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Mahen Mahendran - One of the best experts on this subject based on the ideXlab platform.
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Fire Design of LSF wall systems made of web-stiffened lipped channel studs
Thin-walled Structures, 2018Co-Authors: Mohamed Rusthi, Anthony Deloge Ariyanayagam, Mahen MahendranAbstract:Cold-formed steel stud sections are commonly used as compression members in Fire rated load-bearing light gauge steel frame (LSF) wall systems. Although conventional lipped channel section (LCS) studs are commonly used in LSF wall systems, there is a growing interest in developing innovative stud sections to increase the load carrying capacities when used in Fire rated LSF wall systems. One such section is the web-stiffened section (WSS), which has increased load carrying capacities as well as enhanced acoustic properties. However, the applicability of the existing structural Fire Design rules has not been investigated for the WSS stud sections while the advantages of using such sections have not been demonstrated. Therefore, the structural behaviour of WSS stud sections was investigated under ambient and Fire conditions using finite element analyses and their capacities were compared with those of conventional LCS studs. Three different LSF wall configurations and three stud thicknesses were considered for both stud sections. The applicability of existing structural Fire Design rules for LCS and WSS studs used in Fire rated LSF wall systems was then investigated based on finite element analyses, effective width method and direct strength method. The results show that WSS studs have much higher load carrying capacities than LCS studs under ambient and Fire conditions and that direct strength method based Design rules are simpler to use than the effective width based Design rules for the structural Fire Design of LSF wall systems made of both LCS and WSS studs. This paper presents the details of this investigation and the results.
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Numerical modelling and direct strength method based Fire Design of LSF walls
2016Co-Authors: Mohamed Rusthi Mohamed Ibralebbe, Anthony Deloge Ariyanayagam, Mahen MahendranAbstract:In this research study the application of the direct strength method (DSM) was investigated for lipped channel wall studs under combined bending and compression actions at non-uniform elevated temperatures. Finite element models of the wall studs subject to varying load ratios were developed, validated and used in a detailed parametric study to develop extensive Fire performance data, which were then used in the development of DSM based Fire Design rules. This paper presents the details of this study and the results.
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Fire Design of LSF floors using hollow flange channel joists
Journal of Constructional Steel Research, 2016Co-Authors: Varathananthan Jatheeshan, Mahen MahendranAbstract: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.
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Fire Design rules to predict the moment capacities of thin-walled floor joists subject to non-uniform temperature distributions
Science & Engineering Faculty, 2016Co-Authors: Balachandren Baleshan, Mahen MahendranAbstract:Thin-walled floor joists in LSF floor panels are protected by gypsum plasterboards and are subjected to a non-uniform temperature distribution across their cross-section in Fires. Fire tests have shown that the failure of floor panels was governed by the section moment capacity of joists governed by local buckling effects. This research was aimed at developing simple Design rules to predict the failure times (Fire resistance) of LSF floors made of lipped channel section joists exposed to standard Fires. The use of ambient temperature section modulus led to over-estimation of the moment capacity as the mechanical properties of steel varied across the joist cross-section while deteriorating with increasing joist temperatures in Fires. New simplified Fire Design rules were proposed to determine the section moment capacities of joists at elevated temperatures based on the current cold-formed steel Design specifications. Their accuracy was verified using finite element analysis and Fire test results.
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Fire Design rules for LSF walls made of hollow flange channel sections
Science & Engineering Faculty, 2016Co-Authors: Sivakumar Kesawan, Mahen MahendranAbstract: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.
Antonio Hospitaler - One of the best experts on this subject based on the ideXlab platform.
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Recent developments and Fire Design provisions for CFST columns and slim-floor beams
Journal of Constructional Steel Research, 2020Co-Authors: Manuel L. Romero, A. Espinos, A. Lapuebla-ferri, Vicente Albero, Antonio HospitalerAbstract:Abstract This paper summarizes the latest technical and scientific progresses on steel-concrete composite structures exposed to Fire, presenting the recent research carried out on this subject and the progress of the Design codes. In particular, this review focuses on concrete-filled steel tubular columns and slim-floor beams, topics where the authors have carried out extensive research during the last years. The more recent experimental and numerical studies performed by the authors as well as those available in the literature are presented, along with applications where these composite elements have been used in practice. The use of advanced materials, such as high strength steel and concrete, stainless steel, lightweight concrete or geopolymer concrete is considered for the enhancement of the Fire behaviour of concrete-filled steel tubular columns and slim-floor beams. Finally, the currently available Design methods for the calculation of isolated members at elevated temperatures are reviewed and the recent progress of the code provisions for the Fire Design of these composite elements is presented.
