Fire behaviour and resistance of cold-formed steel beams with sigma cross-sections

PurposeSigma cross-section profiles are often chosen for their lightness and ability to support large spans, offering a favourable bending resistance. However, they are more susceptible to local, distortional and lateral-torsional buckling, as possible failure modes when compared to common I-sections and hollow cross-sections. However, the instability phenomena associated to these members are not completely understood in fire situation. Therefore, the purpose of this study is to analyse the behaviour of beams composed of cold-formed sigma sections at elevated temperatures.Design/methodology/approachThis study presents a numerical analysis, using advanced methods by applying the finite element software SAFIR. A numerical analysis of the behaviour of simply supported cold-formed sigma beams in the case of fire is presented considering different cross-section slenderness values, elevated temperatures, steel grades and bending moment diagrams. Comparisons are made between the obtained numerically ultimate bending capacities and the design bending resistances from Eurocode 3 Part 1–2 rules and its respective French National Annex (FN Annex).FindingsThe current design expressions revealed to be over conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the general prescriptions, the first having a better agreement with the numerical results.Originality/valueFollowing the previous comparisons, new fire design formulae are analysed. This new methodology, which introduces minimum changes in the existing formulae, provides at the same time safety and accuracy when compared to the numerical results, considering the occurrence of local, distortional and lateral-torsional buckling phenomena in these members at elevated temperatures.

Download Full-text

Fire resistance of DELTABEAM® composite beams: a numerical investigation

Journal of Structural Fire Engineering ◽

10.1108/jsfe-05-2016-0003 ◽

2017 ◽

Vol 8 (4) ◽

pp. 338-353 ◽

Cited By ~ 1

Author(s):

Chrysanthos Maraveas

Keyword(s):

Numerical Investigation ◽

Cross Section ◽

Cross Sections ◽

Fire Resistance ◽

Elevated Temperatures ◽

Ambient Conditions ◽

Content Type ◽

Technical Manual ◽

Manufacturing Company ◽

Parametric Analyses

Purpose The DELTA® beam composite floor system is a recently developed shallow floor type that has seen many applications in contemporary construction. It involves partially encasing DELTA® steel beams in concrete, with the lower flange remaining exposed. Besides the satisfactory behavior of the system at ambient conditions, understanding its response under elevated temperatures is critical in evaluating its overall performance. Despite certification from the manufacturing company that the system has adequate fire resistance, its behavior under fire conditions has neither been investigated to depth nor reported in detail. The purpose of this paper is the detailed numerical investigation of their behavior in fire. For this reason, the finite element method was implemented in this paper to simulate the response of such beams subjected to fire. Material properties were modeled according to the Eurocodes. The coupled thermal-structural parametric analyses involved four different variations of the “shortest” and “deepest” cross-section (eight case studies in total) specified by the manufacturing company. Other simulations of these cross-sections, in which either the thermal expansion or the structural load were not taken into account, were carried out for comparison purposes. Design/methodology/approach The methodology for simulating such systems, which has been successfully implemented and validated against fire test results elsewhere (Maraveas et al., 2012) was also followed here. To investigate the statement made by Maraveas et al. (2014) and the equations proposed by Zaharia and Franssen (2012) that the insulation is not so effective for “short” cross-sections, two beams, one with a D20-200 (Deltabeam Technical Manual, 2013) cross-section (shallowest section) and one with a D50-600 (Deltabeam Technical Manual, 2013) cross-section (deepest section), were simulated in this paper for comparison purposes. Additionally, reasonable assumptions were made for the cross-sectional dimensions not specified by the manufacturer (Deltabeam Technical Manual, 2013) and parametric analyses were carried out to investigate their effect on the structural response of the system. Findings Composite DELTA® beams can achieve fire resistances ranging from 120 to 180 min, depending on the depth and geometry of their cross-section, with deeper sections displaying a better fire response. The intense thermal bowing that occurs when these beams are heated from below has a more pronounced effect, in terms of thermally induced deflections for deeper sections. The satisfactory fire resistance of these beams is achieved due to the action of the concrete encased web and the reinforcement which compensate for the loss of the exposed lower flange. Increasing the thickness of the web in deeper sections improves their fire rating up to 180 min. The thickness of the lower flange affects the fire rating of the beams only in a minor way. Practical/implications The paper describes a numerical methodology to estimate the fire resistance of complex flooring systems.

