Stainless Steel RHS Research Articles

Design of cold-formed ferritic stainless steel RHS perforated beams

Ferritic stainless steel has been increasingly used in construction industry due to its excellent mechanical properties and a relatively low price compared with other grades of stainless steel materials. Experimental and numerical investigation was performed to examine the structural behavior of ferritic stainless steel perforated beams. The experimental program consisted of twenty specimens of rectangular hollow sections subjected to four-point bending, based on which finite element model has been developed for further parametric study. The influence of hole size and section slenderness on the test and numerical specimens was evaluated. It was shown that moment capacity and curvature at ultimate moment had negligible effect for specimens with hole diameter up to 20% of web depth, but reduced when hole size beyond 20% of web depth in this study. The section slenderness of perforated beams was found to have little influence on reduction of moment capacity for the hole diameter up to 70% of web depth. The test and numerical results were also compared with design strengths predicted by the current direct strength method for cold-formed carbon steel perforated beams. It was shown that the current design rules provide conservative predictions to the cold-formed ferritic stainless steel perforated beams. In this study, modified design rules based on the direct strength method were proposed, and shown to improve the accuracy of these design rules in a reliable manner.

Design of cold-formed stainless steel RHS and SHS beam–columns at elevated temperatures

Numerical investigation of cold-formed stainless steel beam–columns at elevated temperatures ranged from 24–960 °C has been performed. The beam–column specimens were subjected to axial compression and minor axis bending. A finite element model was developed and validated against available experimental results at ambient temperature. An extensive parametric study with 308 lean duplex, austenitic and duplex stainless steel beam–column specimens of square and rectangular hollow section was carried out, and the numerical results were compared with the design strengths calculated by the American Specification, Australian/New Zealand Standard, European Code, and direct strength method. The suitability of these design rules for cold-formed stainless steel beam–columns at elevated temperatures were assessed by reliability analysis. It is shown that the existing design specifications are generally capable of predicting the cold-formed stainless steel beam–column strengths at elevated temperatures, and they are all considered to be reliable according to reliability analysis. The direct strength method provides the most accurate prediction when the carbon steel curve was used. The European Code provided the most conservative prediction among the design rules assessed in this study.

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

Ferritic stainless steels, with their lower nickel content, supplement the desirable features offered by different stainless steel grades with a more controlled and lower initial investment requirements, which have encouraged the use of these materials in construction. The nonlinear behaviour of stainless steel grades is not usually considered when extending design expressions codified for carbon steel to these alloyed materials, leading to overconservative design approaches and the applicability of the different design expressions initially developed for carbon steel needs to be adjusted for every stainless steel grade. The study of stainless steel elements subjected to combined flexural buckling and bending moment loading conditions only covers the most usual austenitic, duplex and lean duplex grades, but experimental results on ferritic grades are still necessary to complete the analysis. Hence, an experimental programme on ferritic stainless steel RHS and SHS pin-ended elements has been conducted where the flexural buckling and beam-column behaviour of these elements has been investigated. Furthermore, the assessment of the different design approaches for flexural buckling and interaction expressions for combined loading has been derived from the obtained experimental results, and current specifications provided in Standards have been found to be, in general, safe but overconservative.

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

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 stress–strain 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.

Interaction of bending and axial load for ferritic stainless steel RHS columns

Stainless steels are ideal for sustainable structural performances due to their excellent corrosion resistance, appropriate mechanical properties, aesthetic appearance and easy maintenance. However, the nonlinear behaviour and strain-hardening effects characterizing these materials make them different from carbon steel and some specific guidance is necessary. Although some investigations regarding the behaviour of stainless steel beam–columns subjected to combined compression and bending moment have already been published, most of them are based on the most commonly used austenitic and duplex grades. Hence, the work presented in this paper deals with the flexural buckling resistance of ferritic stainless steel RHS and SHS columns subjected to combined loading. The assessment of several design approaches codified in EN1993-1-4 and proposed in the literature has been conducted by comparing numerical results with the predicted ultimate capacities. The partial safety factor γM1 currently coded in EN1993-1-4 has been found to provide unsafe ultimate flexural buckling resistance predictions and new coefficients for the k interaction factor for ferritic RHS and SHS elements are proposed.