Structural performance and design of S960 ultra-high strength steel non-slender welded I-sections subjected to combined loading

The structural performance of S960 ultra-high strength steel non-slender welded I-sections subjected to combined loading is studied in the present paper. Nonlinear finite element (FE) models were first created and validated with reference to test results collected from the literature, and then used for conducting parametric studies to derive numerical data over an extensive spectrum of cross-sectional geometries, aspect ratios, as well as loading combinations. Given the lack of existing design rules for S960 ultra-high strength steel structures, the suitability of the current provisions for lower strength steels given in the European, Australian and American specifications to S960 ultra-high strength steel was assessed based on the generated numerical data. It was found that (i) the European code and Australian standard can accurately predict the strengths of Class 1 and 2 (i.e. compact) S960 ultra-high strength steel welded I-sections subjected to both strong- and weak-axis combined loading, but results generally in conservative strength predictions for Class 3 I-sections, and (ii) the American specification yields accurate strength predictions for S960 ultra-high strength steel welded I-sections subjected to strong-axis combined loading, but leads to conservative strength predictions for weak-axis combined loading. Finally, the continuous strength method (CSM) was applied to the studied S960 ultra-high strength steel non-slender welded I-sections subjected to combined loading and found to offer significantly improved design consistency and accuracy relative to the current codified provisions. The reliability of the latter design method was also confirmed by means of statistical analyses.