GroundRules
N.Y.C. Admin. Code § BC 722: Section BC 722: Calculated Fire Resistance
Where this section sits in the code
- New York City Administrative Code
- Title 28
- Chapter 7: New York City Building Code
722.1 General.
The provisions of this section contain procedures by which the fire resistance of specific materials or combinations of materials is established by calculations. These procedures apply only to the information contained in this section and shall not be otherwise used. The calculated fire resistance of concrete, concrete masonry and clay masonry assemblies shall be permitted in accordance with ACI 216.1/TMS 216. The calculated fire resistance of steel assemblies shall be permitted in accordance with Chapter 5 of ASCE 29. The calculated fire resistance of exposed wood members and wood decking shall be permitted in accordance with Chapter 16 of ANSI/AWC National Design Specification for Wood Construction (NDS).
722.1.1 Definitions.
The following terms are defined in Chapter 2 of this code:
CERAMIC FIBER BLANKET.
CONCRETE, CARBONATE AGGREGATE.
CONCRETE, CELLULAR.
CONCRETE, LIGHTWEIGHT AGGREGATE.
CONCRETE, PERLITE.
CONCRETE, SAND-LIGHTWEIGHT.
CONCRETE, SILICEOUS AGGREGATE.
CONCRETE, VERMICULITE.
GLASS FIBERBOARD.
MINERAL BOARD.
722.2 Concrete assemblies.
The provisions of this section contain procedures by which the fire-resistance ratings of concrete assemblies are established by calculations.
722.2.1 Concrete walls.
Cast-in-place and precast concrete walls shall comply with Section 722.2.1.1. Multi-wythe concrete walls shall comply with Section 722.2.1.2. Joints between precast panels shall comply with Section 722.2.1.3. Concrete walls with gypsum wallboard or plaster finish shall comply with Section 722.2.1.4.
722.2.1.1 Cast-in-place or precast walls.
The minimum equivalent thicknesses of cast-in-place or precast concrete walls for fire-resistance ratings of 1 hour to 4 hours are shown in Table 722.2.1.1. For solid walls with flat vertical surfaces, the equivalent thickness is the same as the actual thickness. The values in Table 722.2.1.1 apply to plain, reinforced or prestressed concrete walls.
Table 722.2.1.1 Minimum Equivalent Thickness of Cast-In-Place or Precast Concrete Walls, Load-Bearing or Nonload-Bearing
Concrete Type
Minimum Slab Thickness (inches) for Fire-Resistance Rating of
1 hour
1 1/2 hours
2 hours
3 hours
4 hours
Siliceous
3.5
4.3
5.0
6.2
7.0
Carbonate
3.2
4.0
4.6
5.7
6.6
Sand- lightweight
2.7
3.3
3.8
4.6
5.4
Lightweight
2.5
3.1
3.6
4.4
5.1
For SI: 1 inch = 25.4 mm.
722.2.1.1.1 Hollow-core precast wall panels.
For hollow-core precast concrete wall panels in which the cores are of constant cross section throughout the length, calculation of the equivalent thickness by dividing the net cross-sectional area (the gross cross section minus the area of the cores) of the panel by its width shall be permitted.
722.2.1.1.2 Core spaces filled.
Where all of the core spaces of hollow-core wall panels are filled with loose-fill material, such as expanded shale, clay or slag, or vermiculite or perlite, the fire-resistance rating of the wall is the same as that of a solid wall of the same concrete type and of the same overall thickness.
722.2.1.1.3 Tapered cross sections.
The thickness of panels with tapered cross sections shall be that determined at a distance 2t or 6 inches (152.4 mm), whichever is less, from the point of minimum thickness, where t is the minimum thickness.
722.2.1.1.4 Ribbed or undulating surfaces.
The equivalent thickness of panels with ribbed or undulating surfaces shall be determined by one of the following expressions:
For s ³ 4t, the thickness to be used shall be t
For s £ 2t, the thickness to be used shall be t
e
For 4t > s > 2t, the thickness to be used shall be
(Equation 7-3)
where:
s = Spacing of ribs or undulations.
t = Minimum thickness.
t
e
= Equivalent thickness of the panel calculated as the net cross-sectional area of the panel divided by the width, in which the maximum thickness used in the calculation shall not exceed 2t.
722.2.1.2 Multi-wythe walls.
For walls that consist of two wythes of different types of concrete, the fire-resistance ratings shall be permitted to be determined from Figure 722.2.1.2.
For SI: 1 inch = 25.4 mm.
Figure 722.2.1.2 Fire-resistance Ratings of Two-wythe Concrete Walls
722.2.1.2.1 Two or more wythes.
The fire-resistance rating for wall panels consisting of two or more wythes shall be permitted to be determined by the formula:
R = (R
1
0.59
+ R
2
0.59
+ . . . + R
n
0.59
)1.7
(Equation 7-4)
where:
R = The fire endurance of the assembly, minutes.
R
1
, R
2
, and R
n
= The fire endurances of the individual wythes, minutes. Values of R
n
0.59
for use in Equation 7-4 are given in Table 722.2.1.2(1). Calculated fire-resistance ratings are shown in Table 722.2.1.2(2).
Table 722.2.1.2(1) Values of R
n
0.59
for Use in Equation 7-4
Type of Material
Thickness of Material (inches)
1 1/2
2
2 1/2
3
3 1/2
4
4 1/2
5
5 1/2
6
6 1/2
7
Siliceous aggregate concrete
5.3
6.5
8.1
9.5
11.3
13.0
14.9
16.9
18.8
20.7
22.8
25.1
Carbonate aggregate concrete
5.5
7.1
8.9
10.4
12.0
14.0
16.2
18.1
20.3
21.9
24.7
27.2
c
Sand-lightweight concrete
6.5
8.2
10.5
12.8
15.5
18.1
20.7
23.3
26.0
c
Note c
Note c
Note c
Lightweight concrete
6.6
8.8
11.2
13.7
16.5
19.1
21.9
24.7
27.8
c
Note c
Note c
Note c
Insulating concrete
a
9.3
13.3
16.6
18.3
23.1
26.5
c
Note c
Note c
Note c
Note c
Note c
Note c
Airspace
b
–
–
–
–
–
–
–
–
–
–
–
–
For SI: 1 inch = 25.4 mm, 1 pound per cubic foot = 16.02 kg/m
3
.
a. Dry unit weight of 35 pcf or less and consisting of cellular, perlite or vermiculite concrete.
b. The R
n
0.59
value for one 1/2" to 3 1/2" airspace is 3.3. The R
n
0.59
value for two 1/2" to 3 1/2" airspaces is 6.7.
c. The fire-resistance rating for this thickness exceeds 4 hours.
