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Thursday, 14 August 2014. Calculation of PFP Thickness. The thickness of fire protection required is determined by: Duration Critical Steel Temperature Steel section size and type Hp/A ratio Thickness stated in the local or international approval. SI Units: Hp/A = M/D = A/V =
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Thursday, 14 August 2014 Calculation of PFP Thickness
The thickness of fire protection required is determined by: • Duration • Critical Steel Temperature • Steel section size and type • Hp/A ratio • Thickness stated in the local or international approval
SI Units: Hp/A = M/D = A/V = Imperial (US) Units: W/D = A/P = metres Heated Perimeter = = m-1 or /m metres² Cross Section Area Kilograms / metre Mass of Section = = kg/m² metres Heated Perimeter metres² Heated Surface Area = = m-1 or /m metres³ Volume of Steel Pounds/foot Weight of section = = lb/ft/in inches Heated Perimeter Cross Section Area Square inches = = in2/in Heated Perimeter inches All express the relationship between the amount of steel capable of absorbing heat to the area of steel surface exposed to the fire.
How much PFP do I need? Hp/A - Section Factors Heated Perimeter (Hp = m) Cross Sectional Area (A = m²) Low Hp/A = Thinner PFP 305 x 305 x 240 kg/mHp/A = 1.905m / 0.0305m² Hp/A = 62 m-1 For H120 (400°C): Chartek 7 = 11 mm High Hp/A = Thicker PFP 305 x 305 x 97 kg/m Hp/A = 1.789m / 0.0123m² Hp/A = 145 m-1 For H120 (400°C): Chartek 7 = 16 mm
How much PFP do I need? How Hp/A changes with sides exposed to fire. (Example 305 x 305 x240 Kg/m UC) Wall, Floor or Deck Wall, Floor or Deck Flange only exposed Hp/A= Hp/A = 13 m-1 3 Sides exposed Hp/A= Hp/A = 52 m-1 4 Sides exposed Hp/A= Hp/A = 62 m-1 0.393 m 1.587 m 1.905 m 0.0305 m² 0.0305 m² 0.0305 m² Note: Cross Sectional Area Remains the same in all cases!
How to calculate an Hp/A? The Yellow Book! www.asfp.org.uk
What do I do with my Hp/A? Chartek 7 Certificate Interchar 963 loadings Example of Certificate of Fire Approval with table of Hp/A v required PFP thickness
What do I do with my Hp/A? Interchar 963 loadings
What about other section shapes? Wall, Floor or Deck Wall, Floor or Deck Decreasing Hp/A = Lower PFP thickness required