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1 – 10 of 212
Article
Publication date: 24 September 2010

Wee Toh and Nick Bernabè

This paper presents a comparison, based on real practical case studies, between the simple analytical BRE-Bailey method (BRE-BM) and the advanced finite element model (FEM) Vulcan…

Abstract

This paper presents a comparison, based on real practical case studies, between the simple analytical BRE-Bailey method (BRE-BM) and the advanced finite element model (FEM) Vulcan for the membrane action of composite slab panels with unprotected secondary beams at elevated temperatures. Both approaches predicted the membrane behaviour of the composite slabs, comprising compressive membrane action around the slabs' perimeter and tensile membrane action in the central span region of the slabs. This paper mainly studies the effects of the orientation of unprotected secondary beams and the boundary conditions on tensile membrane action of composite slab panels. The results show that the application of the BRE-BM is generally restricted by the conservative assumption of the maximum allowable vertical displacement. In contrast, the FEM estimates higher load-carrying capacities as well as providing a full displacement-time relationship throughout the heating of the slabs. For slab panels with unprotected secondary beams with an orientation in the short span, tensile membrane action can be easily mobilised without increasing fire protection to the boundary supporting beams. However, the FEM predictions on the slab capacities and deflections in fire are very sensitive to the continuity of the reinforcement over the protected boundary beams.

Details

Journal of Structural Fire Engineering, vol. 1 no. 3
Type: Research Article
ISSN: 2040-2317

Article
Publication date: 12 December 2016

Serdar Selamet and Caner Bolukbas

This paper aims to present a numerical investigation on the fire performance of a single plate shear connection in a steel-framed composite floor. Large-scale fire experiments…

Abstract

Purpose

This paper aims to present a numerical investigation on the fire performance of a single plate shear connection in a steel-framed composite floor. Large-scale fire experiments show that the tensile membrane action of the concrete slab enhances the fire performance of composite floors. The enhancement in the performance is contributed to large slab deflections. However, these deflections cause significant rotations and tensile force in the single plate connection.

Design/methodology/approach

A finite element model is constructed, which consists of a secondary steel beam, concrete slab and shear connection components. The interaction between the connection components such as bolts and single plate is defined by contact surfaces. The analysis is conducted in two uncoupled phases: thermal analysis by creating fire boundaries on the composite floor model with convective and radiative heat transfer, and mechanical analysis by considering thermal expansion and changes in the material stiffness and strength due to temperature.

Findings

The thermo-mechanical analysis of the composite floor finite element model shows that the structure survives the 2-h Standard fire, but the connection fails by bolt shear and buckling of the connection plate.

Originality/value

This paper investigates the fire performance of a shear connection in a steel-framed concrete slab. Previous work generally focused on the concrete slab behavior only. The originality of the research is that the connection is considered as part of a sub-assembly and is subjected to forces due to concrete and steel beam interaction.

Details

Journal of Structural Fire Engineering, vol. 7 no. 4
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 27 December 2011

Olivier Vassart, C. Bailey, M. Hawes, A. Nadjai, W. Simms, B. Zhao, T. Gernay and J.-M. Franssen

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the…

Abstract

This paper describes a full scale fire test performed the 27th of February 2010 on a composite floor for analysing the possibility of tensile membrane action to develop when the unprotected steel beams in the central part of the floor are made of cellular beams. The natural fire was created by a wood crib fire load of 700 MJ/m2 and the 9 × 15 m floor survived the fire that peaked at 1000°C and lasted for 90 minutes. Blind predictions of the air temperature development by the software OZone and of the structural behaviour by the software SAFIR which proved quite satisfactory are also described.

Details

Journal of Structural Fire Engineering, vol. 2 no. 4
Type: Research Article
ISSN: 2040-2317

Article
Publication date: 21 March 2022

Jason Martinez and Ann Jeffers

A methodology for producing an elevated-temperature tension stiffening model is presented.

