Hollow Flange Channel Section Research Articles

Thermal modelling of LSF floor-ceiling systems with varying configurations

Light gauge steel frame (LSF) floor-ceiling systems are increasingly used in buildings without a full understanding of their thermal and fire resistance performance. Hence a numerical study was undertaken on the thermal performance of LSF floor-ceiling systems with varying configurations under standard fire conditions. The configurations included Lipped Channel and rivet fastened Rectangular Hollow Flange Channel section joists, gypsum plasterboard lining, steel sheathing, structural plywood and rockwool fibre insulation. The measured elevated temperature thermal property data of the above floor system components were included in the 3D thermal finite element models and the results were compared with fire test results. A good comparison showed that the developed finite element models can be used to simulate the thermal behaviour of LSF floor-ceiling systems with varying configurations. A parametric study was then undertaken to extend the thermal performance data in terms of time-temperature profiles for LSF floor-ceiling systems. Finite element analyses showed that the new LSF floor-ceiling system with the addition of thin steel sheathing performed significantly better than conventional systems. The use of thin steel sheathing on both sides of plasterboard showed further improvements. The use of cavity insulation was shown to be detrimental and thus improved floor-ceiling configurations were proposed.

Predicting the fire performance of LSF walls made of web stiffened channel sections

Fire performance of plasterboard lined Light-gauge Steel Framed (LSF) walls has been investigated using numerical and experimental studies in the past. However, past research has been limited to lipped channel sections (LCS) and welded hollow flange channel (HFC) sections. This paper investigates the fire performance of LSF walls made of a new web-Stiffened Channel Section (SCS) stud using numerical models, validated using available fire test results. The SCS succeeds in eliminating both local and distortional buckling when used as 3 m long LSF wall studs at ambient temperature. Ambient temperature compression capacity evaluations showed that the performance of the SCS is equivalent to the welded HFC, but is superior to the LCS. Fire performance of load bearing and non-load bearing LSF walls made with each of the three stud sections was assessed for three common wall configurations using thermal and structural finite element analyses. Extended FRL versus Load Ratio curves were developed using a combination of steady state and transient state coupled temperature-displacement analyses. The results showed that the effect of stud geometry on the fire performance of LSF wall configurations is minimal. Under the same load ratio, all three stud sections perform similarly in each of the wall configurations. Considering the ambient and fire performance results, the reduced cost and also the potential double connectivity to plasterboard via its lip elements, the SCS is recommended for use in LSF walls. This paper has also highlighted the susceptibility of non-load bearing LSF walls to fail in fire under structural inadequacy.

07.04: Web crippling design of hollow flange channel beams under one flange load cases

ABSTRACTThe advantage of having no unstiffened elements coupled with material located away from the neutral axis makes hollow flange channel (HFC) beam sections structurally efficient in bending when compared with other commonly used open cold‐formed steel sections. This concept is similar to hot‐rolled steel sections such as the universal beam and channel beam sections, which are very efficient in bending. However, the hot‐rolled sections are heavier, torsionally weak, and have low resistance to flexural‐torsional buckling. The two hollow flanges in HFC beams make them torsionally strong and also eliminate the occurrence of distortional and local flange buckling modes in most cases. However, HFC beams have slender webs, making them vulnerable to web crippling failure modes. To understand the web crippling behaviour of HFC beams and develop accurate design rules, finite element models of HFC beams were developed and validated using available experimental results under End One Flange (EOF) and Interior One Flange (IOF) load cases. Using the validated finite element models, a detailed parametric study was conducted for many HFC sections. Finite element analyses provided the required elastic buckling and ultimate loads of HFC beams in web crippling (EOF and IOF load cases). New predictive equations were proposed to determine the elastic buckling coefficients of HFC beams, followed by Direct Strength Method (DSM) based design rules using the test, elastic buckling and nonlinear analysis results from finite element analyses. This paper presents the details of the web crippling design rules developed based on the detailed numerical study on the web crippling behaviour of hollow flange channel beams under one flange load cases.

