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Dinar Camotim - One of the best experts on this subject based on the ideXlab platform.
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DSM Design of Cold-Formed Steel Columns Failing in Distortional Modes at Elevated Temperatures
International Journal of Steel Structures, 2019Co-Authors: Alexandre Landesmann, Dinar Camotim, Fernanda C. M. SilvaAbstract:This paper aims at investigating the structural behaviour, strength and Direct Strength Method (DSM) design of cold-formed steel columns failing in Distortional modes at elevated temperatures. The results concern pin-ended and fixed-ended columns displaying four cross-section shapes, with various dimensions, subjected to 8 temperatures. It is shown that the current DSM Distortional design is unable to handle adequately Distortional failures at elevated temperatures. Then, a modified DSM design approach is proposed: it consists of incorporating a temperature-dependent reduction factor ratio, based on the EC3-1.2 model, in the existing strength curve—the modified design curves are shown to yield adequate failure load predictions for the set of columns under consideration. This finding provides motivation and encouragement to continue the ongoing search for an efficient DSM-based design approach for columns failing in Distortional modes under elevated temperatures.
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post buckling behaviour of thin walled regular polygonal tubular columns undergoing local Distortional interaction
Thin-walled Structures, 2019Co-Authors: Dinar Camotim, André Dias Martins, Rodrigo GoncalvesAbstract:Abstract This work presents and discusses numerical results of an ongoing investigation concerning the elastic post-buckling behaviour and imperfection sensitivity of regular convex polygonal cross-section (RCPS) tubular columns affected by local-Distortional (L-D) interaction. This investigation is conducted by means of geometrically non-linear Generalized Beam Theory (GBT) analyses, extending the knowledge on the “pure” local and Distortional post-buckling behaviours of RCPS tubes recently reported by Martins et al. [1] . Due to their inherent modal nature, the GBT analyses make it possible to acquire in-depth knowledge on the structural behaviour of RCPS tubes and also to include, in a straightforward fashion, arbitrary member initial geometrical imperfections. Columns with Distortional-to-local critical buckling load ratios (i) close to 1 (“true L-D interaction” – the most trivial L-D interaction type) and (ii) significantly above 1 (“secondary-Distortional bifurcation L-D interaction” – the most relevant L-D interaction type) are investigated. Local/Distortional critical-mode initial geometrical imperfections and (linear) combinations of both are considered in the former columns, while only local initial imperfections are dealt with in the latter ones – several amplitudes are dealt with to assess the imperfection sensitivity. For comparison and validation purposes, ABAQUS shell finite element analysis results are also reported.
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on the mechanics of local Distortional interaction in thin walled lipped channel beams
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This paper investigates the elastic post-buckling behaviour of simply supported thin-walled lipped channel beams undergoing local-Distortional (L-D) interaction. The beams are uniformly bent about the major-axis and experience flange-triggered local buckling (most common situation in practice). Three beam geometries are considered, each exhibiting a different type of L-D interaction, namely (i) “true L-D interaction” (close local and Distortional critical buckling moments – two critical-mode initial geometrical imperfections are used, akin to the competing critical buckling modes), (ii) “secondary local-bifurcation L-D interaction” or (iii) “secondary Distortional-bifurcation L-D interaction” (critical Distortional-to-local buckling moment ratio well below or above 1.0, respectively, with “high enough” yield stresses). The results presented and discussed are obtained through elastic geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the beam deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth knowledge on the beam L-D interaction mechanics. Particular attention is devoted to interpreting the quantitative and qualitative differences exhibited by the beam post-buckling behaviours associated with the three aforementioned L-D interaction types.
