Geometric Imperfection Measurements and Validations on Cold-Formed Steel Channels Using 3D Noncontact Laser Scanner

A three-dimensional (3D) noncontact laser-scanning method to quantify the deviations in cold-formed steel (CFS) channel sections (plain and lipped) is presented. The methodologies to segregate the different categories of imperfections from the deviations in the geometry of CFS member are also presented. A total of 24 different C-sections (minimum of six samples in each section) with varying cross-sectional parameters totaling 188 specimens were studied. The nature of imperfections in the CFS members was found to correlate with geometric properties such as slenderness ratios, torsional constant, and plate slenderness. The bow and camber imperfection (global out-of-straightness) in the members is presented with respect to the minor and major axis slenderness ratios. A new combined global and cross-sectional parameter (J/L) is introduced against the deviation caused by twisting of the CFS member. To predict the imperfection magnitudes based on their geometrical properties, a new set of expressions are suggested. (C) 2018 American Society of Civil Engineers.