Experimental study of press-braked austenitic stainless steel and press-braked ferritic stainless steel channel columns

• Main Author: Tan, Joshua Kai Wen
• Other Authors: Zhao Ou
• Format: Final Year Project
• Language: English
• Published: Nanyang Technological University 2021
• Subjects: Engineering::Civil engineering
• Online Access: https://hdl.handle.net/10356/154168
• Institution: Nanyang Technological University

Experimental investigation of ten slender press-braked austenitic (Grade EN 1.4301) and ten slender press-braked ferritic (Grade 1.4512) stainless steel channel section columns were conducted, and their behaviour were discussed in this report. The experimental study comprised of material tensile coupon tests, initial geometric imperfection measurements and compression loading tests on class 4 pin-ended stainless steel columns. The obtained failure loads were analysed and evaluated against predictions from Eurocode EN 1993-1-4 for stainless steel sections. It is shown here that the Eurocode predictions provided overly conservative values. In this regard, two methods were proposed to improve the accuracy of predictions. The first method was to modify two parameters in the current EN 1993-1-4 for stainless steel that affect the flexural buckling curves. The two parameters were three values of α that affect the characteristics of flexural buckling curves and two values of slenderness limits λ ̄_0. It should be noted that (a) the flexural buckling curves and (b) the effective width formulas in EN 1993-1-4 for stainless steel were simply taken from the corresponding equations in EN 1993-1-1 for carbon steel. It was found that the modifications on the two parameters (α and λ ̄_0) produced marginal improvements in accuracy. The source of conservatism stemmed from the effective width formulas for local buckling for the stainless steel sections. Stainless steel material exhibits monotonically increasing stress-strain values and does not have a well-defined yield point or a yield plateau compared to carbon steel which has both well-defined yield strength and yield plateau. Thus, the effective width calculations from EN 1993-1-4 were far too conservative for stainless steel column sections. Further examinations of the failure mode confirmed this finding, i.e. only the flange buckled and the web remained flat. Thus, the improvement on predictions was marginal. An alternative approach known as the Rankine method was tried. This was the first time the approach was applied to stainless steel columns. A preliminary study showed that the Rankine method gave promising results in terms of accuracy, although with greater scatter compared to the first method.