Circular Web Holes Research Articles

Experimental investigation of cold-formed stainless steel built-up closed section stub columns

This paper presents an experimental investigation on the performance of cold-formed stainless steel built-up closed section stub columns. The built-up sections were composed by assembling two channel components at the flanges, which were brake-pressed from high-strength austenitic and duplex stainless steel thin sheets. Three types of built-up sectional profiles were formed by connecting two unstiffened channels (i.e., unlipped channels), two edge-stiffened channels (i.e., lipped channels) as well as one unstiffened channel and one edge-stiffened channel, respectively, using self-plugging rivets. Four sectional series were devised to cover nominal overall web height-to-plate thickness ratio values of 50, 60, 67 and 80. In order to obtain the actual material properties considering the cold-work effect, tensile coupon tests were carried out on both flat and corner longitudinal coupon specimens. In addition, a total of 29 fixed-ended stub columns including 19 specimens without holes and 10 specimens with circular web holes were tested under axial compression. The experimental results involving failure modes, ultimate capacities and responses of load versus axial shortening were obtained and fully documented. The effects of sectional profile types, overall web height-to-plate thickness ratio and hole diameter-to-overall web height ratio on the performance of cold-formed stainless steel built-up closed section stub columns were examined. Moreover, the appropriateness of design rules as prescribed in the recently updated American Specification ASCE/SEI 8–22 was evaluated. It was revealed that the codified design provisions generally provided unconservative strength predictions for the high-strength austenitic and duplex stainless steel built-up closed section stub columns both without and with circular web holes. Reliability analyses were performed in this study, and the compressive strength predictions of the built-up closed sections according to the existing design rules were found to be unreliable for the high-strength austenitic stainless steel stub columns without holes as well as the duplex stainless steel stub columns without and with circular web holes.

Numerical investigation of cold-formed steel channels with edge-stiffened and unstiffened elongated web holes under shear

Over the past decade, cold-formed steel (CFS) channel sections having edge-stiffened circular web holes have been developed in New Zealand. Such edge-stiffened holes increase the strength of the CFS channel sections, compared to an equivalent section having unstiffened web holes, while still allowing full building service integration. In the case of shear, previous research has found that the use of edge-stiffened web holes significantly improves the shear strength of such channel sections. However, no studies are available in the literature investigating the shear strength of CFS channel sections with edge-stiffened elongated web holes. The issue is addressed herein. Non-linear finite element (FE) analyses are used to investigate the shear strength of CFS channel sections with a shear span aspect ratio of 2.0. The FE models were validated against the experimental test results of sections having unstiffened elongated web holes and edge-stiffened circular web holes; good agreement in terms of the load-displacement curves and failure behaviour was shown. Using the validated FE models, a parametric study was conducted, comprising 2124 finite element analyses (FEA) results. The parametric results were then compared to the design predictions of the American Iron and Steel Institute (AISI 2016), and Australia/New Zealand Standards (AS/NZS 2018) and Wanniarchchi et al. (2017) for unstiffened elongated web holes, showing that the design predictions are unconservative in comparison results. Moreover, the direct strength method (DSM) approach of Pham et al. (2020a and 2023) provides conservative results for channels with unstiffened elongated web holes. It was also found that the design equations proposed by Chen et al. (2022) for edge-stiffened circular web holes were unconservative in predicting the shear strength of channels having edge-stiffened elongated web holes. Therefore, design equations in the form of a shear reduction factor and a modified DSM approach for CFS channel sections having unstiffened and edge-stiffened elongated web holes were proposed. Finally, a reliability analysis was carried out to ensure that the proposed equations are reliable to predict the shear strength of CFS channel sections with edge-stiffened and unstiffened web holes.