Table 722.2.1.2(2) Fire-resistance Ratings Based on R
0.59
R
a
, Minutes
R
0.59
60 120 180 240
11.20 16.85 21.41 25.37
a. Based on Equation 7-4.
722.2.1.2.2 Foam plastic insulation.
The fire-resistance ratings of precast concrete wall panels consisting of a layer of foam plastic insulation sandwiched between two wythes of concrete shall be permitted to be determined by use of Equation 7-4. Foam plastic insulation with a total thickness of less than 1 inch (25.4 mm) shall be disregarded. The R
n
value for thickness of foam plastic insulation of 1 inch (25.4 mm) or greater, for use in the calculation, is 5 minutes; therefore R
n
0.59
= 2.5.
722.2.1.3 Joints between precast wall panels.
Joints between precast concrete wall panels that are not insulated as required by this section shall be considered as openings in walls. Uninsulated joints shall be included in determining the percentage of openings permitted by Table 705.8. Where openings are not permitted or are required by this code to be protected, the provisions of this section shall be used to determine the amount of joint insulation required. Insulated joints shall not be considered openings for purposes of determining compliance with the allowable percentage of openings in Table 705.8.
722.2.1.3.1 Ceramic fiber joint protection.
Figure 722.2.1.3.1 shows thicknesses of ceramic fiber blankets to be used to insulate joints between precast concrete wall panels for various panel thicknesses and for joint widths of 3/8 inch (9.5 mm) and 1 inch (25.4 mm) for fire-resistance ratings of 1 hour to 4 hours. For joint widths between 3/8 inch (9.5 mm) and 1 inch (25.4 mm), the thickness of ceramic fiber blanket is allowed to be determined by direct interpolation. Other tested and labeled materials are acceptable in place of ceramic fiber blankets.
For SI: 1 inch = 25.4 mm.
Figure 722.2.1.3.1 Ceramic Fiber Joint Protection
722.2.1.4 Walls with gypsum wallboard or plaster finishes.
The fire-resistance rating of cast-in-place or precast concrete walls with finishes of gypsum wallboard or plaster applied to one or both sides shall be permitted to be calculated in accordance with the provisions of this section.
Table 722.2.1.4(1) Multiplying Factor for Finishes on Nonfire-Exposed Side of Wall
Type of Finish Applied to Concrete or Concrete Masonry Wall
Type of Aggregate Used in Concrete or Concrete Masonry
Concrete: siliceous or carbonate Concrete Masonry: siliceous or carbonate; solid clay brick
Concrete: sand- lightweight Concrete Masonry: clay tile; hollow clay brick; concrete masonry units of expanded shale and <20% sand
Concrete: lightweight Concrete Masonry: concrete masonry units of expanded shale, expanded clay, expanded slag, or pumice < 20% sand
Concrete Masonry: concrete masonry units of expanded slag, expanded clay, or pumice
Portland cement-sand plaster
1.00
0.75
a
0.75
a
0.50
a
Gypsum-sand plaster
1.25
1.00
1.00
1.00
Gypsum-vermiculite or perlite plaster
1.75
1.50
1.25
1.25
Gypsum wallboard
3.00
2.25
2.25
2.25
For SI: 1 inch = 25.4 mm.
a. For Portland cement-sand plaster 5/8 inch or less in thickness and applied directly to the masonry on the nonfire-exposed side of the wall, the multiplying factor shall be 1.00.
Table 722.2.1.4(2) Time Assigned to Finish Materials on Fire-Exposed Side of Wall
Finish Description
Time (minute)
Gypsum wallbound
3/8 inch
10
1/2 inch
15
5/8 inch
20
2 layers of 3/8 inch
25
1 layer of 3/8 inch, 1 layer of 1/2 inch
35
2 layers of 1/2 inch
40
Type X gypsum wallboard
1/2 inch
25
5/8 inch
40
Portland cement-sand plaster applied directly to concrete masonry
See Note a
Portland cement-sand plaster on metal lath
3/4 inch
20
7/8 inch
25
1 inch
30
Gypsum sand laster on 3/8-inch gypsum lath
1/2 inch
35
5/8 inch
40
3/4 inch
50
Gypsum sand plaster on metal lath
3/4 inch
50
7/8 inch
60
1 inch
80
For SI: 1 inch = 25.4 mm.
a. The actual thickness of portland cement-sand plaster, provided it is 5/8 inch or less in thickness, shall be permitted to be included in determining the equivalent thickness of the masonry for use in Table 722.3.2.
722.2.1.4.1 Nonfire-exposed side.
Where the finish of gypsum wallboard or plaster is applied to the side of the wall not exposed to fire, the contribution of the finish to the total fire-resistance rating shall be determined as follows: The thickness of the finish shall first be corrected by multiplying the actual thickness of the finish by the applicable factor determined from Table 722.2.1.4(1) based on the type of aggregate in the concrete. The corrected thickness of finish shall then be added to the actual or equivalent thickness of concrete and fire-resistance rating of the concrete and finish determined from Tables 722.2.1.1 and 722.2.1.2(1), and Figure 722.2.1.2.
