scholarly journals A detailed investigation on thermal behaviour of slim floor beams with web openings at elevated temperatures

2019 ◽  
Vol 10 (4) ◽  
pp. 446-467
Author(s):  
Naveed Alam ◽  
Ali Nadjai ◽  
Olivier Vassart ◽  
Francois Hanus
Keyword(s):  
Finite Element ◽  
Thermal Behaviour ◽  
Elevated Temperatures ◽  
Major Influence ◽  
Web Openings ◽  
Content Type ◽  
Composite Action ◽  
Temperature Development ◽  
In Fire ◽  
Steel Section

Purpose In recent times, the use of steel sections with web openings has become common as slim floor beams because they offer a reduction in weight of the steelwork, accommodate services within the floor depth and provide the composite action. The composite action in these beams is achieved either through the concrete dowels or through concrete plugs. Though these web openings offer several benefits in slim floor beams, they induce the material discontinuity in the steel web, which may affect their shear capacity and/or thermal behaviour. The purpose of this study is to investigate the thermal behaviour of slim floor beams with web openings in fire. Design/methodology/approach This research presents findings from experimental and analytical investigations conducted to study the thermal behaviour of slim floor beams with web openings in fire. For this purpose, an experimental investigation was conducted, which shows that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. The behaviour of the tested slim floor beam is validated using finite element modelling. The validated finite element model is then used to conduct a sensitivity study to analyse the influence of different opening spacings, sizes and shapes on the thermal performance of slim floor beams in fire. Findings Test results show that the presence of web openings has a major influence on temperature development across the steel section as well as along the span of these beams. Temperatures on the web below the openings are found to be higher as compared to those recorded on the adjacent solid steel web. It is also observed that temperatures on the steel web above the openings are lesser than those on the adjacent solid steel web. Parametric studies conducted using the verified analytical modelling methods show that different opening spacings, sizes and shapes have a variable impact on the thermal behaviour of slim floor beams in fire. Closely spaced and larger opening sizes were found to have a more severe influence on their thermal behaviour in fire as compared to widely spaced and smaller openings. It was also found that the behaviour of these beams is influenced by the shape of the openings with rectangular openings resulting in more severe thermal distributions as compared to circular openings. Originality/value The findings from this research study are highly valuable as they contribute to the existing knowledge database. There is a lack of experimental and analytical investigation on performance of slim floor beams with web openings at elevated temperatures. The results and conclusions from this study will help in developing innovative designs for slim floor beams and will help in reducing the fire related risk associated with structures comprising of slim floor beams with web openings.

scholarly journals Effect of air-gap on response of fabricated slim floor beams in fire

2019 ◽  
Vol 10 (2) ◽  
pp. 155-174 ◽  
Author(s):  
Naveed Alam ◽  
Ali Nadjai ◽  
Chrysanthos Maraveas ◽  
Konstantinos Tsarvdaridis ◽  
Charles Kahanji
Keyword(s):  
Thermal Behaviour ◽  
Design Methodology ◽  
Elevated Temperatures ◽  
Structural Response ◽  
Structural Members ◽  
Considerable Influence ◽  
Content Type ◽  
Modelling Method ◽  
Perform Sensitivity Analysis ◽  
In Fire

PurposeThe purpose of this study is to investigate the effect of the airgap on thermal behaviour and structural response of fabricated slim floor beams (FSFBs) in fire.Design/methodology/approachA detailed analytical model is established and validated by replicating the response of FSFBs. The validated finite element modelling method is then used to perform sensitivity analysis. First, the influence of the airgap presence is analysed, and later, the effect of the airgap size on thermal behaviour and structural response of FSFBs at elevated temperatures is investigated.FindingsResults from the study demonstrate that the presence of the airgap has a considerable influence on their thermal behaviour and structural response of FSFBs. The size of the airgap, however, has no significant influence on their thermal and structural response in fire.Originality/valueNo investigations, experimental or analytical, are available in literature addressing the effect of airgap on the structural response of FSFBs in fire. The presence of airgap is helpful and beneficial; hence, the findings of this research can be used to develop designs for structural members with airgap as an efficient and inexpensive way to improve their response in fire.

