EN 1992-1-2:2004*. Structural fire design - QuickField simulation example
The fire may destroy not only wooden construction but also damage a concrete structure. At high temperature concrete loses its structural integrity.
How to find temperature distribution in concrete slabs under ISO 834 fire?
Answer Typical applications Geometry
Given
Concrete thermal conductivity λ(T) = 1.36 - 0.136*(T/100) + 0.0057*(T/100)² W/m-K
Concrete specific heat capacity C depends on temperature
Task
Solution
Results
References:
This is an example of a concrete column subjected to the high temperature of the standard fire (ISO 834**). The task is to calculate the temperature distribution in the column in time.
Engineering question
Apply the ISO 834 fire temperature-time boundary in a transient heat-transfer model with temperature-dependent concrete properties and calculate the slab temperature distribution.
concrete structural slabs, fire-resistance concrete elements, structural fire test specimens
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Simulation problem
Problem Type
Plane-parallel problem of Transient heat transfer.
The standard fire temperature-time curve is defined by the ISO 834*:
T(t) = T0 + 345*log10(8*t + 1), where t is time in minutes and T0=20°C is an initial temperature.
Convection coefficient is 25 W/K-m², emissivity coefficient of concrete surface is 0.7.
Concrete density ρ variation with temperature is influenced by water loss.
Calculate the temperature field.
In EN 1992-1-2:2004** only a quarter of the slab is simulated. So we also utilize symmetry of the model and simulate only a quarter.
In QuickField the density ρ must be a constant. We specify density to be ρ(20°C) and attenuated specific heat dependency to take into account ρ(T):
C'(T) = C(T) * ρ(T)/ρ(20°C);
Temperature profiles 30 minutes and 60 minutes after the fire is started.
*ISO 834-1:1999. Fire-resistance tests — Elements of building construction — Part 1: General requirements
**EN 1992-1-2:2004 Design of concrete structures - Part 1-2: General rules - Structural fire design.
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