722.2.1.4.2 Fire-exposed side.
Where gypsum wallboard or plaster is applied to the fire-exposed side of the wall, the contribution of the finish to the total fire-resistance rating shall be determined as follows: The time assigned to the finish as established by Table 722.2.1.4(2) shall be added to the fire-resistance rating determined from Tables 722.2.1.1 and 722.2.1.2(1) and Figure 722.2.1.2 for the concrete alone, or to the rating determined in Section 722.2.1.4.1 for the concrete and finish on the nonfire-exposed side.
722.2.1.4.3 Nonsymmetrical assemblies.
For a wall having no finish on one side or different types or thicknesses of finish on each side, the calculation procedures of Sections 722.2.1.4.1 and 722.2.1.4.2 shall be performed twice, assuming either side of the wall to be the fire-exposed side. The fire-resistance rating of the wall shall not exceed the lower of the two values.
Exception: For an exterior wall with a fire separation distance greater than 5 feet (1524 mm), the fire shall be assumed to occur on the interior side only.
722.2.1.4.4 Minimum concrete fire-resistance rating.
Where finishes applied to one or both sides of a concrete wall contribute to the fire-resistance rating, the concrete alone shall provide not less than one-half of the total required fire-resistance rating. Additionally, the contribution to the fire resistance of the finish on the nonfire-exposed side of a load-bearing wall shall not exceed one-half the contribution of the concrete alone.
722.2.1.4.5 Concrete finishes.
Finishes on concrete walls that are assumed to contribute to the total fire-resistance rating of the wall shall comply with the installation requirements of Section 722.3.2.5.
722.2.2 Concrete floor and roof slabs.
Reinforced and prestressed floors and roofs shall comply with Section 722.2.2.1. Multicourse floors and roofs shall comply with Sections 722.2.2.2 and 722.2.2.3, respectively.
722.2.2.1 Reinforced and prestressed floors and roofs.
The minimum thicknesses of reinforced and prestressed concrete floor or roof slabs for fire-resistance ratings of 1 hour to 4 hours are shown in Table 722.2.2.1.
Exception: Minimum thickness shall not be required for floors and ramps within open and enclosed parking garages constructed in accordance with Section 406.
Table 722.2.2.1 Minimum Slab Thickness (inches)
Concrete Type
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
Siliceous
3.5
4.3
5
6.2
7
Carbonate
3.2
4
4.6
5.7
6.6
Sand- Lightweight
2.7
3.3
3.8
4.6
5.4
Lightweight
2.5
3.1
3.6
4.4
5.1
For SI: 1 inch = 25.4 mm.
722.2.2.1.1 Hollow-core prestressed slabs.
For hollow-core prestressed concrete slabs in which the cores are of constant cross section throughout the length, the equivalent thickness shall be permitted to be obtained by dividing the net cross-sectional area of the slab including grout in the joints, by its width.
722.2.2.1.2 Slabs with sloping soffits.
The thickness of slabs with sloping soffits (see Figure 722.2.2.1.2) shall be determined at a distance 2t or 6 inches (152.4 mm), whichever is less, from the point of minimum thickness, where t is the minimum thickness.
For SI: 1 inch = 25.4 mm.
Figure 722.2.2.1.2 Determination of Slab Thickness For Sloping Soffits
722.2.2.1.3 Slabs with ribbed soffits.
The thickness of slabs with ribbed or undulating soffits (see Figure 722.2.2.1.3) shall be determined by one of the following expressions, whichever is applicable:
For s ³ 4t, the thickness to be used shall be t
For s £ 2t, the thickness to be used shall be t
e
For 4t > s > 2t, the thickness to be used shall be
(Equation 7-5)
where:
s = Spacing of ribs or undulations.
t = Minimum thickness.
t
e
= Equivalent thickness of the slab calculated as the net area of the slab divided by the width, in which the maximum thickness used in the calculation shall not exceed 2t.
For SI: 1 inch = 25.4 mm.
Figure 722.2.2.1.3 Slabs with Ribbed or Undulating Soffits
722.2.2.2 Multicourse floors.
The fire-resistance ratings of floors that consist of a base slab of concrete with a topping (overlay) of a different type of concrete shall comply with Figure 722.2.2.2.
For SI: 1 inch = 25.4 mm.
Figure 722.2.2.2 Fire-Resistance Ratings for Two-Course Concrete Floors
722.2.2.3 Multicourse roofs.
The fire-resistance ratings of roofs that consist of a base slab of concrete with a topping (overlay) of an insulating concrete or with an insulating board and built-up roofing shall comply with Figures 722.2.2.3(1) and 722.2.2.3(2).
For SI: 1 inch = 25.4 mm.
Figure 722.2.2.3(1) Fire-resistance Ratings for Concrete Roof Assemblies
For SI: 1 inch = 25.4 mm.
Figure 722.2.2.3(2) Fire-Resistance Ratings for Concrete Roof Assemblies
722.2.2.3.1 Heat transfer.
For the transfer of heat, three-ply built-up roofing contributes 10 minutes to the fire-resistance rating. The fire-resistance rating for concrete assemblies such as those shown in Figure 722.2.2.3(1) shall be increased by 10 minutes. This increase is not applicable to those shown in Figure 722.2.2.3(2).
722.2.2.4 Joints in precast slabs.
Joints between adjacent precast concrete slabs need not be considered in calculating the slab thickness provided that a concrete topping not less than 1 inch (25.4 mm) thick is used. Where no concrete topping is used, joints must be grouted to a depth of not less than one-third the slab thickness at the joint, but not less than 1 inch (25.4 mm), or the joints must be made fire resistant by other approved methods.
722.2.3 Concrete cover over reinforcement.
The minimum thickness of concrete cover over reinforcement in concrete slabs, reinforced beams and prestressed beams shall comply with this section.
Table 722.2.3(1) Cover Thickness for Reinforced Concrete Floor or Roof Slabs (inches)
Concrete Aggregate Type
Fire-Resistance Rating (hours)
Restrained
Unrestrained
1
1 1/2
2
3
4
1
1 1/2
2
3
4
Siliceous
3/4
3/4
3/4
3/4
3/4
3/4
3/4
1
1 1/4
1 5/8
Carbonate
3/4
3/4
3/4
3/4
3/4
3/4
3/4
3/4
1 1/4
1 1/4
Sand-lightweight or lightweight
3/4
3/4
3/4
3/4
3/4
3/4
3/4
3/4
1 1/4
1 1/4
For SI: 1 inch = 25.4 mm.
