722.214.171.124.5 Masonry Protection
The fire resistance of structural steel columns protected with concrete masonry units or clay masonry units as illustrated in Figure 722.5.1(7) shall be permitted to be determined from the following expression:
R = Fire-resistance rating of column assembly (hours).
W = Average weight of structural steel column (pounds per foot).
D = Heated perimeter of structural steel column (inches) [see Figure 722.5.1(7)].
As = Cross-sectional area of structural steel column (square inches).