Code of Massachusetts Regulations
780 CMR - STATE BOARD OF BUILDING REGULATIONS AND STANDARDS
Chapter 7 - Fire and Smoke Protection Features
Section 721 - CALCULATED FIRE RESISTANCE
Subsection 721.5 - Steel assemblies

Universal Citation: 780 CMR MA Code of Regs 721.5

Current through Register 1531, September 27, 2024

The provisions of this section contain procedures by which the fire-resistance ratings of steel assemblies are established by calculations.

721.5.1 Structural steel columns. The fire-resistance ratings of steel columns shall be based on the size of the element and the type of protection provided in accordance with this section.

TABLE 721.5.1(1) W/D RATIOS FOR STEEL COLUMNS

STRUCTURAL SHAPE CONTOUR PROFILE BOX PROFILE STRUCTURAL SHAPE CONTOUR PROFILE BOX PROFILE
W14 × 233 2.49 3.65 W10 × 112 1.78 2.57
× 211 2.28 3.35 × 100 1.61 2.33
× 193 2.10 3.09 × 88 1.43 2.08
× 176 1.93 2.85 × 77 1.26 1.85
× 159 1.75 2.60 × 68 1.13 1.66
× 145 1.61 2.39 × 60 1.00 1.48
× 132 1.52 2.25 × 54 0.91 1.34
× 120 1.39 2.06 × 49 0.83 1.23
× 109 1.27 1.88 × 45 0.87 1.24
× 99 1.16 1.72 × 39 0.76 1.09
× 90 1.06 1.58 × 33 0.65 0.93
× 82 1.20 1.68
× 74 1.09 1.53 W8 × 67 1.34 1.94
× 68 1.01 1.41 × 58 1.18 1.71
× 61 0.91 1.28 × 48 0.99 1.44
× 53 0.89 1.21 × 40 0.83 1.23
× 48 0.81 1.10 × 35 0.73 1.08
× 43 0.73 0.99 × 31 0.65 0.97
× 28 0.67 0.96
W12 × 190 2.46 3.51 × 24 0.58 0.83
× 170 2.22 3.20 × 21 0.57 0.77
× 152 2.01 2.90 × 18 0.49 0.67
× 136 1.82 2.63
× 120 1.62 2.36 W6 × 25 0.69 1.00
× 106 1.44 2.11 × 20 0.56 0.82
× 96 1.32 1.93 × 16 0.57 0.78
× 87 1.20 1.76 × 15 0.42 0.63
× 79 1.10 1.61 × 12 0.43 0.60
× 72 1.00 1.48 × 9 0.33 0.46
× 65 0.91 1.35
× 58 0.91 1.31 W5 × 19 0.64 0.93
× 53 0.84 1.20 × 16 0.54 0.80
× 50 0.89 1.23
× 45 0.81 1.12 W4 × 13 0.54 0.79
× 40 0.72 1.00

For SI: 1 pound per linear foot per inch = 0.059 kg/m/mm.

TABLE 721.5.1(2) PROPERTIES OF CONCRETE

PROPERTY NORMAL-WEIGHT CONCRETE STRUCTURAL LIGHTWEIGHT CONCRETE
Thermal conductivity (kc) 0.95 Btu/hr · ft · °F 0.35 Btu/hr · ft · °F
Specific heat (cc) 0.20 Btu/lb °F 0.20 Btu/lb °F
Density (Pc) 145 lb/ft3 110 lb/ft3
Equilibrium (free) moisture content (m) by volume 4% 5%

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 lb/ft3 = 16.0185 kg/m3, Btu/hr . ft . °F = 1.731 W/(m . K).

TABLE 721.5.1(3) THERMAL CONDUCTIVITY OF CONCRETE OR CLAY MASONRY UNITS

DENSITY (dm) OF UNITS (lb/ft 3) THERMAL CONDUCTIVITY (K) OF UNITS (Btu/hr . ft . °F)
Concrete Masonry Units
80 0.207
85 0.228
90 0.252
95 0.278
100 0.308
105 0.340
110 0.376
115 0.416
120 0.459
125 0.508
130 0.561
135 0.620
140 0.685
145 0.758
150 0.837
Clay Masonry Units
120 1.25
130 2.25

For SI: 1 pound per cubic foot = 16.0185 kg/m3, Btu/hr . ft . °F = 1.731 W/(m . K).

