Flexural buckling behaviour and residual strengths of stainless steel CHS columns after exposure to fire

Abstract

The flexural buckling behaviour and residual strengths of stainless steel circular hollow section (CHS) columns after exposure to fire were studied, based on a thorough experimental and numerical modelling programme, and reported in this paper. The experimental programme was performed on three series of specimens, and each series contained five geometrically identical specimens, with one unheated and the other four heated to different levels of elevated temperatures (namely 300 °C, 600 °C, 800 °C and 1000 °C). The detailed heating, soaking and cooling processes, material testing and pin-ended column tests were described, with the derived key experimental results fully presented. The testing programme was supplemented by a numerical modelling programme, including a validation study where finite element models were developed and validated against the test results, and a parametric study where the validated finite element models were employed to derive further numerical results over an extended range of cross-section dimensions and member lengths. Due to the absence of existing design codes for stainless steel structures after exposure to fire, the codified design provisions for stainless steel CHS columns at ambient temperature, as established in the Europe, America and Australia/New Zealand, were assessed for their applicability to stainless steel CHS columns after exposure to fire, based on the obtained test and numerical data. The assessment results generally revealed that the design buckling curve, as adopted in the European code, and the tangent modulus method, as employed in the American specification, lead to unsafe and scattered design flexural buckling strengths for stainless steel CHS columns after exposure to fire, while the explicit approach, as used in the Australian/New Zealand standard, yields a high level of accuracy and consistency in predicting the post-fire flexural buckling strengths of stainless steel CHS columns. • The flexural buckling responses and residual strengths of stainless steel circular hollow section (CHS) columns after exposure to fire were investigated. • Three series of stainless steel CHS column specimens were tested, with each series containing one unheated specimen and four specimens heated to different levels of elevated temperatures. • Finite element models were developed and validated against test results, and then utilised to perform parametric studies. • The accuracy of the codified flexural buckling design rules for stainless steel CHS columns at ambient temperature was assessed for their post-fire counterparts.