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

2016 ◽  
Vol 7 (4) ◽  
pp. 365-387 ◽  
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.

The Performance of Steel Beams in the High Temperature

2012 ◽  
Vol 246-247 ◽  
pp. 3-6
Author(s):  
Xiu Ying Yang ◽  
Qiang Qin ◽  
Yang Yang Cui
Keyword(s):  
High Temperature ◽  
Elevated Temperatures ◽  
Axial Stress ◽  
Steel Beams ◽  
Steel Beam ◽  
Finite Element Program ◽  
Steel Material ◽  
Different Temperatures ◽  
Element Program ◽  
Stress And Deformation

To study the performance of steel at elevated temperatures, the stress and deformation of steel beam were analyzed under high temperature in this paper. During the analysis, the properties of steel material must be defined firstly, which are the decisive factor affecting the carrying capacity of steel beam. The mechanical and physical properties of steel at high temperatures were accessed accordance to the provisions of the European specification in analysis. The finite element program ANSYS was used to analyze the constraints steel beam, which subjected to the uniformly line loads, then the steel beam was heated up continuously, and the mechanical properties and deformation of the steel beam was analyzed at different temperatures. The regularity of mid-span deflection changing with temperature was concluded, so as the variation of axial stress at both ends of the steel beam.

Experimental and numerical study on the fire response of cold-formed steel beams with elastically restrained thermal elongation

2016 ◽  
Vol 7 (4) ◽  
pp. 388-402 ◽  
Author(s):  
Luis Laím ◽  
João Paulo C. Rodrigues
Keyword(s):  
Cross Sections ◽  
Failure Modes ◽  
Numerical Study ◽  
Research Work ◽  
Experimental Tests ◽  
Steel Beams ◽  
Structural Behaviour ◽  
Content Type ◽  
Axial Forces ◽  
Cold Formed Steel

Purpose This paper is mainly aimed at the structural performance of compound cold-formed galvanised steel beams under fire conditions based on the results of a large programme of experimental tests and numerical simulations. The main objective of this research was to assess the critical temperature and time of the studied beams. Other important goals of this research work were to investigate the influence of the cross-sections (C, lipped-I, R and 2R beams) and, above all, of the axial restraint (0, 0.45, 3, 7.5, 15, 30, ∞ kN/mm) to the thermal elongation of the beam and the rotational restraint at beam supports (0, 15, 80, 150, 300, 1,200 and ∞ kN.m/rad) on the fire resistance of this kind of beams. Design/methodology/approach This paper still provides details of the simulation methodology for achieving numerical stability and faithful representation of detailed structural behaviour and compares the simulation and experimental results, including beam failure modes, measured beam axial forces and beam mid-span deflections. Findings Good agreement between Abaqus simulations and experimental observations confirms that the finite element models developed with the Abaqus/standard solver are suitable for predicting the structural fire behaviour of restrained cold-formed steel beams. Originality/value The results showed above all that the effect of the stiffness of the surrounding structure seems to decrease with the increasing slenderness of the beams.

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

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Flávio Arrais ◽  
Nuno Lopes ◽  
Paulo Vila Real
Keyword(s):  
Numerical Analysis ◽  
Cross Section ◽  
Cross Sections ◽  
Failure Modes ◽  
Elevated Temperatures ◽  
Numerical Results ◽  
Lateral Torsional Buckling ◽  
Torsional Buckling ◽  
Content Type ◽  
Finite Element Software

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.

Residual shear capacity of cold-formed steel-to-sheathing screwed connections at elevated temperatures

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Kun Liu ◽  
Wei Chen ◽  
Jihong Ye ◽  
Jian Jiang ◽  
Wenwen Chen ◽  
...  
Keyword(s):  
Shear Strength ◽  
Elevated Temperatures ◽  
Input Parameter ◽  
Single Layer ◽  
Shear Capacity ◽  
Base Layer ◽  
Residual Shear Strength ◽  
Content Type ◽  
Cold Formed Steel ◽  
Fire Conditions

