Testing and numerical modelling of lean duplex stainless steel hollow section columns

Abstract

Stainless steels are employed in a wide range of structural applications. The austenitic grades, particularly EN 1.4301 and EN 1.4401 and their low-carbon variants EN 1.4307 and EN 1.4404 are the most commonly used within construction and these typically contain around 8-11% nickel. The nickel represents a large portion of the total material cost and thus high nickel prices and price volatility have a strong bearing on both the cost and price stability of stainless steel. While austenitic stainless steel remains the most favourable material choice in many applications, greater emphasis is now being placed on the development of alternative grades with lower nickel content. In this study, the material behaviour and compressive structural response of a lean duplex stainless steel (EN 1.4162), which contains approximately 1.5% nickel are examined. A total of eight stub column tests and twelve long column tests on lean duplex stainless steel square (SHS) and rectangular hollow sections (RHS) are reported.Precise measurements of material and geometric properties of the test specimens were also made, including the assessment of local and global geometric imperfections. The experimental studies were supplemented by finite element analysis and parametric studies were performed to generate results over a wider range of cross-sectional and member slenderness. Both the experimental and numerical results were used to assess the applicability of the Eurocode 3: Part 1-4 provisions regarding the Class 3 slenderness limit and effective width formula for internal elements in compression and the column buckling curve for hollow sections to lean duplex structural components. Comparisons between the structural performance of lean duplex stainless steel and that of other more commonly used stainless steel grades are also presented, showing lean duplex to be an attractive choice for structural applications.

Experimental study of the shear response of lean duplex stainless steel plate girders

“…The obtained values are close to those reported by Saliba and Gardner [8] (n = 10.0 and n' 0.2,1.0 = 2.0) following coupon tests on similar lean duplex stainless steel plate material used to form welded I-sections. The values reported by Theofanous and Gardner [6,7] from tests on cold-formed lean duplex stainless steel hollow section material (n = 7.0 and n' 0.2,1.0 = 3.3), indicate a more rounded stress-strain response, which is typical of cold-formed material.…”

“…(3), where σ 0.2 is the tensile 0.2% proof stress and σ cr is the elastic critical buckling stress of the most slender constituent plate element in the section, determined on the basis of the flat width of the element. This imperfection amplitude prediction model has been successfully employed for the modelling of lean duplex stainless steel welded I-sections in compression and bending [8], and further similar applications [6,7,27]. The imperfection amplitude ω D&W is given by Eq.…”

“…The finite element type used for the numerical analyses was the four-noded doubly curved general-purpose shell element S4R with finite membrane strains. This element has been shown to be suitable for the modelling of a range of shell thicknesses and has been successfully employed in the modelling of lean duplex stainless steel welded Isections [8] and other similar structural components [6,7,23,24].…”

“…In order to overcome this, a comprehensive programme of experimental and numerical research is underway at Imperial College London to investigate the structural performance of lean duplex stainless steel. Initial research concentrated on cold-formed hollow sections [6,7], while more recently the focus has moved to welded I-sections [8] and, in the present paper, plate girders. Other recent studies of cold-formed lean duplex stainless steel hollow sections have been performed by Huang and Young [9] and Patton and Singh [10].…”

Bearing failure in stainless steel bolted connections

“…Corrosion resistance is the property most often cited as the reason for its adoption while the high initial material cost acts to limit the number of suitable applications. This situation may, however, be about to alter with the introduction of low nickel (lean duplex) stainless steel [2] at a material cost of around twice that of carbon steel -this could make hitherto prohibitively expensive applications much more cost effective.…”