Table 722.2.3(2) Cover Thickness for Prestressed Concrete Floor or Roof Slabs (inches)
Concrete Aggregate Type
Fire-Resistance Rating (hours)
Restrained
Unrestrained
1
1 1/2
2
3
4
1
1 1/2
2
3
4
Siliceous
3/4
3/4
3/4
3/4
3/4
1 1/8
1 1/2
1 3/4
2 3/8
2 3/4
Carbonate
3/4
3/4
3/4
3/4
3/4
1
1 3/8
1 5/8
2 1/8
2 1/4
Sand-lightweight or lightweight
3/4
3/4
3/4
3/4
3/4
1
1 3/8
1 1/2
2
2 1/4
For SI: 1 inch = 25.4 mm.
Table 722.2.3(3) Minimum Cover for Main Reinforcing Bars of Reinforced Concrete Beams
c
(Applicable to All Types of Structural Concrete)
Restrained or Unrestrained
a
Beam Width
b
(inches)
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
Restrained
5
3/4
3/4
3/4
1
a
1 1/4
a
7
3/4
3/4
3/4
3/4
3/4
³10
3/4
3/4
3/4
3/4
3/4
Unrestrained
5
3/4
1
1 1/4
—
—
7
3/4
3/4
3/4
1 3/4
3
³10
3/4
3/4
3/4
1
1 3/4
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Tabulated values for restrained assemblies apply to beams spaced more than 4 feet on center. For restrained beams spaced 4 feet or less on center, minimum cover of 3/4 inch is adequate for ratings of 4 hours or less.
b. For beam widths between the tabulated values, the minimum cover thickness can be determined by direct interpolation.
c. The cover for an individual reinforcing bar is the minimum thickness of concrete between the surface of the bar and the fire-exposed surface of the beam. For beams in which several bars are used, the cover for corner bars used in the calculation shall be reduced to one-half of the actual value. The cover for an individual bar must be not less than one-half of the value given in Table 722.2.3(3) nor less than 3/4 inch.
Table 722.2.3(4) Minimum Cover for Prestressed Concrete Beams 8 Inches or Greater in Width
Restrained or Unrestrained
a
Concrete Aggregate Type
Beam Width
b
(inches)
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
Restrained
Carbonate or siliceous
8
1 1/2
1 1/2
1 1/2
1 3/4
a
2 1/2
a
Carbonate or siliceous
³12
1 1/2
1 1/2
1 1/2
1 1/2
1 7/8
a
Sand-lightweight
8
1 1/2
1 1/2
1 1/2
1 1/2
2
a
Sand-lightweight
³12
1 1/2
1 1/2
1 1/2
1 1/2
1 5/8
a
Unrestrained
Carbonate or siliceous
8
1 1/2
1 3/4
2 1/2
5
c
—
Carbonate or siliceous
³12
1 1/2
1 1/2
1 7/8
a
2 1/2
3
Sand-lightweight
8
1 1/2
1 1/2
2
3 1/4
—
Sand-lightweight
³12
1 1/2
1 1/2
1 5/8
2
2 1/2
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Tabulated values for restrained assemblies apply to beams spaced more than 4 feet on center. For restrained beams spaced 4 feet or less on center, minimum cover of 3/4 inch is adequate for 4-hour ratings or less.
b. For beam widths between 8 inches and 12 inches, minimum cover thickness can be determined by direct interpolation.
c. Not practical for 8-inch-wide beam but shown for purposes of interpolation.
Table 722.2.3(5) Minimum Cover for Prestressed Concrete Beams of All Widths
Restrained or Unrestrained
a
Concrete Aggregate Type
Beam Area
b
A (square inches)
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
Restrained
All
40 £ A £ 150
1 1/2
1 1/2
2
2 1/2
—
Carbonate or siliceous
150 < A £ 300
1 1/2
1 1/2
1 1/2
1 3/4
2 1/2
300 < A
1 1/2
1 1/2
1 1/2
1 1/2
2
Sand-lightweight
150 < A
1 1/2
1 1/2
1 1/2
1 1/2
2
Unrestrained
All
40 £ A £ 150
2
2 1/2
—
—
—
Carbonate or siliceous
150 < A £ 300
1 1/2
1 3/4
2 1/2
—
—
300 < A
1 1/2
1 1/2
2
3
c
4
c
Sand-lightweight
150 < A
1 1/2
1 1/2
2
3
c
4
c
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
a. Tabulated values for restrained assemblies apply to beams spaced more than 4 feet on center. For restrained beams spaced 4 feet or less on center, minimum cover of 3/4 inch is adequate for 4-hour ratings or less.
b. The cross-sectional area of a stem is permitted to include a portion of the area in the flange, provided the width of the flange used in the calculation does not exceed three times the average width of the stem.
c. U-shaped or hooped stirrups spaced not to exceed the depth of the member and having a minimum cover of 1 inch shall be provided.
The minimum thickness of concrete cover to the positive moment reinforcement shall comply with Table 722.2.3(1) for reinforced concrete and Table 722.2.3(2) for prestressed concrete. These tables are applicable for solid or hollow-core one-way or two-way slabs with flat undersurfaces. These tables are applicable to slabs that are either cast in place or precast. For precast prestressed concrete not covered elsewhere, the procedures contained in PCI MNL 124 shall be acceptable.
722.2.3.2 Reinforced beam cover.
The minimum thickness of concrete cover to the positive moment reinforcement (bottom steel) for reinforced concrete beams is shown in Table 722.2.3(3) for fire-resistance ratings of 1 hour to 4 hours.
