On the distortional-global interaction in cold-formed steel columns: Relevance, post-buckling behaviour, strength and DSM design

Martins, André Dias; Camotim, Dinar; Dinis, Pedro Borges

doi:10.1016/j.jcsr.2018.02.031

Cited by 30 publications

(31 citation statements)

References 25 publications

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“…The first two are used in this investigation, but it should be noted that the currently codified MND is replaced by the strength curves proposed in [9], which were found to yield much more accurate failure moment predictions. The same approach adopted for columns affected by D-G interaction [11] is followed in this work, leading to two strength curves for D-G interactive failures: (i) the NDG approach (MNDG), involving the replacement of My by MNG, and (ii) the NGD approach (MNGD), where My is replaced by MND  both approaches include the additional elastic-plastic strength reserve prescribed by the current North-American specification [10]. The NDG approach, which was found to yield better quality failure moment predictions, reads   , 0.673…”

Section: Direct Strength Methods (Dsm) Designmentioning

confidence: 99%

07.03: Distortional‐global interaction in lipped channel beams: Part II: Strength, relevance and DSM design

2017

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This work aims at presenting and discussing numerical results concerning the post‐buckling behaviour, strength and design of two types of simply supported lipped channel (LC) beams under uniform major‐axis bending and undergoing distortional‐global (D‐G) interaction. The relevance of the interaction effects is assessed by determining the beams whose ultimate strength and/or failure mode are visibly affected by them. Distinct (i) global‐to‐distortional critical buckling moment ratios (RGD) and (ii) yield‐to‐non critical buckling (distortional or global) moment ratios (Ry) are considered and, thus, different failure mode natures (global, distortional or interactive) are expected. For each beam type, combinations of 41 geometries and 11 yield stresses are dealt with, in order to (i) characterise the beams experiencing “true D‐G interaction” (RGD≈1.0) and “secondary global‐bifurcation D‐G interaction” (RGD >1.0 + high Ry) and (ii) investigate the possible occurrence of “secondary distortional‐bifurcation D‐G interaction” (RGD <1.0 + high Ry). The results presented consist of (i) relevant non‐linear equilibrium paths, (ii) deformed configuration evolutions along those paths and (iii) figures providing the failure mode characterisation. Then, the numerical failure moments obtained are compared with their predictions by (i) the currently codified DSM (Direct Strength Method) beam global and distortional strength curves, and (ii) proposed DSM‐based design approaches, specifically developed to handle D‐G interactive failures.

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Section: Direct Strength Methods (Dsm) Designmentioning

confidence: 99%

07.03: Distortional‐global interaction in lipped channel beams: Part II: Strength, relevance and DSM design

2017

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“…There is considerably less research activity devoted to columns prone to D-G interaction than to the coupling phenomena addressed before. Indeed, the existing studies addressing this type of interaction, relevant in intermediateto-long columns, consist of i) experimental investigations on rack-section uprights with and without holes [25,26], lipped channel columns [13] (originally intended to investigate L-D-G interaction) and web-stiffened lipped channel columns [27], and ii) SFE numerical investigations on simply supported and fixed-ended lipped channel columns [28,29], simply supported and warping-prevented racksection uprights with or without holes [30] and fixed-ended lipped channel, web-stiffened lipped channel and zedsection columns [31]. It is also worth noting i) a GBTbased numerical study on the D-G interactive mechanics in fixed-ended C and Z columns [32], and ii) an investigation involving cold-formed stainless steel lipped channel columns [33,34].…”

Section: Distortional-global Interaction In Columnsmentioning

confidence: 99%

“…The DSM design considerations concerning CFS columns failing in D-G interactive modes addressed here are due to Martins et al [31] and almost exclusively based on numerical failure load data acquired by these authors through parametric studies involving singly symmetric (C and WSLC -web-stiffened lipped channels) and pointsymmetric (Z) columns. The columns analysed exhibit a wide range of critical global-to-distortional buckling load ratios R GD (varying from 0.5 to 2.0), which means that all the three types of D-G interaction (True, SGB and SDB) were dealt with -naturally, D-FT interaction occurs in C and WSLC columns, while Z columns undergo D-F interaction.…”

