Lean duplex stainless steel tubular sections undergoing web crippling at elevated temperatures

Codified design rules for web crippling of stainless steel tubular sections at elevated temperatures are currently not available. In this study, non-linear finite element models (FEMs) were developed for the web crippling of cold-formed lean duplex stainless steel (CFLDSS) square and rectangular hollow sections under the concentrated interior bearing loads, namely, the loading conditions of Interior-One-Flange (IOF), Interior-Two-Flange (ITF) and Interior Loading (IL). After successful validation of the FEMs, an extensive parametric study of 210 CFLDSS tubular sections at elevated temperatures (up to 950 °C) was performed. The appropriateness of the web crippling design rules in the current international specifications and literature was examined by comparing their ultimate strength predictions with those obtained from the numerical parametric study. During the calculation, the material properties at room (ambient) temperature condition were substituted by those at elevated temperatures. It was found that the predictions by the North American Specification were generally unconservative and not reliable, while the European Code provided reliable but generally very conservative predictions. New design method is proposed, including a new equation and the modified Direct Strength Method, for the web crippling of CFLDSS tubular sections at elevated temperatures under the loading conditions of IOF, ITF and IL. The assessment indicated that the predictions by using the new method are generally conservative and reliable.