Investigation on single-bolted cold-formed steel angles with geometric imperfections under compression

Abstract

The behaviour of cold-formed steel angle members with bolted connections under compression is usually complicated, whereas not significant number of experimental tests is found in the literature. This study offers a better insight on the issue, by comparing experimental tests with a thorough numerical study, both carried out at the Institute of Steel Structures of NTUA. Significant attention is paid for the elaborate measurement of initial geometric imperfections along the member's length. An in-house built deformation plotter was designed and upgraded for this reason. The compression failure loads of the experimental tests are illustrated both in graphical and tabular form and compared with similar tests of the literature. The results denote a prediction of the EN 1993-3-1 towards the safe side, for the case of the examined bolted cold-formed angles. A simple formula is proposed for the accurate prediction of angle columns' buckling deformation, wherein the rigidity of the connection is also included. Finally, interesting conclusions are derived for the numerical simulation of cold-forming effects, as well as the shape and amplitude of the initial imperfect geometry, on the basis of the critical buckling load. Further research is in progress, aiming to capture the stochastic buckling response for the case of bolted cold-formed steel angles.