Section: Dsm Designmentioning

confidence: 99%

Mode interaction in cold‐formed steel members: state‐of‐art report

et al. 2020

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Extended keynote paper of Eurosteel 2021 This is Part 2 of a two‐part paper providing a state‐of‐art report of the most recent findings concerning the behaviour, strength and Direct Strength Method (DSM) design of cold‐formed steel (CFS) columns and beams affected by mode coupling phenomena not adequately covered by the current specifications for CFS members. This second paper covers interactions involving global buckling modes, namely local‐distortional‐global (L‐D‐G), distortional‐global (D‐G) and global‐global (flexural‐torsional/flexural – FT‐F) interaction – note that local‐global (L‐G) interaction, already well mastered by the technical/scientific community, is not dealt with. Like Part 1 [1], this paper also addresses experimental tests, numerical simulations and DSM‐based design approaches, intended to i) acquire in‐depth knowledge on the non‐linear behaviour (elastic and elastic‐plastic), load‐carrying capacity and failure mode nature of the members under consideration, and ii) make use of the above knowledge to develop, propose and assess the merits of efficient DSM‐based design approaches to estimate their failure loads/moments. Taking into account the fundamental concepts and DSM design curves presented in Part 1 [1], the paper addresses separately each mode coupling phenomenon dealt with, for columns, and only D‐G interaction for beams – recall that L‐D interaction (columns and beams) was covered in Part 1 [1]. For columns undergoing L‐D‐G interaction and angle columns susceptible to FT‐F interaction, the work reported includes experimental studies, numerical simulations and DSM‐based design considerations and/or guidelines. For columns and beams experiencing D‐G interaction and channel columns prone to FT‐F coupling, only numerical results are reported – they reveal surprising behavioural features that will be very useful in planning future test campaigns and achieving efficient design approaches. Finally, the two‐part paper closes with a few concluding remarks and a perspective about future developments in this field.

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“…1(a1)-(c1) are now studied, in order to shed fresh light on the mechanics of D-G interaction, taking full advantage of the GBT modal nature. It is well known that distinct IGI may cause, to a smaller or larger extent, different qualitative postbuckling behaviours and, in some cases, may also lead to coupling phenomena of distinct natures (still unfamiliar to the technical community [5,6]). Therefore, the consideration of different IGI shapes is crucial in mode interaction investigations.…”

Section: True D-g Interactionmentioning

confidence: 99%

07.02: Distortional‐global interaction in lipped channel beams: Part I: Mechanics and elastic behaviour

Martins

Camotim

Gonçalves³

et al. 2017

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This work aims at presenting and discussing Generalised Beam Theory (GBT) numerical results concerning the elastic geometrically non-linear behaviour of simply supported lipped channel (LC) beams under uniform major-axis bending and experiencing distortional-global (D-G) interaction, making it possible to shed fresh light on the mechanics underlying this coupling phenomenon. Two LC beams geometries are considered, each exhibiting a different type of D-G interaction, namely (i) "true D-G interaction" (close global, McrG, and distortional, McrD, critical buckling moments), containing three critical-mode initial geometrical imperfection shapes (two global, due to the lack of symmetry, and one distortional) and (ii) "secondary global-bifurcation interaction -SGI" (McrD<

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On the distortional-global interaction in cold-formed steel columns: Relevance, post-buckling behaviour, strength and DSM design

Cited by 30 publications

References 25 publications

07.03: Distortional‐global interaction in lipped channel beams: Part II: Strength, relevance and DSM design

07.03: Distortional‐global interaction in lipped channel beams: Part II: Strength, relevance and DSM design

Mode interaction in cold‐formed steel members: state‐of‐art report

07.02: Distortional‐global interaction in lipped channel beams: Part I: Mechanics and elastic behaviour

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