Experimental and numerical study on stainless steel hexagonal hollow section stub columns subjected to combined compression and bending

Hexagonal hollow section is a novel type of polygonal hollow sections. In comparison with traditional rectangular hollow sections, hexagonal hollow sections with the same perimeter have higher cross-section resistances, owing to their smaller flat element widths, and offer more faces to facilitate connections in more than four directions. This paper reports experimental and numerical studies on the cross-section behaviour and resistances of stainless steel hexagonal hollow sections under combined compression and bending. A testing programme was firstly performed and included tensile coupon tests, initial local geometric imperfection measurements and eccentric compression tests on twelve grade 304 austenitic stainless steel hexagonal hollow section stub column specimens. The testing programme was accompanied by a numerical modelling programme, including a validation study, where finite element models were developed and validated against the test results, and a series of parametric studies, where the validated finite element models were used to generate further numerical data. The test and numerical data were used to evaluate the applicability of relevant design interaction curves for stainless steel rectangular hollow sections and carbon steel hexagonal hollow sections, as specified in the European code, American specification and ASCE standard, to stainless steel hexagonal hollow sections. The evaluation results generally revealed that the design interaction curves of the European code and American specification provided acceptable levels of accuracy and consistency, though some unsafe and conservative resistance predictions were also found, while the design interaction curve of the ASCE standard led to inaccurate and scattered resistance predictions. Finally, a revised ASCE design interaction curve was proposed and shown to outperform the original ASCE design interaction curve.