Section Factors † these are criteria found in tabulated fire
protection data such as the Loss Prevention Certification Board's
Standards. These factors can be used to establish the minimum
thickness or cover of protective material for structural sections.
This interpretation is usually preferred by buildings insurance
companies, as it often provides a standard in excess of the Building
Regulations. Section factors are categorised: <90, 90 † 140 and
- They can be calculated by the following formula:
Section Factor = Hp/A (m^1 )
Hp = Perimeter of section exposed to fire (m)
A = Cross sectional area of steel (m^2 ) [see BS 4-1 or Structural
Steel Tables]
Examples:
Hp = (2 ¾ 124„3) + (2 ¾ 306„6) + 2(124„3 † 8) = 1„0944 m
A = 53„2 cm^2 or 0„00532 m^2
Section Factor, Hp/A = 1„0944/0„00532 = 205
As beam above, but 3 sides only exposedfire protectionUBcompartment concrete
floor, f.r. = 120 minutesHp = 124„3 + (2 ¾ 306„6) + 2(124„3 † 8) = 0„9701 m
A = 53„2 cm^2 or 0„00532 m^2
Section Factor, Hp/A = 0„9701/0„00532 = 182
Structural Steelwork---Fire Protection