Cross-section stability of lean duplex stainless steel welded I-sections

Abstract

Despite growing interest in the use of stainless steel in construction and the development of a number of national and regional design codes, stainless steel is often still regarded as only suitable for specialised applications. This is partly due to the high initial material cost associated with the most commonly adopted austenitic grades. The initial material cost of stainless steel is largely controlled by the alloy content, in particular the level of nickel, which is around 8%–10% for the common austenitic grades. A recently developed grade, known as lean duplex stainless steel (EN 1.4162), has a far lower nickel content, around 1.5%, and hence lower cost. Despite the low nickel content, it possesses higher strength than the common austenitic stainless steels, along with good corrosion resistance and high temperature properties and adequate weldability and fracture toughness. The structural performance of lean duplex stainless steel remains relatively unexplored to date with only a few studies having been performed. For this reason, an experimental and analytical research programme investigating the structural characteristics of lean duplex stainless steel was initiated. The present paper summarises the laboratory tests performed on lean duplex stainless steel welded I-sections. The experiments include material testing, stub column tests and 3-point and 4-point bending tests. The experimental data were supplemented by results generated by means of a comprehensive numerical investigation including parametric studies covering a wide range of cross-sections. The obtained experimental and numerical results, together with the results of previous tests performed on lean duplex stainless steel cold-formed hollow sections are reported and used to assess the applicability of existing cross-section classification limits and the continuous strength method (CSM) to lean duplex stainless steel. Furthermore, the structural performance of lean duplex stainless steel was compared to the more commonly used stainless steel grades. Finally, based on the obtained results, design recommendations suitable for incorporation into Eurocode 3: Part 1.4 are proposed.