Yield line mechanism analysis on web crippling of cold-formed stainless steel tubular sections under two-flange loading

The yield line mechanism analysis on web crippling of cold-formed stainless steel square and rectangular hollow sections under two-flange loading is presented in this paper. A concentrated load was applied by means of bearing plates which act across the full flange width of the sections. Two-flange loading conditions of the End-Two-Flange and Interior-Two-Flange, as specified in the American Specification and the Australian/New Zealand Standard for cold-formed stainless steel structures, have been investigated in this study. In addition, the end loading condition, where the test specimens were seated on a fixed flat solid base plate, which is not specified in the specifications, is also investigated. Four design procedures for predicting the web crippling strengths of cold-formed stainless steel tubular sections, based on the failure mode but using different assumptions, have been considered. Three of the web crippling design procedures were derived theoretically using yield line mechanism analysis, and one design procedure was derived through a combination of theoretical and empirical analyses. The web crippling test strengths were compared with the design strengths obtained using the four design procedures. Generally, it is shown that the proposed web crippling design equations that were derived through a combination of theoretical and empirical analyses accurately predicted the test strengths of cold-formed stainless steel square and rectangular hollow sections under two-flange loading.