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Dinar Camotim - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on cold formed steel Lipped Channel beams affected by local distortional interaction under non uniform bending
Thin-walled Structures, 2021Co-Authors: Mantai Chen, Ben Young, Dinar Camotim, André Dias Martins, Pedro Borges DinisAbstract:Abstract This paper reports an experimental investigation, carried out at The University of Hong Kong, on the behaviour of cold-formed steel Lipped Channel beams affected by local-distortional (L-D) interaction under non-uniform bending – to the authors’ best knowledge, these are the first tests specifically devoted to this topic. This investigation consists of 16 non-conventional four-point simply supported bending tests involving twin Lipped Channel beams arranged in a “back-to-back” configuration and laterally restrained at the loading points. The 32 Lipped Channel specimens were brake-pressed from high-strength zinc-coated G450 grade structural steel sheets. Tensile coupon tests were performed to obtain the specimen material properties and initial geometrical imperfections were measured prior to testing. The beam geometries were carefully selected to enable testing beams that are prone to “true L-D interaction” (close critical distortional-to-local buckling moments) when acted by trapezoidal bending moment diagrams with four distinct gradients – all the tested specimens exhibited the sought L-D interactive nature. The output of the experimental investigation consists of (i) applied moment vs. displacement equilibrium paths, (ii) photos showing beam deformed configurations along those paths (including the failure modes) and (iii) the failure moment data. Lastly, the experimental failure moments obtained are compared with their predictions provided by the (i) current local and distortional Direct Strength Method (DSM) strength curves and (ii) available DSM-based approaches against L-D interactive failures, which were developed and calibrated exclusively in the context of beams subjected to uniform bending.
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Uniformly bent CFS Lipped Channel beams experiencing local-distortional interaction: Experimental investigation
Journal of Constructional Steel Research, 2020Co-Authors: Mantai Chen, Ben Young, Dinar Camotim, André Dias Martins, Pedro Borges DinisAbstract:Abstract This paper describes a test campaign concerning the behaviour and strength of cold-formed steel (CFS) Lipped Channel (LC) beams experiencing local-distortional (L-D) interaction made of G450-G500 high-strength steel grades. This investigation involves the performance of 20 tests on simply supported beams arranged in a “back-to-back” configuration, subjected to four-point major-axis bending and laterally restrained at the loading points. All tested specimens failed in the expected L-D interactive modes and exhibited critical distortional-to-local buckling moment ratios ranging between 1.09 and 1.46 (i.e., prone to “true L-D interaction”). The experimental results obtained and reported consist of beam (i) moment-displacement equilibrium paths, (ii) photos evidencing the evolution of the beam deformed configurations along those equilibrium paths (including the failure modes) and (iii) failure moments - it is found that these results are in good agreement with recently performed numerical simulations. Finally, the experimental failure moments obtained are compared with their estimates provided by the (i) currently codified Direct Strength Method (DSM) strength curves associated with local and distortional failures, and (ii) other available DSM-based design approaches developed to handle L-D interactive failures. This comparison provides solid evidence that the CFS specifications must include a DSM-based design approach able to handle beam L-D interactive failures - the current L and D design curves clearly overestimate all the experimental failure moments.
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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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CFS Lipped Channel columns affected by L-D-G interaction. Part I: Experimental investigation
Computers & Structures, 2018Co-Authors: Ben Young, Pedro Borges Dinis, Dinar CamotimAbstract:Abstract This work deals with the structural behaviour and ultimate strength of fixed-ended cold-formed steel (CFS) Lipped Channel columns experiencing various levels of local-distortional-global buckling mode interaction. After briefly addressing the column specimen geometry selection (carefully chosen to ensure more or less closeness between the critical buckling stresses associated with these three buckling mode types), the paper reports the results of an experimental investigation involving a set of 17 columns with several cross-section dimensions, lengths and yield stresses, which is aimed at (i) providing experimental evidence of the occurrence of the triple mode interaction under consideration and (ii) quantifying its effect on the column deformed configuration evolution and failure load erosion (drop). Various aspects concerning the test set-up and procedure are described in some detail before presenting and discussing the obtained column experimental results, which basically consist of (i) measured cross-section dimensions, lengths and initial displacements (geometrical imperfections), (ii) stress-strain curves and yield stresses determined from tensile coupon tests, (iii) recorded non-linear equilibrium paths (applied load vs. various relevant displacements) and ultimate strength values, and (iv) observed deformed configurations and collapse mechanisms. The test results are used, in a companion paper (Part II), (i) to calibrate and validate numerical simulations and (ii) to support the proposal and to assess the merits of design approaches based on the Direct Strength Method (DSM) and intended to handle L-D-G interactive failures.
