Local-Distortional Interaction in Web-Stiffened Lipped Channel Columns Exhibiting Critical Distortional Instability

Abstract

This work revisits an experimental investigation carried out at The University of Hong Kong concerning the post-buckling and ultimate strength behaviour of fixed-ended cold-formed steel webstiffened lipped channel columns that buckle in distortional modes — the test results provide clear evidence of the occurrence of flange-triggered local-distortional interaction. The experimental ultimate strength values obtained in the above tests, together with additional failure load data reported in the literature, are used to assess whether the available Direct Strength Method (DSM) design approaches are capable of predicting them efficiently (safely and accurately). It is found that this is not the case, mainly because of the fact that the mechanics of flange-triggered and web-triggered local-distortional interaction are quite different. Although fairly good failure load predictions are provided by a new DSM design approach proposed in this work, further research is required, in order to unveil on the mechanics of local-distortional interaction in web-stiffened lipped channel columns.