Cold-formed Steel Channel Columns Research Articles

Sectional capacities of cold-formed perforated steel channel columns

Holes are pre-punched in the web of cold-formed steel channel columns to accommodate the technical systems. Many research studies have considered and illustrated the impacts of web holes on the capacities of such steel channel columns. These impacts have been accounted for in the American Specification AISI S100-16 using a new design method termed as the Direct Strength Method (DSM). This method allows designers to predict the capacities of cold-formed steel members on the basis of elastic buckling analyses. These analyses can be carried out by using a new module software package CUFSM recently developed by The American Iron and Steel Institute to analyse the buckling behaviors of cold-formed steel sections with perforations. This paper is aimed to apply the DSM to investigate the sectional capacities of cold-formed steel channel columns with a variety of hole dimensions. The behaviors and strengths of these perforated steel channel sections are analysed; recommendations are subsequently provided for the optimum of capacities in terms of the same hole areas. It was found that perforated channel columns with smaller heights and longer lengths are more beneficial for sectional capacities in general. .

Optimization of Cold-Formed Steel Channel Columns

Sixteen cold-formed steel channel columns with different combinations of edge and web stiffeners under axial compression forces up to failure were numerically investigated using finite element (FE) analysis program, ANSYS. The behavior characteristics; the ultimate load, stiffness, ductility and energy absorption have been selected and separately analyzed in relation to column parameters. To determine the single-performance optimization of each characteristic, Taguchi method was applied. The multi-performance optimization was also investigated using Taguchi method coupled with grey relational analysis to achieve the favorable column characteristics and to investigate the multiple-performance characteristics index of each column. The results indicated that for multi-response and a single response, the predicted results are confirmed and the errors in the predicted values using the Taguchi method with respect to the numerical values using ANSYS are acceptable and also they indicated that broken straight line web stiffener factor (WS3) was the highest contributing parameters for variation of the ultimate load of CFS columns.

Experimental investigation and finite element analysis of cold-formed steel channel columns with complex edge stiffeners

Abstract Presented in this paper are results obtained from experimental and numerical investigations on the axial behavior of cold-formed thin-walled steel channel columns with complex edge stiffeners, which are referred to as G-section columns. In the experimental investigation, a total of 36 G-section columns, with and without perforations, were tested under pin-ended boundary conditions, and their structural behavior was described. In these tests, the perforations were found to affect the ultimate strength and deformed shape of the G-section columns. In the numerical investigation, finite element models for G-section columns with and without perforations were developed with use of ABAQUS. The models were validated based on the test results. The calibrated finite element model was subsequently adopted for an extensive parametric study by varying the dimensions and locations of perforations. The numerical results indicated that increasing the perforation dimension resulted in a greater reduction on the column ultimate strength than changing the perforation location. But the location of the perforation could affect the deformed shape of the column significantly. Based on the results obtained from the parametric analysis, it is recommended that the spacing of circular holes is between three and six times the nominal diameter of the hole for engineering practice.

A Review and Development of Cold-formed Steel Channel Columns with Oriented Strand Board Sections

Abstract Cold-formed steel (CFS) is a steel-based material that is always used as a structural or non-structural component in construction activities. In Malaysia, CFS is broadly utilised in roof truss systems to replace timber and hot-rolled steel in residential houses and small industrial buildings. Some of the advantages of CFS include being lightweight, recyclable, and durable and having highest strength-to-weight ratio. It is also becoming excessively popular as a building material. However, CFS with its thin surface tends to fail in buckling on short and slender sections either at the compression or flexural members especially for the web element. In this study, the CFS channel section with 100 mm of the web, 50 mm of flange, 12 mm of lip, 1.55 mm of thickness and without any web stiffener has been selected. With the intention of solving the buckling failure, CFS has been formed as a symmetrical and closed section and filled with oriented strand board (OSB) at the gap of each section. The main objective of this study was to review the previous study of CFS with other materials to produce the composite material and introduce the development and preliminary study of the new section. The CFS with OSB was proposed as a solid symmetrical section to solve the local, distortional, and global buckling, as well as establish a stable and stiffened section under compressed conditions. Therefore, the local and distortional buckling of the compressed member was completely solved by the built-up and box-up of CFS with the OSB section however the CFS channel section with OSB managed to minimise the effect of local and distortional buckling. There was a 9.20%, 5.16% and 5.84% percentage difference of the ultimate load between the CFS without and with OSB sections. The new section reduced the production cost, while also reducing the material usage. It also has the potential to be an innovative section by supporting the Malaysian sustainable development programme.