TABLE 721.5.1(4) WEIGHT-TO-HEATED-PERIMETER RATIOS (W/D) FOR TYPICAL WIDE FLANGE BEAM AND GIRDER SHAPES

STRUCTURAL SHAPE CONTOUR PROFILE BOX PROFILE STRUCTURAL SHAPE CONTOUR PROFILE BOX PROFILE
W36 × 300 2.47 3.33 W24 × 68 0.92 1.21
× 280 2.31 3.12 × 62 0.92 1.14
× 260 2.16 2.92 × 55 0.82 1.02
× 245 2.04 2.76
× 230 1.92 2.61 W21 × 147 1.83 2.60
× 210 1.94 2.45 × 132 1.66 2.35
× 194 1.80 2.28 × 122 1.54 2.19
× 182 1.69 2.15 × 111 1.41 2.01
× 170 1.59 2.01 × 101 1.29 1.84
× 160 1.50 1.90 × 93 1.38 1.80
× 150 1.41 1.79 × 83 1.24 1.62
× 135 1.28 1.63 × 73 1.10 1.44
× 68 1.03 1.35
W33 × 241 2.11 2.86 × 62 0.94 1.23
× 221 1.94 2.64 × 57 0.93 1.17
× 201 1.78 2.42 × 50 0.83 1.04
× 152 1.51 1.94 × 44 0.73 0.92
× 141 1.41 1.80
× 130 1.31 1.67 W18 × 119 1.69 2.42
×118 1.19 1.53 ×106 1.52 2.18
×97 1.39 2.01
W30 ×211 2.00 2.74 ×86 1.24 1.80
×191 1.82 2.50 ×76 1.11 1.60
×173 1.66 2.28 ×71 1.21 1.59
×132 1.45 1.85 ×65 1.11 1.47
×124 1.37 1.75 ×60 1.03 1.36
×116 1.28 1.65 ×55 0.95 1.26
×108 1.20 1.54 ×50 0.87 1.15
×99 1.10 1.42 ×46 0.86 1.09
×40 0.75 0.96
W27 ×178 1.85 2.55 ×35 0.66 0.85
×161 1.68 2.33
×146 1.53 2.12 W16 ×100 1.56 2.25
×114 1.36 1.76 ×89 1.40 2.03
×102 1.23 1.59 ×77 1.22 1.78
×94 1.13 1.47 ×67 1.07 1.56
×84 1.02 1.33 ×57 1.07 1.43
×50 0.94 1.26
×45 0.85 1.15
W24 ×162 1.85 2.57 ×40 0.76 1.03
×146 1.68 2.34 ×36 0.69 0.93
×131 1.52 2.12 ×31 0.65 0.83
×117 1.36 1.91 ×26 0.55 0.70
×104 1.22 1.71
×94 1.26 1.63 W14 ×132 1.83 3.00
×84 1.13 1.47 ×120 1.67 2.75
×76 1.03 1.34 ×109 1.53 2.52
W14 × 99 1.39 2.31 W10 × 30 0.79 1.12
× 90 1.27 2.11 × 26 0.69 0.98
× 82 1.41 2.12 × 22 0.59 0.84
× 74 1.28 1.93 × 19 0.59 0.78
× 68 1.19 1.78 × 17 0.54 0.70
× 61 1.07 1.61 × 15 0.48 0.63
× 53 1.03 1.48 × 12 0.38 0.51
× 48 0.94 1.35
× 43 0.85 1.22 W8 × 67 1.61 2.55
× 38 0.79 1.09 × 58 1.41 2.26
× 34 0.71 0.98 × 48 1.18 1.91
× 30 0.63 0.87 × 40 1.00 1.63
× 26 0.61 0.79 × 35 0.88 1.44
× 22 0.52 0.68 × 31 0.79 1.29
× 28 0.80 1.24
W12 × 87 1.44 2.34 × 24 0.69 1.07
× 79 1.32 2.14 × 21 0.66 0.96
× 72 1.20 1.97 × 18 0.57 0.84
× 65 1.09 1.79 × 15 0.54 0.74
× 58 1.08 1.69 × 13 0.47 0.65
× 53 0.99 1.55 × 10 0.37 0.51
× 50 1.04 1.54
× 45 0.95 1.40 W6 × 25 0.82 1.33
× 40 0.85 1.25 × 20 0.67 1.09
× 35 0.79 1.11 × 16 0.66 0.96
× 30 0.69 0.96 × 15 0.51 0.83
× 26 0.60 0.84 × 12 0.51 0.75
× 22 0.61 0.77 × 9 0.39 0.57
× 19 0.53 0.67
× 16 0.45 0.57 W5 × 19 0.76 1.24
× 14 0.40 0.50 × 16 0.65 1.07
W10 × 112 2.14 3.38 W4 × 13 0.65 1.05
× 100 1.93 3.07
× 88 1.70 2.75
× 77 1.52 2.45
× 68 1.35 2.20
× 60 1.20 1.97
× 54 1.09 1.79
× 49 0.99 1.64
× 45 1.03 1.59
× 39 0.94 1.40
× 33 0.77 1.20

For SI: Pounds per linear foot per inch = 0.059 kg/m/mm.

