1. Eurocode 1: Actions on structures –
Part 1–2: General actions – Actions on structures exposed to fire
Annex D (informative)
Advanced fire models
Part of the One Stop Shop program

2. Introduction Models of increasing complexity One-zone models
Post flashover fires
Homogenous temp, density, internal energy and gas pressure assumed in compartment
Two-zone models
Upper/lower layer
Mass and energy balances calculated
Field models
Based on Computational Fluid Dynamics
PDE’s solved over entire numerical grid underlying domain to give solutions to various dynamic variables

3. One-zone models Temperature calculation based on
Conservation of energy/mass equations
Mass exchange (internal, external, and fire)
Energy exchange (between fire, gas, walls, etc.)
The ideal gas law considered is
Internal compartment pressure
Gas temperature
Gas density
Molar constant

4. Mass balance – one-zone model
Mass balance of compartment gases
Rate of pyrolysis products generated
Rate of gas mass going out through the openings
Rate of gas mass coming in through openings
The rate of change of mass gas and the pyrolysis rate may be neglected to give:
which may be calculated based on static pressure due to density differences between air at ambient and high temperatures

5. Energy balance – one-zone model
Energy balance of compartment gases
External energy in to compartment
Loss of energy by radiation through openings
RHR of the fire
- internal energy of gas
Energy out of compartment
Loss of energy to enclosure surfaces
See Section 3 of main Code

6. Two-zone models Different zones are defined
Upper layer
Lower layer
Fire and its plume
Walls
Energy and mass exchanges between these zones are calculated
A two-zone model may be approximated by a one-zone model if
Gas temp in upper layer exceeds 500oC
Upper layer grows to exceed 80% of compartment height
“OZone” is a common software package of a two-zone model

7. Field models
Field models are computational fluid dynamics based models
They solve partial differential equations over the entire compartment
Utilising an underlying numerical grid
The result is an array of variables solved over the entire compartment
The basis of field models can be separated into
Hydrodynamic model
State, mass, energy and momentum equations
Turbulence and fluid modelling
Combustion and radiation sub-models