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on the mechanics of Distortional global interaction in fixed ended columns
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This work reports the results of a numerical investigation concerning the elastic post-buckling behaviour of fixed-ended thin-walled lipped channel and zed-section columns affected by Distortional-global (D-G) interaction – “unexpected” features associated with the global buckling nature are unveiled in both cases. The columns analysed (i) exhibit cross-section dimensions and lengths ensuring the simultaneous occurrence of Distortional and global critical buckling, and (ii) contain critical-mode initial geometrical imperfections (linear combinations of the critical Distortional and global buckling mode shapes). For comparison and clarification purposes, the post-buckling behaviour of lipped channel columns buckling in an “isolated” Distortional mode and containing “pure” Distortional and global (flexural-torsional) initial geometrical imperfections are also analysed. The results presented and discussed are obtained through geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the column deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth insight on the mechanics underlying D-G interaction in columns. Finally, particular attention is paid to interpreting the differences exhibited by the various column post-buckling behaviours investigated.
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Distortional-global interaction in lipped channel and zed-section beams: Strength, relevance and DSM design
Thin-Walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Pedro Borges DinisAbstract:Abstract This work aims at presenting and discussing numerical results concerning the post-buckling behaviour, strength and design of cold-formed steel simply supported lipped channel and zed-section beams under uniform bending and undergoing Distortional-global (D-G) interaction – two different support conditions are considered in the lipped channel beams. The relevance of the interaction effects is assessed by identifying 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, which are expected to lead to different failure mode natures (global, Distortional or interactive). For each beam type, combinations of 41 geometries and 11 yield stresses are considered, in order (i) to characterise the beams experiencing “true D-G interaction” (RGD ≈ 1.0) and “secondary global-bifurcation D-G interaction” (RGD > 1.0 and high Ry) and (ii) to investigate the possible occurrence of “secondary Distortional-bifurcation D-G interaction” (RGD
Pedro Borges Dinis - One of the best experts on this subject based on the ideXlab platform.
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on the mechanics of local Distortional interaction in thin walled lipped channel beams
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This paper investigates the elastic post-buckling behaviour of simply supported thin-walled lipped channel beams undergoing local-Distortional (L-D) interaction. The beams are uniformly bent about the major-axis and experience flange-triggered local buckling (most common situation in practice). Three beam geometries are considered, each exhibiting a different type of L-D interaction, namely (i) “true L-D interaction” (close local and Distortional critical buckling moments – two critical-mode initial geometrical imperfections are used, akin to the competing critical buckling modes), (ii) “secondary local-bifurcation L-D interaction” or (iii) “secondary Distortional-bifurcation L-D interaction” (critical Distortional-to-local buckling moment ratio well below or above 1.0, respectively, with “high enough” yield stresses). The results presented and discussed are obtained through elastic geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the beam deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth knowledge on the beam L-D interaction mechanics. Particular attention is devoted to interpreting the quantitative and qualitative differences exhibited by the beam post-buckling behaviours associated with the three aforementioned L-D interaction types.
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on the mechanics of Distortional global interaction in fixed ended columns
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This work reports the results of a numerical investigation concerning the elastic post-buckling behaviour of fixed-ended thin-walled lipped channel and zed-section columns affected by Distortional-global (D-G) interaction – “unexpected” features associated with the global buckling nature are unveiled in both cases. The columns analysed (i) exhibit cross-section dimensions and lengths ensuring the simultaneous occurrence of Distortional and global critical buckling, and (ii) contain critical-mode initial geometrical imperfections (linear combinations of the critical Distortional and global buckling mode shapes). For comparison and clarification purposes, the post-buckling behaviour of lipped channel columns buckling in an “isolated” Distortional mode and containing “pure” Distortional and global (flexural-torsional) initial geometrical imperfections are also analysed. The results presented and discussed are obtained through geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the column deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth insight on the mechanics underlying D-G interaction in columns. Finally, particular attention is paid to interpreting the differences exhibited by the various column post-buckling behaviours investigated.