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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
Ben Young - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation on cold formed steel Lipped Channel beams affected by local distortional interaction under non uniform bending
Thin-walled Structures, 2021Co-Authors: Mantai Chen, Ben Young, Dinar Camotim, André Dias Martins, Pedro Borges DinisAbstract:Abstract This paper reports an experimental investigation, carried out at The University of Hong Kong, on the behaviour of cold-formed steel Lipped Channel beams affected by local-distortional (L-D) interaction under non-uniform bending – to the authors’ best knowledge, these are the first tests specifically devoted to this topic. This investigation consists of 16 non-conventional four-point simply supported bending tests involving twin Lipped Channel beams arranged in a “back-to-back” configuration and laterally restrained at the loading points. The 32 Lipped Channel specimens were brake-pressed from high-strength zinc-coated G450 grade structural steel sheets. Tensile coupon tests were performed to obtain the specimen material properties and initial geometrical imperfections were measured prior to testing. The beam geometries were carefully selected to enable testing beams that are prone to “true L-D interaction” (close critical distortional-to-local buckling moments) when acted by trapezoidal bending moment diagrams with four distinct gradients – all the tested specimens exhibited the sought L-D interactive nature. The output of the experimental investigation consists of (i) applied moment vs. displacement equilibrium paths, (ii) photos showing beam deformed configurations along those paths (including the failure modes) and (iii) the failure moment data. Lastly, the experimental failure moments obtained are compared with their predictions provided by the (i) current local and distortional Direct Strength Method (DSM) strength curves and (ii) available DSM-based approaches against L-D interactive failures, which were developed and calibrated exclusively in the context of beams subjected to uniform bending.
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Uniformly bent CFS Lipped Channel beams experiencing local-distortional interaction: Experimental investigation
Journal of Constructional Steel Research, 2020Co-Authors: Mantai Chen, Ben Young, Dinar Camotim, André Dias Martins, Pedro Borges DinisAbstract:Abstract This paper describes a test campaign concerning the behaviour and strength of cold-formed steel (CFS) Lipped Channel (LC) beams experiencing local-distortional (L-D) interaction made of G450-G500 high-strength steel grades. This investigation involves the performance of 20 tests on simply supported beams arranged in a “back-to-back” configuration, subjected to four-point major-axis bending and laterally restrained at the loading points. All tested specimens failed in the expected L-D interactive modes and exhibited critical distortional-to-local buckling moment ratios ranging between 1.09 and 1.46 (i.e., prone to “true L-D interaction”). The experimental results obtained and reported consist of beam (i) moment-displacement equilibrium paths, (ii) photos evidencing the evolution of the beam deformed configurations along those equilibrium paths (including the failure modes) and (iii) failure moments - it is found that these results are in good agreement with recently performed numerical simulations. Finally, the experimental failure moments obtained are compared with their estimates provided by the (i) currently codified Direct Strength Method (DSM) strength curves associated with local and distortional failures, and (ii) other available DSM-based design approaches developed to handle L-D interactive failures. This comparison provides solid evidence that the CFS specifications must include a DSM-based design approach able to handle beam L-D interactive failures - the current L and D design curves clearly overestimate all the experimental failure moments.
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behaviour of aluminium alloy plain and Lipped Channel columns
Thin-walled Structures, 2019Co-Authors: Jihua Zhu, Ben YoungAbstract:Abstract Aluminium alloys have high strength-to-weight ratios and great durability; thus, they have been extensively used in structural applications. Channel sections have a smooth and aesthetically pleasing line shape, good integrity, and are easy to connect. An experimental program using 28 specimens and a numerical study that generated 100 results were conducted on aluminium alloy columns of plain and Lipped Channel sections. The nominal length of columns ranged from 300 mm to 3000 mm. The generated 128 results were evaluated with respect to the existing design specifications from America, Australia/New Zealand, Europe and China. Furthermore, the direct strength method (DSM) and the continuous strength method (CSM) were also used to predict results for comparison. The results showed that the design specifications produced conservative compression strengths of aluminium alloy columns of both plain and Lipped Channel sections. The CSM provided more accurate and consistent design strengths. In addition, the reliability levels of the four international design codes, DSM and CSM for Channel sections of aluminium alloy columns were also evaluated.
