INVESTIGATION OF DISTORTIONAL AND GLOBAL BUCKLING INTERACTION ON COLD FORMED STEEL LIPPED CHANNEL COLUMNS (original) (raw)
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Programa de Engenharia Civil COPPE/UFRJ, 2020
The goal of the present research is the distortional-global (D-G) buckling interaction of cold-formed steel (CFS) lipped channel (LC) columns, in its buckling, structural behavior and strength nature. Some studies on this topic have been conducted in the literature, however, the D-G interaction is not well known and needs more attention. For an elastic buckling analysis, a software entitled FStr Computer Application Program is developed. The application is based on the Finite Strip Method, mainly focused in a simple and accessible interface. The FStr program generates the modal shapes and insert as initial geometric imperfections in the finite element software ANSYS, in order to perform a geometric and material nonlinear analysis. Both, the FStr program and the finite element model are validated with available numerical examples and laboratory tests from the literature. Moreover, for the structural behavior and column strength, it is carried out stability paths from previous nonlinear analysis, for different combination of initial geometric imperfection of global and distortional modes. The buckling mode combination as initial geometric imperfection helps to understand the D-G buckling interaction, which is difficult to predict with a simple elastic buckling analysis. The results of the initial imperfection combination have shown that, for high yielding steel, the global initial geometric imperfection provides the most detrimental ultimate load. Additionally, a parametric study varying the column’s length have shown that the nominal axial strength for global buckling equation, already in the standards, is enough to cover the DG coupled phenomenon.
Distortional-Global Buckling Interaction Relevance in Cold-Formed Steel Lipped Channel Columns
Latin American Journal of Solids and Structures, 2020
Buckling mode interaction in cold-formed steel (CFS) members must be considered for the structural design, which 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. 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, 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 is already suitable to cover the DG buckling interaction for the case of lipped channel columns.
BEHAVIOR AND STRENGTH OF DISTORTIONAL-GLOBAL INTERACTION IN COLD FORMED STEEL LIPPED CHANNEL COLUMNS
XL CILAMCE Ibero-Latin-American Congress on Computational Methods in Engineering, 2019
The cold formed steel members (CFS) are light steel options widely applied in the civil construction. Furthermore, the CFS is a very slender option that allows the buckling behavior to develop on local, distortional and global modes. In this away, it is expected that a greater attention over this structural solution is necessary to guarantee the reliability and safety of the structure. On recent studies, it has been shown that when the local, distortional and global modes occur with similar critical loads, the strength capacity of the structural member is reduced due to a coupled phenomenon. The proposed paper will discuss the distortional-global (D-G) buckling interaction of CFS lipped channels columns under axial load. Additionally, it is developed a computer program (FStr) for elastic buckling analysis, based on Finite Strip Method (FSM), in order to find CFS columns experiencing D-G interaction. The program is developed on MATLAB with an easy graphical user interface. After settled the profiles under strong interaction, a non-linear analysis using Finite Element Method (FEM) is used to find the strength of the columns. Additional analysis and comments are discussed in order to understand the behavior and the strength capacity of the CFS lipped channel columns under the proposed buckling interaction.
Springer Proceedings in Materials, 2021
This paper describes the numerical investigation carried out on coldformed steel fixed-ended web stiffened lipped channel (WSLC) column sections undergoing local-distortional interaction mode buckling. The ultimate strength erosion caused by L-D interaction are presented. The sections failing due to L-D interaction are identified by "trial and error method" from GBTul. The column sections are carefully selected to ensure that would be fairly high level of L-D interaction by the ratio (P crl /P crd = 0.8-1.2). The elastic buckling analysis is performed predicting the section properties and length of the columns by using GBTul software. Finite Element Models were developed by using ABAQUS and comparative study on load results was made with DSM (direct strength method), NLD, NLD, MNLD approaches and whether they are capable of predicting them efficiently. The parametric studies on the identified sections are presented. Keywords Web stiffened lipped channel columns • ABAQUS • Finite element analysis • Interactive buckling • Gbtul • Numerical simulations • Direct strength method
Calculation of Critical Load for Pure Distortional Buckling of Lipped Channel Columns
This paper presents a method that allows calculating the elastic critical stress for the distortional buckling mode, based on the buckling mode classification of typical lipped channel columns. In our case, Cold-Formed Steel Lipped Channel Columns are subjected to compression. Moreover, in order to consolidate the important findings of this work, a comparative study was carried out to assess the reliability of various distortional buckling models that are provided by different design Standards. It was found that the American and Australian approaches, given in the codes of practice, are closer to the Finite Strip Method than to the European method. An analytical solution was proposed for the determination of the distortional buckling stress on the basis of a statistical method; it corresponds to lipped channel sections with a flange width to web width ratio b/h ranging from 0.1 to 1, and a lip width to web width ratio c/h between 0 and 0.5. After comparison with the results given by the finite strip method for pure distortional buckling, it turned out that the proposed approach provides a reasonable prediction for the elastic distortional buckling stress for lipped channel sections subjected to compression. In fact, this method gives better results than the American approach.