Abstract

Purpose

A methodology for producing an elevated-temperature tension stiffening model is presented.

Design/methodology/approach

The energy-based stress–strain model of plain concrete developed by Bažant and Oh (1983) was extended to the elevated-temperature domain by developing an analytical formulation for the temperature-dependence of the fracture energy Gf. Then, an elevated-temperature tension stiffening model was developed based on the modification of the proposed elevated-temperature tension softening model.

Findings

The proposed tension stiffening model can be used to predict the response of composite floor slabs exposed to fire with great accuracy, provided that the global parameters TS and Kres are adequately calibrated against global structural response data.

Originality/value

In a finite element analysis of reinforced concrete, a tension stiffening model is required as input for concrete to account for actions such as bond slip and tension stiffening. However, an elevated-temperature tension stiffening model does not exist in the research literature. An approach for developing an elevated-temperature tension stiffening model is presented.

Article
Publication date: 27 July 2017

Simon Mwangi

This paper aims to present the findings of a numerical investigation into the performance of the steel-concrete composite floor involved in Broadgate Phase 8 fire.

Abstract

Purpose

This paper aims to present the findings of a numerical investigation into the performance of the steel-concrete composite floor involved in Broadgate Phase 8 fire.

Design/methodology/approach

The investigation is conducted by carrying out a 3-D thermomechanical analysis of a composite floor similar to the one involved in the fire using ANSYS. Four fire scenarios are investigated, with each producing a unique stress – strain pattern. The results obtained are compared with the observations made after the fire and inferences drawn.

Findings

The results obtained are found to be correlated with the observations made after the fire. The performance of the composite floor is found to be dominated by development of large strains, leading to large deflections. Furthermore, colder parts of the structure, through redistribution of forces, are found to have a profound impact on the ability of a composite floor to resist heating effects. From the findings, it is concluded that connections’ design, occurrence of membrane action and thermal restraints were the key reasons the floor did not fail.

Originality value

The study takes a more forensic approach. This is a departure from majority of published literature, where comparison is usually between experimental and numerical results. By comparing the findings from a real fire with those of a numerical investigation, the study provides an insight into the accuracy of applying numerical models for the prediction of effects of fire on structural behaviour.

Details

Journal of Structural Fire Engineering, vol. 8 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 8 December 2010

Florian Block, Chaoming Yu and Neal Butterworth

The British Building Regulations allow the application of performance based design methods to ensure the fire resistance of buildings. This has led to significant amounts of…

Abstract

The British Building Regulations allow the application of performance based design methods to ensure the fire resistance of buildings. This has led to significant amounts of research and testing on the fire performance of structures. This research generated the understanding that steel framed buildings have an inherent fire resistance, which has in turn resulted in the development of specialist numerical calculation tools as well as simplified design methods for the fire design of steel-framed structures. The paper describes the practical application of these structural fire engineering methods using a large retail and cinema complex in the UK as a case study. The finite element software Vulcan has been used to analyse the behaviour of large parts of this multi-storey building during a number of likely design fire scenarios in order to optimise the amount of applied passive fire protection to the structure. The building is constructed as a steel composite structure with normal down-stand composite beams supporting a composite floor on trapezoidal metal deck. This type of structure is ideal to utilise the benefits of tensile membrane action during a fire which can be used to omit fire protection from off grid secondary beams. Due to the size and the multiple usage and changing floor construction of the buildings five different sub-frames haven been analysed. In the UK a number of simplified methods are currently applied to justify partially protected steel structures. These methods are based on individual bays only and therefore do not consider the effects of the surrounding structure. In order to investigate the differences further, the behaviour of the large sub-frame models has been compared with the results of individual bay analysis methods.