TABLE 721.5.1(5) FIRE RESISTANCE OF CONCRETE MASONRY PROTECTED STEEL COLUMNS

COLUMN SIZE CONCRETE MASONRY DENSITY, POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CONCRETE MASONRY PROTECTION ASSEMBLY, Te(inches) COLUMN SIZE CONCRETE MASONRY DENSITY POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CONCRETE MASONRY PROTECTION ASSEMBLY, Te(inches)
1-hour 2-hour 3-hour 4-hour 1-hour 2-hour 3-hour 4-hour
W14 × 82 80 0.74 1.61 2.36 3.04 W10 ×68 80 0.72 1.58 2.33 3.01
100 0.89 1.85 2.67 3.40 100 0.87 1.83 2.65 3.38
110 0.96 1.97 2.81 3.57 110 0.94 1.95 2.79 3.55
120 1.03 2.08 2.95 3.73 120 1.01 2.06 2.94 3.72
W14 × 68 80 0.83 1.70 2.45 3.13 W10 ×54 80 0.88 1.76 2.53 3.21
100 0.99 1.95 2.76 3.49 100 1.04 2.01 2.83 3.57
110 1.06 2.06 2.91 3.66 110 1.11 2.12 2.98 3.73
120 1.14 2.18 3.05 3.82 120 1.19 2.24 3.12 3.90
W14 × 53 80 0.91 1.81 2.58 3.27 W10 ×45 80 0.92 1.83 2.60 3.30
100 1.07 2.05 2.88 3.62 100 1.08 2.07 2.90 3.64
110 1.15 2.17 3.02 3.78 110 1.16 2.18 3.04 3.80
120 1.22 2.28 3.16 3.94 120 1.23 2.29 3.18 3.96
W14 × 43 80 1.01 1.93 2.71 3.41 W10 ×33 80 1.06 2.00 2.79 3.49
100 1.17 2.17 3.00 3.74 100 1.22 2.23 3.07 3.81
110 1.25 2.28 3.14 3.90 110 1.30 2.34 3.20 3.96
120 1.32 2.38 3.27 4.05 120 1.37 2.44 3.33 4.12
W12 × 72 80 0.81 1.66 2.41 3.09 W8 ×40 80 0.94 1.85 2.63 3.33
100 0.91 1.88 2.70 3.43 100 1.10 2.10 2.93 3.67
110 0.99 1.99 2.84 3.60 110 1.18 2.21 3.07 3.83
120 1.06 2.10 2.98 3.76 120 1.25 2.32 3.20 3.99
W12 × 58 80 0.88 1.76 2.52 3.21 W8 ×31 80 1.06 2.00 2.78 3.49
100 1.04 2.01 2.83 3.56 100 1.22 2.23 3.07 3.81
110 1.11 2.12 2.97 3.73 110 1.29 2.33 3.20 3.97
120 1.19 2.23 3.11 3.89 120 1.36 2.44 3.33 4.12
W12 × 50 80 0.91 1.81 2.58 3.27 W8 ×24 80 1.14 2.09 2.89 3.59
100 1.07 2.05 2.88 3.62 100 1.29 2.31 3.16 3.90
110 1.15 2.17 3.02 3.78 110 1.36 2.42 3.28 4.05
120 1.22 2.28 3.16 3.94 120 1.43 2.52 3.41 4.20
W12 × 40 80 1.01 1.94 2.72 3.41 W8 ×18 80 1.22 2.20 3.01 3.72
100 1.17 2.17 3.01 3.75 100 1.36 2.40 3.25 4.01
110 1.25 2.28 3.14 3.90 110 1.42 2.50 3.37 4.14
120 1.32 2.39 3.27 4.06 120 1.48 2.59 3.49 4.28
4 × 4 ×1/2 wall thickness 80 0.93 1.90 2.71 3.43 4 double extra strong 0.674 wall thickness 80 0.80 1.75 2.56 3.28
100 1.08 2.13 2.99 3.76 100 0.95 1.99 2.85 3.62
110 1.16 2.24 3.13 3.91 110 1.02 2.10 2.99 3.78
120 1.22 2.34 3.26 4.06 120 1.09 2.20 3.12 3.93
4 × 4 × 3/8 wall thickness 80 1.05 2.03 2.84 3.57 4 extra strong 0.337 wall thickness 80 1.12 2.11 2.93 3.65
100 1.20 2.25 3.11 3.88 100 1.26 2.32 3.19 3.95
110 1.27 2.35 3.24 4.02 110 1.33 2.42 3.31 4.09
120 1.34 2.45 3.37 4.17 120 1.40 2.52 3.43 4.23
4 × 4 × 1/4 wall thickness 80 1.21 2.20 3.01 3.73 4 standard 0.237 wall thickness 80 1.26 2.25 3.07 3.79
100 1.35 2.40 3.26 4.02 100 1.40 2.45 3.31 4.07
110 1.41 2.50 3.38 4.16 110 1.46 2.55 3.43 4.21
120 1.48 2.59 3.50 4.30 120 1.53 2.64 3.54 4.34
6 × 6 × 1/2 wall thickness 80 0.82 1.75 2.54 3.25 5 double extra strong 0.750 wall thickness 80 0.70 1.61 2.40 3.12
100 0.98 1.99 2.84 3.59 100 0.85 1.86 2.71 3.47
110 1.05 2.10 2.98 3.75 110 0.91 1.97 2.85 3.63
120 1.12 2.21 3.11 3.91 120 0.98 2.02 2.99 3.79
6 × 6 × 3/8 wall thickness 80 0.96 1.91 2.71 3.42 5 extra strong 0.375 wall thickness 80 1.04 2.01 2.83 3.54
100 1.12 2.14 3.00 3.75 100 1.19 2.23 3.09 3.85
110 1.19 2.25 3.13 3.90 110 1.26 2.34 3.22 4.00
120 1.26 2.35 3.26 4.05 120 1.32 2.44 3.34 4.14
6 × 6 × 1/4 wall thickness 80 1.14 2.11 2.92 3.63 5 standard 0.258 wall thickness 80 1.20 2.19 3.00 3.72
100 1.29 2.32 3.18 3.93 100 1.34 2.39 3.25 4.00
110 1.36 2.43 3.30 4.08 110 1.41 2.49 3.37 4.14
120 1.42 2.52 3.43 4.22 120 1.47 2.58 3.49 4.28
8 × 8 × 1/2 wall thickness 80 0.77 1.66 2.44 3.13 6 double extra strong 0.864 wall thickness 80 0.59 1.46 2.23 2.92
100 0.92 1.91 2.75 3.49 100 0.73 1.71 2.54 3.29
110 1.00 2.02 2.89 3.66 110 0.80 1.82 2.69 3.47
120 1.07 2.14 3.03 3.82 120 0.86 1.93 2.83 3.63
8 × 8 × 3/8 wall thickness 80 0.91 1.84 2.63 3.33 6 extra strong 0.432 wall thickness 80 0.94 1.90 2.70 3.42
100 1.07 2.08 2.92 3.67 100 1.10 2.13 2.98 3.74
110 1.14 2.19 3.06 3.83 110 1.17 2.23 3.11 3.89
120 1.21 2.29 3.19 3.98 120 1.24 2.34 3.24 4.04
8 × 8 × 1/4 wall thickness 80 1.10 2.06 2.86 3.57 6 standard 0.280 wall thickness 80 1.14 2.12 2.93 3.64
100 1.25 2.28 3.13 3.87 100 1.29 2.33 3.19 3.94
110 1.32 2.38 3.25 4.02 110 1.36 2.43 3.31 4.08
120 1.39 2.48 3.38 4.17 120 1.42 2.53 3.43 4.22