Purpose Most previous thermal-mechanical modeling of cold-formed steel (CFS) walls did not consider the failure of screwed connections under fire conditions because of the limited data of such connections at elevated temperatures. Design/methodology/approach In this study, 285 steady-state tests are conducted on CFS screwed connections with single-layer gypsum plasterboard (GPB) and Bolivian magnesium board (BMB) sheathing at ambient and elevated temperatures. The failure of these connections is described as the breaking of the loaded sheathing edge. Findings For the BMB sheathing screwed connections, hydrochloric acid gas is generated and released above 300°C, and the shear strength becomes much less than that of the GPB sheathing screwed connection above 370°C. Hence, BMB may not be suitable for use as the face-layer sheathing of CFS walls but is still recommended to replace GPB as the base-layer sheathing. The major influencing parameters on the shear strength of screwed connections are identified as the type of sheathing material and the loaded sheathing edge distance. Originality/value Based on the previous and present test results, a unified expression for the residual shear strength of screwed connections with GPB and BMB is proposed at ambient and elevated temperatures with acceptable accuracy. It can be used as the basic input parameter of the numerical simulation of the CFS structures under fire conditions.

Stability check of tapered steel beams in fire

2019 ◽  
Vol 10 (4) ◽  
pp. 373-398 ◽  
Author(s):  
Carlos Couto ◽  
Élio Maia ◽  
Paulo Vila Real ◽  
Nuno Lopes
Keyword(s):  
Design Methodology ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Numerical Models ◽  
Design Methods ◽  
Steel Beams ◽  
Content Type ◽  
Design Methodologies ◽  
Accurate Design ◽  
Improved Design

Purpose The purpose of this paper is to assess whether the adaptation to fire of current proposals/design methodologies at normal temperature is capable of producing accurate predictions of resistance for the out-of-plane stability of tapered beams. Design/methodology/approach The adaptation of these methodologies to fire has been done by accounting for the reduction in steel material properties with the temperature. Results were then compared to FEM calculations by performing GMNIA analyses to determine the ultimate strength of the numerical models and to ascertain the validity and accuracy of the adapted methodologies. Findings Although all methodologies produce safe results at normal temperatures, only the general method is recommended for the safety verification at elevated temperatures, although the data points were overly conservative. This investigation demonstrates the need of proper and accurate design methods for tapered beams at elevated temperatures, which should be the subject of future developments. Research limitations/implications The research in this paper is limited to the adaptation of existing room temperature design methods to fire. Therefore, possible assumptions made during the conception of the initial formulae, which may be valid exclusively for 20ºC, may have been disregarded. Originality/value For the time being, design methodologies for the safety check of tapered beams for the case of fire are inexistent. This paper investigates the adaptation of existing room temperature design to the fire situation by providing insights on their accuracy level, as well as on how to proceed. Finally, a safe design methodology for tapered beams in case of fire is provided until improved design methods are developed.

Behavior of Concrete as a Barrier Material for Nuclear Waste Disposal

1989 ◽  
Vol 176 ◽  
Author(s):  
R. J. James ◽  
Y. R. Rashid
Keyword(s):  
Constitutive Model ◽  
Material Property ◽  
Nuclear Waste ◽  
Waste Disposal ◽  
Elevated Temperatures ◽  
Nuclear Waste Disposal ◽  
Functional Requirements ◽  
Barrier Material ◽  
Finite Element Program ◽  
Element Program

SummaryThe foundation necessary for a constitutive model to simulate the response of concrete at elevated temperature has been presented. A model including temperature dependent creep, material property degradation, and cracking is needed to evaluate the long term functional requirements of concrete as a barrier material for nuclear waste disposal. Since the stress due to thermal load is proportional to the modulus, the degradation of the modulus with time even at constant elevated temperatures requires continual redistribution of load. Furthermore, since this degradation is not recoverable, the response of the material at elevated temperatures exhibits a complex dependence not only on the temperature distribution, but on the prior thermal history of the structure.This constitutive model for the response of concrete at elevated temperatures has been implemented into an implicit, finite element program called ANACAP [8]. Because of the direct coupling with temperature, both through thermal loads and material property dependency, ANACAP also contains a heat transfer module that includes thermal effects due to fluid flow and moving material boundaries. This program has been applied to problems involving underground waste storage tanks and grout vaults at the DOE Hanford site in Richland, Washington.

scholarly journals Displacement and Stress Function-based Linear and Quadratic Triangular Elements for Saint-Venant Torsional Problems

2018 ◽  
Vol 20 (2) ◽  
pp. 70 ◽  
Author(s):  
Joko Purnomo ◽  
Wong Foek Tjong ◽  
Wijaya W.C. ◽  
Putra J.S.
Keyword(s):  
Cross Sections ◽  
Stress Function ◽  
Torsional Rigidity ◽  
Structural Members ◽  
Finite Element Program ◽  
Element Program ◽  
Standard Linear ◽  
Triangular Elements ◽  
Displacement Based ◽  
High Degree