Assessment of Eurocode 3 Shear Design Provisions for Cold‐Formed Steel Beams with Web Holes

AbstractCold‐formed steel beams are often provided with web holes to accommodate service conduits. These web holes result in reduced structural strength. Accurate estimation of the structural strength, including shear strength, is crucial during the design phase. There are a lot of studies available in the literature investigating the shear strength reduction in cold‐formed steel beams due to web holes. However, the experiments and parametric finite element results were not assessed against Eurocode 3 shear design provisions. Therefore, the shear design of cold‐formed steel beams with web holes is investigated herein. Existing experimental and parametric finite element analysis data on cold‐formed steel beams with circular web holes were collected from the literature. The accuracy of the current Eurocode 3 shear design provisions was then assessed using the collected data. The comparisons showed that the current Eurocode 3 shear design provisions were not suitable to estimate the shear strength of cold‐formed steel beams with web holes. Finally, Eurocode 3 shear design provisions are extended to capture the effect of web holes and verified against the available shear tests and finite element results. It was found that the new extended shear design proposal offers improved accuracy and consistency in shear strength predictions.

Elastic shear buckling of cold-formed steel channels with edge stiffened web holes

Cold-formed steel (CFS) beams are commonly deployed in construction with web holes to accommodate service conduits. The web holes are subjected to stiffening methods aiming to restore the load-carrying strength reduction. In the shear design of CFS channels with stiffened web holes, the elastic shear buckling strength is the basis for the design irrespective of the available post-buckling strength. Therefore, this paper investigates the elastic shear buckling characteristics of CFS channels with stiffened circular web holes, which is still unresearched. Numerical simulations were conducted using the Abaqus finite element analysis software to study the elastic shear buckling response. Parametric studies were then performed, where a data pool was generated for CFS channels with no web holes, unstiffened web holes, and stiffened web holes, covering a range of parameters including web slenderness, web hole size, corner radius and edge stiffening element length. It was shown that edge stiffening of the web hole improves the shear buckling capacity compared to the CFS channels with no web holes and unstiffened web holes. New unified design proposals to estimate the elastic shear buckling strength of CFS channels with no web holes, unstiffened web holes, and edge stiffened web holes were developed based on the generated data. The new unified design proposals of modified shear buckling coefficient and equivalent thickness method offer accurate elastic shear buckling strength predictions.

Finite element analysis and proposed design rules for cold-formed stainless steel channels with web holes under end-one-flange loading

This paper presents a finite element analysis of cold-formed stainless steel channels with circular web holes, subjected to end-one-flange loading condition. The material properties of stainless steel types EN 1.4509 (Ferritic), EN 1.4462 (Duplex) and EN 1.4301 (Austenitic) were taken from the literature. To investigate the effect of web hole size, web hole location and bearing length on the web crippling strength of such sections, a parametric study involving a total of 1728 FE models was performed. The parametric study results were used to propose new web crippling strength equations and strength reduction factor equations which outperformed the equations of American Society of Civil Engineers Specification (ASCE 8–02), American Iron and Steel Institute Specification and Australia/New Zealand Standard (AISI&AS/NZS) and Lian et al (2016). A reliability analysis was then performed, which showed that the proposed design equations can closely predict the web crippling strength of cold-formed stainless steel channels with and without web holes under end-one-flange loading condition.

Tests of cold-formed steel built-up sections with web holes subjected to web crippling

This paper presents an experimental study on web crippling behaviour of cold-formed steel built-up Isections with circular web holes. The built-up sections were formed by connecting two identical unlipped channels with self-tapping screws. The web hole was located at mid-height of the web and directly beneath the bearing plates. Web crippling tests were conducted on 6 built-up sections without web holes and 19 built-up sections with perforated web under End-Two-Flange and Interior-Two-Flange loading conditions. The web crippling strengths, failure modes and load-displacement curves were reported. The experimental ultimate strengths for specimens without web holes were compared to the nominal strengths predicted from North American Specification, Australian/New Zealand Standard and European Code for cold-formed steel structures. It should be mentioned that the existing international design codes do not have explicit design formula to predict the web crippling strength of cold-formed steel built-up sections with perforated web. Therefore, the test strengths of specimens with perforated web were compared with the strengths derived from the design equations proposed in the literature. It is shown that the design strengths predicted from current design specifications are either conservative or unconservative for the specimens without web holes, while the design equations in the literature are generally unconservative for the specimens with perforated web.

