TeDisOn - Temperature Distribution Online

A program for a 1D calculation of temperature distribution over a concrete wall or slab during fire using the FDM

Author: Radek Štefan, Jakub Holan

Input parameters

Thickness: m

Duration of fire: minutes

Exposure^[1]:

Initial density: kg/m³

Initial water content: %

Thermal conductivity:

Advice

When modelling a symmetric problem, i.e. two-sided exposure, only one half of the problem can be modelled to achieve lower computing time. To model the symmetric half, set the length to half and select exposure type as "one-sided zero flux".

Important assumptions

The thermal conductivity of concrete, λ_c(θ), is assumed as specified in [1, sec. 3.3.3].
The specific heat of concrete, c_p(θ), is assumed as specified in [1, sec. 3.3.2].
The variation of density of concrete with temperature, ρ(θ), is assumed as specified in [1, sec. 3.3.2].
The emissivity related to the concrete surface is assumed as specified in [1, sec. 2.2], i.e. ε = 0.7.
The coefficient of heat transfer by convection on the fire-exposed side is assumed as specified in [2, sec. 3.2.1 (2)], i.e. α_c = 25 W/(m²k).
The coefficient of heat transfer by convection on the unexposed side is assumed as specified in [2, sec. 3.1 (5)], i.e. α_c = 4 W/(m²k) when assuming non-zero radiation and α_c = 9 W/(m²k) when assuming zero emissivity.

The fire temperature evolution in time is assumed using the Standard temperature-time curve (ISO-834) as specified in [2, sec. 3.2.1 (1)], i.e θ(t) = 20+345*log₁₀(8*t+1).

References

[1] EN 1992-1-2 Eurocode 2: Design of concrete structures - Part 1-2: General rules - Structural fire design. CEN, 2004.
[2] EN 1991-1-2 Eurocode 1: Actions on structures - Part 1-2: General actions - Actions on structures exposed to fire. CEN, 2002.

Footnotes

^[1] Two-sided exposure assumes a fire exposure at both ends. One-sided exposure assumes fire only on the left end. Zero flux means that both emissivity and coefficient of heat transfer by convection are assumed as zero. Zero emissivity means that emissivity is assumed as zero and coefficient of heat transfer by convection is assumed as containing the effects of heat transfer by radiation, i.e. α_c = 9 W/(m²k). Full flux means that emissivity is assumed as specified in [1, sec. 2.2], i.e. ε = 0.7, and coefficient of heat transfer by convection is assumed as α_c = 4 W/(m²k).

Cite as: Holan, J. and Štefan, R. Numerical analysis of temperature distribution throughout a concrete slab during fire using a web-based solver. 26th International Conference Concrete Days, 2019. Solid State Phenomena.

Author: Radek Štefan, Jakub Holan
radek.stefan@fsv.cvut.cz, jakub.holan@fsv.cvut.cz

This work was supported by the Grant Agency of the Czech Technical University in Prague, project no. SGS19/034/OHK1/1T/11.