Abstract
Tubular structural members with slender cross-sections are susceptible to failure through local buckling of their tube walls. Previous numerical studies of steel elliptical hollow sections in compression predicted the local buckling modes and the ultimate loads of particularly slender specimens, with the results used to calibrate design methods for slender elliptical sections. Although these numerical parametric studies were conducted across a wide slenderness range, it was only possible to validate the models against experimental results in the low slenderness range since commercially-available steel EHS are intended to satisfy non-slender geometric limits prescribed by structural design codes. Such limitations to the experimental scope are circumvented in the present study through testing of highly-slender specimens produced using additive manufacturing techniques. A total of eight specimens of various cross-sectional aspect ratios and tube wall thicknesses were fabricated at London South Bank University using additive manufacturing techniques, which were then tested in compression; the observed load-deflection behaviour, ultimate loads, longitudinal strains and failure modes are discussed. Through appropriate rescaling of relevant parameters, design predictions for the ultimate load of the 3D-printed analogues are obtained using a design method intended for use with steel elliptical hollow sections. It is shown that the design predictions are safe-sided when compared to the present experimental results, with the accuracy generally increasing with aspect ratio and slenderness.
Highlights
Steel elliptical hollow sections (EHS) have found increased use in recent years in construction, having been employed in landmark projects such as Heathrow Terminal 5, Madrid Barajas Airport and Cork Airport (Chan et al, 2010)
The objective of the present study is to examine the behaviour of highly slender steel elliptical hollow sections in compression through the use of polymer analogues fabricated using additive manufacturing techniques; the use of such techniques for educational purposes in structural mechanics has been demonstrated successfully by Virgin (2018)
2.1 Geometry of EHS specimens Eight additive-manufactured EHS specimens were fabricated at London South Bank University (LSBU) with cross-sectional aspect ratios a/b = 1.5, 2.0 and 3.0, and nominal tube wall thickness t between 1.5 mm and 3.0 mm
Summary
Steel elliptical hollow sections (EHS) have found increased use in recent years in construction, having been employed in landmark projects such as Heathrow Terminal 5, Madrid Barajas Airport and Cork Airport (see Fig. 1a) (Chan et al, 2010). The combination of the mechanical efficiency offered by having a greater major axis flexural resistance and the aesthetic appeal of elliptical geometry has been a factor in the increased popularity of EHS in steel construction (Ruiz-Teran & Gardner, 2008). Reflecting this increased usage, the sections are included in European structural specifications (Comité Européen de Normalisation, 2006) and the recent revision to EN 1993-1-1 (Comité Européen de Normalisation, 2018). Studies have been conducted on stainless steel EHS (Theofanous et al, 2009) and on cold-formed steel EHS (Chen & Young, 2020)
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