Web crippling behaviour of cold-formed steel channel sections with edge-stiffened and unstiffened circular holes under interior-two-flange loading condition

Abstract Recently, a new generation of cold-formed steel (CFS) channel sections with edge-stiffened circular holes have been developed by industry in New Zealand. No previous research, however, has considered the web crippling strength of CFS channel sections with edge-stiffened circular web holes under the interior-two-flange (ITF) loading conditions. In this paper, a combination of experimental investigation and non-linear finite element analysis (FEA) are used to investigate the effect of edge-stiffened holes under ITF loading conditions; for comparison, channel sections without holes and with unstiffened holes are also considered. In total, 30 web crippling test results are reported. A non-linear finite element (FE) model is described, and the results were compared against the test results, which showed a good agreement in terms of both the web crippling strength and failure modes. The results indicate that the stiffened web holes can significantly improve the web crippling strength of CFS channel sections. Using the validated FE model, a parametric study was conducted which include 1116 FE analyses, covering the effect of different hole sizes, edge-stiffener lengths and fillet radii, length of the bearing plates and position of the holes in the web. From the results of the parametric study, design recommendations in the form of web crippling strength reduction factors are proposed, that are conservative to both the experimental and FE results.

Effect of web holes on the web crippling capacity of cold-formed LiteSteel beams under End-Two-Flange load case

LiteSteel (LSB) beams are made of two rectangular hollow flanges and a slender web. Although the flexural capacity and bending stiffness are enhanced due to hollow flanges, they are vulnerable to the web crippling failure under concentrated loads and reactions due to high web slenderness values. In current steel buildings, cold-formed steel sections with web holes have been used to accommodate service ducts in floor systems. These LiteSteel beams (LSBs) are innovative new sections, hence current web crippling equations cannot be used to predict the web crippling capacities of them. Keerthan et al. (2014, 2016) and Steau et al. (2015) proposed coefficients to the unified web crippling equation which is available in Australian/New Zealand standard (AS/NZS 4600) and North American Specification (AISI S100) for unfastened and fastened supports, respectively for LSB sections without web holes under four load cases based on their experimental studies. However web crippling behaviour of these sections with web holes is still unknown under all four load cases. In past studies, the web holes are classified into two groups such as centred beneath and offset web holes to investigate their effect on the web crippling behaviour. This study investigates web crippling behaviour of LiteSteel beams with centred beneath and offset circular web holes with unfastened supports under End-Two-Flange load case (ETF) using finite element analysis in ANSYS. Accurate validations have been performed for five different web crippling datasets, and the parametric study was conducted using validated FE models. Web crippling equations were proposed for LiteSteel beams with centred beneath and offset web holes and without web holes based on 1067 FE model values.

Shear Strengthening of Composite Concrete Steel Plate Girders with Web Openings Using Steel Strips

The study aims to investigate behaviour plus influence on the final load resistance of strengthen girders containing openings in web which were 40% of web height. This paper presents an experimental study of applying of five steel-concrete composite plate girder specimens that were loaded in shear predominantly. Three of those girders were considered as control girders, without web openings, containing circular web holes, and containing square web holes, respectively. Other two girders were strengthen girders. The slab reinforcement, dimensions of girders and compressive strength of concrete slabs were constant. Strengthening was made by using steel rings and strips which were welded to webs of strengthen girders to investigate influence of strengthening plan by steel welding on behaviour and final load strength for these girders. Findings illustrate increasing in final load strength of strengthen girders with circular and square web holes with about 57.38% and 43.75%, respectively in comparing to that for control girders. Moreover, the final shear capacity for the tested girders was also compared with that predicted by von Mises stresses.

