Discrete and continuous treatment of local buckling in stainless steel elements

Abstract

a b s t r a c tCross-section classification is an important concept in the design of metallic structures, as it addresses the susceptibility of a cross-section to local buckling and defines its appropriate design resistance. For structural stainless steel, test data on cross-section capacity have previously been relatively scarce. Existing design guidance has been developed based on the limited experimental results and conservative assumptions, generally leading to unduly strict slenderness limits. In recent years, available test data for stainless steel cross-sections have increased significantly, enabling these slenderness limits to be re-assessed. In this paper all available stainless steel test data have been collected and additional moment-rotation curves have been presented. The study covers both cold-formed and welded plated elements as well as CHS. Following analysis of the test results, new slenderness limits for all loading conditions have been proposed and statistically validated. In addition to re-assessment of the current slenderness limits, a new approach to the treatment of local buckling in structural elements -the Continuous Strength Method -has been outlined. The Continuous Strength Method (CSM) is based on a continuous relationship between cross-section slenderness and deformation capacity and is applied in conjunction with accurate material modelling. The method enables more rational and precise prediction of local buckling than can be achieved with the traditional cross-section classification approach, thus allowing better utilization of material and more economic design.

Comparative experimental study of hot-rolled and cold-formed rectangular hollow sections

“…The results indicate that the current slenderness limit of 42 given in Eurocode 3 is suitable for both hot-rolled and cold-formed sections, though a wider range of data is required for hot-rolled sections; this is in contrast the findings of the stub column tests, though more favourable performance would be anticipated from the bending tests due to the less onerous stress distribution in the web and therefore additional support offered to the compression flange and possible partial plastification of the tension flange. Similar findings have been observed for structural stainless steel sections [21]. In Fig.…”

“…The graphs are arranged such that a direct comparison between the hot-rolled and cold-formed sections of similar nominal dimensions can be made. In one out of the six simple bending tests, the bending moment fell below Mpl on the unloading path prior to the termination of the experiment, whilst for the remaining specimens rotation capacity was calculated on the basis of max (the maximum attained rotation prior to the test being terminated), though this does not necessarily reflect the full rotation capacity of the specimens [21]. Despite the full rotation capacity not being attained in some tests, all specimens were deemed to have sufficient rotation capacity (R > 3) for plastic design according to Eurocode 3 [22], as shown in Table 4.…”

Laser-welded stainless steel I-sections: Residual stress measurements and column buckling tests

“…18, the experimentally derived ultimate loads from the tested stub columns, normalised by their compressive yield load Afyc, are plotted against the element width-tothickness ratio c/tε for both outstand and internal elements, where c is the flat width of the element, t is the thickness and ε=[(235/fyc)(E/210000)] 0.5 . The EN 1993-1-4 Class 3 slenderness limits for internal and outstand elements, which were recently updated following research reported in [28], are also depicted. For the outstand flanges shown in Fig.…”

“…This is attributed to the significant strain hardening exhibited by stocky stainless steel cross-sections, which is not accounted for in EN 1993-1-4 [6]. Strain hardening is however accounted for in the deformation based continuous strength method (CSM) [28][29][30][31][32]. Comparisons between the ultimate capacities obtained in the stub column tests Nu and the predicted capacities according to EN 1993-1-4 NEN1993-1-4 and the CSM Ncsm are presented in Table 12, where the benefit of considering strain hardening, in term of both mean predictions and reduction in coefficient of variation (COV), is clear.…”

Flexural behaviour of stainless steel oval hollow sections

“…This has been highlighted in previous studies investigating the ultimate capacity of stainless steel cross-sections and members and an alternative design method, termed the continuous strength method (CSM) has been developed [22,37,50] and statistically validated [51]. The CSM has also been applied successfully to structural carbon steel [52].…”