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

Current through Register 1525, July 5, 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
							 (
d
m) 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,
T
e(inches)
COLUMN SIZE
CONCRETE MASONRY DENSITY
							 POUNDS PER
CUBIC FOOT
MINIMUM
							 REQUIRED EQUIVALENT THICKNESS FOR FIRE-RESISTANCE RATING OF CONCRETE MASONRY
							 PROTECTION ASSEMBLY,
T
e(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,
T
e(inches)
COLUMN SIZE
CLAY MASONRY DENSITY, POUNDS PER CUBIC
							 FOOT
MINIMUM REQUIRED EQUIVALENT
							 THICKNESS FOR FIRE-RESISTANCE RATING OF CLAY MASONRY PROTECTION ASSEMBLY,
T
e(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,
T
e (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,
T
e (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).
Click to view
							 image
FIGURE 721.5.1(1) DETERMINATION OF THE HEATED PERIMETER
				  OF STRUCTURAL STEEL COLUMNS
Click to view
							 image
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.
Click to view
							 image
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.
Click to view
							 image
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.
Click to view
							 image
FIGURE 721.5.1(5) WIDE FLANGE STRUCTURAL STEEL COLUMNS
				  WITH SPRAYED FIRE-RESISTANT MATERIALS
Click to view
							 image
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
L
1 and
L
2. When the thickness of concrete
							 cover is not constant,
h
shall be taken as the average of
h
1 and
h
2.
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).
Click to view
							 image
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).
t
web =
							 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.