Axially Loaded Stainless Steel Columns in Case of Fire

Abstract

The simple model of Eurocode 3, for the fire resistance evaluation of stainless steel members, are based on the procedures used for carbon steel structural elements. However, due to the existing differences in the constitutive laws of these two materials, it is expected that it would not be possible to use, in both materials, the same formulae for the member stability calculation, as proposed in Eurocode 3. This paper aims at increasing the knowledge on the behaviour of stainless steel axially loaded columns at elevated temperatures. For this purpose, a geometrical and material non linear computer code has been used to determine the buckling load of these elements. The Eurocode formulae are evaluated and a new proposal, that ensures accurate and conservative results when compared with the numerical simulations, is presented. reduction factor for the flexural buckling in axis in case of fire χ min,fi minimum of the reduction factor χ i,fi NOTATIONS INTRODUCTIONThe use of stainless steel for structural purposes has been limited to projects with high architectural value, where the innovative character of the adopted solutions is intended to add value to the structure. The high initial cost of stainless steel, coupled with: (i) limited design rules, (ii) reduced number of available sections and (iii) lack of knowledge on the additional benefits of its use as a structural material, are some of the reasons that force designers to avoid its use. However, more accurate analyses point to a good performance of stainless steel when compared against conventional carbon steel in fire situation [1,2,3].The most important advantage of stainless steels is their corrosion resistance, however, their aesthetic appearance, ease of maintenance, durability and the low life-cycle costs are also valuable characteristics. Engineers often disregard these advantages of stainless steel due to its high initial cost. Nevertheless, greater importance is being given to total life costing because of high maintenance, shutdown, demolition and parts replacement costs. Experience has shown that the benefits of a long life with low maintenance and repair requirements more than compensates for the higher initial purchase cost of stainless steel.Part 1-4 of Eurocode 3 (EC3) "Supplementary rules for stainless steels" [4] gives design rules for stainless steel structural elements at room temperature, and only mentions the stainless steel structural elements fire resistance by referring to the fire part of the same Eurocode, EN 1993-1-2 [5]. Although carbon steel and stainless steel have different constitutive laws, EC3 states that the structural elements made of these two materials must be checked for their fire resistance with the same formulae. Thus, based on the formulae in Part 1-4 of EC3, Uppfeldt [6] presented a design model for stainless steel hollow columns in case of fire based on both experimental and numerical tests. Regarding the study of axially loaded carbon steel columns, Franssen in 1996 [7,8] proposed a procedure for the safety...

Investigating the role of gradual yielding in stainless steel columns and beams by virtual testing

“…This section presents a comparison of the parametric study results with the existing design rules provided in EN 1993-1-2 (2005) and its modified versions proposed by Ng and Gardner (2007), Uppfeldt et al (2008) and Lopes et al (2010). Based on EN 1993-1-2, the design fire resistance of stainless steel structures, assuming a uniform temperature distribution, is based on the room temperature design resistance, supplied in EN 1993EN -1-4 (2006, modified to take account of the mechanical properties at elevated temperature and with a revised buckling curve.…”

“…Parametric studies were performed to investigate the effects of variation of load level and global slenderness on the elevated temperature buckling response of ferritic stainless steel columns, and to extend the range of structural performance data. Both the experimental and numerical parametric study results were compared with the current design rules in EN 1993EN -1-2 (2005 and recent proposed modifications thereof by Ng and Gardner (2007), Uppfeldt et al (2008) and Lopes et al (2010).…”

P10.01: Comparative numerical buckling analysis: Of compressed carbon and stainless steel members at elevated temperatures

“…In contrast, ultimate buckling loads of stainless steel hot-rolled HE200A column are under predicted, with deviations of -9% and -14% regarding FE results. The similar outcome that indicates to inadequate level of the structural safety in EN 1993-1-2 [1] was gained in the extensive numerical investigation performed by Lopes et al [16]. Eurocode for fire design of steel structures EN1993-1-2 [1] does not explicitly define use of the simplified method for verification of the stainless steel compressed members related to different stainless steel grades and different manufacturing techniques.…”

Fire Resistance of Stainless Steel Axially Loaded Elliptical Hollow Section Columns

“…According to a previous study carried out on Class 1 and 2 I-section columns [10] a new proposal for the fire design of axial compression resistance of columns was developed, maintaining the main design approach from EC3 and modifying the following parameters.…”

“…The parameter is 1.0 for the cases of buckling about the strong axis and 1.5 for the cases of buckling about the weak axis. Although this previous study [10] did not cover tubular elliptical columns and all cross-section classes, EC3 also does not specify calculation rules for those section types. Therefore, it was assumed that the same design approach could be applied, independently of the section concerned.…”