Experimental and numerical investigations on stub column behaviour of cold-formed high strength steel irregular octagonal hollow sections

Abstract

Comprehensive experimental and numerical investigations into the structural behaviour of cold-formed high-strength steel (HSS) irregular octagonal hollow sections (IOctHS) are presented in this paper. A total of 13 IOctHS stub columns were tested. Material properties measurements were conducted on the tensile coupons taken from both parent plates and within the cross-sections of HSS IOctHS stub columns. Initial local geometric imperfection measurements were also carried out. In conjunction with experimental tests on the stub columns, finite element (FE) models were developed to replicate the test results and failure modes. Afterwards, the validated FE models were employed to conduct parametric studies to supplement the experimental data by generating further structural performance data covering a broader range of cross-section slenderness. Cross-section slenderness limits set out in design codes such as EN 1993-1-1, ANSI/AISC 360-16, AS 4100 as well as ASCE/SEI 48, and design methods of DSM as well as CSM were evaluated against the experimental and numerical data. It was found that the current limits for internal compression plate elements of rectangular hollow sections set out in the design standards are not suitable for the design of cold-formed HSS IOctHS under compression load. Cross-section strength predictions obtained from EN 1993-1-12, ANSI/AISC 360-16, AS 4100, ASCE/SEI 48, DSM, CSM and modified design methods were also compared with the tests and numerical results. Relatively accurate predictions are provided by design codes. Non-conservative results are obtained from DSM and the CSM yields more consistent and precise results than DSM. The modified design approaches were also assessed and discussed.