722.2.3.3 Prestressed beam cover.
The minimum thickness of concrete cover to the positive moment prestressing tendons (bottom steel) for restrained and unrestrained prestressed concrete beams and stemmed units shall comply with the values shown in Tables 722.2.3(4) and 722.2.3(5) for fire-resistance ratings of 1 hour to 4 hours. Values in Table 722.2.3(4) apply to beams 8 inches ( 203.2 mm) or greater in width. Values in Table 722.2.3(5) apply to beams or stems of any width, provided the cross-section area is not less than 40 square inches ( 25 806.4 mm
2
). In case of differences between the values determined from Table 722.2.3(4) or 722.2.3(5), it is permitted to use the smaller value. The concrete cover shall be calculated in accordance with Section 722.2.3.3.1. The minimum concrete cover for nonprestressed reinforcement in prestressed concrete beams shall comply with Section 722.2.3.2.
722.2.3.3.1 Calculating concrete cover.
The concrete cover for an individual tendon is the minimum thickness of concrete between the surface of the tendon and the fire-exposed surface of the beam, except that for ungrouted ducts, the assumed cover thickness is the minimum thickness of concrete between the surface of the duct and the fire-exposed surface of the beam. For beams in which two or more tendons are used, the cover is assumed to be the average of the minimum cover of the individual tendons. For corner tendons (tendons equal distance from the bottom and side), the minimum cover used in the calculation shall be one-half the actual value. For stemmed members with two or more prestressing tendons located along the vertical centerline of the stem, the average cover shall be the distance from the bottom of the member to the centroid of the tendons. The actual cover for any individual tendon shall be not less than one-half the smaller value shown in Tables 722.2.3(4) and 722.2.3(5), or 1 inch (25.4 mm), whichever is greater.
722.2.4 Concrete columns.
Concrete columns shall comply with this section.
Table 722.2.4 Minimum Dimension of Concrete Columns (inches)
Types of Concrete
Fire-Resistance Rating (hours)
1
1 1/2
2
a
3
a
4
b
Siliceous
8
9
10
12
14
Carbonate
8
9
10
11
12
Sand-lightweight
8
8 1/2
9
10 1/2
12
For SI: 1 inch = 25 mm.
a. The minimum dimension is permitted to be reduced to 8 inches for rectangular columns with two parallel sides at least 36 inches in length.
b. The minimum dimension is permitted to be reduced to 10 inches for rectangular columns with two parallel sides at least 36 inches in length.
722.2.4.1 Minimum size.
The minimum overall dimensions of reinforced concrete columns for fire-resistance ratings of 1 hour to 4 hours for exposure to fire on all sides shall comply with this section.
722.2.4.1.1 Concrete strength less than or equal to 12,000 psi.
For columns made with concrete having a specified compressive strength, f'
c
, of less than or equal to 12,000 psi (82.7 MPa), the minimum dimension shall comply with Table 722.2.4.
722.2.4.1.2 Concrete strength greater than 12,000 psi.
For columns made with concrete having a specified compressive strength, f'
c
, greater than 12,000 psi (82.7 MPa), for fire-resistance ratings of 1 hour to 4 hours the minimum dimension shall be 24 inches (609.6 mm).
722.2.4.2 Minimum cover for R/C columns.
The minimum thickness of concrete cover to the main longitudinal reinforcement in columns, regardless of the type of aggregate used in the concrete and the specified compressive strength of concrete, f'
c
, shall be not less than 1 inch (25.4 mm) times the number of hours of required fire resistance or 2 inches (50.8 mm), whichever is less.
722.2.4.3 Tie and spiral reinforcement.
For concrete columns made with concrete having a specified compressive strength, f'
c
, greater than 12,000 psi (82.7 MPa), tie and spiral reinforcement shall comply with the following:
1. The free ends of rectangular ties shall terminate with a 135-degree (2.4 rad) standard tie hook.
2. The free ends of circular ties shall terminate with a 90-degree (1.6 rad) standard tie hook.
3. The free ends of spirals, including at lap splices, shall terminate with a 90-degree (1.6 rad) standard tie hook.
The hook extension at the free end of ties and spirals shall be the larger of six bar diameters and the extension required by Section 7.1.3 of ACI 318. Hooks shall project into the core of the column.
722.2.4.4 Columns built into walls.
The minimum dimensions of Table 722.2.4 do not apply to a reinforced concrete column that is built into a concrete or masonry wall provided all of the following are met:
1. The fire-resistance rating for the wall is equal to or greater than the required rating of the column;
2. The main longitudinal reinforcing in the column has cover not less than that required by Section 722.2.4.2; and
3. Openings in the wall are protected in accordance with Table 716.5.
Where openings in the wall are not protected as required by Section 716.5, the minimum dimension of columns required to have a fire-resistance rating of 3 hours or less shall be 8 inches (203.2 mm), and 10 inches (254 mm) for columns required to have a fire-resistance rating of 4 hours, regardless of the type of aggregate used in the concrete.
722.2.4.5 Precast cover units for steel columns.
See Section 722.5.1.4.
722.3 Concrete masonry.
The provisions of this section contain procedures by which the fire-resistance ratings of concrete masonry are established by calculations.
722.3.1 Equivalent thickness.
The equivalent thickness of concrete masonry construction shall be determined in accordance with the provisions of this section.
722.3.1.1 Concrete masonry unit plus finishes.
The equivalent thickness of concrete masonry assemblies, T
ea
, shall be computed as the sum of the equivalent thickness of the concrete masonry unit, T
e
, as determined by Section 722.3.1.2, 722.3.1.3, or 722.3.1.4, plus the equivalent thickness of finishes, T
ef
, determined in accordance with Section 722.3.2:
T
ea
= T
e
+ T
ef
(Equation 7-6)
722.3.1.2 Ungrouted or partially grouted construction.
T
e
shall be the value obtained for the concrete masonry unit determined in accordance with ASTM C 140.
722.3.1.3 Solid grouted construction.
The equivalent thickness, T
e
, of solid grouted concrete masonry units is the actual thickness of the unit.
