Steel Buildings in Europe

Part 7: Fire Engineering 7 - 24 5.3.2 Simple design method for steel members According to EN 1993-1-2, the load-bearing function of a steel member should be assumed to be maintained at a time t if: d,fi,t fi,d E R  (16) where: fi,d E is the design effect of actions for the fire design situation, according to EN 1991-1-2 d,fi,t R is the corresponding design resistance of the steel member, for the fire design situation, at time t The following simplified calculation methods allow the designer to assess the design fire resistance (buckling resistance, resistance moment) of steel members. They are mainly based on the assumption of constant temperature within the section. Steel columns under compression only The design resistance for the fire design situation at time t of a compression member with a Class 1, 2 or 3 cross-sections at a uniform temperature θ a should be determined from:   Rd θ y, M,f M0 f fi,t,Rd k N N i i       (17) where: θ y, k is the reduction factor for the yield strength of steel at the steel temperature θ reached at time t M,fi  is the partial safety factor for fire situation ( 1 M,fi   ) M0  is the partial safety factor at normal temperature ( 1 M0   ) Rd N is the design resistance of the cross-section N pl,Rd for the normal temperature design according to EN 1993-1-1 fi  is the reduction factor for flexural buckling in the fire design situation The reduction factor fi  for flexural buckling is obtained from the non- dimensional slenderness   at temperature θ using: 2 θ 2 θ θ f 1        i but  fi  1.0 (18) with   2 θ θ θ 1 2 1      