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Fire Design method for concrete filled tubular columns based on equivalent concrete core cross-section
Fire Safety Journal, 2015Co-Authors: Carmen Ibañez, Jose Vicente Aguado, Manuel L. Romero, A. Espinos, Antonio HospitalerAbstract:Abstract In this work, a method for a realistic cross-sectional temperature prediction and a simplified Fire Design method for circular concrete filled tubular columns under axial load are presented. The generalized lack of simple proposals for computing the cross-sectional temperature field of CFT columns when their Fire resistance is evaluated is evident. Even Eurocode 4 Part 1-2, which provides one of the most used Fire Design methods for composite columns, does not give any indications to the Designers for computing the cross-sectional temperatures. Given the clear necessity of having an available method for that purpose, in this paper a set of equations for computing the temperature distribution of circular CFT columns filled with normal strength concrete is provided. First, a finite differences thermal model is presented and satisfactorily validated against experimental results for any type of concrete infill. This model consideres the gap at steel–concrete interface, the moisture content in concrete and the temperature dependent properties of both materials. Using this model, a thermal parametric analysis is executed and from the corresponding statistical analysis of the data generated, the practical expressions are derived. The second part of the paper deals with the development of a Fire Design method for axially loaded CFT columns based on the general rules stablished in Eurocode 4 Part 1-1 and employing the concept of room temperature equivalent concrete core cross-section. In order to propose simple equations, a multiple nonlinear regression analysis is made with the numerical results generated through a thermo-mechanical parametric analysis. Once more, predicted results are compared to experimental values giving a reasonable accuracy and slightly safe results.
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Fire Design method for bar reinforced circular and elliptical concrete filled tubular columns
Engineering Structures, 2013Co-Authors: A. Espinos, Manuel L. Romero, Antonio HospitalerAbstract:Abstract A method for calculating the Design axial buckling load in the Fire situation of unreinforced axially loaded concrete filled circular hollow section columns was presented by the authors in a previous paper [1] . In the present paper, the method is extended to bar-reinforced columns of circular and elliptical cross-section, as a necessary continuation to complete the proposal. The method presented here is based on the guidelines of Clause 4.3.5.1 in Eurocode 4 Part 1.2 for the Fire Design of composite columns and is developed on the basis of the results of new parametric studies, with varying values of the outer diameter of the column, steel tube wall thickness, relative slenderness, percentage of reinforcement and Fire exposure time. From the results of these parametric studies, appropriate expressions and tables for the different parts which integrate the Design method are derived. The proposed method is valid for centrally loaded bar-reinforced circular and elliptical concrete filled tubular columns, with a maximum percentage of reinforcement of a 5% and makes allowance for columns with a high slenderness, extending the current limits of Eurocode 4 Part 1.2.
João Paulo C. Rodrigues - One of the best experts on this subject based on the ideXlab platform.
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Fire Design methodologies for cold-formed steel beams made with open and closed cross-sections
Engineering Structures, 2018Co-Authors: Luís Laím, João Paulo C. RodriguesAbstract:Abstract This paper focuses on developing a simplified Fire Design methodology for single and built-up cold-formed steel beams based on the European guidelines. Open and closed cross-sections made with (lipped and unlipped) channel sections were selected for this research work. Existing experimental tests and shell finite element analysis using an advanced commercial program were used as the basis for the novel study conducted herein. Numerical results were then compared with predictions from available European Fire Design rules and appropriate recommendations are made. Such Design rules were found to be unsafe or over-conservative depending on the relative slenderness and serviceability load of the beams. Comparisons with numerical moment capacities also demonstrated good precision of the new Fire Design methodology. The results obtained by this methodology may have an average error of half of those obtained by using the available European Design curves.
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On the applicability and accuracy of Fire Design methods for open cold-formed steel beams
Journal of building engineering, 2016Co-Authors: Luís Laím, João Paulo C. RodriguesAbstract:Abstract This paper presents the results of an experimental and numerical investigation on the structural behaviour of cold-formed steel C and lipped-I beams subjected to uniform temperature distributions under standard Fire conditions. A total of 18 specimens divided into four-point bending tests under Fire conditions and under 3 different restraining conditions (including no restraints, partial axial restraint to the thermal elongation of the beam and both partial axial and rotational restraints at the beam supports) have been conducted. Local buckling, distortional buckling, lateral-torsional buckling and their interactions were observed in the tests. Then, the tests were modelled by the finite element programme Abaqus and, at the end, the numerical results showed good agreement with the experimental results in terms of axial restraining forces, vertical displacements, critical temperatures and buckling modes. The simulated results were still compared with the predictions from the currently European Design rules (EN 1993-1.2:2005), in order to observe if there are safe and consistent regulations for Fire Design of these members. Finally, the numerical simulations have mainly shown that these Design methods for CFS beams may be quite unsafe or over-conservative depending strongly on their boundary conditions.
