Assessment of Eurocode 5 Charring Rate Calculation Methods

Cachim, Paulo; Franssen, Jean‐Marc

doi:10.1007/s10694-009-0092-x

Cited by 36 publications

(32 citation statements)

References 8 publications

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“…The most important effects for timber members exposed to fire are pyrolysis and mass transport of moisture. The most obvious effect of fire exposure is pyrolysis, which has been Fire Technology 2014 investigated excessively [17][18][19][20][21][22]. Since the zero-strength layer of the RCSM does not depend on the charring rate, the charring rate is discussed here only briefly.…”

Section: Thermal and Mechanical Boundary Conditions Of Fire-exposed Tmentioning

confidence: 99%

The Reduced Cross-Section Method for Evaluation of the Fire Resistance of Timber Members: Discussion and Determination of the Zero-Strength Layer

et al. 2014

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The reduced cross-section method (RCSM) is included in Eurocode 5 (EN-1995-1-2) for the design of timber members in fire conditions. The method considers the strength and stiffness reduction beneath the charred layer by adding an additional depth (known as the 'zero-strength' layer) to the charring depth. The zerostrength layer is one of the key parameters for the fire design of timber members. Recently, some concerns have been raised that the zero-strength layer might be nonconservative in some applications. This paper presents the background to the RCSM, followed by a short discussion on the mechanical assumptions, simplifications and possible limitations of the method itself. Further, it discusses determination of the zero-strength layer thickness for members in bending, tension and compression, and provides guidelines on the use of standard experimental tests to determine this quantity. For demonstration of the determination procedure, the results of fire tests in bending, tension and compression were analysed following the described procedure. Results show that the zero-strength layer exceeds the value used in practice, indicate that the method of Eurocode 5 may be non-conservative and should be revised.

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Section: Thermal and Mechanical Boundary Conditions Of Fire-exposed Tmentioning

confidence: 99%

The Reduced Cross-Section Method for Evaluation of the Fire Resistance of Timber Members: Discussion and Determination of the Zero-Strength Layer

et al. 2014

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“…Some studies [12], give the range of ratios as between 1.75 and 2.25. As reported by [12,14] the conductivity of wood along the grain is between 1.5 to 2.8 times the conductivity across the grain. In this work, a value equal to 1.5 of perpendicular or transverse (T) direction was used to calculate the thermal conductivity in parallel or longitudinal (L) direction.…”

Section: Thermal Proprietiesmentioning

confidence: 65%

“…As reported by [7] the char-layer in longitudinal grain orientation is presumed to be higher than transverse orientation. Following some authors [12,14] charring rate of wood along the grain is higher than across the grain with ratio between them ranging from 1.3 to 2.0.…”

Section: Resultsmentioning

confidence: 81%

High temperatures in parallel or perpendicular wood grain direction: a numerical and experimental study

Fonseca

Barreira

2011

WIT Transactions on the Built Environment

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The high vulnerability of wood due to accidental conditions requires a rigorous thermal and mechanical assessment. In this work, an experimental and numerical study will be presented to determine the char-layer evolution in pine wood crosssection, submitted at high temperatures due to an anaerobic process. A non-linear thermal and transient analysis will be conducted using the numerical program. A thermal unit and electro ceramic resistances will be used during the experimental program. The evolution of a char-layer by the orientation of different fibres will be determined. The experimental results obtained with several wood samples will be compared using a numerical program with a finite element formulation.

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“…The analytical failure predictions were computed using the reduced cross section method proposed by Eurocode 5 to calculate the residual cross section of timber elements under standard fire exposure and a variation of this method recommended by Cachim and Franssen . The Eurocode 5 assumes the same value of charring rate for all sides of a cross section even if it would be more realistic to assume a greater charring rate on the narrow sides for very small cross sections as shown by the experimental data.…”

Section: Fire Resistance Predictionmentioning

confidence: 99%

Predicting the fire resistance of timber members loaded in tension

et al. 2012

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SUMMARY The paper presents a numerical model for predicting the fire resistance of timber members. Fire resistance is evaluated in a two‐step process implemented in the Abaqus finite element code: first, a time‐dependent thermal analysis of the member exposed to fire and then a structural analysis under a constant load are performed. The structural analysis considers the reduction in mechanical properties (modulus of elasticity and strength) of timber with temperature. The analysis terminates when the member can no longer redistribute stresses from the hottest to the coldest parts, leading to structural failure. The model was used to simulate fire tests carried out on specimens made from laminated veneer lumber loaded in tension. Experimental data in terms of temperature, charring depth, displacement and failure time were compared with the numerical results obtained by assuming the thermal properties and degradation of mechanical properties with temperature as suggested by Eurocode 5, showing an overall acceptable approximation. The fire resistance of the timber member was then predicted depending upon the applied tensile loads using the numerical model and analytical formulas. The proposed finite element model can be used to predict the fire resistance of timber structures as an alternative to expensive and complicated experimental tests. Copyright © 2012 John Wiley & Sons, Ltd.

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Assessment of Eurocode 5 Charring Rate Calculation Methods

Cited by 36 publications

References 8 publications

The Reduced Cross-Section Method for Evaluation of the Fire Resistance of Timber Members: Discussion and Determination of the Zero-Strength Layer

The Reduced Cross-Section Method for Evaluation of the Fire Resistance of Timber Members: Discussion and Determination of the Zero-Strength Layer

High temperatures in parallel or perpendicular wood grain direction: a numerical and experimental study

Predicting the fire resistance of timber members loaded in tension

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