Steel Buildings in Europe

Part 6: Fire Engineering 6 - 23 composite members to their load level (the load level is denoted as  fi,t and is described in Sections 4.4.2 and 4.4.3 of this guide), the h / b ratio, the member type and the area of reinforcement A s . Generally, an increase of the fire resistance or the load level requires larger cross-sections and additional reinforcement for partially encased sections. The datasheets can be used to determine the minimum cross-sectional dimensions (such as the section width b min ) and reinforcement ratio A s,min of partially encased sections, to achieve the required fire resistance period. c A A u u s s e e w b s f h Figure 3.11 Partially encased column Table 3.7 shows a datasheet taken from EN 1994-1-2 for the fire design of partially encased sections. When using this type of design data, the load level η fi,t may be calculated as follows: fi,t d fi,d, t R R    where: R fi,d,t is the design resistance of the member in fire conditions at time, t . R d is the design resistance of the member for room temperature design. When calculating the load level, EN 1994-1-2 recommends that the design resistance for room temperature design, R d , is calculated for a buckling length that is twice the buckling length used for fire design.