Experimental investigation of local-flexural interactive buckling of cold-formed steel channel columns

This paper presents the results of a comprehensive experimental programme aimed at studying the interaction of local and overall flexural buckling in cold-formed steel (CFS) plain and lipped channels under axial compression. The results were further used to verify the accuracy of the current design procedures in Eurocode 3, as well as to evaluate the effectiveness of a previously proposed optimisation methodology. A total of 36 axial compression tests on CFS channels with three different lengths (1 m, 1.5 m and 2 m) and four different cross-sections were conducted under a concentrically applied load and pin-ended boundary conditions. The initial geometric imperfections of the specimens were measured using a specially designed set-up with laser displacement transducers. Material tests were also carried out to determine the tensile properties of the flat parts of the cross-sections, as well as the cold-worked corner regions. A comparison between the experimental results and the Eurocode 3 predictions showed that the effective width approach combined with the P–M interaction equation proposed in Eurocode 3 to take into account the shift of the effective centroid consistently provided safe results. However, the Eurocode 3 procedures were also quite conservative in predicting the capacity pertaining to local-global interaction buckling, especially for plain channels. Furthermore, the experimental data confirmed the results of an optimisation study and demonstrated that the optimised CFS columns exhibited a capacity which was up to 26% higher than the standard channel with the same amount of material taken as a starting point.

Evaluation on Effectiveness of Cold-Formed Steel Column with Various Types of Edge Stiffener

In this study, four series of cold formed steel channel columns with different types of edge stiffeners is analyzed under pinned end conditions subjected to axial compression. The selected cross-sectional profiles are met with the interactive failure modes. The cross-sectional dimensions are satisfied the pre-qualified section properties of cold-formed steel structures. Test results are simulated with finite element analysis software using ANSYS, and good agreement has been achieved. After the validation of the proposed numerical model, the effect of variation of thickness, yield stress and overall slenderness in the strength and behaviour of the section are carried out. Interaction of distortional and flexural buckling is the governing failure modes of the column section. All the findings of FEA are compared with the Direct Strength Specification for cold-formed steel structures, and the strength of the member is also determined by using the modified equations from the literature. Based on the results, a new design equation is proposed, and also it is validated by the results available from the literature.

RESISTANCE OF BUILT-UP COLD-FORMED STEEL CHANNEL COLUMNS FILLED WITH CONCRETE

Cold-formed steel (CFS) channel infilled with concrete could increase its ability and stiffness by avoiding failure due to local buckling. Besides, the built-up bolted CFS channel column could serve as permanent formwork, decreased waste material and yet increase economical construction. This study aims to investigate the strength of built-up CFS channel columns infilled with concrete. Two CFS channel sections are situated face to face, connected and strengthen by using M10 bolts and nuts. Then, the 900 mm built-up column is filled with normal concrete of grade C30. Six samples with different end and central bolt spacing were tested. Material properties of CFS and concrete, and the mechanical properties of bolts are also investigated. From the result, the column with concrete on shortest end bolt spacing gave highest ultimate load and reported 68 – 78 % different when compared to similar column without concrete infilled. The failure mode of the column is global buckling and supports yielding, and the concrete is failed due to cracking and breaking. Equation of the relationship between bolt spacing either at the end or central and ultimate load is established.