Thermal behaviour of a novel non-composite cellular beam floor system in fire

2019 ◽  
Vol 10 (3) ◽  
pp. 354-372 ◽  
Author(s):  
Hendrig Marx ◽  
Richard Walls
Keyword(s):  
Finite Element ◽  
Thermal Behaviour ◽  
Structural Damage ◽  
Steel Structures ◽  
Finite Element Models ◽  
Content Type ◽  
Rapid Construction ◽  
In Fire ◽  
Floor System ◽  
Practical Implications

Purpose The Southern African Institute of Steel Construction has developed a novel cellular beam structure (CBS) for multi-storey buildings that is entirely devoid of concrete. Channel sections between the cellular beams support a complex sandwich flooring system, which contains a fire-resistant ceiling board, metal sheeting, an interior fibre-cement board and an access-flooring system. As for all structures, the CBS requires a fire rating. This paper aims to investigate the thermal behaviour of the CBS using numerical modelling and experimental fire testing, as it has a unique setup. Design/methodology/approach Experimental fire tests on the flooring system were conducted to validate finite element models, which were developed in ABAQUS. These models were then extended to include floor beams and the structural steelwork. Findings Good correlations were found between the experimental and numerical results, with temperature variations typically in the range of 0-5%, although with localised differences of up to 20%. This allowed larger finite element models, representing the sandwich floor system of the CBS, to be developed and analysed. A 1-hour rating can be obtained by the system in terms of insulation and integrity requirements. Practical implications The CBS allows for more economical steel structures, due to the rapid construction of its modular panels. A suitable fire resistance will ensure the safety of the occupants and prevent major structural damage. Steelwork and flooring temperatures are determined which has allowed for global structural analyses to be carried out. Originality/value The originality of this study lies in thermal analysis and testing of a new cellular beam flooring system, through determining behaviour in fire, along with beam temperatures.

The Effects of Geometric Nonlinearity on Elasto-Plastic Analysis of Plane Steel Frames in Fire

2012 ◽  
Vol 446-449 ◽  
pp. 3513-3516
Author(s):  
Bing Xia ◽  
Yu Ching Wu
Keyword(s):  
Finite Element ◽  
Geometric Nonlinearity ◽  
Elevated Temperatures ◽  
Steel Frames ◽  
External Loading ◽  
Element Analysis ◽  
Stiffness Matrices ◽  
Plastic Analysis ◽  
In Fire ◽  
Incremental Step

In this paper, the co-rotational total Lagrangian forms of finite element formulations are derived to make elasto-plastic analysis for plane steel frames either under increasing external loading at ambient temperature or under constant external loading at elevated temperatures. Geometric nonlinearity and thermal-expansion effect are taken into account. A series of programs are developed based on the formulations. To verify the accuracy and efficiency of the nonlinear finite element programs, a couple of numerical benchmark tests are carried out. And the results are in a good agreement with solutions from literature. The effects of nonlinear terms of the stiffness matrices on the computational results are investigated in detail. It is demonstrated that the influence of geometric nonlinearity on the incremental step by step finite element analysis for plane steel frames in fire is limited.

Experimental study of two-way post-tensioned flat slabs in fire

2018 ◽  
Vol 9 (3) ◽  
pp. 237-251 ◽  
Author(s):  
Li Zhang ◽  
Ya Wei ◽  
Francis Tat Kwong Au ◽  
Jing Li
Keyword(s):  
Design Methodology ◽  
Structural Integrity ◽  
Elevated Temperatures ◽  
Testing Temperature ◽  
Structural Behaviour ◽  
Content Type ◽  
Flat Slabs ◽  
Temperature Distributions ◽  
In Fire ◽  
Post Tensioned

Purpose This study aims to investigate the influence of tendon layout, pre-stressing force, bond condition and concrete spalling on the structural behaviour of two-way post-tensioned flat slabs at elevated temperatures. Design/methodology/approach Fire tests of four scale specimens of two-way post-tensioned concrete flat slabs were performed and analysed. Three of them were provided with bonded tendons, while the other was unbonded for comparison. The fabrication of specimens, phenomena observed during testing, temperature distributions, deflections and occurrence of concrete spalling were examined. Findings Different degrees of concrete spalling observed at the soffit had significant effects on the temperature distribution and stress redistribution. This was the major reason for the progressive concrete spalling observed, resulting in loss of structural integrity and stiffness. Originality/value The structural behaviour of two-way post-tensioned concrete flat slabs at elevated temperatures is less understood compared to their one-way counterparts. Therefore, the present study has focused on the structural behaviour of two-way post-tensioned concrete flat slabs with bonded tendons in fire, a field in which relatively little information on experimental work can be found.

scholarly journals Shear connection requirements for composite cellular beams

2018 ◽  
Author(s):  
Eleftherios Aggelopoulos ◽  
Francois Hanus ◽  
Mark Lawson
Keyword(s):  
Finite Element ◽  
Minimum Degree ◽  
Composite Beams ◽  
Beam Test ◽  
Current Version ◽  
Web Openings ◽  
Shear Connection ◽  
Low Degree ◽  
Steel Sections ◽  
Steel Section