10.15: Thermal modelling of LSF floor systems made of lipped channel and hollow flange channel section joists

ABSTRACTBuildings that are not designed to have fire safety measures are not able to endure the extreme conditions in a fire event. Hence considerably more attention is being placed on the fire safety of buildings in recent times. Light gauge steel framed (LSF) floor systems are commonly used in buildings as they provide significant benefit by reducing weight and cost while increasing construction efficiencies. To obtain a satisfactory fire resistance level, floor systems must comply with a number of requirements specified in codes relating to fire resistance level. However, to understand the heat transfer process within LSF floor systems usually requires numerous complex fire tests. These tests are extremely expensive and time consuming. Therefore three‐dimensional finite element models were developed and used in this study to investigate the heat transfer in LSF floor systems made of different joist sections such as Lipped Channel and Hollow Flange Channel beam sections. Standard fire curve was defined as an amplitude curve following a time‐temperature profile based on ISO 834 standard fire curve. The time‐temperature curves obtained from the finite element analyses were compared with available experimental results to determine their accuracy in predicting the heat transfer in LSF floor systems made of the two chosen joist sections. Results showed that the proposed three‐dimensional finite element models can accurately predict the heat transfer of LSF floor systems made with lipped channel and hollow flange channel section joists. They also highlighted the differences in the thermal performance when different joist types are used. This paper presents the details of a three‐dimensional thermal modelling study of LSF floor systems made of lipped Channel and hollow flange channel section joists and the results. Innovative LSF floor systems were also proposed using the validated thermal models to enhance the fire resistant rating.

Fire performance of LSF walls made of hollow flange channel studs

PurposeThis paper aims to present an investigation conducted to evaluate the effects of important parameters affecting the structural fire performance of light gauge steel frame (LSF) walls. It also evaluates the applicability of commonly used critical hot flange temperature method to determine the fire resistance ratings (FRR) of different LSF walls.Design/methodology/approachThe effects of important parameters such as stud section profiles and their dimensions, elevated temperature mechanical property reduction factors of the steel used, types of wall configurations and fire curves on the FRR of LSF walls were investigated. An extensive finite element analysis-based parametric study was conducted to evaluate their effects (finite element analysis – FEA). For this purpose, finite element models which were validated using the full-scale fire test results were used. Using the structural capacities obtained from FEAs, the load ratio versus FRR curves were produced for all the different LSF walls considered.FindingsStud depth and thickness significantly affected the fire performance of LSF walls because of the differences in temperature development pattern, thermal bowing deflections and the failure modes of stud. The FRR of LSF walls increased significantly when steel studs with higher elevated temperature mechanical property reduction factors were used. FRR significantly changed when realistic design fire curves were used instead of the standard fire curve. Furthermore, both the critical hot and average flange temperature methods were found to be unsuitable to predict the FRR of LSF walls.Originality/valueThe developed comprehensive fire performance data would facilitate the development of LSF walls with enhanced fire performance, and, importantly, it would facilitate and advance the successful applications of hollow flange channel section studs in LSF walls.

Compression tests of built-up cold-formed steel hollow flange sections

Cold-formed steel hollow flange sections are structurally efficient compared to the conventional open channel sections. They can be of different forms including hollow flange I- and channel sections, which are generally fabricated by first cold-forming a single sheet to form the desired shape and then connecting their flange and web elements by continuous welding. Instead of welding, intermittently screw/rivet fastened or spot welded connection can also be used. A detailed investigation is currently under way on the structural performance characteristics of such intermittently screw/rivet fastened steel hollow flange sections. This paper presents the details of an experimental study performed to investigate the behaviour of built-up cold-formed steel hollow flange sections in compression, where more than 45 stub columns were tested. Both hollow flange I- and channel sections built-up using either single steel sheet or three steel elements were tested. Tests also included built-up hollow flange channel sections with stiffened web elements. Test results including the failure loads, load versus axial deformation plots and failure characteristics are presented in this paper. Test failure loads are compared with the predictions based on both effective width and direct strength methods to verify their adequacy in predicting the section compression capacity of built-up hollow flange sections. This paper has shown that although hollow flange I-sections made of three elements with a 100mm fastener spacing can perform similar to continuously welded sections, hollow flange channel sections undergo premature failures even with a 50mm fastener spacing, and the reasons are discussed.