For SI: 1 inch = 25.4 mm, 1 pound per cubic feet = 16.02 kg/m3.
Note: Tabulated values assume 1-inch air gap between masonry and steel section.

TABLE 721.5.1(6) FIRE RESISTANCE OF CLAY MASONRY PROTECTED STEEL COLUMNS

COLUMN SIZE CLAY MASONRY DENSITY, POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CLAY MASONRY PROTECTION ASSEMBLY, Te(inches) COLUMN SIZE CLAY MASONRY DENSITY, POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CLAY MASONRY PROTECTION ASSEMBLY, Te(inches)
1-hour 2-hour 3-hour 4-hour 1-hour 2-hour 3-hour 4-hour
W14 × 82 120 1.23 2.42 3.41 4.29 W10 × 68 120 1.27 2.46 3.26 4.35
130 1.40 2.70 3.78 4.74 130 1.44 2.75 3.83 4.80
W14 × 68 120 1.34 2.54 3.54 4.43 W10 × 54 120 1.40 2.61 3.62 4.51
130 1.51 2.82 3.91 4.87 130 1.58 2.89 3.98 4.95
W14 × 53 120 1.43 2.65 3.65 4.54 W10 × 45 120 1.44 2.66 3.67 4.57
130 1.61 2.93 4.02 4.98 130 1.62 2.95 4.04 5.01
W14 × 43 120 1.54 2.76 3.77 4.66 W10 × 33 120 1.59 2.82 3.84 4.73
130 1.72 3.04 4.13 5.09 130 1.77 3.10 4.20 5.13
W12 × 72 120 1.32 2.52 3.51 4.40 W8 × 40 120 1.47 2.70 3.71 4.61
130 1.50 2.80 3.88 4.84 130 1.65 2.98 4.08 5.04
W12 × 58 120 1.40 2.61 3.61 4.50 W8 × 31 120 1.59 2.82 3.84 4.73
130 1.57 2.89 3.98 4.94 130 1.77 3.10 4.20 5.17
W12 × 50 120 1.43 2.65 3.66 4.55 W8 × 24 120 1.66 2.90 3.92 4.82
130 1.61 2.93 4.02 4.99 130 1.84 3.18 4.28 5.25
W12 × 40 120 1.54 2.77 3.78 4.67 W8 × 18 120 1.75 3.00 4.01 4.91
130 1.72 3.05 4.14 5.10 130 1.93 3.27 4.37 5.34
STEEL TUBING STEEL PIPE
NOMINAL TUBE SIZE (inches) CLAY MASONRY DENSITY, POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CLAY MASONRY PROTECTION ASSEMBLY, Te (inches) NOMINAL PIPE SIZE (inches) CLAY MASONRY DENSITY, POUNDS PER CUBIC FOOT MINIMUM REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CLAY MASONRY PROTECTION ASSEMBLY, Te (inches)
1-hour 2-hour 3-hour 4-hour 1-hour 2-hour 3-hour 4-hour
4 × 4 × 1/2 wall thickness 120 1.44 2.72 3.76 4.68 4 double extra strong 0.674 wall thickness 120 1.26 2.55 3.60 4.52
130 1.62 3.00 4.12 5.11 130 1.42 2.82 3.96 4.95
4 × 4 × 3/8 wall thickness 120 1.56 2.84 3.88 4.78 4 extra strong 0.337 wall thickness 120 1.60 2.89 3.92 4.83
130 1.74 3.12 4.23 5.21 130 1.77 3.16 4.28 5.25
4 × 4 × 1/4 wall thickness 120 1.72 2.99 4.02 4.92 4 standard 0.237 wall thickness 120 1.74 3.02 4.05 4.95
130 1.89 3.26 4.37 5.34 130 1.92 3.29 4.40 5.37
6 × 6 × 1/2 wall thickness 120 1.33 2.58 3.62 4.52 5 double extra strong 0.750 wall thickness 120 1.17 2.44 3.48 4.40
130 1.50 2.86 3.98 4.96 130 1.33 2.72 3.84 4.83
6 × 6 × 3/8 wall thickness 120 1.48 2.74 3.76 4.67 5 extra strong 0.375 wall thickness 120 1.55 2.82 3.85 4.76
130 1.65 3.01 4.13 5.10 130 1.72 3.09 4.21 5.18
6 × 6 × 1/4 wall thickness 120 1.66 2.91 3.94 4.84 5 standard 0.258 wall thickness 120 1.71 2.97 4.00 4.90
130 1.83 3.19 4.30 5.27 130 1.88 3.24 4.35 5.32
8 × 8 × 1/2 wall thickness 120 1.27 2.50 3.52 4.42 6 double extra strong 0.864 wall thickness 120 1.04 2.28 3.32 4.23
130 1.44 2.78 3.89 4.86 130 1.19 2.60 3.68 4.67
8 × 8 × 3/8 wall thickness 120 1.43 2.67 3.69 4.59 6 extra strong 0.432 wall thickness 120 1.45 2.71 3.75 4.65
130 1.60 2.95 4.05 5.02 130 1.62 2.99 4.10 5.08
8 × 8 × 1/4 wall thickness 120 1.62 2.87 3.89 4.78 6 standard 0.280 wall thickness 120 1.65 2.91 3.94 4.84
130 1.79 3.14 4.24 5.21 130 1.82 3.19 4.30 5.27