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CFS Lipped Channel columns affected by L-D-G interaction. Part I: Experimental investigation
Computers & Structures, 2018Co-Authors: Ben Young, Pedro Borges Dinis, Dinar CamotimAbstract:Abstract This work deals with the structural behaviour and ultimate strength of fixed-ended cold-formed steel (CFS) Lipped Channel columns experiencing various levels of local-distortional-global buckling mode interaction. After briefly addressing the column specimen geometry selection (carefully chosen to ensure more or less closeness between the critical buckling stresses associated with these three buckling mode types), the paper reports the results of an experimental investigation involving a set of 17 columns with several cross-section dimensions, lengths and yield stresses, which is aimed at (i) providing experimental evidence of the occurrence of the triple mode interaction under consideration and (ii) quantifying its effect on the column deformed configuration evolution and failure load erosion (drop). Various aspects concerning the test set-up and procedure are described in some detail before presenting and discussing the obtained column experimental results, which basically consist of (i) measured cross-section dimensions, lengths and initial displacements (geometrical imperfections), (ii) stress-strain curves and yield stresses determined from tensile coupon tests, (iii) recorded non-linear equilibrium paths (applied load vs. various relevant displacements) and ultimate strength values, and (iv) observed deformed configurations and collapse mechanisms. The test results are used, in a companion paper (Part II), (i) to calibrate and validate numerical simulations and (ii) to support the proposal and to assess the merits of design approaches based on the Direct Strength Method (DSM) and intended to handle L-D-G interactive failures.
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design of cold formed stainless steel Lipped Channel sections with web openings subjected to web crippling under end one flange loading condition
Advances in Structural Engineering, 2017Co-Authors: Amir M Yousefi, Ying Lian, Asraf Uzzaman, James B.p. Lim, Charles G Clifton, Ben YoungAbstract:This article presents a numerical investigation on the web crippling strength of cold-formed stainless steel Lipped Channel sections with circular web openings under end-one-flange loading condition. In order to take into account the influence of the circular web openings, a parametric study involving 1992 finite element analyses was performed, covering duplex EN1.4462, austenitic EN1.4404 and ferritic EN1.4003 stainless steel grades; from the results of the parametric study, strength reduction factor equations are proposed. The web crippling strengths predicted by the reduction factor equations are first compared to the strengths calculated using the equations recently proposed for cold-formed carbon steel Lipped Channel sections. It is demonstrated that the strength reduction factor equations proposed for cold-formed carbon steel are unconservative for the stainless steel grades by up to 7%. Unified strength reduction factor equations are then proposed that can be applied to all three stainless steel gr...
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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distortional global interaction in Lipped Channel columns
Proceedings of the Institution of Civil Engineers - Structures and Buildings, 2013Co-Authors: Dinar Camotim, Pedro B. DinisAbstract:This work presents and discusses numerical results concerning the post-buckling behaviour (elastic and elastic–plastic) and ultimate strength of cold-formed steel Lipped Channel columns experiencing distortional–global interaction. The analyses cover columns with (a) geometries selected to ensure very close global and distortional buckling loads, and (b) the support conditions usually adopted in experimental investigations: fixed-ended and pin-ended columns. A fairly large number of columns are analysed, differing in the initial geometrical imperfection shape and/or yield stress – the various initial geometrical imperfection shapes are linear combinations of the competing buckling modes with amplitudes equal to (a) 10% of the wall thickness, t (D) and (b) L/1000 (G). For clarification purposes, the column pure global elastic post-buckling behaviours are also addressed. These results are (a) elastic (mostly) and elastic–plastic non-linear equilibrium paths, (b) figures and curves providing the evolution, a...
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local distortional global interaction in Lipped Channel columns experimental results numerical simulations and design considerations
Thin-walled Structures, 2012Co-Authors: Pedro B. Dinis, Dinar Camotim, Eduardo De Miranda Batista, Eliane SantosAbstract:Abstract This work aims at contributing towards understanding the structural response and predicting the ultimate strength of cold-formed steel Lipped Channel columns affected by local–distortional–global (LDG) interaction. Initially, the most relevant aspects concerning the buckling and elastic–plastic post-buckling behaviours of fixed-ended Lipped Channel columns with nearly coincident local, distortional and global (flexural–torsional) buckling loads are briefly addressed. Then, the paper (i) summarises the most important test results obtained in a recently reported experimental investigation carried out at the Federal University of Rio de Janeiro, (ii) addresses their numerical simulation by means of A baqus shell finite element analyses (SFEA) and (iii) presents the outcome of a fairly extensive numerical parametric study performed to obtain ultimate strength data concerning fixed-ended Lipped Channel columns experiencing LDG interaction. Finally, the ultimate strength “data bank” gathered, consisting of 12 experimental and 134 values, are used as the starting point to assess the performance (accuracy and safety) of design approaches, based on the currently available Direct Strength Method (DSM) strength curves and intended to estimate the failure loads of cold-formed steel Lipped Channel columns affected by the triple mode interaction under consideration.
