The fire resistance of wide-flange structural steel columns protected with spray-applied fire-resistant materials, as illustrated in Figure 721.5.1(5), shall be permitted to be determined from the following expression:
where:
R = Fire resistance (minutes).
h = Thickness of spray-applied fire-resistant material (inches).
D = Heated perimeter of the structural steel column (inches).
C1 and C2 = Material-dependent constants.
W = Weight of structural steel columns (pounds per linear foot).
The fire resistance of structural steel columns protected with intumescent or mastic fire-resistant coatings shall be determined on the basis of fire-resistance tests in accordance with Section 703.2.
| R = [C1(W/D) + C2]h | (Equation 7-13) |
where:
R = Fire resistance (minutes).
h = Thickness of spray-applied fire-resistant material (inches).
D = Heated perimeter of the structural steel column (inches).
C1 and C2 = Material-dependent constants.
W = Weight of structural steel columns (pounds per linear foot).
The fire resistance of structural steel columns protected with intumescent or mastic fire-resistant coatings shall be determined on the basis of fire-resistance tests in accordance with Section 703.2.
The material-dependent constants, C1 and C2 , shall be determined for specific fire-resistant materials on the basis of standard fire endurance tests in accordance with Section 703.2. Unless evidence is submitted to the building official substantiating a broader application, this expression shall be limited to determining the fire resistance of structural steel columns with weight-to-heated-perimeter ratios ( W/D ) between the largest and smallest columns for which standard fire-resistance test results are available.
Spray-applied fire-resistant materials shall be identified by density and thickness required for a given fire-resistance rating.