Cold-formed steel channel sections under end-two-flange loading condition: Design for edge-stiffened holes, unstiffened holes and plain webs

Abstract In cold-formed steel (CFS) channel sections, web holes are becoming increasingly popular. Such holes, however, result in the sections becoming more susceptible to web crippling, especially under concentrated loads applied near the web holes. Traditional web holes are normally punched or bored and are unstiffened. Recently, a new generation of CFS channel sections with edge-stiffened web holes has been developed by the CFS industry and is being widely used. However, no research is available in the literature which investigated the web crippling strength of CFS channel sections with edge-stiffened circular web holes under the end-two-flange (ETF) loading conditions. A combination of experimental tests and non-linear FEA were used to investigate the effect of such stiffened holes on web crippling behaviour under ETF loading conditions. The results of 30 web crippling tests are presented. Non-linear FE models are described, and the results are compared against the laboratory test results; a good agreement was obtained in terms of both the strength and failure modes. The results indicate that the stiffened holes can significantly improve the web crippling strength of CFS channel sections. A parametric study involving 1116 FEA was then performed, covering the effect of different hole sizes, edge-stiffener lengths and fillet radii, length of the bearing plates and position of holes in the web. Finally, design recommendations in the form of web crippling strength reduction factors are proposed, that are conservative to both the experimental and FE results.

Design of cold-formed steel built-up sections with web perforations subjected to bending

The flexural behaviour including the moment capacities and failure modes of cold-formed steel built-up sections with circular web holes was investigated. Finite element analysis was performed on a wide range of cold-formed steel built-up section beams with different sizes of perforations under four-point bending. The built-up sections included both I-shaped open sections assembled from two lipped channels back-to-back and box-shaped closed sections assembled from two plain channels face-to-face. Finite element (FE) models have been developed to simulate the simply-supported cold-formed steel built-up section beams. The FE models for the built-up open sections and built-up closed sections were verified against the test results that have been conducted by the authors. The validated models were employed to carry out extensive parametric studies on cold-formed steel built-up section beams with various section slenderness and hole sizes. The beam strengths obtained from the numerical analysis together with the available test data were compared with the design strengths calculated from the current direct strength method (DSM). The critical elastic local and distortional buckling moments including the influence of holes that are required in DSM calculation were determined by rational finite strip analysis. It is shown that the DSM formulae in the North American Specification AISI S100-16 are capable for predicting the design strengths of the built-up open section beams with holes, while are quite conservative for the closed section beams with holes. Modifications are proposed for the DSM formulae for built-up closed section beams with holes. In this study, the current DSM was extended to cover the cold-formed steel built-up open and closed section beams with holes.

Direct Strength Method of Design for Channel Sections in Shear with Square and Circular Web Holes

AbstractThe direct strength method (DSM) design rules for cold-formed steel members in shear have been incorporated recently into the North American specification for the design of cold-formed stee...

Effect of Web Holes and Bearing Stiffeners on Flexural-Shear Interaction Strength of Steel Cold-Formed C-Channel Sections

This paper presents an investigation on interaction equation between the required flexural strength, M, and the required shear strength, V, of cold-formed C-channels with web holes and bearing stiffeners. The primarily shear condition test was employed to study total 8 back to back lipped C channel sections of 95 and 100 mm depth when bearing stiffeners and circular holes were placed at center and both ends of specimens. The interaction equation were evaluated via Direct Strength Method, DSM, in accordance with the American Iron and Steel Institute for the design of cold-formed steel structural members, AISI 2007. A nonlinear finite element model was developed and verified against the test results in terms of failure buckling modes. It was concluded that the M-V interaction equation for specimens with web stiffeners was conservative where these specimens experienced plastic failure mode rather than local (Msl) or distortional (Msd) buckling mode. Moreover, the results indicated that proposed M-V interaction equation calculated by local buckling strength (Msl) adequately predicted the behavior of specimens with circular web holes.