Cold-formed steel channel columns optimization with simulated annealing method

Cold-formed profiles have been largely used in the building industry because they can be easily produced and because they allow for a wide range of sections and thus can be utilized to meet different project requirements. Attainment of maximum performance by structural elements with low use of material is a challenge for engineering projects. This paper presents a numerical study aimed at minimizing the weight of lipped and unlipped cold-formed channel columns, following the AISI 2007 specification. Flexural, torsional and torsional-flexural buckling of columns was considered as constraints. The simulated annealing method was used for optimization. Several numerical simulations are presented and discussed to validate the proposal, in addition to an experimental example that qualifies its implementation. The ratios between lips, web width, and flange width are analyzed. Finally, it may be concluded that the optimization process yields excellent results in terms of cross-sectional area reduction.

Experimental Study of Axially Compressed Cold Formed Steel Channel Columns

Analysis and design of axially compressed cold formed steel channel section presented in this paper was conducted through experimental study, design based on British standards and North American Specification for the design of cold-formed steel structural members. More than 18 laboratory experiments were undertaken first on these steel channel columns under axial compression. A series of parametric studies were also carried out by varying the thickness and column length. All of these columns failed by local and distortional buckling. The test results were compared with American (AISI-2007) and British Standards (BS5950-Part5) for the design of cold-formed steel structural members. The details of these investigation and the outcomes are presented in this paper.

Experimental Study of Axially Compressed Cold Formed Steel Channel Columns

Experimental Study of Axially Compressed Cold Formed Steel Channel Columns

Local buckling and shift of effective centroid of cold-formed steel columns

Local buckling is a major consideration in the design of thin-walled cold-formed steel sections. The main effect of local buckling in plate elements under longitudinal compressive stresses is to cause a redistribution of the stresses in which the greatest portion of the load is carried near the supporting edges of the plate junctions. The redistribution produces increased stresses near the plate junctions and high bending stresses as a result of plate flexure, leading to ultimate loads below the squash load of the section. In singly symmetric cross-sections, the redistribution of longitudinal stress caused by local buckling also produces a shift of the line of action of internal force (shift of effective centroid). The fundamentally different effects of local buckling on the behaviour of pin-ended and fixed-ended singly symmetric columns lead to inconsistencies in traditional design approaches. The paper describes local buckling and shift of effective centroid of thin-walled cold-formed steel channel columns. Tests of channel columns have been described. The experimental local buckling loads were compared with the theoretical local buckling loads obtained using an elastic finite strip buckling analysis. The shift of the effective centroid was also compared with the shift predicted using the Australian/New Zealand and American specifications for cold-formed steel structures.

Design of Cold-Formed Steel Channel Columns with Complex Edge Stiffeners by Direct Strength Method

The design of cold-formed steel channels with complex stiffeners could be quite tedious in calculating the effective area using the effective width method in the current design rules of North American Specification and Australian/New Zealand Standard. The direct strength method could be used in the design without calculating the effective area. An experimental investigation of fixed-ended cold-formed steel channel columns with complex edge stiffeners has been reported. The test strengths were compared with design strengths predicted using the direct strength method as well as the North American Specification and Australian/New Zealand Standard for cold-formed steel structures. The failure modes observed in the tests were also compared with the failure modes predicted by the direct strength method. It is shown that the design strengths predicted by the direct strength method are generally conservative for the channel columns with complex edge stiffeners. Furthermore, the reliability of the direct strength method was evaluated using reliability analysis. It is shown that the direct strength method is reliable using the existing resistance factor as recommended by the current North American Specification and Australian/New Zealand Standard.

Numerical investigation of channel columns with complex stiffeners—part II: parametric study and design

A parametric study of cold-formed steel channel columns with complex stiffeners is performed using finite element analysis. An accurate and reliable finite element model is used for the parametric study in which different sizes of complex stiffeners are investigated. Column strengths predicted by the finite element analysis are compared with the unfactored design column strengths calculated using the American Specification and the Australian/New Zealand Standard for cold-formed steel structures. It is shown that the design strengths obtained from the specification and standard are generally conservative for fixed-ended cold-formed steel channel columns with complex stiffeners for the more slender sections having a plate thickness of 1 mm with the flat flange width to thickness ratio of 57, but unconservative for sections having a plate thickness of 2 mm with the flat flange width to thickness ratio of 27.

