Flexural–torsional failure and DSM design of fixed-ended cold-formed steel columns at elevated temperatures

Distortional‐Global Interactive Failure and DSM Design of CFS Lipped Channel Columns at Elevated Temperatures

“…The column D-FT post-buckling equilibrium paths and failure loads are determined by means of ABAQUS [16] SFE GMNIA, employing models similar to those used in recent studies involving CFS columns at room and elevated temperatures (e.g., [7,8,14]). The columns are discretised into fine S4 element meshes (ABAQUS nomenclature -4-node generalpurpose shell finite elements with six degrees of freedom per node and full integration).…”

“…The DSM-based prediction of the D-FT interactive failure loads gathered in the previous section, concerning the selected CFS fixed-ended LC columns at elevated temperatures, is addressed in this section. The first step consists of assessing the merits/adequacy of the available D and FT columns strength curves, developed in the context of elevated temperatures, namely 𝑃 𝑛𝐷.𝑇 * and 𝑃 𝑛𝐹𝑇.𝑇 * , proposed in [13,14] and defined in Eqs. ( 4) and ( 5), respectively.…”

“…( 4)) and 𝑃 𝑛𝐹𝑇.𝑇 * (see Eq. ( 5)) DSM-based strength curves, proposed in [13,14], are unable to predict adequately the failure loads of fixed-ended LC columns affected by D-FT interaction at both room and elevated temperatures. Nevertheless, it should be noted that the failure load prediction qualities provided by 𝑃 𝑛𝐷.𝑇 * and 𝑃 𝑛𝐹𝑇.𝑇 * differ visibly: while the former are clear overestimations (except for columns with D.T≤1.0), the latter are (i) reasonably accurate estimates for columns with  FT.T ≤2.5 at temperatures not exceeding 300 ºC, and (ii) moderate overestimations for the remaining columns.…”

“…Landesmann et al [13] and Bicelli et al [14] numerically investigated the post-buckling behaviour, ultimate strength and DSM design of CFS columns failing in pure D and FT modes, respectively, at elevated temperatures. Initially, these authors gathered extensive failure load data, concerning CFS columns with (i) several cross-section shapes, dimensions and lengths, (ii) different room-temperature yield stresses (covering wide D or FT slenderness ranges), (iii) 8 uniform elevated temperatures (T800 ºC), and (iv) temperature-dependent steel material behaviours following the model prescribed in EC3-1-2 [15].…”

“…Therefore, the aim of this work is to present and discuss the results of an extensive numerical investigation concerning the DSM-based design of CFS fixed-ended lipped channel columns undergoing different D-FT interaction levels at elevated temperatures. As done previously (e.g., in [14]), all the numerical D-FT interactive failure loads obtained in this work (i) concern columns containing initial geometrical imperfections with critical-mode FT shapes (shown to be the most detrimental ones in [8]) and L/1000 amplitude, and (ii) are obtained by means of ABAQUS [16] SFE GMNIA, adopting a model often employed by the authors in the past. The LC columns analysed (i) display a wide variety of crosssection dimensions, lengths and room-temperature yield stresses (selected to cover wide slenderness ranges), and (ii) are subjected to several uniform elevated temperatures, up to 800 ºC.…”