Experimental and numerical studies of austenitic stainless steel CHS stub columns after exposed to elevated temperatures

• Main Authors: He, An, Liang, Yating, Zhao, Ou
• Other Authors: School of Civil and Environmental Engineering
• Format: Article
• Language: English
• Published: 2021
• Subjects: Engineering::Civil engineering; Continuous Strength Method; Circular Hollow Sections
• Online Access: https://hdl.handle.net/10356/151645
• Institution: Nanyang Technological University

This paper presents a thorough testing and finite element modelling study of the material response and structural behaviour of austenitic stainless steel circular hollow section (CHS) stub columns after exposed to elevated temperatures. The testing programme was conducted on two cold-formed austenitic stainless steel circular hollow sections: CHS 73 × 3 and CHS 89 × 3, and involved 16 material tensile coupon tests and 16 stub column tests after exposure to eight levels of elevated temperatures ranging from 30 °C to 1000 °C. The experimental investigation was supplemented by a finite element modelling study, where numerical models were firstly developed and validated against the post-fire stub column experimental results, and afterwards utilised to carry out numerical parametric studies to extend the test data pool over a wider range of cross-section geometric dimensions. The measured post-fire tensile coupon test results indicated that the Young's modulus and the ultimate stress of austenitic stainless steel generally remained unchanged after exposure to elevated temperatures, while the post-fire 0.2% proof (yield) stress and ultimate strain were similar to the corresponding room temperature properties for temperatures up to around 600 °C–800 °C, but experienced a reduction and an increase after exposure to higher elevated temperatures, respectively. Given that there have been no established design standards for stainless steel structures after exposure to fire, the corresponding room temperature design rules, as set out in the European code, American specification and Australia/New Zealand standard, were evaluated for austenitic stainless steel CHS stub columns after exposed to elevated temperatures, revealing safe but conservative cross-section compression resistance predictions, owing principally to the adoption of the 0.2% proof (yield) stress as the design stress without considering strain hardening. The deformation-based continuous strength method accounts for material strain hardening in calculating cross-section capacities at ambient temperature. Its applicability to the design of austenitic stainless steel CHS stub columns after exposed to elevated temperatures was also assessed. The results of the assessment indicated that the continuous strength method leads to both precise and consistent compression resistance predictions of austenitic stainless steel CHS stub columns after exposed to elevated temperatures.