Numerical investigation of channel columns with complex stiffeners—part I: test verification

A numerical investigation on fixed-ended cold-formed steel channel columns with complex stiffeners subjected to axial load is described in this paper. The complex stiffeners of the channel sections consist of simple lips with return lips. The specimens were brake-pressed from high strength zinc-coated structural steel sheets having a nominal yield stress of 450 MPa. A non-linear finite element model is developed and verified against experimental results of fixed-ended channel columns with complex stiffeners. Initial geometric imperfections and material non-linearity are included in the model. The calibrated model is shown to provide accurate predictions of the experimental ultimate loads and failure modes of the tested columns.

Design of channel columns with inclined edge stiffeners

Design and numerical investigations of cold-formed steel channel columns with inclined edge stiffeners are presented in this paper. The edge stiffeners of the channel sections consisted of simple lips that inclined at different angles both outwards and inwards. Finite el ement analysis was used in the numerical investigation. A non-linear finite element model was developed and verified against fixed-ended column tests. Geometric and material non-linearities were included in the finite element model. It is shown that the finite element model closely predicted the experimental ultimate loads of the cold-formed steel channel columns with inclined edge stiffeners. Hence, the model was used for a parametric study of cross-section geometries. The column strengths predicted by the finite element analysis were compared with the design column strengths calculated using the American and Australian/New Zealand specifications for cold-formed steel structures. The design rules in the American and Australian/New Zealand specifications for designing an edge-stiffened element are mainly based on tests of channels with simple edge stiffeners perpendicular to the flanges. However, these specifications allow the design of inclined edge stiffeners that are purely intuitive. It is shown that the design column strengths calculated from the specifications are generally conservative for cold-formed steel channel columns with inclined edge stiffeners.

Structural behaviour of cold-formed thin-walled short steel channel columns at elevated temperatures. Part 2: Design calculations and numerical analysis

The companion paper has presented results of elevated temperature tests on 52 cold-formed thin-walled channels under compressive load. This paper presents the results of theoretical studies using a number of different calculation tools, these including simple design calculations based on modifying a few current design methods and a commercial finite element package ABAQUS. The design methods considered in this paper include the British standard BS5950 Part 5, Eurocode 3 Part 1.3 and the American Specification AISI. Modifications of the current design equations are made to enable them to include distortional buckling, the effects of service holes and elevated temperatures. To enable BS5950 Part 5 and Eurocode 3 Part 1.3 to predict the ultimate strength of thin-walled columns with a service hole, the AISI (1996) design method is introduced. To extend the capacity of these design methods to deal with distortional buckling failure mode, the method of Young, Kwon and Hancock for calculating distortional buckling capacity is introduced in these codes. Finally, the ambient temperature design methods are modified to take into account changes in the strength and stiffness of steel at elevated temperatures. From extensive comparisons between the results of tests, code predictions and numerical analyses, it may be concluded that by adopting the aforementioned modifications, the current code design methods can be easily modified to consider these advanced modes of behaviour. For finite element analyses, both geometrical and material non-linearities are taken into account. The high temperature stress–strain relationships of steel are determined according to Eurocode 3, Part 1.2 or Outinen et al.

Structural behaviour of cold-formed thin-walled short steel channel columns at elevated temperatures. Part 1: experiments

Cold-formed thin-walled steel structures are increasingly being used as primary load bearing members. However, there is a lack of study of their performance in fire. This paper presents a detailed description of an experimental study of the axial strength of cold-formed thin-walled channel sections under ambient and uniform high temperatures. The objectives of this study are two-fold: to gain an insight into the physical behaviour and failure modes of this type of structure and to provide some experimental results for detailed numerical studies. A total of 52 strength tests were carried out on short cold-formed lipped channels with and without service holes and unlipped channels at ambient and various elevated temperatures. From these experimental studies, it has been observed that the failure mode of two nominally identical columns can be different even though the failure loads are close. Depending on the thickness of a channel and the location of the service hole, perforation can have an important effect on the strength of the channel, irrespective of the temperature. The companion paper will describe the results of design calculations and numerical studies.