Numerical modeling of lean duplex stainless steel hollow columns of square, L-, T-, and þ -shaped cross sections under pure axial compression M. Longshithung Patton, Konjengbam Darunkumar Singh n Department of Civil Engineering, Indian Institute of Technology Guwahati, India article info Article history: Received 5 August 2011 Received in revised form 2 January 2012 Accepted 4 January 2012 Available online 24 January 2012 Keywords: Buckling Lean duplex stainless steel section Finite element modeling Square and NRCs sections abstract In this paper, finite element (FE) studies for LDSS (Lean Duplex Stainless Steel) hollow columns with square, L-, T-, and þ-shaped cross sections (i.e., SHC, LHC, THC and þHC respectively) are presented using ABAQUS, to gain an understanding of the cross sectional shape effects. The LDSS hollow columns having equal material cross-sectional areas with thickness varying from 5 m to 20 mm were subjected to uniform axial compression. Short/Stocky columns with lengths ( 1800 mm) of about three times the outer width of square were considered for the analyses. Based on the analyses, it has been found that for all the NRHCs (i.e., LHC, THC and þHC) considered, a nearly linear variation of P u with section thicknesses has been observed, although the increase for SHC was relatively slower in thinner sections (t o12.5 mm). The % increase in P u with 300% increase in t (from 5 m to 20 mm) has been found to be 1273%, 1252%, 1041% and 679%, respectively, for square, L-, T-, and þ-shaped sections. The gain in P u for LHC, THC and þHC sections as compared (expressed as P u /P u(sq) ) to SHC are in the range 120%–150%, 130%–170%, 140%–230%, respectively. Ductility at ultimate load has been observed to be  0.1–0.6% for SHC, LHC and THC (all thicknesses), and þHC (t r10 mm). & 2012 Elsevier Ltd. All rights reserved. 1. Introduction Construction industry is generally dominated by carbon steel due to low cost, long experience, applicable design rules and a large variety of strength classes; however it suffers inherently from comparatively low corrosion resistance and higher material cost. As an improvement over carbon steel, various stainless steel types can provide a very wide range of mechanical properties and material characteristics to suit the demands of numerous and diverse engineering applications, along with the advantages of not needing for surface corrosion protection in moderate to highly aggressive environments. Its main advantages include high corro- sion resistance, high strength, smooth and uniform surface, esthetic appearance, high ductility, impact resistance and ease of maintenance and construction. These benefits have prompted a moderately upsurge of using stainless steel in construction industry in the recent years. Traditionally, in the constructional industry, austenitic steel grades are used prominently. However, with increasing nickel prices (nickel content of  8%–11% in austenitic stainless steel) there is an escalation in the demand for lean duplexes stainless steel (LDSS) with low nickel content of  1.5%, such as grade EN 1.4162 [1–3]. LDSS grade EN 1.4162 in particular, with twice the mechanical strength of conventional austenitic and ferritic stainless steel, has a potential for use in constructions, and its use has seen significant growth and devel- opment over the last 20 years. The prime movers for this development have been soaring raw material costs, such as nickel, along with increasing demand for improved corrosion resistance and strength, enabling a reduction in section sizes leading to higher strength to weight ratios. As such, several recent investi- gations have been attempted on both normal and high strength stainless steel hollow (tube) columns with square, rectangular, circular and elliptical sections [4–11]. In addition to the aforementioned conventional cross-sectional shapes of columns, it is worthwhile to mention that, in the past two decades, the construction industry has shown increasing interest in the use of Non Rectangular Columns (NRCs) (e.g., L-, T-, and þ -shaped cross-sections) especially for reinforced concrete columns [12]. Compared with columns with rectangu- lar/square cross-sections, columns with NRCs have the advantage of providing a flushed wall face, resulting in an enlarged usable indoor floor space area and also in making the interior space more regular. So, NRCs (reinforced concrete) were applied in residential high-rise buildings and were welcomed by architects. These NRCs with L- or T-sections also share unique advantages of having large stiffness and strength in the direction of their longer sections. Whilst several experimental and numerical studies (e.g., [13,14]) on the behavior of reinforced concrete NRCs with L- or T-sections was reported, to the best of authors’ knowledge, there is an apparent lack of systematic studies relating to NRCs hollow columns, particularly for LDSS. Hence, in this paper an attempt has been made to investigate the behavior and strength of LDSS Contents lists available at SciVerse ScienceDirect journal homepage: www.elsevier.com/locate/tws Thin-Walled Structures 0263-8231/$ - see front matter & 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.tws.2012.01.002 n Corresponding author. Tel.: þ91 361 258 2423; fax: þ91 361 258 2440. E-mail address: darun@iitg.ernet.in (K.D. Singh). Thin-Walled Structures 53 (2012) 1–8