Testing, numerical modelling and design of S890 and S960 ultra-high strength steel circular hollow sections under combined loading

Abstract

The present paper reports the experimental and numerical investigations into the structural behavior and resistances of S890 and S960 ultra-high strength steel circular hollow sections (CHS) under combined loading. The experimental investigation was performed firstly, comprising the tensile coupon tests on S890 and S960 ultra-high strength steel materials, precise measurements of initial local geometric imperfections and eccentrically loaded tests on 12 stub columns, with each 6 respectively conducted on S890 and S960 ultra-high strength steel CHS. The numerical investigation was subsequently conducted, where numerical models were created and verified against the experimental responses and adopted to conduct parametric studies to produce more numerical data over an extensive variety of loading combinations and cross-section geometries. The design interaction curves, as codified in the European, Australian and American standards, were assessed for their applicability, based on the numerical and test data, to S890 and S960 ultra-high strength steel CHS under combined loading. The evaluation findings demonstrated that (i) the European code leads to the slightly conservative failure load predictions for Class 1 (and 2) S890 and S960 ultra-high strength steel CHS under combined loading, but overly conservative predictions for Class 3 and 4 counterparts, (ii) the predicted failure loads by American specification for non-compact (i.e. Class 3 and 4) are more accurate due to the more precise compression and bending end points and (iii) the resistance predictions by Australian standard for compact (i.e. Class 1 and 2) sections are rather conservative due mainly to its inaccurate design interaction curve.