For SI: 1 inch = 25.4 mm, 1 pound per cubic feet = 16.02 kg/m3.

TABLE 721.5.1(7) MINIMUM COVER (inch) FOR STEEL COLUMNS ENCASED IN NORMAL-WEIGHT CONCRETEa [FIGURE 721.5.1(6)(c)]

STRUCTURAL SHAPE FIRE-RESISTANCE RATING (hours)
1 11/2 2 3 4
W14 × 233 1 1 1 11/2 2
× 176 21/2
× 132 2
× 90 11/2
× 61 3
× 48 11/2 21/2
× 43
W12 × 152 1 1 1 2 21/2
× 96
× 65 11/2 11/2 3
× 50 21/2
× 40
W10 × 88 1 11/2
11/2		 2 3
× 49 1 21/2
× 45
× 39 31/2
× 33 2
W8 × 67 1 1 11/2 21/2 3
× 58
× 48 11/2 31/2
× 31 2 3
× 21
× 18 4
W6 × 25 1 11/2 2 3 31/2
× 20 2 21/2 4
× 16
× 15 11/2
× 9 31/2

For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of normal-weight concrete given in Table 721.5.1(2).

TABLE 721.5.1(8) MINIMUM COVER (inch) FOR STEEL COLUMNS ENCASED IN STRUCTURAL LIGHTWEIGHT CONCRETEa [FIGURE 721.5.1(6)(c)]

STRUCTURAL SHAPE FIRE-RESISTANCE RATING (HOURS)
1 11/2 2 3 4
W14 × 233 1 1 1 1 11/2
× 193 11/2
× 74 2
× 61 21/2
× 43 11/2 2
W12 × 65 1 1 1 11/2 2
× 53 2 21/2
× 40 11/2
W10 × 112 1 1 1 11/2 2
× 88
× 60 2 21/2
× 33 11/2
W8 × 35 1 1 11/2 2 21/2
× 28 3
× 24 21/2
× 18 11/2

For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of structural lightweight concrete given in Table 721.5.1(2).

TABLE 721.5.1(9) MINIMUM COVER (inch) FOR STEEL COLUMNS IN NORMAL-WEIGHT PRECAST COVERSa [FIGURE 721.5.1(6)(a)]

STRUCTURAL SHAPE FIRE-RESISTANCE RATING (HOURS)
1 11/2 2 3 4
W14 × 233 1 1 1 1 11/2
× 193 11/2
× 74 2
× 61 21/2
× 43 11/2 2
W12 × 65 1 1 1 11/2 2
× 53 2 21/2
× 40 11/2
W10 × 112 1 1 1 11/2 2
× 88
× 60 2 21/2
× 33 11/2
W8 × 35 1 1 11/2 2 21/2
× 28 3
× 24 21/2
× 18 11/2

For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of normal-weight concrete given in Table 721.5.1(2).

TABLE 721.5.1(10) MINIMUM COVER (inch) FOR STEEL COLUMNS IN STRUCTURAL LIGHTWEIGHT PRECAST COVERSa [FIGURE 721.5.1(6)(a)]

STRUCTURAL SHAPE FIRE-RESISTANCE RATING (hours)
1 11/2 2 3 4
W14 * 233 11/2 11/2 11/2 2 21/2
× 176 3
× 145 21/2
× 132
× 109
× 99 2
× 68 31/2
× 43 3
W12 ×190 11/2 11/2 11/2 2 21/2
× 152
× 136 3
× 106 21/2
× 96 31/2
× 87
× 65 2
× 40 3
W10 ×112 11/2 11/2 11/2 2 3
×100 21/2
× 88
× 77 2 31/2
× 60
× 39 3
× 33 2
W8 × 67 11/2 11/2 11/2 21/2 3
× 48 2 3 31/2
× 35
× 28 2
× 18 21/2 4
W6 × 25 11/2 2 2 3 31/2
×15 21/2 4
× 9 31/2

For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of structural lightweight concrete given in Table 721.5.1(2).