Section compression capacity of high strength cold-formed hollow flange channels

Thin-walled cold-formed hollow flange channel (HFC) sections are increasingly becoming popular due to their potential benefits such as increase in buckling capacities provided by the presence of two torsionally rigid hollow flanges and the elimination of free edges. Past research studies of HFC sections were limited to their shear and bending capacities. This paper investigates their section compression capacities through a series of stub column tests, followed by finite element modelling of welded HFC columns. The developed finite element models were validated using experimental results, and then used to investigate the section compression capacity of HFCs made by welding rectangular sections to a steel plate or cold-forming and rivet/screw fastening to hollow flanges, where steel plates with different strengths and thicknesses were used as web and flange elements. Extensive structural performance data of HFC stub columns subject to local buckling was thus obtained covering the effects of varying slenderness of plate elements and the use of different strength steels for web and flange elements. Furthermore, the applicability of the available design rules such as effective width and direct strength methods to predict the compression capacity of such HFC sections was also evaluated. Suitable recommendations are then proposed to improve their accuracy. This study facilitates and advances the use of HFC sections as compression members.

Thermal performance of LSF floors made of hollow flange channel section joists under fire conditions

Light gauge steel frame (LSF) floor systems used in the building industry are made of cold-formed lipped channel section (LCS) joists and lined using gypsum plasterboards. The recently developed LSF floor systems made of welded hollow flange channel (HFC) section joists exhibited superior fire performance in the full scale fire tests. Since full scale fire tests are expensive and time consuming, finite element (FE) models were used in this research on LSF floor systems. In this paper 2-dimensional FE models were developed using a finite element analysis software SAFIR to predict the thermal performance of LSF floors made of HFC joists, and validated using the fire test results. The developed FE models predicted the thermal performance of LSF floor systems exposed to standard fires reasonably well. The validated model was then modified to include plywood subfloor and was used to investigate the effects of important parameters such as joist size, shape and subfloor thickness on the time–temperature profiles of the outer hot and cold flanges of HFC joists. These time–temperature profiles can be directly used to estimate the fire resistance ratings (FRR) of LSF floors made of HFC joists without performing expensive full scale fire tests. This paper presents the details of this thermal analysis study and the results.

Fire design of LSF floors using hollow flange channel joists

Predicting the fire performance of commonly used Light gauge Steel Frame (LSF) floor systems is important in designing them for fire situations. In the past, many researchers conducted full scale fire tests and numerical analyses for this purpose. However, some researchers have proposed fire design rules to predict the fire resistance ratings of LSF floor systems to avoid expensive fire tests. Their proposals were developed only for LSF floors made of conventional lipped channel section (LCS) joists. Therefore this research was aimed at developing fire design rules for the new LSF floor systems made of hollow flange channel (HFC) section joists. It used the fire performance data from an extensive parametric study based on validated finite element models of the new floor system with varying floor component configurations. Three different fire design rules were proposed to predict the fire resistance ratings of LSF floors based on the available design equations from past research and current design standards. The proposed design equations were validated by comparing the fire resistance rating predictions with the finite element analysis results obtained from the parametric study. Further a new Direct Strength Method based fire design rule was also developed and validated using finite element analysis results. The fire design rules proposed in this paper can be used to predict the fire resistance ratings of LSF floors made of HFC section joists with varying sizes and steel types, and plasterboard/insulation configurations without the need for further fire testing and numerical analyses.

Fire resistance of LSF floors made of hollow flange channels

Light gauge Steel Frame (LSF) floor systems are generally made of conventional lipped channel section (LCS) joists and lined using fire resistive gypsum boards. Although the use of LSF floor systems has significantly increased in the construction of fire rated buildings, it is limited to those made of LCS joists. Since the fire resistance ratings (FRR) for steel sections other than LCS joists are not available, engineers are reluctant to use innovative steel joists in LSF floor systems exposed to fire conditions. To overcome these limitations, a new LSF floor system recently developed using a welded hollow flange channel (HFC) section as joists was investigated using both experimental and numerical studies under standard fire conditions. Both these studies demonstrated higher fire resistance ratings in comparison to those made of LCS joists. However, they were limited to one welded HFC joist section. Hence a detailed parametric study of LSF floor systems made of HFC joists was undertaken to investigate the effects of joist sizes and shapes, steel types and service openings on the FRR using the validated finite element models. This paper presents the details of this finite element analysis based parametric study and the load ratio versus time curves. These results can be used in designing the LSF floors made of HFC joists with varying sizes for different industry applications without the use of expensive fire tests.