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A simplified calculation method for Fire Design of steel columns with restrained thermal elongation
Computers & Structures, 2012Co-Authors: António J. P. Moura Correia, João Paulo C. Rodrigues, Fernando C. T. GomesAbstract:The simplified calculation methods proposed in EN1993-1-2 for Fire Design of steel columns do not take into account the restraining to its thermal elongation. In order to provide data for developing a new simplified calculation method for Fire Design of HEA, HEB and HEM steel columns with restrained thermal elongation a parametric study using the advanced calculation model ABAQUS, was carried out. This method was established taking into account the axial and rotational restraint to the column in case of Fire, the column slenderness and the load level. The critical times and temperatures can be obtained directly from formulae.
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Buckling length of a steel column for Fire Design
Engineering Structures, 2007Co-Authors: Fernando C. T. Gomes, João Paulo C. Rodrigues, Paulo M. Providência E Costa, Ildefonso C. NevesAbstract:Abstract The Eurocode 3 part 1-2 gives some simple rules to determine the buckling length l f i of a steel column for Fire Design. In the case of a braced frame in which each storey comprises a separate Fire compartment with sufficient Fire resistance, Eurocode 3 suggests that the buckling length may be taken as l f i = 0.5 L in an intermediate storey and as l f i = 0.7 L in the top storey, where L is the system length in the relevant storey. Stability analyses for the evaluation of the buckling length and critical load of columns in braced frames show that the Eurocode 3 rule may be rather inaccurate in many practical situations. The authors propose alternative formulas to determine the buckling length at elevated temperatures, as an improvement of the actual rule of the Eurocode 3 part 1.2.
Mario Fontana - One of the best experts on this subject based on the ideXlab platform.
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Modeling elevated-temperature mechanical behavior of high and ultra-high strength steels in structural Fire Design
Materials & Design, 2017Co-Authors: Martin Neuenschwander, Markus Knobloch, Claudio Scandella, Mario FontanaAbstract:Abstract High and ultra-high strength steels are increasingly used in structures of tall and super-tall buildings, where Fire safety has a substantial impact on the structural Design. However, more widespread employment in engineering practice is substantially impeded by the lack of suitable Design models for the constitutive mechanical behavior of such steels at elevated temperatures; and respective available experimental research is limited to investigations of unusually thin plate material with respect to structural applications. The present study completes the current database with an extensive series of strain-rate controlled tensile tests at different strain-rates with coupon specimens from high and ultra-high strength steel plates of varying thickness, and approves on the basis of this novel most comprehensive and consistent database that existing constitutive Fire Design models for mild carbon steels are only restrictedly adoptable for high strength steels. Analysis of the impact of the revealed model shortcomings at the material level on structural Fire Designs shows that the model's overestimation of the elevated-temperature yield strength leads to unsafe Fire Designs of structural applications with strength-induced failure modes, whereas in contrast the model's underestimation of the elevated-temperature Young's modulus leads to occasionally highly overconservative Fire Designs of structural applications with stability-induced failure modes.
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Fire Design of steel-to-timber dowelled connections
Engineering Structures, 2010Co-Authors: Carsten Erchinger, Andrea Frangi, Mario FontanaAbstract:Abstract The load-carrying capacity of timber structures is often limited by the resistance of the connections. Thus, highly efficient connections such as multiple shear steel-to-timber connections with slotted-in steel plates and steel dowels are needed for an efficient Design. The load-carrying capacity of multiple shear steel-to-timber dowelled connections with slotted-in steel plates in Fire primarily depends on the temperature-dependent reduction of embedment strength of the timber members. In order to accurately predict the Fire resistance of the connection, knowledge of the temperature distribution in the cross-section as well as the influence of steel elements (slotted-in steel plates and steel dowels) on the charring of the timber members is essential. Based on an extensive experimental and numerical analysis, a Design model for the calculation of the load-carrying capacity in Fire of multiple shear steel-to-timber dowelled connections with slotted-in steel plates subjected to tension was developed and is presented. The Design model is in analogy with the reduced cross-section method according to EN 1995-1-2 commonly used for the Fire Design of timber members. The proposed Design model takes into account different geometries of the connection and the influence of the steel elements on the temperature distribution in the cross-section.
