The fire resistance of wide-flange structural steel columns protected with sprayed fire-resistant materials, as illustrated in Figure 722.5.1(5), shall be permitted to be determined from the following expression:
|R = [C1 (W / D) + C2)h||(Equation 7-13)|
|R||=||Fire resistance (minutes).|
|h||=||Thickness of sprayed 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 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.