Experimental and numerical investigations of S960 ultra-high strength steel welded I-section beams with in-plane flexural failure

A testing and numerical modelling programme was performed to investigate the in-plane flexural behaviour and cross-section bending capacities of S960 ultra-high strength steel welded I-section beams and presented in this paper. The testing programme included material testing, membrane residual stress measurements, initial local geometric imperfection measurements and eight in-plane four-point bending tests, with four performed about each of the cross-section minor and major principal axes. This was followed by the numerical modelling programme, where finite element models were developed and validated against the test results and then used to perform parametric studies to generate further numerical data over a wide variety of cross-section dimensions and span lengths. The obtained test and numerical data were used to evaluate the applicability of the design rules for cross-section classification and bending capacities, as prescribed in the European code, Australian standard and American specification, to S960 ultra-high strength steel welded I-section beams. The evaluation results revealed that all codified slenderness limits were safe (though conservative to different extents) when used for classifying the constituent plate elements of S960 ultra-high strength steel welded I-sections in bending. Moreover, all three considered design codes were shown to result in accurate and consistent bending capacity predictions for Class 1 and 2 (or compact) S960 ultra-high strength steel welded I-sections, but conservative bending capacity predictions, to different extents, for Class 3 (or non-compact) and Class 4 (or slender) S960 ultra-high strength steel welded I-sections.