Experimental Study on Ferritic Stainless Steel RHS and SHS Cross-sectional Resistance Under Combined Loading

Abstract

The excellent corrosion resistance presented by all stainless steel grades, together with their appropriate mechanical properties, aesthetic appearance and easy maintenance, makes these metallic alloys perfect for sustainable structural performances. However, their nonlinear stressstrain behaviour together with their strong strain hardening features, makes them different from carbon steel and makes the development of some specific guidance necessary. Although the compressive and flexural behaviour of stainless steel Rectangular and Square Hollow Sections (RHS and SHS) has been widely analysed and advanced design approaches considering strain hardening have been developed, more general loading conditions such as combined axial compression and bending moment loading conditions still need to be investigated. Within this scenario, this paper presents an experimental programme on several ferritic RHS and SHS stub column tests subjected to concentric and eccentric compression. The objective is to extend the recent research on austenitic and lean duplex stainless steel RHS under combined loading to ferritic grades by assessing the applicability and accuracy of the interaction expressions currently codified in EN1993-1-4 and those proposed in the literature.

Experimental study on ferritic stainless steel RHS and SHS beam-columns

“…This allowed for the evaluation of the cold-forming effects, which led into an increase in both the proof stress  0.2 and the ultimate tensile strength  u , while ductility was considerably reduced. Since the experimental programme described in this paper was part of a more general experimental programme, where different ultimate responses of ferritic stainless steel RHS and SHS elements were investigated, the more in detail aspects of the material behaviour of the analysed specimens has already been published in [12,13]. Therefore, a summary of the most relevant information regarding tensile coupon testing is described in this section.…”

“…Strain hardening exponents n and m corresponding to the material model proposed by Mirambell and Real [17] are also reported. However, for the analysis of experimental tests and the assessment of different predicting expressions the weighted average material properties are usually determined [6,12,13,18] from coupon tests, calculating the weights according to the area of the flat/corner parts referred to the total area of the cross-section. Weighted average material parameters are presented in Table 2 and will be used throughout the different analyses in this paper.…”

“…Stub column test results reported in [13] have also been included in this analysis, together with the different buckling curves analysed in this section. hence, the ultimate capacity predictions are slightly more conservative but still safe.…”

“…For the evaluation of these interaction expressions, the same procedure followed by [11], [13] has been adopted, where U ratios by which each experimental data point exceeds or falls short of its respective design interaction curve have been calculated assuming proportional loading, as defined in Eq. (15) and Figure 17.…”

Structural performance of additive manufactured metallic material and cross-sections

“…This limit, and the slightly modified CSM yield slenderness limit of c/t" = 38.6 [85], may be seen to be generally applicable to PBF manufactured stainless steel SHS. The PBF stub column results have also been compared with existing, conventionally formed austenitic [76,78,81,70,86,69,87,88,89], duplex [77,78,81,89] and ferritic [79,82,90,91,92] SHS stub column data, as shown in Figure 25.…”