Experimental Study of Cold-Formed Ferritic Stainless Steel Hollow Sections

Abstract

Stainless steel is gaining increasing usage in construction owing to its durability, favorable mechanical properties and its aesthetic appearance, with the austenitic grades being the most commonly utilized. Austenitic stainless steels have a high nickel content (8%-11%), resulting in high initial material cost and significant price fluctuations; this, despite its desirable properties, represents a considerable disadvantage in terms of material selection. Ferritic stainless steels, having no or very low nickel content, may offer a more viable alternative for structural applications, reducing both the level and variability of the initial material cost, while maintaining adequate corrosion resistance. There is currently limited information available on the structural performance of this type of stainless steel. Therefore, to overcome this limitation, a series of material, cross-section and member tests have been performed, covering both the standard EN 1.4003 grade (similar to the chromium weldable structural steel 3Cr12) and the EN 1.4509 grade (441), which has improved weldability and corrosion resistance. In total, twenty tensile coupon tests, sixteen compressive coupon tests, eight stub column tests, sixteen flexural buckling tests and eight in-plane bending tests were carried out. Precise measurements of the geometric properties of the test specimens, including the local and global geometric imperfections were also made. The experimental results are used to assess the applicability of the current European (EN 1993(EN -1-4:2006 and North American (SEI/ASCE-8:2002) provisions to ferritic stainless steel structural components. In addition, the relative structural performance of ferritic stainless steel to 1 PhD Student, Dept. of Civil and Environmental Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ,U.K. (corresponding author) E-mail: sheida.afshan06@imperial.ac.uk 2 Reader, Dept. of Civil and Environmental Engineering, South Kensington Campus, Imperial College London, London SW7 2AZ, U.K. E-mail: leroy.gardner@imperial.ac.uk 2 that of more commonly used stainless steel grades is also presented, showing ferritic stainless steel to be an attractive choice for structural applications.

Experimental study on ferritic stainless steel simply supported and continuous beams

“…Figure 14 indicates that both Class 1 cross-sectional classification limits appear to be unsafe for the tested specimens, since none of them reach the required rotation limit expected from their c/t slenderness. This can be attributed to the less ductile behaviour of ferritic stainless steel grades compared to austenitic and duplex grades and is in line with existing results reported by Afshan and Gardner [16]. Regardless, the 3 R  criterion should be revised when stainless steel crosssections are considered, as the plastic moment capacity of these cross-sections is not clearly defined due to their nonlinear stress-strain behaviour.…”

Strength enhancements in cold-formed structural sections — Part II: Predictive models

“…The AS/NZS 4673 [34] and SEI/ASCE-8 [35] standards provide both tensile and compressive material properties while the EN 1993-1-4 [2] only considers tensile material properties. Existing data on tensile and compressive coupon tests from the literature [9,11,[24][25][26][27]36] were analysed, see Fig. 6, and it was shown that the compressive 0.2% proof strength is on average 5% lower than that for tension.…”

“…In order to assess the wider applicability of the predictive models presented in Sections 3.3 and 3.4, tensile coupon data from a broad spectrum of existing testing programs have been gathered [9,10,13,[16][17][18][19][20][21][22][23][24][25][26][27][28] to supplement those obtained in the companion paper [1]. The collated database covers a range of structural section types -CHS, SHS, RHS, angles, lipped channel sections (LCS) and hollow flange channel sections (HFCS) from both cold-rolling and press-braking fabrication processes, as illustrated in Fig.…”

Behaviour of structural stainless steel cross-sections under combined loading – Part I: Experimental study

“…Steel transfer plates were placed between the specimen and the two loading points to distribute the load and wooden blocks were inserted into the tube at the loading points to prevent web crippling. A similar arrangement has been successfully employed in previous studies [12,41]. Strain gauges were attached to the top and bottom flanges of the test specimens at a distance of 5 mm from the mid-span to avoid contact with the string potentiometer, which was placed at mid-span to measure the vertical deflection.…”