FIGURE 721.5.1(1) DETERMINATION OF THE HEATED PERIMETER OF STRUCTURAL STEEL COLUMNS

FIGURE 721.5.1(2) GYPSUM WALLBOARD PROTECTED STRUCTURAL STEEL COLUMNS WITH SHEET STEEL COLUMN COVERS

For SI: 1 inch = 25.4 mm, 1 foot = 305 mm, 1 inch per linear foot = 83.3 mm/linear meter.
1. Structural steel column, either wide flange or tubular shapes.
2. Type X gypsum wallboard in accordance with ASTM C 36. For single-layer applications, the wallboard shall be applied vertically with no horizontal joints. For multiple-layer applications, horizontal joints are permitted at a minimum spacing of 8 feet, provided that the joints in successive layers are staggered at least 12 inches. The total required thickness of wallboard shall be determined on the basis of the specified fire-resistance rating and the weight-to-heated-perimeter ratio (W/D) of the column. For fire-resistance ratings of 2 hours or less, one of the required layers of gypsum wallboard may be applied to the exterior of the sheet steel column covers with 1-inch- long Type S screws spaced 1 inch from the wallboard edge and 8 inches on center. For such installations, 0.0149-inch minimum thickness galvanized steel corner beads with 11/2-inch legs shall be attached to the wallboard with Type S screws spaced 12 inches on center.
3. For fire-resistance ratings of 3 hours or less, the column covers shall be fabricated from 0.0239-inch minimum thickness galvanized or stainless steel. For 4-hour fire-resistance ratings, the column covers shall be fabricated from 0.0239-inch minimum thickness stainless steel. The column covers shall be erected with the Snap Lock or Pittsburgh joint details.
For fire-resistance ratings of 2 hours or less, column covers fabricated from 0.0269-inch minimum thickness galvanized or stainless steel shall be permitted to be erected with lap joints. The lap joints shall be permitted to be located anywhere around the perimeter of the column cover. The lap joints shall be secured with 1/2-inch-long No. 8 sheet metal screws spaced 12 inches on center.
The column covers shall be provided with a minimum expansion clearance of 1/8 inch per linear foot between the ends of the cover and any restraining construction.

FIGURE 721.5.1(3) GYPSUM WALLBOARD PROTECTED STRUCTURAL STEEL COLUMNS WITH STEEL STUD/SCREW ATTACHMENT SYSTEM

For SI: 1 inch = 25.4 mm, 1 foot = -305 mm.
1. Structural steel column, either wide flange or tubular shapes.
2. 15/8-inch deep studs fabricated from 0.0179-inch minimum thickness galvanized steel with 15/16 or 17/16-inch legs. The length of the steel studs shall be 1/2 inch less than the height of the assembly.
3. Type X gypsum wallboard in accordance with ASTM C 36. For single-layer applications, the wallboard shall be applied vertically with no horizontal joints. For multiple-layer applications, horizontal joints are permitted at a minimum spacing of 8 feet, provided that the joints in successive layers are staggered at least 12 inches. The total required thickness of wallboard shall be determined on the basis of the specified fire-resistance rating and the weight-to-heated-perimeter ratio (W/D) of the column.
4. Galvanized 0.0149-inch minimum thickness steel corner beads with 11/2-inch legs attached to the wallboard with 1-inch-long Type S screws spaced 12 inches on center.
5. No. 18 SWG steel tie wires spaced 24 inches on center.
6. Sheet metal angles with 2-inch legs fabricated from 0.0221-inch minimum thickness galvanized steel.
7. Type S screws, 1 inch long, shall be used for attaching the first layer of wallboard to the steel studs and the third layer to the sheet metal angles at 24 inches on center. Type S screws 13/4-inch long shall be used for attaching the second layer of wallboard to the steel studs and the fourth layer to the sheet metal angles at 12 inches on center. Type S screws 21/4 inches long shall be used for attaching the third layer of wallboard to the steel studs at 12 inches on center.

For SI: 1 inch = 25.4 mm, 1 pound per linear foot/inch = 0.059 kg/m/mm.
FIGURE 721.5.1(4) FIRE RESISTANCE OF STRUCTURAL STEEL COLUMNS PROTECTED WITH VARIOUS THICKNESSES OF TYPE X GYPSUM WALLBOARD

a. The W/D ratios for typical wide flange columns are listed in Table 721.5.1(1). For other column shapes, the W/D ratios shall be determined in accordance with Section 720.5.1.1.

FIGURE 721.5.1(5) WIDE FLANGE STRUCTURAL STEEL COLUMNS WITH SPRAYED FIRE-RESISTANT MATERIALS

FIGURE 721.5.1(6) CONCRETE PROTECTED STRUCTURAL STEEL COLUMNSa,b

a. When the inside perimeter of the concrete protection is not square, L shall be taken as the average of L1 and L2. When the thickness of concrete cover is not constant, h shall be taken as the average of h1 and h2.
b. Joints shall be protected with a minimum 1 inch thickness of ceramic fiber blanket but in no case less than one-half the thickness of the column cover (see Section 720.2.1.3).

For SI: 1 inch = 25.4 mm.