Fire design rules for LSF walls made of hollow flange channel sections

Cold-formed Hollow Flange Channel (HFC) sections can be used in Light gauge Steel Frame (LSF) wall systems due to their structural efficiency. Recent experimental and finite element analysis based investigations conducted by the authors have demonstrated the superior fire performance of LSF walls made of welded HFC sections. The authors have developed a wide range of fire performance data of LSF walls through a finite element analysis (FEA) based extensive parametric study. This paper investigates the applicability of the available fire design rules to predict their structural capacities. Since fire design rules were not available for HFC sections, the latest design rules for LCS studs subjected to non-uniform temperature distributions were selected for evaluation from the pool of various design rules given in standards and previous studies. Suitable modifications were then incorporated for simplification and improved accuracy. Two improved design methods based on AS/NZS 4600 and Eurocode 3 were proposed. The structural capacity of HFC section stud found from the design rule predictions was converted into load ratio which is the ratio between the structural capacities under fire and ambient conditions, and the load ratio versus FRR curve were produced for different LSF walls. These were then compared with the FEA results, to verify the accuracy of the proposed design rules. This paper also presents suitable DSM based design method proposed for HFC section studs subject to non-uniform temperature distributions in LSF walls, and verifies its accuracy.

Thermal performance of load‐bearing walls made of cold‐formed hollow flange channel sections in fire

SummaryTypical load‐bearing light gauge steel frame (LSF) walls are made of conventional lipped channel section studs and gypsum plasterboards. Current research at the Queensland University of Technology is investigating the effects of using new thin‐walled stud sections on the fire‐resistant rating of LSF walls, in particular, the use of hollow flange channel (HFC) sections. A sound knowledge on the thermal performance of these LSF walls is essential, but expensive and time‐consuming nature of fire tests has acted as a barrier. In this study, finite element models were developed to predict the thermal performance of load‐bearing LSF walls made of HFC section studs exposed to fire on one side. The developed models were validated using the results of five full‐scale standard fire tests of LSF walls. They were then extended to perform a parametric study where the effects of stud dimensions, geometries, spacings and wall configuration were evaluated. The hot and cold flange time‐temperature profiles of HFC studs were developed as a function of the aforementioned parameters, which can be used to predict the fire resistance ratings of LSF walls. This paper presents the fire tests, and the details of the developed finite element models and the thermal performance results of LSF walls made of HFC studs. Copyright © 2015 John Wiley & Sons, Ltd.

Experimental Study of Cold-Formed Steel Floors Made of Hollow Flange Channel Section Joists under Fire Conditions

AbstractFire safety plays a vital role in building design because appropriate level of fire safety is important to safeguard lives and property. Cold-formed steel channel sections along with fire-resistive plasterboards are used to construct light-gauge steel frame (LSF) floor systems to provide adequate fire resistance ratings (FRR). It is common practice to use lipped channel sections (LCS) as joists in LSF floor systems, and past research has only considered such systems. This research focuses on adopting improved joist sections such as hollow flange channel (HFC) sections to improve the structural performance and FRR of cold-formed LSF floor systems under standard fire conditions. The structural and thermal performances of LSF floor systems made of a welded HFC, LiteSteel Beams (LSB), with different plasterboard and insulation configurations, were investigated using four full-scale fire tests under standard fires. These fire tests showed that the new LSF floor system with LSB joists improved the FRR i...