Download Full-text

Behaviour and resistance of cold-formed steel beams with lipped channel sections under fire conditions

Journal of Structural Fire Engineering ◽

10.1108/jsfe-12-2016-025 ◽

2016 ◽

Vol 7 (4) ◽

pp. 365-387 ◽

Cited By ~ 1

Author(s):

Flávio Arrais ◽

Nuno Lopes ◽

Paulo Vila Real

Keyword(s):

Cross Sections ◽

Elevated Temperatures ◽

Numerical Results ◽

Steel Beams ◽

Finite Element Program ◽

Content Type ◽

Current Design ◽

Element Program ◽

Steel Grades ◽

Cold Formed Steel

Purpose Steel beams composed of cold-formed sections are common in buildings because of their lightness and ability to support large spans. However, the instability phenomena associated to these members are not completely understood in fire situation. Thus, the purpose of this study is to analyse the behaviour of beams composed of cold-formed lipped channel sections at elevated temperatures. Design/methodology/approach A numerical analysis is made, applying the finite element program SAFIR, on the behaviour of simply supported cold formed steel beams at elevated temperatures. A parametric study, considering several cross-sections with different slenderness’s values, steel grades and bending diagrams, is presented. The obtained numerical results are compared with the design bending resistances determined from Eurocode 3 Part 1-2 and its French National Annex (FN Annex). Findings The current design expressions revealed to be too conservative when compared with the obtained numerical results. It was possible to observe that the FN Annex is less conservative than the Annex E, the first having a better agreement with the numerical results. Originality/value Following the previous comparisons, new fire design formulae are tested. This new methodology, which introduces minimum changes in the existing formulae, provides safety and accuracy at the same time when compared to the numerical results, considering the occurrence of local, distortional and lateral torsional buckling phenomena in these members at elevated temperatures.

Download Full-text

Optimisation of Shear and Lateral–Torsional Buckling of Steel Plate Girders Using Meta-Heuristic Algorithms

Applied Sciences ◽

10.3390/app10103639 ◽

2020 ◽

Vol 10 (10) ◽

pp. 3639 ◽

Cited By ~ 2

Author(s):

Celal Cakiroglu ◽

Gebrail Bekdaş ◽

Sanghun Kim ◽

Zong Geem

Keyword(s):

Cross Sections ◽

Failure Modes ◽

Heuristic Algorithms ◽

Search Algorithm ◽

Harmony Search ◽

Lateral Torsional Buckling ◽

Torsional Buckling ◽

Cross Sectional ◽

Plate Girders ◽

The Cross

The shear buckling of web plates and lateral–torsional buckling are among the major failure modes of plate girders. The importance of the lateral–torsional buckling capacity of plate girders was further evidenced when several plate girders of a bridge in Edmonton, Alberta, Canada failed in 2015, because insufficient bracing led to the lateral buckling of the plate girders. In this study, we focus on the optimisation of the cross-sections of plate girders using a well-known and extremely efficient meta-heuristic optimisation algorithm called the harmony search algorithm. The objective of this optimisation is to design the cross-sections of the plate girders with the minimum area that satisfies requirements, such as the lateral–torsional buckling load and ultimate shear stress. The base geometry, material properties, applied load and boundary conditions were taken from an experimental study and optimised. It was revealed that the same amount of load-carrying capacity demonstrated by this model can be achieved with a cross-sectional area 16% smaller than that of the original specimen. Furthermore, the slenderness of the web plate was found to have a decisive effect on the cost-efficiency of the plate girder design.

