Design of Cold-Formed Channels Subjected to Web Crippling

Abstract

A series of tests on cold-formed unlipped channels with comparatively stocky webs and subjected to web crippling is presented in this paper. The web slenderness values of the channels ranged from 15.3 to 45. The tests were conducted under the four loading conditions (End-One-Flange, Interior-One-Flange, End-Two-Flange, and Interior-Two-Flange) specified in the Australian/New Zealand and American specifications for cold-formed steel structures. The test strengths are compared with the design strengths obtained using the specifications. It is demonstrated that the design strengths predicted by the specifications are generally unconservative for unlipped channels. Test strengths as low as 43% of the design strengths were obtained. Hence, new web crippling design equations for unlipped channels are proposed in this paper. The proposed design equations are derived based on a simple plastic mechanism model, and the web crippling strength is obtained by dispersing the bearing load through the web. It is shown that the web crippling strengths predicted by the proposed design equations are generally conservative for unlipped channels with web slenderness values of less than or equal to 45. It is concluded that the proposed design equations for unlipped channels having stocky webs are reliable.