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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.
Eduardo De Miranda Batista - One of the best experts on this subject based on the ideXlab platform.
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distortional global buckling interaction relevance in cold formed steel Lipped Channel columns
Latin American Journal of Solids and Structures, 2020Co-Authors: Joao Alfredo De Lazzari, Eduardo De Miranda BatistaAbstract:BUCKLING MODE INTERACTION IN COLD-FORMED STEEL (CFS) MEMBERS MUST BE CONSIDERED FOR THE STRUCTURAL DESIGN, SINCE THE MODAL INTERACTION MAY LEAD TO A SIGNIFICANT REDUCTION OF THE STRUCTURAL STRENGTH, USUALLY RECOGNIZED AS EROSION OF THE LIMIT LOAD. SO FAR, THE DISTORTIONAL-GLOBAL (DG) BUCKLING INTERACTION IS NOT COVERED BY CODES, E.G. BRAZILIAN CODE NBR 14762 (2010). THE PRESENT INVESTIGATION IS AIMED AT THE DG INTERACTION OF CFS Lipped Channel (LC) COLUMNS, WHICH IS THE MOST USUAL SECTION IN MANY APPLICATIONS. THE METHODOLOGY EVOLVES A PARAMETRIC ANALYSIS, OVER A SINGLE LC COLUMN UNDER DG BUCKLING INTERACTION. FIRST, A STUDY OF INITIAL GEOMETRIC IMPERFECTION (IGI) SENSIBILITY IS PERFORMED, WITH THE PURPOSE OF UNDERSTANDING THE INFLUENCE OF THE IGI ON THE COLUMN’S BEHAVIOR. MOREOVER, THE PARAMETRIC ANALYSIS IS EXTENDED TO A SET OF YIELDING STRESS AND COLUMN LENGTHS, IN ORDER TO UNDERSTAND THE ULTIMATE LOAD UNDER DIFFERENT TYPES OF DG BUCKLING INTERACTION NATURES. CONCLUSIONS ON THIS RESEARCH HAVE BEEN SHOWN THAT THE ACTUAL GLOBAL BUCKLING EQUATION FROM THE DIRECT STRENGTH METHOD (DSM) IS ALREADY SUITABLE TO COVER THE DG BUCKLING INTERACTION FOR THE CASE OF Lipped Channel MEMBERS UNDER AXIAL COMPRESSION.
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experimental analysis of built up cold formed steel Lipped Channel stub column
REM - International Engineering Journal, 2019Co-Authors: Cristiane Cruxen Daemon Oliveira D E Bastos, Eduardo De Miranda BatistaAbstract:Abstract This article reports the results of experimental tests conducted on built-up cold-formed steel (CFS) stub columns, composed of double Lipped Channel members connected with self-drilling screws, which will be applied as the chord members of laced columns. These experiments aim to quantify the effect of four distinct web fastener layouts on the composite action, including the ultimate strength, buckling modes and collapse mechanism for built-up CFS members. The tested stub columns are of 480mm length, double 88x86x40x42x12mm Lipped Channel cross-section and 0.8mm thickness. The built-up CFS Lipped Channel members were analyzed with help of the Generalized Beam Theory in order to identify their buckling loads and modes. The Direct Strength Method (DSM) was adopted to obtain the analytical strength of the built-up members, to be compared with the experimental results. The axially compressed built-up members displayed local and distortional buckling, negligible composite behavior and minor effect of number and distribution of the screws. The results indicate (i) inefficient behavior of the self-drilling screws for composite condition purposes and (ii) the DSM rules for non-composite CFS are able to estimate the ultimate strength of this type of built-up Lipped Channel section.