722.3.1.4 Airspaces and cells filled with loose-fill material.
The equivalent thickness of completely filled hollow concrete masonry is the actual thickness of the unit where loose-fill materials are: sand, pea gravel, crushed stone, or slag that meet ASTM C 33 requirements; pumice, scoria, expanded shale, expanded clay, expanded slate, expanded slag, expanded fly ash, or cinders that comply with ASTM C 331; or perlite or vermiculite meeting the requirements of ASTM C 549 and ASTM C 516, respectively.
722.3.2 Concrete masonry walls.
The fire-resistance rating of walls and partitions constructed of concrete masonry units shall be determined from Table 722.3.2. The rating shall be based on the equivalent thickness of the masonry and type of aggregate used.
Table 722.3.2 Minimum Equivalent Thickness (inches) of Bearing or Nonbearing Concrete Masonry Walls
a, b, c, d
Type of Aggregate
Fire-Resistance Rating (hours)
1/2
3/4
1
1 1/4
1 1/2
1 3/4
2
2 1/4
2 1/2
2 3/4
3
3 1/4
3 1/2
3 3/4
4
Pumice or expanded slag
1.5
1.9
2.1
2.5
2.7
3.0
3.2
3.4
3.6
3.8
4.0
4.2
4.4
4.5
4.7
Expanded shale, clay or slate
1.8
2.2
2.6
2.9
3.3
3.4
3.6
3.8
4.0
4.2
4.4
4.6
4.8
4.9
5.1
Limestone, cinders or unexpanded slag
1.9
2.3
2.7
3.1
3.4
3.7
4.0
4.3
4.5
4.8
5.0
5.2
5.5
5.7
5.9
Calcareous or siliceous gravel
2.0
2.4
2.8
3.2
3.6
3.9
4.2
4.5
4.8
5.0
5.3
5.5
5.8
6.0
6.2
For SI: 1 inch = 25.4 mm.
a. Values between those shown in the table can be determined by direct interpolation.
b. Where combustible members are framed into the wall, the thickness of solid material between the end of each member and the opposite face of the wall, or between members set in from opposite sides, shall be not less than 93 percent of the thickness shown in the table.
c. Requirements of ASTM C 55, ASTM C 73, ASTM C 90 or ASTM C 744 shall apply.
d. Minimum required equivalent thickness corresponding to the hourly fire-resistance rating for units with a combination of aggregate shall be determined by linear interpolation based on the percent by volume of each aggregate used in manufacture.
Where plaster or gypsum wallboard is applied to the side of the wall not exposed to fire, the contribution of the finish to the total fire-resistance rating shall be determined as follows: The thickness of gypsum wallboard or plaster shall be corrected by multiplying the actual thickness of the finish by applicable factor determined from Table 722.2.1.4(1). This corrected thickness of finish shall be added to the equivalent thickness of masonry and the fire-resistance rating of the masonry and finish determined from Table 722.3.2.
722.3.2.2 Finish on fire-exposed side.
Where plaster or gypsum wallboard is applied to the fire-exposed side of the wall, the contribution of the finish to the total fire-resistance rating shall be determined as follows: The time assigned to the finish as established by Table 722.2.1.4(2) shall be added to the fire-resistance rating determined in Section 722.3.2 for the masonry alone, or in Section 722.3.2.1 for the masonry and finish on the nonfire-exposed side.
722.3.2.3 Nonsymmetrical assemblies.
For a wall having no finish on one side or having different types or thicknesses of finish on each side, the calculation procedures of this section shall be performed twice, assuming either side of the wall to be the fire-exposed side. The fire-resistance rating of the wall shall not exceed the lower of the two values calculated.
Exception: For exterior walls with a fire separation distance greater than 5 feet (1524 mm), the fire shall be assumed to occur on the interior side only.
722.3.2.4 Minimum concrete masonry fire-resistance rating.
Where the finish applied to a concrete masonry wall contributes to its fire-resistance rating, the masonry alone shall provide not less than one-half the total required fire-resistance rating.
722.3.2.5 Attachment of finishes.
Installation of finishes shall be as follows:
1. Gypsum wallboard and gypsum lath applied to concrete masonry or concrete walls shall be secured to wood or steel furring members spaced not more than 16 inches (406.4 mm) on center (o.c.).
2. Gypsum wallboard shall be installed with the long dimension parallel to the furring members and shall have all joints finished.
3. Other aspects of the installation of finishes shall comply with the applicable provisions of Chapters 7 and 25.
722.3.3 Multi-wythe masonry walls.
The fire-resistance rating of wall assemblies constructed of multiple wythes of masonry materials shall be permitted to be based on the fire-resistance rating period of each wythe and the continuous airspace between each wythe in accordance with the following formula:
R
A
= (R
1
0.59
+
R
2
0.59
+ . . . +
R
n
0.59
+
A
1
+ A
2
+ . . . A
n
)
1.7
(Equation 7-7)
where:
R
A
= Fire-resistance rating of the assembly (hours).
R
1
, R
2
, . . ., R
n
= Fire-resistance rating of wythes for 1, 2, n (hours), respectively.
A
1
, A
2
, . . ., A
n
= 0.30, factor for each continuous airspace for 1, 2, . . .n, respectively, having a depth of 1/2 inch (12.7 mm) or more between wythes.
722.3.4 Concrete masonry lintels.
Fire-resistance ratings for concrete masonry lintels shall be determined based upon the nominal thickness of the lintel and the minimum thickness of concrete masonry or concrete, or any combination thereof, covering the main reinforcing bars, as determined in accordance with Table 722.3.4, or by approved alternate methods.
Table 722.3.4 Minimum Cover of Longitudinal Reinforcement in Fire-Resistance-Rated Reinforced Concrete Masonry Lintels (inches)
Nominal Width of Lintel (inches)
Fire-Resistance Rating (hours)
1
2
3
4
6
1 1/2
2
—
—
8
1 1/2
1 1/2
1 3/4
3
10 or greater
1 1/2
1 1/2
1 1/2
1 3/4
For SI: 1 inch = 25.4 mm.
