Light Gauge Steel Frame Walls Research Articles

Fire tests of non-load bearing light gauge steel frame walls lined with calcium silicate boards and gypsum plasterboards

Light gauge Steel Frame (LSF) wall systems are made of cold-formed steel studs and tracks, and lined with wall lining materials. Conventionally, gypsum plasterboards are used as wall lining material in LSF wall systems. The fire performance of LSF walls is mainly dependent on the type and configuration of wall lining material, which delays the heat transfer through the wall and protects the steel studs from being heated rapidly. Recently, calcium silicate board lining is increasingly used in LSF wall systems because of its improved physical and thermal properties while being lightweight, cost effective, impact and moisture resistant. However, their fire performance has not been investigated in detail. Hence two full scale fire tests were conducted on non-load bearing LSF walls lined with calcium silicate boards. For comparison purposes two fire tests were also conducted on conventional gypsum plasterboard lined LSF walls. This paper presents the details of this experimental study on the fire performance of LSF walls and the results including fire resistance levels and time-temperature profiles across the wall panels. Effects of using calcium silicate board lining are discussed by comparing the fire test results of LSF wall lined with gypsum plasterboards and previously conducted studies on magnesium oxide board lined LSF walls. The results showed that the fire performance of calcium silicate board lined walls was similar to that of conventional gypsum plasterboard lined walls, but was superior to that of magnesium oxide board lined walls. The failure criterion of these calcium silicate board lined walls was found to be insulation as opposed to being the integrity failure observed in previous studies.

Detrimental effects of plasterboard joints on the fire resistance of light gauge steel frame walls

Light gauge Steel Frame (LSF) walls are commonly used in building construction. In general, they are lined with single or double layers of gypsum plasterboards with and without cavity insulation. Gypsum plasterboards act as a thermal barrier to protect the thin-walled steel studs from rapid temperature rise. In these walls, plasterboard joints are located along the studs for ease of construction and are protected by filler materials. During fires, these plasterboard joints crack and open up, and thus allow the stud temperatures to rise rapidly and initiate premature structural failures in LSF walls. This research investigated the detrimental effects of these plasterboards joints on the fire resistance rating of single and double plasterboard lined walls based on the hot flange time-temperature profiles of studs from full scale fire tests. To overcome the detrimental effects of plasterboard joints, the back-blocking technique was used, where plasterboard joints were placed between studs with 150mm wide plasterboards as back-blocks. Full scale fire tests and numerical studies were performed on single plasterboard lined load bearing LSF wall panels to investigate the improved fire performance by using this technique. They showed that the fire resistance rating of these LSF walls was increased by 25% in comparison to the conventional plasterboard joint arrangement over the studs. This paper presents the details of this research on the detrimental effects of plasterboard joints on the fire resistance of load bearing LSF walls, and the results. It also includes a discussion and results for non-load bearing LSF walls.

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.

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.

Fire design rules for load bearing cold-formed steel frame walls exposed to realistic design fire curves

Light gauge Steel Frame (LSF) walls are extensively used in the building industry due to the many advantages they provide over other wall systems. Although LSF walls have been used widely, fire design of LSF walls is based on approximate prescriptive methods based on limited fire tests. Also these fire tests were conducted using the standard fire curve (ISO 834-1, 1999 [1]) and the applicability of available design rules to realistic design fire curves has not been verified. This paper investigates the accuracy of existing fire design rules in the current cold-formed steel standards and the modifications proposed by previous researchers. Of these the recently developed design rules by Gunalan and Mahendran (2013) [2] based on Eurocode 3 Part 1.3 (EN 1993-1-3, 2006 [3]) and AS/NZS 4600 (Standards Australia (SA), 2005 [4]) for standard fire exposure (ISO 834-1, 1999 [1]) were investigated in detail to determine their applicability to predict the axial compression strengths and fire resistance ratings of LSF walls exposed to realistic design fire curves. This paper also presents the fire performance results of LSF walls exposed to a range of realistic fire curves obtained using a finite element analysis based parametric study. The results from the parametric study were used to develop a simplified design method based on the critical hot flange temperature to predict the fire resistance ratings of LSF walls exposed to realistic fire curves. Finally, the stud failure times (fire resistance rating) obtained from the fire design rules and the simplified design method were compared with parametric study results for LSF walls lined with single and double plasterboards, and externally insulated with rock fibres under realistic fire curves.

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.

