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

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

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 density Gas temperature Molar constant

Mass balance – one-zone model Mass balance of compartment gases Rate of gas mass coming in through openings Rate of gas mass going out through the openings Rate of pyrolysis products generated 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

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

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 500 o C –Upper layer grows to exceed 80% of compartment height “OZone” is a common software package of a two-zone model

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