Numerical study of LSF floors made of hollow flange channels in fire

Light gauge steel frame (LSF) floor systems are generally made of lipped channel section joists and lined with gypsum plasterboards to provide adequate fire resistance rating under fire conditions. Recently a new LSF floor system made of welded hollow flange channel (HFC) section was developed and its fire performance was investigated using full scale fire tests. The new floor systems gave higher fire resistance ratings in comparison to conventional LSF floor systems. To avoid expensive and time consuming full scale fire tests, finite element analyses were also performed to simulate the fire performance of LSF floors made of HFC joists using both steady and transient state methods. This paper presents the details of the developed finite element models of HFC joists to simulate the structural fire performance of the LSF floor systems under standard fire conditions. Finite element analyses were performed using the measured time–temperature profiles of the failed joists from the fire tests, and their failure times, temperatures and modes, and deflection versus time curves were obtained. The developed finite element models successfully predicted the structural performance of LSF floors made of HFC joists under fire conditions. They were able to simulate the complex behaviour of thin cold-formed steel joists subjected to non-uniform temperature distributions, and local buckling and yielding effects. This study also confirmed the superior fire performance of the newly developed LSF floors made of HFC joists.

Fire tests of load-bearing LSF walls made of hollow flange channel sections

Fire resistant and load bearing Light gauge Steel Frame (LSF) wall systems are generally made of cold-formed steel stud sections lined with gypsum plasterboards. Structural stability of these steel frames at elevated temperatures is important for the load bearing LSF walls for survival during fire events. The studs in these frames are usually Lipped Channel Section (LCS) studs. However, there are other more structurally efficient stud sections such as the hollow flange section studs, which can be effectively used in LSF walls. However, lack of fire research on these sections has inhibited their usage in LSF walls. This paper proposes the use of hollow flange channel (HFC) section studs in LSF walls with a view to increase their fire resistant ratings (FRR). In this study, five full scale fire tests of LSF walls made of welded hollow flange channel section studs were conducted under standard fire conditions. Three different wall configurations and three load ratios were considered in these tests. This paper presents the details of fire tests and their results including the time-temperature profiles of plasterboard and steel stud surfaces, lateral displacement and axial deformation profiles, failure modes and failure temperatures. It also presents the effects of using different wall configurations and load ratios on the FRR of LSF walls. Comparison of the fire performance of LSF walls made of welded HFC section studs with those made of conventional LCS studs demonstrated the superior fire performance through the use of welded HFC section studs.

Behaviour and strength of hollow flange channel sections under torsion and bending

Hollow flange channel section is a cold-formed high-strength and thin-walled steel section with a unique shape including two rectangular hollow flanges and a slender web. Due to its mono-symmetric characteristics, it will also be subjected to torsion when subjected to transverse loads in practical applications. Past research on steel beams subject to torsion has concentrated on open sections while very few steel design standards give suitable design rules for torsion design. Since the hollow flange channel section is different from conventional open sections, its torsional behaviour remains unknown to researchers. Therefore the elastic behaviour of hollow flange channel sections subject to uniform and non-uniform torsion, and combined torsion and bending was investigated using the solutions of appropriate differential equilibrium equations. The section torsion shear flow, warping normal stress distribution, and section constants including torsion constant and warping constant were obtained. The results were compared with those from finite element analyses that verified the accuracy of analytical solutions. Parametric studies were undertaken for simply supported beams subject to a uniformly distributed torque and a uniformly distributed transverse load applied away from the shear centre. This paper presents the details of this research into the elastic behaviour and strength of hollow flange channel sections subject to torsion and bending and the results.

Predicting the performance of LSF walls made of hollow flange channel sections in fire

Fire resistance of load bearing Light Gauge Steel Frame (LSF) wall systems is important to protect lives and properties in fire accidents. Recent fire tests of LSF walls made of the new cold-formed and welded hollow flange channel (HFC) section studs and the commonly used lipped channel section (LCS) studs have shown the influence of stud sections on the fire resistance rating (FRR) of LSF walls. To advance the use of HFC section studs and to verify the outcomes from the fire tests, finite element models were developed to predict the structural fire performance of LSF walls made of welded HFC section studs. The developed models incorporated the measured non-uniform temperature distributions in LSF wall studs due to the exposure of standard fire on one side, and accurate elevated temperature mechanical properties of steel used in the stud sections. These models simulated the various complexities involved such as thermal bowing and neutral axis shift caused by the non-uniform temperature distribution in the studs. The finite element analysis (FEA) results agreed well with the full scale fire test results including the FRR, outer hot and cold flange temperatures at failure and axial deformation and lateral displacement profiles. They also confirmed the superior fire performance of LSF walls made of HFC section studs. The applicability of both transient and steady state FEA of LSF walls under fire conditions was verified in this study, which also investigated the effects of using various temperature distribution patterns across the cross-section of HFC section studs on the FRR of LSF walls. This paper presents the details of this numerical study and the results.