722.3.5 Concrete masonry columns.
The fire-resistance rating of concrete masonry columns shall be determined based upon the least plan dimension of the column in accordance with Table 722.3.5 or by approved alternate methods.
Table 722.3.5 Minimum Dimension of Concrete Masonry Columns (inches)
Fire-Resistance Rating (hours)
1
2
3
4
8 inches
10 inches
12 inches
14 inches
For SI: 1 inch = 25.4 mm.
722.4 Clay brick and tile masonry.
The provisions of this section contain procedures by which the fire-resistance ratings of clay brick and tile masonry are established by calculations.
722.4.1 Masonry walls.
The fire-resistance rating of masonry walls shall be based upon the equivalent thickness as calculated in accordance with this section. The calculation shall take into account finishes applied to the wall and airspaces between wythes in multi-wythe construction.
Table 722.4.1(1) Fire-Resistance Periods of Clay Masonry Walls
Material Type
Minimum Required Equivalent Thickness for Fire Resistance
a, b, c
(Inches)
1 hour
2 hours
3 hours
4 hours
Solid brick of clay or shale
d
2.7
3.8
4.9
6.0
Hollow brick or tile of clay or shale, unfilled
2.3
3.4
4.3
5.0
Hollow brick or tile of clay or shale, grouted or filled with materials specified in Section 722.4.1.1.3
3.0
4.4
5.5
6.6
For SI: 1 inch = 25.4 mm.
a. Equivalent thickness as determined from Section 722.4.1.1.
b. Calculated fire resistance between the hourly increments listed shall be determined by linear interpolation.
c. Where combustible members are framed in the wall, the thickness of solid material between the end of each member and the opposite face of the wall, or between members set in from opposite sides, shall be not less than 93 percent of the thickness shown.
d. For units in which the net cross-sectional area of cored brick in any plane parallel to the surface containing the cores is at least 75 percent of the gross cross-sectional area measured in the same plane.
Table 722.4.1(2) Fire-Resistance Ratings for Bearing Steel Frame Brick Veneer Walls or Partitions
Wall or Partition Assembly
Plaster Side Exposed (hours)
Brick Faced Side Exposed (hours)
Outside facing of steel studs: 1/2" wood fiberboard sheathing next to studs, 3/4" airspace formed with 3/4" × 1 5/8" wood strips placed over the fiberboard and secured to the studs; metal or wire lath nailed to such strips, 3 3/4" brick veneer held in place by filling 3/4" airspace between the brick and lath with mortar.
Inside facing of studs: 3/4" unsanded gypsum plaster on metal or wire lath attached to 5/16" wood strips secured to edges of the studs.
1.5
4
Outside facing of steel studs: 1" insulation board sheathing attached to studs, 1" airspace, and 3 3/4" brick veneer attached to steel frame with metal ties every 5th course.
Inside facing of studs: 7/8" sanded gypsum plaster (1:2 mix) applied on metal or wire lath attached directly to the studs.
1.5
4
Same as above except use 7/8" vermiculite – gypsum plaster or 1" sanded gypsum plaster (1:2 mix) applied to metal or wire
2
4
Outside facing of steel studs: 1/2" gypsum sheathing board, attached to studs, and 3 3/4" brick veneer attached to steel frame with metal ties every 5th course.
Inside facing of studs: 1/2" sanded gypsum plaster (1:2 mix) applied to 1/2" perforated gypsum lath securely attached to studs and having strips of metal lath 3 inches wide applied to all horizontal joints of gypsum lath.
2
4
For SI: 1 inch = 25.4 mm.
Table 722.4.1(3) Values of R
n
0.59
R
n
0.59
R (hours)
1
1.0
2
1.50
3
1.91
4
2.27
Table 722.4.1(4) Coefficients for Plaster, Pl
a
Thickness of Plaster (inch)
One Side
Two Sides
1/2
0.3
0.6
5/8
0.37
0.75
3/4
0.45
0.90
For SI: 1 inch = 25.4 mm.
a. Values listed in the table are for 1:3 sanded gypsum plaster.
Table 722.4.1(5) Reinforced Masonry Lintels
Nominal Lintel Width (inches)
Minimum Longitudinal Reinforcement Cover For Fire Resistance (inches)
1 hour
2 hours
3 hours
4 hours
6
1 1/2
2
NP
NP
8
1 1/2
1 1/2
1 3/4
3
10 or more
1 1/2
1 1/2
1 1/2
1 3/4
For SI: 1 inch = 25.4 mm.
NP = Not permitted.
Table 722.4.1(6) Reinforced Clay Masonry Columns
Column Size
Fire-Resistance Rating (hours)
1
2
3
4
Minimum column dimension (inches)
8
10
12
14
For SI: 1 inch = 25.4 mm.
722.4.1.1 Equivalent thickness.
The fire-resistance ratings of walls or partitions constructed of solid or hollow clay masonry units shall be determined from Table 722.4.1(1) or 722.4.1(2). The equivalent thickness of the clay masonry unit shall be determined by Equation 7-8 where using Table 722.4.1(1). The fire-resistance rating determined from Table 722.4.1(1) shall be permitted to be used in the calculated fire-resistance rating procedure in Section 722.4.2.
T
e
= V
n
/ LH
(Equation 7-8)
where:
T
e
= The equivalent thickness of the clay masonry unit (inches).
V
n
= The net volume of the clay masonry unit (inch
3
).
L = The specified length of the clay masonry unit (inches).
H = The specified height of the clay masonry unit (inches).
722.4.1.1.1 Hollow clay units.
The equivalent thickness, T
e
, shall be the value obtained for hollow clay units as determined in accordance with Equation 7-8. The net volume, V
n
, of the units shall be determined using the gross volume and percentage of void area determined in accordance with ASTM C 67.
722.4.1.1.2 Solid grouted clay units.
The equivalent thickness of solid grouted clay masonry units shall be taken as the actual thickness of the units.
