Load‐Eccentricity Effects on Cold‐Formed Steel Lipped‐Channel Columns

Abstract

The effects of loading eccentricity on axial strength of cold‐formed steel lipped channels are investigated in a series of 48 individual long‐column tests. Experimental results are compared with flexural and torsional‐flexural buckling‐strength predictions based on the American Iron and Steel Institute (AISI) 1986 specification, with local buckling treated using the uniform‐effective‐width approach. Widely spaced, rectangular web perforations are modeled using an “unstiffened‐strip” method, with the web idealized as two unstiffened elements, one on either side of the perforation. A method for predicting weak‐axis flexural buckling and the load‐versus‐lateral‐deflection response of eccentrically loaded, initially imperfect columns is also examined. Estimates of the actual loading eccentricities are made by comparing the predicted and empirical load‐versus‐deflection responses. Axial strength is shown to be very sensitive to small eccentricities. Conservative strength predictions are obtained with the AISI procedures by including loading eccentricity effects and modeling the perforations using the unstiffened‐strip method.