Nonlinear Buckling Analysis of Cold-Formed Channel Sections
2017
The main objective of this paper is to provide an efficient and accurate finite element model to understand the behavior of cold-formed steel channel columns. The effects of initial local and overall geometric imperfections have been taken into consideration in the analysis. Failure loads and buckling modes as well as load-shortening curves of plain channel columns were investigated in this study. The nonlinear finite element model was verified against experimental results. The finite element analysis was performed on plain channels compressed between pinned ends over different column lengths, and column curves were obtained. An extensive parametric study was carried out using the finite element model to study the load eccentricity on the strength and behavior of channel columns. The column strengths predicted from the finite element model were compared with the design strengths calculated using the European Code, EN 1993-1-3 Eurocode 3: Design of steel structures - Part 1-3: Genera...
2021
This paper presents a comparison investigation into analysis methods to determine the buckling capacity of South African cold-formed steel lipped channel sections. The research considers the evaluation of buckling capacities of five different column lengths using five different methods: 1. experimental tests; 2. the Direct Strength Method (DSM) as prescribed in SANS 10162-2; 3. Eurocode 3; 4. simplified Finite Element Analysis (FEA), i.e. only beam modelling elements; and 5. finely refined FEA, i.e. plate modelling elements. All columns have a 75 x 50 x 20 x 2.0 (h x b x c x t mm) cold-formed lipped channel cross-section. A comparison of the experimental buckling results to the aforementioned methods shows that the Eurocode 3 and DSM buckling resistance values overestimate the buckling loads by 23.8% and 12.7%, respectively. For the two Finite Element Model (FEM) buckling analyses; the simplified FEA method yields an overestimation of 76.9% and the finely refined FEA yields an overe...
BUCKLING ANALYSIS OF COLD FORMED STEEL CHANNEL SECTIONS WITH AND WITHOUT STIFFENERS
IJTIMES, 2019
The Light gauge cold-formed steel sections being used extensively in residential, industrial and commercial building as secondary load bearing members since last three decadez. In this context a study is being made to analyses C Sections with and without stiffeners to arrive at design strength criterion in compression. The direct strength method of design for cold formed steel sections has been validated over the years through research and the same has been incorporated in the standard codes of practice in the countries like USA and Australia. ABAQUS and CUFSM has been extensively used to perform Finite Element analysis and Finite Strip method of thin walled cold formed steel sections and the results are compared to each other. The analysis is being done on CUFSM and ABAQUS. The design strength curves will be arrived at using direct strength method. This is because cold-formed steel sections have a very high strength to weight ratio compared with thicker hot-rolled steel sections, and their manufacturing process is simple and cost-effective. In this context, a study is being made to analyze C sections with and without stiffeners to arrive at design strength criterion in compression members. In this study, the behavior of C sections with and without stiffeners under the action of axial loads has been carried out with various thickness and depths. In ABAQUS, the loads are applied on both ends. The clamped end conditions are considered.
Buckling Behaviour of Cold Formed Steel Channel Section
In the field of structural engineering the design of cost efficient structure is highly important. This led to development of cold-formed steel structures. Cold formed steel members have been widely used in residential and commercial buildings as primary load bearing structural elements. They are often made of thin steel sheets and hence they are more susceptible to local buckling. The present study focuses on understanding the importance of “lip” in cold formed steel sections. As per IS: 801 - 1975, design solution is developed for flexure member design. An experimental program is performed, to gain information on flexural capacity and buckling behaviour of member. Suitable finite element models are then developed to simulate the behaviour of tested beams and are validated using test results. All the ultimate load capacity results for local buckling are compared with codal provisions as well as results obtained by experimental program. This paper mainly focuses on to investigate load carrying capacity and buckling behaviour of two different cold formed steel channel sections i.e., with lip and without lip, by analytically(by developing design solutions),experimentally as well as by finite element analysis(by using ABAQUS software).The „lip‟ is not taking part anywhere in calculation of bending moment capacity. It is important regarding to buckling behaviour of cold formed steel sections. All the specimens are tested under Universal Testing Machine (UTM) and subjected to two point load system. Results are showing that members subjected to pure bending, with „Lip‟ channel section is subjected to web buckling. Channel sections with 'lip' is showing 28.7% higher than without 'lip' sections. In contrast, without „Lip‟ channel section is subjected to flange buckling. With „lip‟ channel section has high load carrying capacity compared to without „Lip‟ channel section. Analytical, experimental and finite element results are showing close to each other.
Study on the Buckling Behaviour of Cold Formed Steel Lipped and Unlipped Column
International Journal for Research in Applied Science & Engineering Technology (IJRASET), 2022
In steel construction, cold-formed structural members are becoming more popular and have growing importance. Its growing popularity in building construction is due to its advantages over other construction materials such as lightness and consequent ease of erection and installation, the economy in transportation and handling. They are mostly used in the construction field as both primary and secondary structural members due to their advantageous features such as high strength to weight ratio, easy handling, fast construction, etc. Cold-formed steel is the common term for steel products shaped by cold working processes carried out near room temperature. The objective of this study is to examine the performance of CFS column subjected to loading. Numerical investigations are carried out by using finite element analysis software ANSYS. Using the ANSYS software the bucking behavior of CFS lipped and unlipped columns with different configurations are examined.