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Distortional-global interaction in lipped channel and zed-section beams: Strength, relevance and DSM design
Thin-Walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Pedro Borges DinisAbstract:Abstract This work aims at presenting and discussing numerical results concerning the post-buckling behaviour, strength and design of cold-formed steel simply supported lipped channel and zed-section beams under uniform bending and undergoing Distortional-global (D-G) interaction – two different support conditions are considered in the lipped channel beams. The relevance of the interaction effects is assessed by identifying 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, which are expected to lead to different failure mode natures (global, Distortional or interactive). For each beam type, combinations of 41 geometries and 11 yield stresses are considered, in order (i) to characterise the beams experiencing “true D-G interaction” (RGD ≈ 1.0) and “secondary global-bifurcation D-G interaction” (RGD > 1.0 and high Ry) and (ii) to investigate the possible occurrence of “secondary Distortional-bifurcation D-G interaction” (RGD
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On the Distortional-global interaction in cold-formed steel columns: Relevance, post-buckling behaviour, strength and DSM design
Journal of Constructional Steel Research, 2018Co-Authors: André Dias Martins, Dinar Camotim, Pedro Borges DinisAbstract:Abstract This work reports the available results of an ongoing numerical (shell finite element) investigation on the post-buckling behaviour, strength and design of fixed-ended cold-formed steel columns undergoing Distortional-global (D-G) interaction. Columns with different cross-section shapes are analysed, namely plain lipped channel (LC), web-stiffened lipped channel (WSLC) and zed-section (Z) columns, in order to investigate distinct D-G interaction natures: involving either Distortional and (global) flexural-torsional buckling (LC and WSLC columns) or Distortional and (global) minor-axis flexural buckling (Z columns). In particular, the relevance of these D-G interaction types is discussed, by assessing when they affect visibly the column ultimate strength and/or failure mode. The results presented and discussed concern columns with various geometries and yield stresses, thus ensuring a wide variety of range combinations involving (i) global-to-Distortional critical buckling load ratios (RGD) and (ii) squash-to-non critical buckling (Distortional or global) load ratios (Ry) and leading to non-negligible failure load erosion. The possible occurrence and failure load impact of “secondary (Distortional or global)-bifurcation D-G interaction” (RGD 1.0 and high Ry) are investigated - it is well known that such impact may be significant in columns experiencing “true D-G interaction” (RGD ≈ 1.0). The above results consist of (i) relevant non-linear (elastic and elastic-plastic) equilibrium paths, (ii) deformed configuration evolutions along those paths, evidencing D-G interactive effects, and (iii) figures providing the failure mode characterisation. Then, the numerical failure load data obtained are compared with their predictions by (i) the currently codified DSM (Direct Strength Method) column global and Distortional strength curves, and (when necessary) (ii) proposed DSM-based design approaches, specifically developed to handle D-G interactive failures - a few design considerations are drawn from these comparisons.
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Distortional failure of cold formed steel beams under uniform bending behaviour strength and dsm design
Thin-walled Structures, 2017Co-Authors: André Dias Martins, Dinar Camotim, Alexandre Landesmann, Pedro Borges DinisAbstract:Abstract This work reports numerical results concerning cold-formed steel simply supported beams buckling and failing in Distortional modes under uniform bending and exhibiting three cross-section shapes, namely (i) lipped channels bent about the major-axis, (ii) zed-sections under skew bending causing uniform flange compression (worst case), and (iii) hat-sections subjected to either major-axis or minor-axis bending (compressed lips in the latter case). Two end support conditions are considered, differing in the warping and local displacement/rotation restraints, which are either completely free or fully prevented. The beams analysed have several cross-section dimension ratios and lengths, in order to assess their influence on the Distortional post-buckling behaviour and ultimate strength – particular attention is paid to the influence of (i) the flange-web and lip-flange width ratios, and (ii) the critical (Distortional) half-wave number. In addition, the beams exhibit different yield stresses, making it possible to cover wide Distortional slenderness ranges. After presenting and discussing the numerical elastic and elastic-plastic post-buckling results obtained, consisting of equilibrium paths, deformed configurations, plastic strain distributions, failure moments and collapse mechanisms, the paper shows that the currently codified Direct Strength Method (DSM) design curve fails to predict adequately the failure moments of some of the beams analysed and addresses the development/proposal of novel DSM strength curves, providing better quality predictions of all the numerical failure moments available.
