In recent years, high-strength steel and high-strength concrete have shown great potential for use in building structures due to their superior mechanical properties, which allow for reduced member sizes and material consumption, thereby offering potential reductions in carbon emissions. However, experimental studies on high-strength concrete encased steel (CES) composite slender columns in fire remain relatively limited, and reliable finite element models for accurately predicting their thermo-mechanical performance are lacking. In addition, the current code provisions for fire design, which are primarily based on normal-strength materials, are inadequate for accurately assessing the structural behaviour and deformation of high-strength CES composite members under fire, thereby limiting their broader application. Therefore, based on a systematic review and analysis of relevant experimental data, this study comprehensively compiles 33 elevated-temperature tests to establish an experimental benchmark and develop a finite element model suitable for such composite members. The accuracy of the numerical model is validated against the experimental results. Subsequently, a comprehensive parametric study comprising 576 numerical cases is conducted to establish a reliable database encompassing material strength, normalized slenderness (as defined in Eurocode), and load ratio. This database is further used to assess the applicability of existing design methods and standards, including the latest European and Chinese design provisions, as well as recently proposed design methods in the literature, in order to clarify their limitations and applicability ranges, facilitate the practical use of high-strength materials, and provide supporting evidence for the refinement and development of design codes. • A FEM was developed for high-strength slender CES columns at elevated temperatures. • The FEM was validated using axial load tests at elevated temperatures. • Parametric study showed influence of material strength, slenderness and load ratio. • Assessment of existing design methods clarified their accuracy and applicability.
Li et al. (Fri,) studied this question.