Download Full-text

Lateral Torsional-Buckling of Class 4 Steel Plate Beams at Elevated Temperature: Experimental and Numerical Comparison

Journal of Structural Fire Engineering ◽

10.1260/2040-2317.6.3.223 ◽

2015 ◽

Vol 6 (3) ◽

pp. 223-236 ◽

Cited By ~ 2

Author(s):

Martin Prachar ◽

Michal Jandera ◽

Frantisek Wald ◽

Bin Zhao

Keyword(s):

Elevated Temperature ◽

Cross Sections ◽

Elevated Temperatures ◽

Numerical Comparison ◽

Lateral Torsional Buckling ◽

Torsional Buckling ◽

Ongoing Research ◽

Steel Members ◽

Set Up ◽

Hot Rolled

This paper presents ongoing research in behaviour of laterally unrestrained beams (I or H section) of Class 4 cross-sections at elevated temperatures, which is based on the RFCS project FIDESC4 - Fire Design of Steel Members with Welded or Hot-rolled Class 4 Cross-sections. Despite the current EC3 contains a number of simple rules for design of slender Class 4 cross-sections at elevated temperature, based on recent numerical simulations they were found to be over-conservative. Therefore, new well representing design models, which simulate the actual behaviour of the structures exposed to fire, are crucial. These design rules should be based on extensive numerical simulation validated on experimental data. Within this task, several tests were carried out to study lateral torsional buckling of Class 4 beams in fire. The design of the test set-up and description of the experiment is given, as well as verification of numerical model.

Download Full-text

GEM – A SOFTWARE FOR STABILITY VERIFICATION OF NON-UNIFORM MEMBERS, Adaptation of the general method procedure to fire design

Applications of Structural Fire Engineering ◽

10.14311/asfe.2015.008 ◽

2016 ◽

Author(s):

João Ferreira ◽

Paulo Vila Real ◽

Carlos Couto ◽

Paulo Cachim

Keyword(s):

Computer Program ◽

Elevated Temperatures ◽

Numerical Results ◽

Lateral Torsional Buckling ◽

Torsional Buckling ◽

Tapered Beam ◽

Eurocode 3 ◽

The Stability ◽

Fire Design ◽

General Method

<span lang="EN-GB">There is currently no specific rules in Part 1-2 of Eurocode 3 for the stability verification of non-uniform members under fire conditions. For normal temperature, Part 1-1 of the same code provides a General Method to check the stability against lateral and lateral-torsional buckling for these type of members, though it requires some extensive calculations. It is here demonstrated in this paper how both problems can be addressed, by exposing a procedure that accounts for the modifications of the method at elevated temperatures, and by showing its implementation within a computer program. It is also shown how the program can be used to assess the study of the method itself, by applying it to a case of a web-tapered beam-column and comparing it to numerical results.</span>

Download Full-text

PARAMETRIC STUDY ON THE LATERAL TORSIONAL BUCKLING OF STAINLESS STEEL I BEAMS WITH CLASS 4 CROSS-SECTIONS IN CASE OF FIRE

Applications of Structural Fire Engineering ◽

10.14311/asfe.2015.020 ◽

2016 ◽

Author(s):

Nuno Lopes ◽

Pedro Gamelas ◽

Paulo Vila Real

Keyword(s):

Stainless Steel ◽

Cross Sections ◽

Elevated Temperatures ◽

Numerical Study ◽

Design Guidelines ◽

Steel Grade ◽

Steel Beams ◽

Lateral Torsional Buckling ◽

Torsional Buckling ◽

Steel Members

For predicting the behaviour of beams with thin-walled I sections, named Class 4 in Eurocode 3 (EC3), it is necessary to account for the occurrence of both local and lateral torsional buckling (LTB). These instability phenomena, which are intensified at elevated temperatures, should be accurately considered in design rules. The fire design guidelines for stainless steel members, given in Part 1-2 of EC3, propose the use of the same formulae developed for carbon steel (CS) elements. However, these two materials have different constitutive laws, leading to believe that the use of those formulae should be validated. This work presents a parametric numerical study on the behaviour of stainless steel beams with Class 4 I sections at elevated temperatures. The influences of several parameters such as stainless steel grade, loading type and cross section slenderness are evaluated, and comparisons between the obtained numerical results and EC3 rules are presented.