Long-yuan Li - One of the best experts on this subject based on the ideXlab platform.
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An analytical solution of Distortional buckling resistance of cold-formed steel channel-section beams with web openings
Thin-walled Structures, 2019Co-Authors: Nan-ting Yu, Wei-bin Yuan, Long-yuan Li, Feng YuAbstract:Abstract Circular holes can be commonly found in the web of cold-formed steel beams to accommodate services such as electric wires and pipelines. The presence of holes will reduce the critical buckling stress of the beams. Hancock proposed solution for determining the Distortional critical stress of channel section beams, but limited to the sections without holes. This paper presents an analytical study on the Distortional buckling of cold-formed steel channel-section beams with circular holes in the web. Hancock's solution has been modified to derive a simple formulation for approximating the elastic critical stress and moment of Distortional buckling of the channel-section beams with circular holes in the web, which are compared with those from the finite element buckling analysis using ANSYS. Finally, the influence of multiple holes on the Distortional buckling behaviour and corresponding elastic buckling stress of beams in bending is discussed.
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Distortional buckling of perforated cold-formed steel channel-section beams with circular holes in web
International Journal of Mechanical Sciences, 2017Co-Authors: Wei-bin Yuan, Nan-ting Yu, Long-yuan LiAbstract:Abstract This paper presents the numerical and analytical investigations on the Distortional buckling of perforated cold-formed steel channel-section beams with circular holes in web. The numerical investigation involves the use of finite element methods. In the analytical analysis the Distortional buckling model recommended in EN1993-1-3 is employed. The influence of the web holes on the Distortional buckling behaviour and corresponding critical stress and moment of perforated cold-formed steel channel-section beams are discussed. Finally, a simple analytical formulation is proposed for evaluating the effect of hole size on the reduction of critical stress and critical moment of the channel-section beams with circular holes in web.
André Dias Martins - One of the best experts on this subject based on the ideXlab platform.
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post buckling behaviour of thin walled regular polygonal tubular columns undergoing local Distortional interaction
Thin-walled Structures, 2019Co-Authors: Dinar Camotim, André Dias Martins, Rodrigo GoncalvesAbstract:Abstract This work presents and discusses numerical results of an ongoing investigation concerning the elastic post-buckling behaviour and imperfection sensitivity of regular convex polygonal cross-section (RCPS) tubular columns affected by local-Distortional (L-D) interaction. This investigation is conducted by means of geometrically non-linear Generalized Beam Theory (GBT) analyses, extending the knowledge on the “pure” local and Distortional post-buckling behaviours of RCPS tubes recently reported by Martins et al. [1] . Due to their inherent modal nature, the GBT analyses make it possible to acquire in-depth knowledge on the structural behaviour of RCPS tubes and also to include, in a straightforward fashion, arbitrary member initial geometrical imperfections. Columns with Distortional-to-local critical buckling load ratios (i) close to 1 (“true L-D interaction” – the most trivial L-D interaction type) and (ii) significantly above 1 (“secondary-Distortional bifurcation L-D interaction” – the most relevant L-D interaction type) are investigated. Local/Distortional critical-mode initial geometrical imperfections and (linear) combinations of both are considered in the former columns, while only local initial imperfections are dealt with in the latter ones – several amplitudes are dealt with to assess the imperfection sensitivity. For comparison and validation purposes, ABAQUS shell finite element analysis results are also reported.
