Steel Buildings in Europe

Part 7: Fire Engineering 7 - 21 Table 5.2 Average materials properties of main fire protection materials Material Density p  [(kg/m 3 ] Conductivity p  [W/mK] Specific heat p C [J/kgK] ) Mineral fibre 300 0,12 1200 Vermiculite and cement 350 0,12 1200 Sprays perlite 350 0,12 1200 vermiculite (or perlite) and cement 550 0,12 1100 High density sprays vermiculite (or perlite) and gypsum 650 0,12 1100 vermiculite (or perlite) and cement 800 0,2 1200 fibre-silicate or fibre calcium-silicate 600 0,15 1200 fibre-cement 800 0,15 1200 Boards gypsum board 800 0,2 1700 Compressed fibre boards fibre-silicate, mineral, stone-wool 150 0,2 1200 5.3 Structural Models According to the Eurocodes, several simple design methods can be used to assess the fire resistance of structures under fire conditions. The first one is the critical temperature method widely applied to steel structural member analysis and the second one is the simple mechanical models developed for both steel and composite steel and concrete structural members. It is important to remember that the design methods available for composite members are only valid for the standard fire exposure. Moreover, design methods given for columns should be only applied to members of braced frames (where the column ends have no horizontal displacement). 5.3.1 Critical temperature method The critical temperature is calculated by using applied mechanical actions, design resistance in the normal temperature condition and the strength loss of steel at elevated temperature. This critical temperature generally varies between 500°C and 800°C. It can be obtained by calculation according to the simple rules given in the EN 1993-1-2 or by referring to default values. According to the critical temperature method, the fire resistance of a steel member without instability effect is satisfied after a time t if the steel temperature a,t  does not exceed the critical temperature cr  of the element: cr a,t    (10)