Elevated temperature mechanical properties of hollow flange channel sections

The fire performance of cold-formed steel members is an important criterion to be verified for their successful use in structural applications. However, lack of clear design guidance on their fire performance has inhibited their usage in buildings. Their elevated temperature mechanical properties, i.e., yield strengths, elastic moduli and stress–strain relationships, are imperative for the fire design. In the past many researchers have proposed elevated temperature mechanical property reduction factors for cold-formed steels, however, large variations exist among them. The LiteSteel Beam (LSB), a hollow flange channel section, is manufactured by a combined cold-forming and electric resistance welding process. Its web, inner and outer flange elements have different yield strengths due to varying levels of cold-working caused by their manufacturing process. Elevated temperature mechanical properties of LSBs are not the same even within their cross-sections. Therefore an experimental study was undertaken to determine the elevated temperature mechanical properties of steel plate elements in LSBs. Elevated temperature tensile tests were performed on web, inner and outer flange specimens taken from LSBs, and their results are presented in this paper including their comparisons with previous studies. Based on the test results and the proposed values from previous studies and fire design standards, suitable predictive equations are proposed for the determination of elevated temperature mechanical properties of LSB web and flange elements. Suitable stress–strain models are also proposed for the plate elements of this cold-formed and welded hollow flange channel section.

Numerical studies and design of hollow flange channel beams subject to combined bending and shear actions

LiteSteel beam (LSB) is a cold-formed steel hollow flange channel section produced using a patented manufacturing process involving simultaneous cold-forming and dual electric resistance welding. It is commonly used as floor joists and bearers in residential, industrial and commercial buildings. Design of the LSB is governed by the Australian cold-formed steel structures code, AS/NZS 4600. Due to the geometry of the LSB, as well as its unique residual stress characteristics and initial geometric imperfections resultant of manufacturing processes, currently available design equations for common cold-formed sections are not directly applicable to the LSB. Many research studies have been carried out to evaluate the behaviour and design of LSBs subject to pure bending actions and predominant shear actions. To date, however, no investigation has been conducted into the strength of LSB sections under combined bending and shear actions. Hence experimental and numerical studies were conducted to assess the combined bending and shear behaviour of LSBs. Finite element models of LSBs were developed to simulate their combined bending and shear behaviour and strength of LSBs. They were then validated by comparing the results with available experimental test results and used in a detailed parametric study. The results from experimental and finite element analyses were compared with current AS/NZS 4600 and AS 4100 design rules. Both experimental and numerical studies show that the AS/NZS 4600 design rule based on circular interaction equation is conservative in predicting the combined bending and shear capacities of LSBs. This paper presents the details of the numerical studies of LSBs and the results. In response to the inadequacies of current approaches to designing LSBs for combined bending and shear, two lower bound design equations are proposed in this paper.

Experimental studies of the shear behavior and strength of LiteSteel beams with stiffened web openings

LiteSteel beam (LSB) is a new cold-formed steel hollow flange channel section produced using a patented manufacturing process. It is commonly used as flexural members in residential, industrial and commercial buildings. Current practice in flooring systems is to include openings in the web element of floor joists or bearers so that building services can be located within them. Test results have shown that the shear capacity of LSBs can be reduced considerably by the inclusion of web openings. A cost effective method of eliminating the detrimental effects of a large web opening is to attach suitable stiffeners around the web openings of LSBs. A detailed experimental study consisting of 17 shear tests was therefore undertaken to investigate the shear behavior and strength of LSBs with stiffened circular web openings. Both plate and stud stiffeners with varying sizes and thicknesses were attached to the web elements of LSBs using a number of screw-fastening arrangements in order to develop a suitable stiffening arrangement for LSBs. Simply supported test specimens of LSBs with an aspect ratio of 1.5 were loaded at mid-span until failure. This paper presents the details of this experimental study of LSBs with stiffened web openings, and the results of their shear capacities and associated behavioral characteristics. Suitable screw-fastened plate stiffener arrangements have been recommended in order to restore the original shear capacity of LSBs.