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Fire Design of timber slabs made of hollow core elements
Engineering Structures, 2008Co-Authors: Andrea Frangi, Markus Knobloch, Mario FontanaAbstract:Abstract The Fire Design of timber structures usually take into account both the loss in cross-section due to charring of wood and the temperature-dependent reduction of strength and stiffness of the uncharred residual cross-section. The Fire behaviour of timber assemblies made of hollow core elements is characterised by different charring phases. After the Fire exposed timber layer is completely charred and the char-layer has fallen off, the thin vertical timber members are exposed to Fire on 3 sides, leading to very irregular residual cross-sections with charring depths much greater than for heavy timber structures. Based on an extensive experimental and parametric study, a simplified calculation model for the Fire resistance of timber slabs made of hollow core elements has been developed. The calculation model bases on the reduced cross-section method and takes into account two different charring phases. The paper first describes and discusses the simplified calculation model, and then compares the test results to the calculation model.
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Fire Design Concepts for Tall Timber Buildings
Structural Engineering International, 2008Co-Authors: Andrea Frangi, Mario Fontana, Markus KnoblochAbstract:Based on the current knowledge in the area of Fire Design of timber structures this paper presents a generic Fire safety concept for tall timber buildings. The first part of the paper gives an over...
Manuel L. Romero - One of the best experts on this subject based on the ideXlab platform.
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Recent developments and Fire Design provisions for CFST columns and slim-floor beams
Journal of Constructional Steel Research, 2020Co-Authors: Manuel L. Romero, A. Espinos, A. Lapuebla-ferri, Vicente Albero, Antonio HospitalerAbstract:Abstract This paper summarizes the latest technical and scientific progresses on steel-concrete composite structures exposed to Fire, presenting the recent research carried out on this subject and the progress of the Design codes. In particular, this review focuses on concrete-filled steel tubular columns and slim-floor beams, topics where the authors have carried out extensive research during the last years. The more recent experimental and numerical studies performed by the authors as well as those available in the literature are presented, along with applications where these composite elements have been used in practice. The use of advanced materials, such as high strength steel and concrete, stainless steel, lightweight concrete or geopolymer concrete is considered for the enhancement of the Fire behaviour of concrete-filled steel tubular columns and slim-floor beams. Finally, the currently available Design methods for the calculation of isolated members at elevated temperatures are reviewed and the recent progress of the code provisions for the Fire Design of these composite elements is presented.
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Fire Design method for concrete filled tubular columns based on equivalent concrete core cross-section
Fire Safety Journal, 2015Co-Authors: Carmen Ibañez, Jose Vicente Aguado, Manuel L. Romero, A. Espinos, Antonio HospitalerAbstract:Abstract In this work, a method for a realistic cross-sectional temperature prediction and a simplified Fire Design method for circular concrete filled tubular columns under axial load are presented. The generalized lack of simple proposals for computing the cross-sectional temperature field of CFT columns when their Fire resistance is evaluated is evident. Even Eurocode 4 Part 1-2, which provides one of the most used Fire Design methods for composite columns, does not give any indications to the Designers for computing the cross-sectional temperatures. Given the clear necessity of having an available method for that purpose, in this paper a set of equations for computing the temperature distribution of circular CFT columns filled with normal strength concrete is provided. First, a finite differences thermal model is presented and satisfactorily validated against experimental results for any type of concrete infill. This model consideres the gap at steel–concrete interface, the moisture content in concrete and the temperature dependent properties of both materials. Using this model, a thermal parametric analysis is executed and from the corresponding statistical analysis of the data generated, the practical expressions are derived. The second part of the paper deals with the development of a Fire Design method for axially loaded CFT columns based on the general rules stablished in Eurocode 4 Part 1-1 and employing the concept of room temperature equivalent concrete core cross-section. In order to propose simple equations, a multiple nonlinear regression analysis is made with the numerical results generated through a thermo-mechanical parametric analysis. Once more, predicted results are compared to experimental values giving a reasonable accuracy and slightly safe results.
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Fire Design method for bar reinforced circular and elliptical concrete filled tubular columns
Engineering Structures, 2013Co-Authors: A. Espinos, Manuel L. Romero, Antonio HospitalerAbstract:Abstract A method for calculating the Design axial buckling load in the Fire situation of unreinforced axially loaded concrete filled circular hollow section columns was presented by the authors in a previous paper [1] . In the present paper, the method is extended to bar-reinforced columns of circular and elliptical cross-section, as a necessary continuation to complete the proposal. The method presented here is based on the guidelines of Clause 4.3.5.1 in Eurocode 4 Part 1.2 for the Fire Design of composite columns and is developed on the basis of the results of new parametric studies, with varying values of the outer diameter of the column, steel tube wall thickness, relative slenderness, percentage of reinforcement and Fire exposure time. From the results of these parametric studies, appropriate expressions and tables for the different parts which integrate the Design method are derived. The proposed method is valid for centrally loaded bar-reinforced circular and elliptical concrete filled tubular columns, with a maximum percentage of reinforcement of a 5% and makes allowance for columns with a high slenderness, extending the current limits of Eurocode 4 Part 1.2.