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on the mechanics of local Distortional interaction in thin walled lipped channel beams
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This paper investigates the elastic post-buckling behaviour of simply supported thin-walled lipped channel beams undergoing local-Distortional (L-D) interaction. The beams are uniformly bent about the major-axis and experience flange-triggered local buckling (most common situation in practice). Three beam geometries are considered, each exhibiting a different type of L-D interaction, namely (i) “true L-D interaction” (close local and Distortional critical buckling moments – two critical-mode initial geometrical imperfections are used, akin to the competing critical buckling modes), (ii) “secondary local-bifurcation L-D interaction” or (iii) “secondary Distortional-bifurcation L-D interaction” (critical Distortional-to-local buckling moment ratio well below or above 1.0, respectively, with “high enough” yield stresses). The results presented and discussed are obtained through elastic geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the beam deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth knowledge on the beam L-D interaction mechanics. Particular attention is devoted to interpreting the quantitative and qualitative differences exhibited by the beam post-buckling behaviours associated with the three aforementioned L-D interaction types.
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on the mechanics of Distortional global interaction in fixed ended columns
Thin-walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Rodrigo Goncalves, Pedro Borges DinisAbstract:Abstract This work reports the results of a numerical investigation concerning the elastic post-buckling behaviour of fixed-ended thin-walled lipped channel and zed-section columns affected by Distortional-global (D-G) interaction – “unexpected” features associated with the global buckling nature are unveiled in both cases. The columns analysed (i) exhibit cross-section dimensions and lengths ensuring the simultaneous occurrence of Distortional and global critical buckling, and (ii) contain critical-mode initial geometrical imperfections (linear combinations of the critical Distortional and global buckling mode shapes). For comparison and clarification purposes, the post-buckling behaviour of lipped channel columns buckling in an “isolated” Distortional mode and containing “pure” Distortional and global (flexural-torsional) initial geometrical imperfections are also analysed. The results presented and discussed are obtained through geometrically non-linear Generalised Beam Theory (GBT) analyses and provide the evolution, along given equilibrium paths, of the column deformed configuration (expressed in GBT modal form), relevant displacement profiles and modal participation diagrams, making it possible to acquire in-depth insight on the mechanics underlying D-G interaction in columns. Finally, particular attention is paid to interpreting the differences exhibited by the various column post-buckling behaviours investigated.
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Distortional-global interaction in lipped channel and zed-section beams: Strength, relevance and DSM design
Thin-Walled Structures, 2018Co-Authors: André Dias Martins, Dinar Camotim, Pedro Borges DinisAbstract:Abstract This work aims at presenting and discussing numerical results concerning the post-buckling behaviour, strength and design of cold-formed steel simply supported lipped channel and zed-section beams under uniform bending and undergoing Distortional-global (D-G) interaction – two different support conditions are considered in the lipped channel beams. The relevance of the interaction effects is assessed by identifying 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, which are expected to lead to different failure mode natures (global, Distortional or interactive). For each beam type, combinations of 41 geometries and 11 yield stresses are considered, in order (i) to characterise the beams experiencing “true D-G interaction” (RGD ≈ 1.0) and “secondary global-bifurcation D-G interaction” (RGD > 1.0 and high Ry) and (ii) to investigate the possible occurrence of “secondary Distortional-bifurcation D-G interaction” (RGD
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On the Distortional-global interaction in cold-formed steel columns: Relevance, post-buckling behaviour, strength and DSM design
Journal of Constructional Steel Research, 2018Co-Authors: André Dias Martins, Dinar Camotim, Pedro Borges DinisAbstract:Abstract This work reports the available results of an ongoing numerical (shell finite element) investigation on the post-buckling behaviour, strength and design of fixed-ended cold-formed steel columns undergoing Distortional-global (D-G) interaction. Columns with different cross-section shapes are analysed, namely plain lipped channel (LC), web-stiffened lipped channel (WSLC) and zed-section (Z) columns, in order to investigate distinct D-G interaction natures: involving either Distortional and (global) flexural-torsional buckling (LC and WSLC columns) or Distortional and (global) minor-axis flexural buckling (Z columns). In particular, the relevance of these D-G interaction types is discussed, by assessing when they affect visibly the column ultimate strength and/or failure mode. The results presented and discussed concern columns with various geometries and yield stresses, thus ensuring a wide variety of range combinations involving (i) global-to-Distortional critical buckling load ratios (RGD) and (ii) squash-to-non critical buckling (Distortional or global) load ratios (Ry) and leading to non-negligible failure load erosion. The possible occurrence and failure load impact of “secondary (Distortional or global)-bifurcation D-G interaction” (RGD 1.0 and high Ry) are investigated - it is well known that such impact may be significant in columns experiencing “true D-G interaction” (RGD ≈ 1.0). The above results consist of (i) relevant non-linear (elastic and elastic-plastic) equilibrium paths, (ii) deformed configuration evolutions along those paths, evidencing D-G interactive effects, and (iii) figures providing the failure mode characterisation. Then, the numerical failure load data obtained are compared with their predictions by (i) the currently codified DSM (Direct Strength Method) column global and Distortional strength curves, and (when necessary) (ii) proposed DSM-based design approaches, specifically developed to handle D-G interactive failures - a few design considerations are drawn from these comparisons.
