Steel Buildings in Europe

Title Worked Example – Fire safety strategies and design approach of steel floor beam 5 of 10 6 - 53 3.3.1. Temperature of beam after 60 minutes fire exposure The temperature rise of the unprotected and protected sections are determined using the incremental calculation procedure and the following models given in EN 1993-1-2; §4.5.2.1. For unprotected section: Δ θ a,t = t h V A c k Δ 1 net . m a a sh  k sh is the correction factor for the shadow effect. For an IPE section it is given as: k sh = 0,9   b m m A V A V = 200 145 0,9 = 0,652 For protected sections (assuming only protection boards are used): Δ θ a,t =     g.t 10 a.t g.t p p a a p Δ 1 Δ 1 3 1                  t e V A d c  = V A d c c p p a a p p   The net heat flux is: net . h = net,r . net,c . h h  Convection: net,c . h =   c g m     =   at g 25     Radiation: net.r . h =       4 m 4 t m f 273 273          =       4 at 4 g 8 273 273 5,67 10 0,7 1,0 1,0            The curve of the nominal standard fire is given by the following expression: θ g = (8 1) 20 345 log 10   t The equations above are evaluated based on the following thermal properties of steel and board protection materials: c a = 600 J/kg  C c p = 1200 J/kg  C d p,5 = 0,005 m ρ a = 7850 kg/m 3 ρ p = 300 kg/m 3 d p,10 = 0,01 m Δ t = 5 sec λ p = 0,1 W/m/  C d p,20 = 0,02 m With these data and equations, the graph in the Figure below can be drawn. This shows the temperature change in the air, the unprotected section and the protected section with 3 protection thicknesses: 5 mm, 10 mm and 20 mm.