Steel Buildings in Europe

Part 7: Fire Engineering 7 - 23 κ 1 , κ 2 are the adaptation factors to take account a non-uniform temperature distribution on steel member. The load level at time t is defined as: d fi,d fi,t R E   (14) where: fi,d E is the design effect of actions for the fire design situation, according to EN 1991-1-2 d R is the ultimate resistance in room temperature For a given fire duration t , assuming that cr a,t    , the maximum value of utilization level 0  of unprotected steel members to satisfy the required fire resistance may be easily calculated from (11), as function of section factor including the shadow effect ( A m / V ) sh . In this way, it may be assumed that fire resistance of unprotected steel members is satisfied after a time t if: max 0    (15) Maximum degrees of utilisation max  calculated for standard fire resistance R15 and R30 are given in Figure 5.6. It should be noted that for a fire resistance R30, unprotected members with a section factor ( A m / V ) sh higher than 50 m -1 can only achieve very low values of the degree of utilisation. Figure 5.6 Maximum utilization level as a function of section factor ( A m / V ) sh 0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 0 50 100 150 200 250 300 350 400 450 500 ( A m / V ) sh = k sh  ( A m / V )(m -1 )  max 10 15 minutes 30 minutes practical field of  0