Torsional problems commonly arise in frame structural members subjected to unsym­metrical loading. Saint-Venant proposed a semi inverse method to develop the exact theory of torsional bars of general cross sections. However, the solution to the problem using an analytical method for a complicated cross section is cumbersome. This paper presents the adoption of the Saint-Venant theory to develop a simple finite element program based on the displacement and stress function approaches using the standard linear and quadratic triangular elements. The displacement based approach is capable of evaluating torsional rigidity and shear stress distribution of homogeneous and nonhomogeneous; isotropic, orthotropic, and anisotropic materials; in singly and multiply-connected sections.  On the other hand, applications of the stress function approach are limited to the case of singly-connected isotropic sections only, due to the complexity on the boundary conditions. The results show that both approaches converge to exact solutions with high degree of accuracy.

Strength reduction factors for S355 to S500 steel grades under steady-state and transient-state heating

2019 ◽  
Vol 11 (2) ◽  
pp. 137-149
Author(s):  
Francois Hanus ◽  
Nicolas Caillet ◽  
Sylvain Gaillard ◽  
Olivier Vassart
Keyword(s):  
Steady State ◽  
Large Scale ◽  
Elevated Temperatures ◽  
Transient State ◽  
Heating Rates ◽  
Content Type ◽  
State Tests ◽  
Steel Grades ◽  
Scope Of Application ◽  
Reduction Factors

Purpose This paper aims to describe coupon tests performed at elevated temperatures on S355 to S500 steel grades and comparison of test results with previous research studies and current EN 1993-1-2 material laws. The objective is to state if these steel grades satisfy to the current material laws and if the scope of application of these laws could be extended to S500 grades. Design/methodology/approach Two experimental programmes were launched to investigate the behaviour of S460M and S500M steel grades developed for hot-rolled sections. The first research programme was focussed on a comparison between S355 and S460 grades, where the second experimental programme was focussed on the recently developed S500M steel grade. The latter one comprised steady-state tests, transient-state tests and two large-scale beam tests. Findings Results of steady-state and transient-state tests correlate well with the reduction factors defined in EN 1993-1-2, currently limited to S460 grade. On the basis of this study, the scope of EN 1993-1-2 applies to S500 grades. For steady-state tests, the testing procedure (with and without acceleration after Rp0,2) led to noticeable differences. Transient-state tests, which are not standardised up to now, have been performed considering 5 K/min and 10 K/min constant heating rates. The slowest rate leads to lower strengths as creep effects are more significant. However, all the results are in line with EN 1993-1-2 material law. Importance should be given to the reference yield strength of steel at ambient temperature. Originality/value The revision of EN 1993-1-2 is on-going and this piece of work provides a contribution for extending the scope of application of material law of steel under fire conditions.

Behavior of an embankment on New York varved clay

1978 ◽  
Vol 15 (2) ◽  
pp. 250-268 ◽  
Author(s):  
Francis D. Leathers ◽  
Charles C. Ladd
Keyword(s):  
New York ◽  
Cross Sections ◽  
New York State ◽  
Three Dimensional ◽  
Field Measurements ◽  
Finite Element Program ◽  
Pore Pressures ◽  
Element Program ◽  
Prediction Techniques ◽  
Varved Clay

The foundation soils for an embankment in New York State constructed on preconsolidated varved clay were instrumented to determine pore pressures and settlements during and after construction. Four embankment cross sections, three of which had sand drains, are analyzed in this paper. Predictions of the in situ undrained pore pressures, initial settlements and final consolidation settlements are presented and compared with the results of field measurements. Undrained pore pressures and initial settlements are predicted using the finite element program FEECON for plane strain embankment conditions and elastic theory for three-dimensional embankment conditions. Final consolidation settlements are predicted using a modification of the Skempton–Bjerrum approach. At cross sections with sand drains, predicted undrained pore pressures are adjusted to account for the effect of the sand drains. In addition, vertical and horizontal coefficients of consolidation are determined from the field measurements and compared with laboratory values of vertical coefficients of consolidation. The results of the investigation indicate that the proposed prediction techniques yield reasonable predictions of undrained pore pressure and initial settlement. Additional case studies are required in order to evaluate the predictive methods for the rate and amount of consolidation settlement.

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