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explicit equations for distortional buckling of cold formed steel Lipped Channel columns
Thin-walled Structures, 2017Co-Authors: Daniel C T Cardoso, Eduardo De Miranda Batista, Guilherme C Salles, Paulo B GoncalvesAbstract:Abstract In this work, the development of rational explicit equations for distortional buckling critical stress of Lipped Channel columns subject to uniform compression is presented. An energy-based approach is adopted along with two different assumed buckled shapes (models) to obtain the analytical expressions. In Model 1, stiffened flange is assumed rigid, i.e., transverse wall bending is neglected, whereas in Model 2 the flange plate flexibility is taken into account. An analytical procedure to determine warping stresses based on cross-section displacements and considering that flange-stiffener assembly rotation center does not coincide with web-flange fold-line is described. To validate proposed equations, a parametric analysis is carried out for Lipped Channels with flange-to-web width ratio, bf/bw, ranging from 0.2 to 1.0 and lip-to-web width ratio, bs/bw, from 0.1 to 0.4. Results are compared to those obtained with a generalized beam theory (GBT) software for ‘pure’ distortional mode and it is shown that, within the range of typical geometries used in industry, average differences are approximately 1.062 ± 0.073 and 0.998 ± 0.001 for Models 1 and 2, respectively. The linear (natural) coupling of pure distortion and local/global deformation modes is also briefly described and its influence on the critical loads is discussed. Finally, comparison is made to benchmark methodologies currently used in design standard and specifications. The obtained results indicate that proposed equations are reliable and valuable for practical design applications.
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cfs Lipped Channel columns affected by l d g interaction part ii numerical simulations and design considerations
Computers & Structures, 2017Co-Authors: Pedro Borges Dinis, Ben Young, Dinar Camotim, Eduardo De Miranda BatistaAbstract:Abstract This work deals with the structural behaviour, ultimate strength and design of fixed-ended cold-formed steel (CFS) Lipped Channel columns experiencing various levels of local-distortional-global buckling mode interaction (more or less close critical local, distortional and global loads). First, a comparison between experimental results, obtained from three tests carried out at The University of Hong Kong (UHK), and the corresponding A baqus shell numerical simulations are presented and discussed – the UHK test campaign is reported in Part I of this two-part paper. The comparison (i) involves equilibrium paths, deformed configurations, failure loads and collapse mechanisms, and (ii) provides enough evidence to ensure that the numerical model developed may be deemed validated. Then, this numerical model is employed to perform a parametric study, aimed at obtaining numerical failure load data concerning Lipped Channel columns experiencing different levels of local-distortional-global interaction – 368 fixed-ended columns, exhibiting different geometries (cross-section dimensions and lengths) and various yield stresses, thus covering a wide slenderness range. Finally, the present (Part II) paper also assesses the quality of the failure load estimates provided by various design approaches, based on the Direct Strength Method (DSM), for CFS columns affected by the triple coupling phenomenon under consideration. This assessment is based on the comparison with both (i) experimental failure loads, namely those reported in Part I and others collected from the literature, and (ii) numerical failure loads, obtained from A baqus shell finite element analyses (SFEA) and either reported in this work or gathered from previous publications by the authors.
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local distortional global interaction in Lipped Channel columns experimental results numerical simulations and design considerations
Thin-walled Structures, 2012Co-Authors: Pedro B. Dinis, Dinar Camotim, Eduardo De Miranda Batista, Eliane SantosAbstract:Abstract This work aims at contributing towards understanding the structural response and predicting the ultimate strength of cold-formed steel Lipped Channel columns affected by local–distortional–global (LDG) interaction. Initially, the most relevant aspects concerning the buckling and elastic–plastic post-buckling behaviours of fixed-ended Lipped Channel columns with nearly coincident local, distortional and global (flexural–torsional) buckling loads are briefly addressed. Then, the paper (i) summarises the most important test results obtained in a recently reported experimental investigation carried out at the Federal University of Rio de Janeiro, (ii) addresses their numerical simulation by means of A baqus shell finite element analyses (SFEA) and (iii) presents the outcome of a fairly extensive numerical parametric study performed to obtain ultimate strength data concerning fixed-ended Lipped Channel columns experiencing LDG interaction. Finally, the ultimate strength “data bank” gathered, consisting of 12 experimental and 134 values, are used as the starting point to assess the performance (accuracy and safety) of design approaches, based on the currently available Direct Strength Method (DSM) strength curves and intended to estimate the failure loads of cold-formed steel Lipped Channel columns affected by the triple mode interaction under consideration.
Nuno Silvestre - One of the best experts on this subject based on the ideXlab platform.