Development of realistic design fire time-temperature curves for the testing of cold-formed steel wall systems

Fire resistance rating of light gauge steel frame (LSF) wall systems is obtained from fire tests based on the standard fire time-temperature curve. However, fire severity has increased in modern buildings due to higher fuel loads as a result of modern furniture and light weight constructions that make use of thermoplastics materials, synthetic foams and fabrics. Some of these materials are high in calorific values and increase both the spread of fire growth and heat release rate, thus increasing the fire severity beyond that of the standard fire curve. Further, the standard fire curve does not include a decay phase that is present in natural fires. Despite the increasing usage of LSF walls, their behavior in real building fires is not fully understood. This paper presents the details of a research study aimed at developing realistic design fire curves for use in the fire tests of LSF walls. It includes a review of the characteristics of building fires, previously developed fire time-temperature curves, computer models and available parametric equations. The paper highlights that real building fire time-temperature curves depend on the fuel load representing the combustible building contents, ventilation openings and thermal properties of wall lining materials, and provides suitable values of many required parameters including fuel loads in residential buildings. Finally, realistic design fire time-temperature curves simulating the fire conditions in modern residential buildings are proposed for the testing of LSF walls.

Thermal Performance of Load Bearing Cold-formed Steel Walls under Fire Conditions using Numerical Studies

Cold-formed Light gauge Steel Frame (LSF) wall systems are increasingly used in low-rise and multi-storey buildings and hence their fire safety has become important in the design of buildings. A composite LSF wall panel system was developed recently, where a thin insulation was sandwiched between two plasterboards to improve the fire performance of LSF walls. Many experimental and numerical studies have been undertaken to investigate the fire performance of non-load bearing LSF wall under standard conditions. However, only limited research has been undertaken to investigate the fire performance of load bearing LSF walls under standard and realistic design fire conditions. Therefore in this research, finite element thermal models of both the conventional load bearing LSF wall panels with cavity insulation and the innovative LSF composite wall panel were developed to simulate their thermal behaviour under standard and realistic design fire conditions. Suitable thermal properties were proposed for plasterboards and insulations based on laboratory tests and available literature. The developed models were then validated by comparing their results with available fire test results of load bearing LSF wall. This paper presents the details of the developed finite element models of load bearing LSF wall panels and the thermal analysis results. It shows that finite element models can be used to simulate the thermal behaviour of load bearing LSF walls with varying configurations of insulations and plasterboards. Failure times of load bearing LSF walls were also predicted based on the results from finite element thermal analyses. Finite element analysis results show that the use of cavity insulation was detrimental to the fire rating of LSF walls while the use of external insulation offered superior thermal protection to them. Effects of realistic design fire conditions are also presented in this paper.

Numerical modelling of load bearing light gauge steel frame wall systems exposed to realistic design fires

Fire safety has become an important part in structural design due to the ever increasing loss of properties and lives during fires. Conventionally the fire rating of load bearing wall systems made of Light gauge Steel Frames (LSF) is determined using fire tests based on the standard time–temperature curve in ISO834 (ISO 834-1, 1999 [1]). However, modern commercial and residential buildings make use of thermoplastic materials, which mean considerably high fuel loads. Hence a detailed fire research study into the fire performance of LSF walls was undertaken using realistic design fire curves developed based on Eurocode parametric (ENV 1991-1-2, 2002 [2]) and Barnett's BFD (Barnett, 2002 [3]) curves using both full scale fire tests and numerical studies. It included LSF walls without cavity insulation, and the recently developed externally insulated composite panel system. This paper presents the details of finite element models developed to simulate the full scale fire tests of LSF wall panels under realistic design fires. Finite element models of LSF walls exposed to realistic design fires were developed, and analysed under both transient and steady state fire conditions using the measured stud time–temperature curves. Transient state analyses were performed to simulate fire test conditions while steady state analyses were performed to obtain the load ratio versus time and failure temperature curves of LSF walls. Details of the developed finite element models and the results including the axial deformation and lateral deflection versus time curves, and the stud failure modes and times are presented in this paper. Comparison with fire test results demonstrate the ability of developed finite element models to predict the performance and fire resistance ratings of LSF walls under realistic design fires.

