Stub column behaviour of high strength steel square hollow sections with semi-circular stiffeners

• A novel high strength steel square hollow section with semi-circular stiffeners was proposed and experimentally investigated. • Stiffened stub columns achieved significantly higher compressive strength with delayed local buckling. • Established finite element models could replicate the test results well. • Existing design codes and methods were evaluated with the test and parametric data. This paper proposes a novel high strength steel square hollow section with semi-circular stiffeners, aiming to delay or eliminate premature local buckling failure of the steel tube and lead to improved compressive performance. A total of 9 stiffened and unstiffened stub columns were tested to investigate the failure modes and compressive responses. The test results showed that the stiffened sections achieved significantly higher compressive strength with delayed local buckling failure compared to the unstiffened counterparts. Tensile coupons were extracted from flat, corner and curve portions of the steel tubes in order to determine the corresponding material properties. Finite element (FE) models were established to numerically simulate the tested stub columns, in which both failure modes and load-end shortening curves could well replicate the test results. Parametric studies were then implemented using the validated FE model to extend the dataset. The obtained test and numerical results were used to assess the applicability of existing design standards and methods. It was found that EC3, ANSI/AISC 360-22, AS 4100 and Direct Strength Method (DSM) could be safely adopted in cross-section classifications and cross-section capacity predictions.