Details

Journal of Structural Fire Engineering, vol. 1 no. 4
Type: Research Article
ISSN: 2040-2317

Article
Publication date: 22 April 2022

Mhd Anwar Orabi, Jin Qiu, Liming Jiang and Asif Usmani

Reinforced concrete slabs in fire have been heavily studied over the last three decades. However, most experimental and numerical work focuses on long-duration uniform exposure to…

Abstract

Purpose

Reinforced concrete slabs in fire have been heavily studied over the last three decades. However, most experimental and numerical work focuses on long-duration uniform exposure to standard fire. Considerably less effort has been put into investigating the response to localised fires that result in planarly non-uniform temperature distribution in the exposed elements.

Design/methodology/approach

In this paper, the OpenSees for Fire framework for modelling slabs under non-uniform fire exposure is presented, verified against numerical predictions by Abaqus and then validated against experimental tests. The thermal wrapper developed within OpenSees for Fire is then utilised to apply localised fire exposure to the validated slab models using the parameters of an experimentally observed localised fire. The effect of the smoke layer is also considered in this model and shown to significantly contribute to the thermal and thus thermo-mechanical response of slabs. Finally, the effect of localised fire heat release rate (HRR) and boundary conditions are studied.

Findings

The analysis showed that boundary conditions are very important for the response of slabs subject to localised fire, and expansive strains may be accommodated as deflections without severely damaging the slab by considering the lateral restraint.

Originality/value

This work demonstrates the capabilities of OpenSees for Fire in modelling structural behaviours subjected to non-uniform fire conditions and investigates the damage pattens of flat slabs exposed to localised fires. It is an advancing step towards understanding structural responses to realistic fires.

Details

Journal of Structural Fire Engineering, vol. 14 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 19 September 2017

Li Zhang, Ya Wei, Francis Tat Kwong Au and Jing Li

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…

Abstract

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.

Details

Journal of Structural Fire Engineering, vol. 9 no. 3
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 14 March 2016

David J. Proe

This paper aims to facilitate verification of computer modelling techniques for complex structures exposed to fire and to test the effect of some steel beams being left…

141

Abstract

Purpose

This paper aims to facilitate verification of computer modelling techniques for complex structures exposed to fire and to test the effect of some steel beams being left unprotected.

Design/methodology/approach

This paper describes a fire test conducted on a large-scale structure representing four corner bays of a typical multi-storey steel-frame office building.

Findings

A new and unexpected mode of damage occurred.

Originality/value

The test results indicate that an alternate reinforcement detail should be used in combination with unprotected beams.

Details

Journal of Structural Fire Engineering, vol. 7 no. 1
Type: Research Article
ISSN: 2040-2317

Keywords

Article
Publication date: 7 October 2021

Lisa Choe, Selvarajah Ramesh, Xu Dai, Matthew Hoehler and Matthew Bundy

The purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building…

Abstract

Purpose

The purpose of this paper is to report the first of four planned fire experiments on the 9.1 × 6.1 m steel composite floor assembly as part of the two-story steel framed building constructed at the National Fire Research Laboratory.

Design/methodology/approach

The fire experiment was aimed to quantify the fire resistance and behavior of full-scale steel–concrete composite floor systems commonly built in the USA. The test floor assembly, designed and constructed for the 2-h fire resistance rating, was tested to failure under a natural gas fueled compartment fire and simultaneously applied mechanical loads.

Findings

Although the protected steel beams and girders achieved matching or superior performance compared to the prescribed limits of temperatures and displacements used in standard fire testing, the composite slab developed a central breach approximately at a half of the specified rating period. A minimum area of the shrinkage reinforcement (60 mm2/m) currently permitted in the US construction practice may be insufficient to maintain structural integrity of a full-scale composite floor system under the 2-h standard fire exposure.

Originality/value

This work was the first-of-kind fire experiment conducted in the USA to study the full system-level structural performance of a composite floor system subjected to compartment fire using natural gas as fuel to mimic a standard fire environment.

Details

Journal of Structural Fire Engineering, vol. 13 no. 2
Type: Research Article
ISSN: 2040-2317

Keywords

1 – 10 of 212