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Cold-Formed Steel Lipped Channel Columns Influenced by Local-Distortional Interaction: Strength and DSM Design
Journal of Structural Engineering, 2013Co-Authors: Ben Young, Nuno Silvestre, Dinar CamotimAbstract:This paper deals with the ultimate strength and design of fixed-ended Lipped Channel columns experiencing local-distortional buckling mode interaction. First, the paper reports the results of an experimental investigation involving a set of 26 columns with several cross-section dimensions and yield stresses that were tested to determine their failure loads and also to provide experimental evidence of the occurrence of local-distortional mode interaction. These results consist of the column geometries, material properties, initial geometric imperfections, nonlinear equilibrium paths, and ultimate strength values. Then, after comparing the experimental column ultimate loads with the estimates provided by the current direct strength method (DSM) design curves against local and distortional failures, which clearly show that they lead to inaccurate and often very unsafe ultimate strength estimates, the paper presents and assesses the quality of DSM-based design procedures based on approaches providing nominal strengths against local-distortional and distortional-local interactive failures. Next, an in-depth comparison is made between all the experimental ultimate strength results available in the literature and their estimates provided by the preceding DSM design procedures. Finally, the paper closes with design considerations and recommendations, motivated by the conclusions drawn from this investigation.
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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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dsm design of Lipped Channel columns undergoing local distortional global mode interaction
2010Co-Authors: Nuno Silvestre, Pedro B. Dinis, Dinar Camotim, Eduardo De Miranda BatistaAbstract:This work aims at contributing towards extending the domain of application of the available DSM, by making it capable of estimating the ultimate strength of cold-formed steel Lipped Channel columns affected by local/distortional/global interaction. The current DSM expressions, as well as those applicable to interactive buckling design, are first introduced and an extensive numerical (shell finite element) study involving fixed columns is reported − the column geometries are selected in order to have nearly coincident local, distortional and global buckling loads. The numerical ultimate strength values obtained are then used to assess the accuracy of the DSM expressions. As a preliminary recommendation, the current DSM expressions are adequate to estimate the collapse load of Lipped Channel columns affected by local/distortional/global interaction.
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ultimate strength and design of Lipped Channel columns experiencing local distortional mode interaction part i experimental investigation
6th International Conference on Advances in Steel Structures and Progress in Structural Stability and Dynamics ICASS 2009, 2009Co-Authors: Ben Young, Dinar Camotim, Nuno SilvestreAbstract:This paper reports the results of an experimental investigation aimed at assessing the post-buckling behaviour and ultimate strength of fixed-ended cold-formed steel Lipped Channel columns experiencing local/distortional mode interaction. A total of 26 columns were tested and the specimens were carefully selected to ensure various levels of local/distortional interaction effects (more or less close local and distortional critical stresses). The experimental results presented consist of the specimen geometries, material properties, initial imperfections, non-linear equilibrium paths and ultimate strength values. Since the collapse of most columns combines local and distortional deformations, these experimental results may be used to (i) assess the relevance of local/distortional interaction, (ii) calibrate and validate numerical simulations and (iii) provide experimental data aimed at developing a Direct Strength Method (DSM) approach to design cold-formed steel Lipped Channel columns against local/distortional interaction such a DSM approach is addressed in Part II of this paper.
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on the use of the ec3 and aisi specifications to estimate the ultimate load of cfrp strengthened cold formed steel Lipped Channel columns
Thin-walled Structures, 2009Co-Authors: Nuno Silvestre, Dinar Camotim, Ben YoungAbstract:Abstract This paper summarises an investigation carried out to predict the structural behaviour of CFRP-strengthened cold-formed steel Lipped Channel columns−more specifically, it addresses the applicability of the provisions of Eurocode 3 (EC3) and the AISI Specification (AISI-DSM, direct strength method), both developed for cold-formed steel members, to estimate their load-carrying capacity. It is worth noting that EC3 and AISI-DSM adopt different approaches to perform this task: while the former is based on the “effective width” concept, the latter may adopt the “Direct Strength Method”. First, the most relevant aspects related to the experimental and numerical investigations carried out to obtain “exact” column collapse loads are briefly presented. Then, an extensive numerical study is performed, which is intended to evaluate the benefits of CFRP-strengthening for different CFRP ply configurations, number of CFRP plies and steel yield stresses. After proposing different methodologies to extend the application of the EC3 and AISI-DSM design provisions to CFRP-strengthened cold-formed steel columns, the estimates provided by them are compared with the experimental values. On the basis of these comparisons, some concluding remarks are drawn concerning the merits and shortcomings of extending the domain of application of the current EC3 and AISI-DSM design approaches, so that they may cover also CFRP-strengthened Lipped Channel columns.