Fire performance of cold-formed steel wall panels and prediction of their fire resistance rating

Recent research at the Queensland University of Technology has investigated the structural and thermal behaviour of load bearing Light gauge Steel Frame (LSF) wall systems made of 1.15mm G500 steel studs and varying plasterboard and insulation configurations (cavity and external insulation) using full scale fire tests. Suitable finite element models of LSF walls were then developed and validated by comparing with test results. In this study, the validated finite element models of LSF wall panels subject to standard fire conditions were used in a detailed parametric study to investigate the effects of important parameters such as steel grade and thickness, plasterboard screw spacing, plasterboard lateral restraint, insulation materials and load ratio on their performance under standard fire conditions. Suitable equations were proposed to predict the time–temperature profiles of LSF wall studs with eight different plasterboard-insulation configurations, and used in the finite element analyses. Finite element parametric studies produced extensive fire performance data for the LSF wall panels in the form of load ratio versus time and critical hot flange (failure) temperature curves for eight wall configurations. This data demonstrated the superior fire performance of externally insulated LSF wall panels made of different steel grades and thicknesses. It also led to the development of a set of equations to predict the important relationship between the load ratio and the critical hot flange temperature of LSF wall studs. Finally this paper proposes a simplified method to predict the fire resistance rating of LSF walls based on the two proposed set of equations for the load ratio–hot flange temperature and the time–temperature relationships.

Review of current fire design rules for cold-formed steel wall systems

Light gauge steel frame wall systems are commonly used in industrial and commercial buildings, and there is a need for simple fire design rules to predict their load capacities and fire resistance ratings. During fire events, the light gauge steel frame wall studs are subjected to non-uniform temperature distributions that cause thermal bowing, neutral axis shift and magnification effects and thus resulting in a combined axial compression and bending action on the studs. In this research, a series of full-scale fire tests was conducted first to evaluate the performance of light gauge steel frame wall systems with eight different wall configurations under standard fire conditions. Finite element models of light gauge steel frame walls were then developed, analysed under transient and steady-state conditions and validated using full-scale fire tests. Using the results from fire tests and finite element analyses, a detailed investigation was undertaken into the prediction of axial compression strength and failure times of light gauge steel frame wall studs in standard fires using the available fire design rules based on Australian, American and European standards. The results from both fire tests and finite element analyses were used to investigate the ability of these fire design rules to include the complex effects of non-uniform temperature distributions and their accuracy in predicting the axial compression strength of wall studs and the failure times. Suitable modifications were then proposed to the fire design rules. This article presents the details of this investigation on the fire design rules of light gauge steel frame walls and the results.

Experimental studies of non-load bearing steel wall systems under fire conditions

Fire safety of buildings has been recognised as very important by the building industry and the community at large. Traditionally, increased fire rating is provided by simply adding more plasterboards to light gauge steel frame (LSF) walls, which is inefficient. Many research studies have been undertaken to investigate the thermal behaviour of traditional LSF stud wall systems under standard fire conditions. However, no research has been undertaken on the thermal behaviour of LSF stud walls using the recently proposed composite panel. Extensive fire testing of both non-load bearing and load bearing wall panels was conducted in this research based on the standard time-temperature curve in AS1530.4. Three groups of LSF wall specimens were tested with no insulation, cavity insulation and the new composite panel based on an external insulation layer between plasterboards. This paper presents the details of this experimental study into the thermal performance of non-load bearing walls lined with various configurations of plasterboard and insulation. Extensive descriptive and numerical results of the tested non-load bearing wall panels given in this paper provide a thorough understanding of their thermal behaviour, and valuable time-temperature data that can be used to validate numerical models. Test results showed that the innovative composite stud wall systems outperformed the traditional stud wall systems in terms of their thermal performance, giving a much higher fire rating.

Thermal Performance of Composite Panels Under Fire Conditions Using Numerical Studies: Plasterboards, Rockwool, Glass Fibre and Cellulose Insulations

In recent times, light gauge steel frame (LSF) wall systems are increasingly used in the building industry. They are usually made of cold-formed and thin-walled steel studs that are fire-protected by two layers of plasterboard on both sides. A composite LSF wall panel system was developed recently, where an insulation layer was used externally between the two plasterboards to improve the fire performance of LSF wall panels. In this research, finite element thermal models of the new composite panels were developed using a finite element program, SAFIR, to simulate their thermal performance under both standard and Eurocode design fire curves. Suitable apparent thermal properties of both the gypsum plasterboard and insulation materials were proposed and used in the numerical models. The developed models were then validated by comparing their results with available standard fire test results of composite panels. This paper presents the details of the finite element models of composite panels, the thermal analysis results in the form of time–temperature profiles under standard and Eurocode design fire curves and their comparisons with fire test results. Effects of using rockwool, glass fibre and cellulose fibre insulations with varying thickness and density were also investigated, and the results are presented in this paper. The results show that the use of composite panels in LSF wall systems will improve their fire rating, and that Eurocode design fires are likely to cause severe damage to LSF walls than standard fires.