Steel Buildings in Europe

Part 6: Fire Engineering 6 - 43 associated phenomena. It uses a series of partial differential equations to determine the temperature within the compartment due to a localised fire. The CFD model is very demanding and requires expertise to define the input parameters and to assess the appropriateness of the results. 6.2.3 Fully developed fire The definition of the fully developed fire is given in Section 4.1.3, where the description of the standard fire and the parametric fire are also given. These fire curves are applicable to advanced models as well as to simple methods. 6.3 Modelling heat transfer The temperature rise of a structural member in fire is due to the heat transfer from the gas in the compartment to the member. The temperature rise of a structural member in fire is predominantly controlled by radiation and convection. Advanced models aim to provide a more realistic solution of temperature rise over the section of a structural member. Advanced models consider:  Thermal actions given in EN 1991-1-2  Non-uniform thermal exposure  Non-uniform heat transfer  Time-dependant boundary conditions  Time and temperature-dependant material properties. Advanced heat transfer models are developed based on 2D or 3D finite difference or finite element techniques. Therefore, they can only be performed by using commercial computer software packages. 6.4 Advanced structural models Advanced models for structural responses to both the thermal actions and the applied actions are based on the fundamentals of structural engineering and carried out by means of finite element techniques. The structure under consideration is generally divided into numerous small 2D or 3D elements with different initial and boundary conditions. Although finite element simulation clearly presents significant information to the designer, such an approach should not be taken without due care. There are potential problems associated with:  The choice of software  The options set within the software  The way the structure is modelled  The acceptance criteria used.