deformation along the minor y-axis, 3. A twisting deformation about the section centroid along the longitudinal z-axis. BS 5950: Part 7 1992 Specifications for material & workmanship: cold formed sections specifies in section 5.2.6 and 5.2.7 that the deviation of a member from sraightness shall not exceed 3mm of L /500 and that the angle of twist shall not excedd 1/m length.