Download Full-text

Ultraviolet Absorption Cross-Sections of Ammonia at Elevated Temperatures for Nonintrusive Quantitative Detection in Combustion Environments

Applied Spectroscopy ◽

10.1177/0003702821990445 ◽

2021 ◽

pp. 000370282199044

Author(s):

Wubin Weng ◽

Shen Li ◽

Marcus Aldén ◽

Zhongshan Li

Keyword(s):

Cross Section ◽

Cross Sections ◽

Absorption Cross Section ◽

Elevated Temperatures ◽

Uv Absorption ◽

Energy Utilization ◽

Quantitative Detection ◽

Absorption Cross ◽

Hot Gas

Ammonia (NH3) is regarded as an important nitrogen oxides (NOx) precursor and also as an effective reductant for NOx removal in energy utilization through combustion, and it has recently become an attractive non-carbon alternative fuel. To have a better understanding of thermochemical properties of NH3, accurate in situ detection of NH3 in high temperature environments is desirable. Ultraviolet (UV) absorption spectroscopy is a feasible technique. To achieve quantitative measurements, spectrally resolved UV absorption cross-sections of NH3 in hot gas environments at different temperatures from 295 K to 590 K were experimentally measured for the first time. Based on the experimental results, vibrational constants of NH3 were determined and used for the calculation of the absorption cross-section of NH3 at high temperatures above 590 K using the PGOPHER software. The investigated UV spectra covered the range of wavelengths from 190 nm to 230 nm, where spectral structures of the [Formula: see text] transition of NH3 in the umbrella bending mode, v2, were recognized. The absorption cross-section was found to decrease at higher temperatures. For example, the absorption cross-section peak of the (6, 0) vibrational band of NH3 decreases from ∼2 × 10−17 to ∼0.5 × 10−17 cm2/molecule with the increase of temperature from 295 K to 1570 K. Using the obtained absorption cross-section, in situ nonintrusive quantification of NH3 in different hot gas environments was achieved with a detection limit varying from below 10 parts per million (ppm) to around 200 ppm as temperature increased from 295 K to 1570 K. The quantitative measurement was applied to an experimental investigation of NH3 combustion process. The concentrations of NH3 and nitric oxide (NO) in the post flame zone of NH3–methane (CH4)–air premixed flames at different equivalence ratios were measured.

Download Full-text

Numerical analysis of damage zones in a bridge

International Journal of Structural Integrity ◽

10.1108/ijsi-03-2019-0017 ◽

2019 ◽

Vol 11 (1) ◽

pp. 1-12

Author(s):

Mohammed Lamine Moussaoui ◽

Mohamed Chabaat

Keyword(s):

Numerical Analysis ◽

Material Properties ◽

Data File ◽

Time Range ◽

Bridge Structure ◽

Time Step ◽

Batch Mode ◽

Content Type ◽

Finite Element Software ◽

Von Mises

Purpose The purpose of this paper is to present a numerical analysis of structural monitoring for damage zones detection. The study is performed with Ansys finite element software, which reads in batch mode programming a previously generated mesh data file and computes the transient dynamic solution for each time-step iteration within an analysis time range. Design/methodology/approach The approach itself is applied on a bridge structure which can be potentially subjected to damage zones due to severe loads cases and or earthquakes vibrations. The ideal Von Mises failure criterion ellipsoid envelope is applied for the detection of overstepped computed stresses and strains. Findings This numerical analysis allows computing, for each time-step iteration, the dynamic displacements at each degree of freedom and the corresponding stresses and strains inside the elements under the action of several times dependent loads cases. Practical implications Several simulations are considered to quantify the external loads. Originality/value The material properties of reinforced concrete RC are calculated for an existing specific bridge structure case. The RC strength is then introduced from the basic compounds material properties using the corresponding volumes fractions.

Download Full-text