722.5.1.4 Concrete-protected columns.
BC § 722.5.1.4
The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 722.5.1(6)(a) and (b), shall be permitted to be determined from the following expression: R = R 0 (1 + 0.03m) (Equation 7-14) where: R 0 = 10 (W/D) 0.7 + 17(h 1.6 /k c0.2 ) × (1 + 26 (h/p c c c h (L + h)) 0.8 ) As used in these expressions: R = Fire endurance at equilibrium moisture conditions (minutes). R 0 = Fire endurance at zero moisture content (minutes). m = Equilibrium moisture content of the concrete by volume (percent). W = Average weight of the steel column (pounds per linear foot). D = Heated perimeter of the steel column (inches). h = Thickness of the concrete cover (inches). k c = Ambient temperature thermal conductivity of the concrete (Btu/hr ft °F). H = Ambient temperature thermal capacity of the steel column = 0.11W (Btu/ft °F). p c = Concrete density (pounds per cubic foot). c c = Ambient temperature specific heat of concrete (Btu/lb °F). L = Interior dimension of one side of a square concrete box protection (inches).
