Lateral–torsional buckling of high-strength steel I-beams: design, parameter and reliability analysis

The aim of this work was to examine the resistance of high-strength steel (HSS) doubly symmetric I-beams according to international codes (BS EN 1993-1-1:2022, ANSI/AISC 360-22 and AS 4100-2020). For this purpose, a database comprising 138 tests conducted between 1969 and 2023 was compiled. An influence parameter analysis was performed using the collected data, followed by a reliability assessment. The parametric influence analysis showed that geometric properties (depth, flange width and thickness) govern bending resistance, whereas material strength plays a secondary role within the investigated range. These findings clarify the relative performance of current design provisions, highlight the parameters that most affect resistance and indicate where refinements may improve the reliability and accuracy of HSS I-beam design. All three standards underestimated the bending resistance of HSS I-beams, although to different degrees. Among the evaluated formulations, the BS EN 1993-1-1:2022 ‘new method’ with the refinements of Tankova et al. achieved the highest accuracy, while ANSI/AISC 360-22 provided the least conservative predictions and AS 4100-2020 showed moderate conservatism. The reliability analysis confirmed these trends, with partial safety factors ranging from 1.423 to 1.490, indicating systematic differences in safety margins between codes.