Probabilistic Study of the Resistance of a Simply-Supported Reinforced Concrete Slab According to Eurocode Parametric Fire

Heidari, Mohammad; Robert, Femi; Lange, David; Rein, Guillermo

doi:10.1007/s10694-018-0704-4

Cited by 23 publications

(20 citation statements)

References 13 publications

(15 reference statements)

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“…The thermal conductivity of steel is higher than concrete; therefore, the steel rebar temperature is assumed to be the same as adjacent concrete. It has been shown that 1D heat transfer with constant effective properties results in conservative in‐depth concrete temperature . The lumped mass heat transfer method is used for thermal analysis of the protected beam (Eq.…”

Section: Comparison For a Generic Structurementioning

confidence: 99%

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Flame extension and the near field under the ceiling for travelling fires inside large compartments

2019

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Summary Structures need to be designed to maintain their stability in the event of a fire. The travelling fire methodology (TFM) defines the thermal boundary condition for structural design of large compartments of fires that do not flashover, considering near field and far field regions. TFM assumes a near field temperature of 1200°C, where the flame is impinging on the ceiling without any extension and gives the temperature of the hot gases in the far field from Alpert correlations. This paper revisits the near field assumptions of the TFM and, for the first time, includes horizontal flame extension under the ceiling, which affects the heating exposure of the structural members thus their load‐bearing capacity. It also formulates the thermal boundary condition in terms of heat flux rather than in terms of temperature as it is used in TFM, which allows for a more formal treatment of heat transfer. The Hasemi, Wakamatsu, and Lattimer models of heat flux from flame are investigated for the near field. The methodology is applied to an open‐plan generic office compartment with a floor area of 960 m2 and 3.60 m high with concrete and with protected and unprotected steel structural members. The near field length with flame extension (fTFM) is found to be between 1.5 and 6.5 times longer than without flame extension. The duration of the exposure to peak heat flux depends on the flame length, which is 53 min for fTFM compared with 17 min for TFM, in the case of a slow 5% floor area fire. The peak heat flux is from 112 to 236 kW/m2 for the majority of fire sizes using the Wakamatsu model and from 80 to 120 kW/m2 for the Hasemi and Lattimer models, compared with 215 to 228 kW/m2 for TFM. The results show that for all cases, TFM results in higher structural temperatures compared with different fTFM models (600°C for concrete rebar and 800°C for protected steel beam), except for the Wakamatsu model that for small fires, leads to approximately 20% higher temperatures than TFM. These findings mitigate the uncertainty around the TFM near field model and confirm that it is conservative for calculation of the thermal load on structures. This study contributes to the creation of design tools for better structural fire engineering.

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Section: Comparison For a Generic Structurementioning

confidence: 99%

“…It has been shown that 1D heat transfer with constant effective properties results in conservative in-depth concrete temperature. 25 The lumped mass heat transfer method 21,22 is used for thermal analysis of the protected beam (Eq. 33) and unprotected steel beam (Eq.…”

Section: Comparison For a Generic Structurementioning

confidence: 99%

Flame extension and the near field under the ceiling for travelling fires inside large compartments

2019

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“…Several fire developments (fully-developed fire) were examined in order to select a critical fire design scenario corresponding to a characteristic fuel load of 1140 MJ/m² and 15% glazing breakage (Heidari et al, 2015). Using OZone model the temperature-time curve of this critical fire design scenario has been obtained and is presented in Fig.…”

Section: Thermal Response Of the Structurementioning

confidence: 99%

Analysis of a Concrete Building Exposed to Natural Fire

Sauca¹,

Gernay²,

Robert³

et al. 2016

ASFE

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In this paper is presented the analysis of a concrete building exposed to OZone fire. The temperature development in the elements and the structural behaviour were calculated in SAFIR using beam elements for the columns and beams and shell elements for the floor slabs. The first floor was modelled and the effects of action from the upper storeys are applied as external loads. It is shown how the numerical analysis allows understanding the behaviour of the structure when exposed to a natural fire until complete cooling by analysing the evolution of displacements, the distributions of bending moments in the beams, the membrane forces in the slab, and the stresses in the elements. All this detailed information would not be available from an experimental test.

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“…For example, Shrivastava et al [3] applied performance based earthquake engineering (PBEE) framework for probabilistic studies in structural fire engineering (SFE), where annual rates of exceedance of hazard intensity and structural response were estimated. At the same time, Heidari et al [4] estimated the failure probability of a fire exposed concrete slab to assess its reliability adopting a Monte-Carlo (MC) method, and Gernay et al [5] developed fragility curves to assess the performance of steel building under fire hazard. Out of the available probabilistic approaches, the development of fragility curves has been found to be popular among researchers as it is conceptually easy to understand and allows faster design iterations [5].…”

Section: Introductionmentioning

confidence: 99%

Generalized fragility curves for concrete columns exposed to fire through surrogate modelling

Chaudhary¹,

Jovanović²,

Gernay³

et al. 2020

Proceedings of the 11th International Conference on Structures in Fire (SiF2020)

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Common structural fire design relies on recommendations from design codes, or (a single or small set of) more advanced numerical analyses. When applying such procedures to the design of structures under normal loading conditions, adequate safety is ensured through calibrated safety factors and ample experience with structural failures. This is however not the case when considering accidental fire loading, where the stochasticity in the structural fire behaviour is rarely fully acknowledged. Therefore, a significant interest in the use of probabilistic approaches to evaluate structural fire performance, which take into account the uncertainty associated with model parameters, can be observed among researchers, with a special focus on the development of fragility curves. The calculation of fragility curves is, however, a laborious task, demanding huge computational expense, mainly attributed to the adoption of advanced calculation procedures and the need for a large number of model evaluations. The present study contributes to addressing the limitations imposed by these computational requirements through the development of surrogate models for fire exposed structural members. To achieve this, a framework for carrying out probabilistic studies of structures under fire through the use of surrogate modelling is presented. The framework is applied to a concrete column subjected to a standard fire and proves efficiency and accurateness for the selected simple example. Future studies will investigate the applicability of the framework to structural assemblies under physically-based fires.

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Probabilistic Study of the Resistance of a Simply-Supported Reinforced Concrete Slab According to Eurocode Parametric Fire

Cited by 23 publications

References 13 publications

Flame extension and the near field under the ceiling for travelling fires inside large compartments

Flame extension and the near field under the ceiling for travelling fires inside large compartments

Analysis of a Concrete Building Exposed to Natural Fire

Generalized fragility curves for concrete columns exposed to fire through surrogate modelling

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