Calculation of PFP Thickness Thursday March 15 2018

Calculation of PFP Thickness Thursday, March 15, 2018

The thickness of fire protection required is determined by: 1. Duration 2. Critical Steel Temperature 3. Steel section size and type • Hp/A ratio 4. Thickness stated in the local or international approval

SI Units: Hp/A = M/D = A/V = Heated Perimeter = Cross Section Area Mass of Section Heated Perimeter Heated Surface Area Volume of Steel = = metres² m-1 or /m Kilograms / metres² metres³ = = kg/m² m-1 or /m Imperial (US) Units: W/D = Weight of section A/P = Cross Section Area Heated Perimeter = = Pounds/foot inches Square inches = lb/ft/in = in 2/in 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) Low Hp/A = Thinner PFP 305 x 240 kg/m Hp/A = 1. 905 m / 0. 0305 m² Hp/A = 62 m-1 For H 120 (400°C): Chartek 7 = 11 mm Cross Sectional Area (A = m²) High Hp/A = Thicker PFP 305 x 97 kg/m Hp/A = 1. 789 m / 0. 0123 m² Hp/A = 145 m-1 For H 120 (400°C): Chartek 7 = 16 mm

How much PFP do I need? How Hp/A changes with sides exposed to fire. (Example 305 x 240 Kg/m UC) Wall, Floor or Deck 4 Sides exposed Hp/A= 1. 905 m 0. 0305 m² Hp/A = 62 m-1 Wall, Floor or Deck 3 Sides exposed Flange only exposed Hp/A= 1. 587 m 0. 0305 m² Hp/A = 52 m-1 Hp/A= 0. 393 m 0. 0305 m² Hp/A = 13 m-1 Note: Cross Sectional Area Remains the same in all cases!

How to calculate an Hp/A? The Yellow Book! www. asfp. org. uk

How to calculate an Hp/A?

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 Decreasing Hp/A = Lower PFP thickness required Wall, Floor or Deck