Pedro B. Dinis - One of the best experts on this subject based on the ideXlab platform.
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Strength, interactive failure and design of web-stiffened lipped channel columns exhibiting Distortional buckling
Thin-Walled Structures, 2014Co-Authors: Pedro B. Dinis, Ben Young, Dinar CamotimAbstract:Abstract The paper reports experimental and numerical results concerning the post-buckling behaviour, strength and failure of fixed-ended cold-formed steel web-stiffened lipped channel columns that buckle in Distortional modes. The experimental results, obtained from the tests carried out at The University of Hong Kong, (i) include initial imperfection measurements, equilibrium paths and failure loads and modes, and (ii) provide evidence of the occurrence of flange-triggered local-Distortional interaction. After presenting and discussing a comparison between some test results and the values yielded by the corresponding Abaqus shell finite element numerical simulations, the experimental failure loads obtained in this work, together with additional data reported in the literature, are used to assess whether the available Direct Strength Method (DSM) design approaches are capable of predicting them efficiently (safely and accurately). It is found that this is not the case, mainly because of the fact that the mechanics of the flange-triggered and web-triggered local-Distortional interactions are quite different. Although fairly good failure load predictions are provided by a new DSM design approach proposed in this work, further research is required on the mechanics of local–Distortional interaction in web-stiffened lipped channel columns.
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post buckling behaviour and direct strength design of lipped channel columns experiencing local Distortional interaction
Journal of Constructional Steel Research, 2012Co-Authors: Nuno Silvestre, Dinar Camotim, Pedro B. DinisAbstract:Abstract This paper reports an investigation aimed at developing a Direct Strength Method (DSM) approach to estimate the ultimate strength of lipped channel columns affected by local/Distortional buckling mode interaction. Following a brief presentation of a few relevant aspects concerning the shell finite element analysis of the geometrically and materially non-linear behaviour of thin-walled members, one illustrates the methodology adopted to obtain a lipped channel column ultimate load “data bank” intended to be used in the development and assessment of a DSM design approach. Next, the current DSM expressions to predict the load-carrying capacity of columns failing in local and Distortional modes are briefly reviewed, devoting special attention to an approach that takes into account the above mode interaction. Then, the results of a parametric study, carried out by means of the code A baqus , are presented and discussed — this study involves the evaluation of the “exact” ultimate loads of 276 lipped channel columns with various geometries and two boundary conditions (pinned and fixed end supports), all exhibiting local/Distortional interaction. Finally, these ultimate strength data are compared with the estimates provided by the available DSM expressions and, on the basis of this comparison, one identifies several features that a DSM approach successfully accounting for local/Distortional interaction must incorporate.