Beam tests of cold-formed steel built-up sections with web perforations

The aim of this study is to investigate the flexural behavior, including the ultimate moment capacities and failure modes, of built-up cold-formed steel members with circular web holes. A total of 43 beams having ten cross-section sizes with different hole diameters were tested under four-point bending. The built-up sections were assembled by self-tapping screws from either two plain channels or lipped channels. Reduction of moment capacities and localized failure due to the presence of holes in the web plates of beams was observed in the tests. It is shown from the test results that when the hole diameter-to-web depth ratio (dh/hw) is 0.5, the influence of the holes on the moment capacities of beams is very small, however this is not the case when dh/hw further increases up to 0.7. Different approaches of determining the critical elastic local and distortional buckling moments including the influence of holes for the built-up open and closed sections were compared and discussed, and appropriate approach for built-up sections was recommended. The current direct strength method (DSM) was extended for the design of cold-formed steel built-up sections with holes in this study. The design strengths predicted by the DSM were compared with the test results. It is shown that the DSM formulae in the North American Specification are capable for predicting the design strengths of the built-up open and closed section beams with holes, using the critical elastic local and distortional buckling moments including the influence of holes determined by the recommended approaches in this study.

Lateral Torsional Buckling of Thin-Walled Cold-Formed Steel Beams with Web Holes - Finite Element Analysis

This paper deals with the problems of analysis and design of thin-walled steel beams with circular web holes. The analysis based on the finite element method modeling is being performed on the case of perforated Sigma beams used in the storage systems and expedient flooring structures. The Sigma beams are generally used as floor girders which are subjected to the bending. In some cases the beams are not laterally restraint and the effect of lateral torsional buckling may occur. In the current engineering practice several design procedures are used to determine the bending resistance with respect to lateral torsional buckling. In this paper the results of FEM analysis are compared with the bending resistances calculated according the Eurocodedesign procedure.

Plastic bending behaviour and section moment capacities of mono-symmetric LiteSteel beams with web openings

Recently developed cold-formed LiteSteel beam (LSB) sections have found increasing popularity in residential, industrial and commercial buildings due to their light weight and cost-effectiveness. Currently, there is significant interest in the use of LSB sections as flexural members in floor joist systems, although they can be used as flexural and compression members in a range of building systems. The plastic bending behaviour and section moment capacity of LSB sections with web holes can be assumed to differ from those without, but have yet to be investigated. Hence, no appropriate design rules for determining the section moment capacity of LSB sections with web holes are yet available. This paper presents the results of an investigation of the plastic bending behaviour and section moment capacity of LSB sections with circular web holes. LSB sections with varying circular hole diameters and degrees of spacing were considered. The paper also describes the simplified finite element (FE) modelling technique employed in this study, which incorporates all of the significant behavioural effects that influence the plastic bending behaviour and section moment capacity of these sections. The numerical and experimental test results and associated findings are also presented.

Web crippling of aluminium tubes with perforated webs

Experimental and numerical investigations of aluminium alloy square hollow sections with a circular hole in the webs subjected to web crippling are presented in this paper. A total of 216 data that include 84 test results and 132 numerical results are presented. The web crippling tests were conducted under two loading conditions of end-two-flange (ETF) and interior-two-flange (ITF). The test specimens were fabricated by extrusion using a 6061-T6 heat-treated aluminum alloy. The web holes were located at the mid-depth of the webs and centred beneath the bearing plates. A non-linear finite element model is developed and verified against the experimental results. Geometric and material non-linearities were included in the finite element model. It was shown that the finite element model closely predicted the web crippling strengths and the failure modes of the tested specimens. Hence, the model was used for an extensive parametric study of the different sizes of the cross-section and circular holes in the webs. The influence of the circular web holes on the web crippling strength of aluminium square hollow sections is investigated in this study. Web crippling strength reduction factor equations are proposed for the ETF and ITF loading conditions. It is shown that the proposed strength reduction factors are generally conservative and agree well with the experimental and numerical results. Furthermore, a unified web crippling equation for the aluminium square hollow sections with circular web holes is also proposed.

Stresses in Beams with Circular Eccentric Web Holes

An approximate method of analysis for stresses in beams with circular web holes, both mid-depth and eccentric, is presented. Regions of a beam around a hole are analyzed as curved beam sections and the stresses are calculated accordingly. Methods of analysis using the theory of elasticity are also examined. Experiments are described and it is shown that the curved beam approximation is more accurate in predicting hole edge stresses for high ratios of hole diameter to beam depth and under high shear-to-moment ratio.