FIGURE 721.5.1(7) CONCRETE OR CLAY MASONRY PROTECTED STRUCTURAL STEEL COLUMNS

d = Depth of a wide flange column, outside diameter of pipe column, or out- side dimension of structural tubing column (inches).
tweb = Thickness of web of wide flange column (inches).
w = Width of flange of wide flange column (inches).
721.5.1.1 General. These procedures establish a basis for determining the fire resistance of column assemblies as a function of the thickness of fire-resistant material and, the weight, W, and heated perimeter, D, of steel columns. As used in these sections, W is the average weight of a structural steel column in pounds per linear foot. The heated perimeter, D, is the inside perimeter of the fire-resistant material in inches as illustrated in Figure 721.5.1(1).
721.5.1.1.1 Nonload-bearing protection. The application of these procedures shall be limited to column assemblies in which the fire-resistant material is not designed to carry any of the load acting on the column.

721.5.1.1.2 Embedments. In the absence of substantiating fire-endurance test results, ducts, conduit, piping, and similar mechanical, electrical, and plumbing installations shall not be embedded in any required fire-resistant materials.

721.5.1.1.3 Weight-to-perimeter ratio. Table 721.5.1(1) contains weight-to-heated-perimeter ratios (W/D) for both contour and box fire-resistant profiles, for the wide flange shapes most often used as columns. For different fire-resistant protection profiles or column cross sections, the weight-to-heated-perimeter ratios (W/D) shall be determined in accordance with the definitions given in this section.

721.5.1.2 Gypsum wallboard protection. The fire resistance of structural steel columns with weight- to-heated-perimeter ratios (W/D) less than or equal to 3.65 and which are protected with Type X gypsum wallboard shall be permitted to be determined from the following expression:

Click to view image (Equation 7-12)

where:

R = Fire resistance (minutes).

h = Total thickness of gypsum wallboard (inches).

D = Heated perimeter of the structural steel column (inches).

W ' = Total weight of the structural steel column and gypsum wallboard protection (pounds per linear foot).

W '= W + 50hD/144.

721.5.1.2.1 Attachment. The gypsum wallboard shall be supported as illustrated in either Figure 721.5.1(2) for fire-resistance ratings of 4 hours or less, or Figure 721.5.1(3) for fire-resistance ratings of 3 hours or less.

721.5.1.2.2 Gypsum wallboard equivalent to concrete. The determination of the fire resistance of structural steel columns from Figure 721.5.1(4) is permitted for various thicknesses of gypsum wallboard as a function of the weight-to-heated-perimeter ratio (W/D) of the column. For structural steel columns with weight- to-heated-perimeter ratios (W/D) greater than 3.65, the thickness of gypsum wallboard required for specified fire-resistance ratings shall be the same as the thickness determined for a W14 * 233 wide flange shape.

721.5.1.3 Sprayed fire-resistant materials. The fire resistance of wide-flange structural steel columns protected with sprayed fire-resistant materials, as illustrated in Figure 721.5.1(5), shall be permitted to be determined from the following expression:

Click to view image (Equation 7-13)

where:

R = Fire resistance (minutes).

h = Thickness of sprayed fire-resistant material (inches).

D = Heated perimeter of the structural steel column (inches).

C 1 and C 2 = 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.

721.5.1.3.1 Material-dependent constants. The material-dependent constants, C 1 and C 2, 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.

721.5.1.3.2 Identification. Sprayed fire-resistant materials shall be identified by density and thickness required for a given fire-resistance rating.

721.5.1.4 Concrete-protected columns. The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 721.5.1(6) (a) and (b), shall be permitted to be determined from the following expression:

R = Ro (1 + 0.03m) (Equation 7-14)

where:

Ro = 10 (W/D) 0.7 + 17 (h1.6/kc0.2) * [ 1 + 26 {H/pccch (L + h)}0.8]

As used in these expressions:

R = Fire endurance at equilibrium moisture conditions (minutes).

Ro = 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).

kc = 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).

pc = Concrete density (pounds per cubic foot).

cc = Ambient temperature specific heat of concrete (Btu/lb °F).

L = Interior dimension of one side of a square concrete box protection (inches).

721.5.1.4.1 Reentrant space filled. For wide-flange steel columns completely encased in concrete with all reentrant spaces filled [Figure 721.5.1(6)(c)], the thermal capacity of the concrete within the reentrant spaces shall be permitted to be added to the thermal capacity of the steel column, as follows:

H = 0.11W + (pccc/144) (bfd -As) (Equation 7-15)

where:

bf = Flange width of the steel column (inches).

d = Depth of the steel column (inches).

As = Cross-sectional area of the steel column (square inches).

721.5.1.4.2 Concrete properties unknown. If specific data on the properties of concrete are not available, the values given in Table 721.5.1(2) are permitted.

721.5.1.4.3 Minimum concrete cover. For structural steel column encased in concrete with all reentrant spaces filled, Figure 721.5.1(6)(c) and Tables 721.5.1(7) and 721.5.1(8) indicate the thickness of concrete cover required for various fire-resistance ratings for typical wide-flange sections. The thicknesses of concrete indicated in these tables also apply to structural steel columns larger than those listed.

721.5.1.4.4 Minimum precast concrete cover. For structural steel columns protected with precast concrete column covers as shown in Figure 721.5.1(6)(a), Tables 721.5.1(9) and 721.5.1(10) indicate the thickness of the column covers required for various fire-resistance ratings for typical wide-flange shapes. The thicknesses of concrete given in these tables also apply to structural steel columns larger than those listed.