Beams with regular circular web openings (cellular beams) are often used in composite construction. Rules for the minimum degree of shear connection in composite beams are presented in Eurocode 4 but were derived for solid web beams in propped construction. This paper investigates the degree of shear connection requirements for composite cellular beams, focusing on the combined effect of using a steel section with regularly spaced, large circular web openings and unpropped construction conditions. The effect of the diameter and the spacing of the openings is also investigated. In order to provide rules for the minimum degree of shear connection in cellular beams, parametric finite element (FE) analyses were carried out for beams in the span range of 9 to 18 m. The results were calibrated against a 15.3 m span composite cellular beam test with a low degree of shear connection. The proposed minimum degree of shear connection requirements for beams with regular circular web openings are presented for both propped and unpropped construction, and for symmetric and asymmetric steel sections. Comparisons are made with equivalent beams with solid webs (no openings) and it is shown that significant relaxation in the codified minimum degree of shear connection to the current version of Eurocode 4 can be justified for composite cellular beams.  

Reliability based design method for buckling of steel columns in fire

2019 ◽  
Vol 11 (2) ◽  
pp. 167-187
Author(s):  
Andrei Kervalishvili ◽  
Ivar Talvik
Keyword(s):  
Reliability Analysis ◽  
Response Function ◽  
Elevated Temperatures ◽  
Design Method ◽  
Content Type ◽  
Practical Applications ◽  
Steel Columns ◽  
Steel Column ◽  
Parameter Ranges ◽  
In Fire

Purpose This paper aims to reliability analysis of axially loaded steel columns at elevated temperatures considering the probabilistic features of fire. Design/methodology/approach The response function used in the reliability analysis is based on the non-linear FEM calculations. The stochastic variability of temperature is integrated with the procedure similar to the parameters of loading and material properties. Direct Monte Carlo simulations (MCSs) are implemented for probabilistic analysis. Computational costs are reduced by polynomial approximation of the response function of the column. Findings A design method for practical applications in the common Eurocode format is proposed. The proposed method can be used to estimate the failure probability of a steel column in fire conditions. If standard reliability criteria are applied, the results of the steel column buckling capacity in the fire according to the proposed procedure deviate from the Eurocode results in certain parameter ranges. Originality/value The proposed method for design calculations makes use of the advantages of MCS results, while the need for the tedious amount of calculations for the end user are avoided as the predefined factors are implemented in the procedure of Eurocode format. The proposed method allows better differentiation of the fire probability in the capacity assessment compared to the existing design methods.

Tests of composite beams with web holes

1983 ◽  
Vol 10 (4) ◽  
pp. 713-721 ◽  
Author(s):  
R. G. Redwood ◽  
G. Poumbouras
Keyword(s):  
Composite Beam ◽  
Concrete Slab ◽  
Composite Beams ◽  
Web Openings ◽  
Composite Action ◽  
Shear Connection ◽  
Moment Ratio ◽  
Construction Loads ◽  
Steel Deck ◽  
Steel Section

Tests of composite beams comprising a concrete slab supported on a steel deck and a steel wide-flange shape containing large web openings are described. Special attention is directed to the amount of shear connection between slab and steel section in the region of a web hole, and on the effect of construction loads acting on the steel section prior to composite action being effective.It is shown that limited shear connection at the hole will significantly affect the strength when loading produces a high shear-to-moment ratio, and a theory is presented which conservatively takes this into account. The effect of construction loads on unshored construction is shown to be small when these do not exceed 60% of the non-composite beam resistance at the hole.

Investigation on the Behaviour of a Composite Floor Made of Cellular Beams in Fire Situation

2014 ◽  
Vol 5 (2) ◽  
pp. 175-188
Author(s):  
Gisèle Bihina ◽  
Bin Zhao ◽  
Abdelhamid Bouchaïr
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Parametric Study ◽  
Elevated Temperatures ◽  
Mechanical Load ◽  
Element Model ◽  
Resistance Rate ◽  
Natural Fire ◽  
In Fire ◽  
The Finite Element Model

The main results from a numerical investigation on a composite floor made of cellular beams at elevated temperatures are presented. From a full-scale natural fire test, a 3D finite element model has been developed under ANSYS code to simulate the thermo-mechanical behaviour of a composite floor with cellular beams. The calibration of this numerical model is based on the measured material properties and temperatures. A good correlation between the test and the numerical simulation is observed, in terms of temperatures, deformed shape and deflections. The finite element model is then used in a parametric study varying bay size, mechanical load and fire resistance rate. The results from this parametric study are compared to those from an analytical method, highlighting the conservativeness of the latter.

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