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local Distortional global mode interaction in simply supported cold formed steel lipped channel columns
International Journal of Structural Stability and Dynamics, 2011Co-Authors: Pedro B. Dinis, Dinar CamotimAbstract:This paper reports the results of a numerical investigation concerning the elastic and elastic-plastic post-buckling behavior of cold-formed steel-lipped channel columns affected by local/Distortional/global (flexural-torsional) buckling mode interaction. The results presented and discussed are obtained by means of analyses performed in the code ABAQUS and adopting column discretizations into fine four-node isoparametric shell element meshes. The columns analysed (i) are simply supported (locally/globally pinned end sections with free warping), (ii) have cross-section dimensions and lengths ensuring equal local, Distortional, and global (flexural-torsional) critical buckling loads, thus maximizing the mode interaction phenomenon under scrutiny, and (iii) contain critical-mode initial geometrical imperfections exhibiting different configurations, all corresponding to linear combination of the three "competing" critical buckling modes. After briefly addressing the lipped channel column "pure" global post-buckling behavior, one presents and discusses in detail numerical results concerning the post-buckling behavior of similar columns experiencing strong local/Distortional/global mode interaction effects. These results consist of (i) elastic (mostly) and elastic-plastic equilibrium paths, (ii) curves and figures providing the evolution of the deformed configurations of several columns (expressed as linear combinations of their local, Distortional, and global components) and, for the elastic-plastic columns, (iii) figures enabling a clear visualization of (iii1) the location and growth of the plastic strains, and (iii2) the characteristics of the failure mechanisms more often detected in this work.
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coupled instabilities with Distortional buckling in cold formed steel lipped channel columns
Thin-walled Structures, 2011Co-Authors: Dinar Camotim, Pedro B. DinisAbstract:Abstract The paper addresses the elastic post-buckling behaviours of cold-formed steel lipped channel simply supported columns affected by mode interaction phenomena involving Distortional buckling, namely local/Distortional, Distortional/global (flexural-torsional) and local/Distortional/global mode interaction. The results presented were obtained by means of Abaqus shell finite element analyses adopting column discretisations into fine 4-node element meshes. In order to enable a thorough assessment of all possible mode interaction effects, the column lengths and cross-section dimensions were carefully selected to ensure similar local, Distortional and/or global buckling loads. One analyses otherwise identical (elastic) columns having initial geometrical imperfections (i) with various configurations (combinations of the competing critical buckling mode shapes) and (ii) sharing the same overall amplitude.
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post buckling behaviour and strength of cold formed steel lipped channel columns experiencing Distortional global interaction
Computers & Structures, 2011Co-Authors: Pedro B. Dinis, Dinar CamotimAbstract:This paper reports the results of a numerical investigation concerning the elastic and elastic-plastic post-buckling behaviour of cold-formed steel lipped channel columns affected by Distortional/global (flexural-torsional) buckling mode interaction. The results presented and discussed were obtained by means of analyses performed using the finite element code Abaqus and adopting column discretisations into fine 4-node isoparametric shell element meshes. The columns analysed (i) are simply supported (locally/globally pinned end sections that may warp freely), (ii) have cross-section dimensions and lengths that ensure equal Distortional and global (flexural-torsional) critical buckling loads, thus maximising the Distortional/global mode interaction effects, and (iii) contain critical-mode initial geometrical imperfections exhibiting different configurations, all corresponding to linear combinations of the two ''competing'' critical buckling modes. After briefly addressing the lipped channel column ''pure'' Distortional and global post-buckling behaviours, one presents and discusses in great detail a fair number of numerical results concerning the post-buckling behaviour and strength of similar columns experiencing strong Distortional/global mode interaction effects. These results consist of (i) elastic (mostly) and elastic-plastic non-linear equilibrium paths, (ii) curves or figures providing the evolution of the deformed configurations of several columns (expressed as linear combination of their Distortional and global components) and, for the elastic-plastic columns, (iii) figures enabling a clear visualisation of (iii"1) the location and growth of the plastic strains and (iii"2) the characteristics of the failure mechanisms more often detected in the course of this research work.
