Major-axis flexural buckling behavior of welded ultra-high-strength steel I-section members

The increasing application of ultra-high-strength steel (UHSS) in high-rise buildings and long-span structures demands a thorough understanding of its structural behavior. This paper presents the systematic study on the major-axis flexural buckling behaviour of Q1100 ultra-high-strength steel built-up I-section columns. The experiments comprised seven Q1100 column tests under compression with the rotations along the minor axis restrained. Complementary finite element models, validated against the experimental measurements, facilitated parametric studies with extended geometric configurations involving a total of 234 models. The reliability of the current European, North American, Australian and Chinese design rules were examined against the test and numerical data following their respective procedures. Furthermore, revised buckling curves were proposed for Q1100 built-up I-section columns, recommending higher-level buckling curves for non-slender sections and lower-level curves for slender sections, which demonstrated improved accuracy and safety compared to the codified ones.