Tests of cold-formed duplex stainless steel SHS beam–columns

• Tests of cold-formed duplex stainless steel SHS beam–columns have been conducted.
• Moment–rotation and load–deflection curves were obtained.
• Test strengths were compared with design strengths predicted by specifications.
• It is shown that the current design predictions are generally conservative.

Stainless steel is gaining widespread use in construction due to its obvious special characteristics – attractive appearance, corrosion resistance and ease of maintenance, whilst beneficial mechanical properties such as high ductility, better fire resistance than carbon steel and high strength demonstrated by the duplex grades add value to its aesthetics. Reliable experimental investigation is a prerequisite to explore the full potential of stainless steel members and to evaluate the performance of the existing design rules. The current study describes a test program on cold-formed stainless steel square hollow section (SHS) members subjected to eccentric compression to examine the beam–column interaction, which is one of the least explored fields in structural stainless steel. Cross-sections are produced from duplex stainless steel grade with the measured yield stress up to 700 MPa, for which material properties were obtained by tensile coupons cut from within the cross-sections. A total of 20 specimens are tested with initial geometric imperfection being measured at mid-height of each beam–column specimen. The specimens were placed between knife-edge supports to simulate an ideal pin-ended boundary condition at both ends. The column lengths were 550 and 1100 mm, and each specimen was subjected to compression loading with eccentricity varying from 0 to 60 mm. The test results were compared with those predicted using the American and the Australian/New Zealand design specifications for cold-formed stainless steel structures. It is observed that the code predictions are mostly conservative for stainless steel beam–columns with rooms for improvement in the current design guidance.