721.5.1.4.5 Masonry protection. The fire resistance of structural steel columns protected with concrete masonry units or clay masonry units as illustrated in Figure 721.5.1(7), shall be permitted to be determined from the following expression:

R = 0.17 (W/D)0.7 + [0.285 (Te1.6/K 0.2)] [1.0 + 42.7 {(As/dm Te)/(0.25p + Te)}0.8](Equation 7-16)

where:

R = Fire-resistance rating of column assembly (hours).

W = Average weight of steel column (pounds per foot).

D = Heated perimeter of steel column (inches) [see Figure 721.5.1(7)].

Te = Equivalent thickness of concrete or clay masonry unit (inches) (see Table 721.3.2 Note a or Section 721.4.1).

K = Thermal conductivity of concrete or clay masonry unit (Btu/hr · ft · °F) [see Table 721.5.1(3)].

As = Cross-sectional area of steel column (square inches).

dm = Density of the concrete or clay masonry unit (pounds per cubic foot).

p = Inner perimeter of concrete or clay masonry protection (inches) [see Figure 721.5.1(7)].

721.5.1.4.6 Equivalent concrete masonry thickness. For structural steel columns protected with concrete masonry, Table 721.5.1(5) gives the equivalent thickness of concrete masonry required for various fire-resistance ratings for typical column shapes. For structural steel columns protected with clay masonry, Table 721.5.1(6) gives the equivalent thickness of concrete masonry required for various fire-resistance ratings for typical column shapes.

721.5.2 Structural steel beams and girders. The fire-resistance ratings of steel beams and girders shall be based upon the size of the element and the type of protection provided in accordance with this section.

FIGURE 721.5.2 DETERMINATION OF THE HEATED PERIMETER OF STRUCTURAL STEEL BEAMS AND GIRDERS

721.5.2.1 Determination of fire resistance. These procedures establish a basis for determining resistance of structural steel beams and girders which differ in size from that specified in approved fire-resistance-rated assemblies as a function of the thickness of fire-resistant material and the weight (W) and heated perimeter (D) of the beam or girder. As used in these sections, W is the average weight of a structural steel member in pounds per linear foot (plf). The heated perimeter, D, is the inside perimeter of the fire-resistant material in inches as illustrated in Figure 721.5.2.
721.5.2.1.1 Weight-to-heated perimeter. The weight-to-heated-perimeter ratios (W/D), for both contour and box fire-resistant protection profiles, for the wide flange shapes most often used as beams or girders are given in Table 721.5.1(4). For different shapes, the weight-to-heated-perimeter ratios (W/D) shall be determined in accordance with the definitions given in this section.

721.5.2.1.2 Beam and girder substitutions. Except as provided for in Section 721.5.2.2, structural steel beams in approved fire-resistance-rated assemblies shall be considered the minimum permissible size. Other beam or girder shapes shall be permitted to be substituted provided that the weight-to-heated-perimeter ratio (W/D) of the substitute beam is equal to or greater than that of the beam specified in the approved assembly.

721.5.2.2 Sprayed fire-resistant materials. The provisions in this section apply to structural steel beams and girders protected with sprayed fire-resistant materials. Larger or smaller beam and girder shapes shall be permitted to be substituted for beams specified in approved unrestrained or restrained fire-resistance-rated assemblies, provided that the thickness of the fire-resistant material is adjusted in accordance with the following expression:

Click to view image (Equation 7-17)

where:

h = Thickness of sprayed fire-resistant material in inches.

W = Weight of the structural steel beam or girder in pounds per linear foot.

D = Heated perimeter of the structural steel beam in inches.

Subscript 1 refers to the beam and fire-resistant material thickness in the approved assembly.

Subscript 2 refers to the substitute beam or girder and the required thickness of fire-resistant material.

The fire resistance of structural steel beams and girders protected with intumescent or mastic fire-resistant coatings shall be determined on the basis of fire-resistance tests in accordance with Section 703.2.

721.5.2.2.1 Minimum thickness. The use of Equation 7-17 is subject to the following conditions:
1. The weight-to-heated-perimeter ratio for the substitute beam or girder (W2/D2) shall not be less than 0.37.

2. The thickness of fire protection materials calculated for the substitute beam or girder (T1) shall not be less than 3/8 inch (9.5 mm).

3. The unrestrained or restrained beam rating shall not be less than 1 hour.

4. When used to adjust the material thickness for a restrained beam, the use of this procedure is limited to steel sections classified as compact in accordance with the AISC Specification for Structural Steel Buildings, (AISC 360-05).

721.5.2.3 Structural steel trusses. The fire resistance of structural steel trusses protected with fire-resistant materials sprayed to each of the individual truss elements shall be permitted to be determined in accordance with this section. The thickness of the fire-resistant material shall be determined in accordance with Section 721.5.1.3. The weight-to-heated-perimeter ratio (W/D) of truss elements that can be simultaneously exposed to fire on all sides shall be determined on the same basis as columns, as specified in Section 721.5.1.1. The weight- to-heated-perimeter ratio (W/D) of truss elements that directly support floor or roof assembly shall be determined on the same basis as beams and girders, as specified in Section 721.5.2.1.

The fire resistance of structural steel trusses protected with intumescent or mastic fire-resistant coatings shall be determined on the basis of fire-resistance tests in accordance with Section 703.2.

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