722.4.1.1.3 Units with filled cores.
The equivalent thickness of the hollow clay masonry units is the actual thickness of the unit where completely filled with loose-fill materials of: sand, pea gravel, crushed stone, or slag that meet ASTM C 33 requirements; pumice, scoria, expanded shale, expanded clay, expanded slate, expanded slag, expanded fly ash, or cinders in compliance with ASTM C 331; or perlite or vermiculite meeting the requirements of ASTM C 549 and ASTM C 516, respectively.
722.4.1.2 Plaster finishes.
Where plaster is applied to the wall, the total fire-resistance rating shall be determined by the formula:
R = (R
n
0.59
+ pl)
1.7
(Equation 7-9)
where:
R = The fire-resistance of the assembly (hours).
R
n
= The fire-resistance of the individual wall (hours).
pl = Coefficient for thickness of plaster.
Values for R
n
0.59
for use in Equation 7-9 are given in Table 722.4.1(3). Coefficients for thickness of plaster shall be selected from Table 722.4.1(4) based on the actual thickness of plaster applied to the wall or partition and whether one or two sides of the wall are plastered.
722.4.1.3 Multi-wythe walls with airspace.
Where a continuous airspace separates multiple wythes of the wall or partition, the total fire-resistance rating shall be determined by the formula:
R = (R
1
0.59
+ R
2
0.59
+ . . . + R
n
0.59
+ as)
1.7
(Equation 7-10)
where:
R = The fire-resistance of the assembly (hours).
R
1
, R
2
and R
n
= The fire-resistance of the individual wythes (hours).
as = Coefficient for continuous airspace.
Values for R
n
0.59
for use in Equation 7-10 are given in Table 722.4.1(3). The coefficient for each continuous air-space of 1/2 inch to 3 1/2 inches (12.7 to 89 mm) separating two individual wythes shall be 0.3.
722.4.1.4 Nonsymmetrical assemblies.
For a wall having no finish on one side or having different types or thicknesses of finish on each side, the calculation procedures of this section shall be performed twice, assuming either side to be the fire-exposed side of the wall. The fire resistance of the wall shall not exceed the lower of the two values determined.
Exception: For exterior walls with more than 5 feet (1524 mm) of horizontal separation, the fire shall be assumed to occur on the interior side only.
722.4.2 Multi-wythe walls.
The fire-resistance rating for walls or partitions consisting of two or more dissimilar wythes shall be permitted to be determined by the formula:
R = (R
1
0.59
+ R
2
0.59
+ . . . + R
n
0.59
)
1.7
(Equation 7-11)
where:
R = The fire-resistance of the assembly (hours).
R
1
, R
2
and R
n
= The fire-resistance of the individual wythes (hours).
Values for R
n
0.59
for use in Equation 7-11 are given in Table 722.4.1(3).
722.4.2.1 Multi-wythe walls of different material.
For walls that consist of two or more wythes of different materials (concrete or concrete masonry units) in combination with clay masonry units, the fire-resistance rating of the different materials shall be permitted to be determined from Table 722.2.1.1 for concrete; Table 722.3.2 for concrete masonry units or Table 722.4.1(1) or 722.4.1(2) for clay and tile masonry units.
722.4.3 Reinforced clay masonry lintels.
Fire-resistance ratings for clay masonry lintels shall be determined based on the nominal width of the lintel and the minimum covering for the longitudinal reinforcement in accordance with Table 722.4.1(5).
722.4.4 Reinforced clay masonry columns.
The fire-resistance ratings shall be determined based on the last plan dimension of the column in accordance with Table 722.4.1(6). The minimum cover for longitudinal reinforcement shall be 2 inches (50.8 mm).
722.5 Steel assemblies.
The provisions of this section contain procedures by which the fire-resistance ratings of steel assemblies are established by calculations.
722.5.1 Structural steel columns.
The fire-resistance ratings of structural steel columns shall be based on the size of the element and the type of protection provided in accordance with this section.
Figure 722.5.1(1) Determination of the Heated Perimeter of Structural Steel Columns
Figure 722.5.1(2) Gypsum-Protected Structural Steel Columns with Sheet Steel Column Covers
For SI: 1 inch = 25.4 mm, 1 foot = 305 mm.
1. Structural steel column, either wide flange or tubular shapes.
2. Type X gypsum board or gypsum panel products in accordance with ASTM C 1177, C 1178, C 1278, C 1396 or C 1658. The total thickness of gypsum board or gypsum panel products calculated as h in Section 722.5.1.2 shall be applied vertically to an individual column using one of the following methods:
1. As a single layer with no horizontal joints.
2. As multiple layers with no horizontal joints permitted in any layer.
3. As multiple layers with horizontal joints are staggered not less than 12 inches vertically between layers and not less than 8 feet vertically in any single layer. The total required thickness of gypsum board or gypsum panel products 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 board or gypsum panel product 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 1 1/2-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 722.5.1(3) Gypsum-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. 1 5/8-inch deep studs fabricated from 0.0179-inch minimum thickness galvanized steel with 15/16 or 1 7/16-inch legs. The length of the steel studs shall be 1/2 inch less than the height of the assembly.
3. Type X gypsum board or gypsum panel products in accordance with ASTM C 177, C 1178, C 1278, C 1396 or C 1658. The total thickness of gypsum board or gypsum panel products calculated as h in Section 722.5.1.2 shall be applied vertically to an individual column using one of the following methods:
1. As a single layer with no horizontal joints.
2. As multiple layer with no horizontal joints permitted in any layer.
3. As multiple layers with horizontal joints staggered not less than 12 inches vertically between layers and not less than 8 feet vertically in any single layer. The total required thickness of gypsum board or gypsum panel products 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 1 1/2-inch legs attached to the gypsum board or gypsum panel products 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 gypsum board or gypsum panel product to the steel studs and the third layer to the sheet metal angles at 24 inches on center. Type S screws 1 3/4-inch long shall be used for attaching the second layer of gypsum board or gypsum panel product to the steel studs and the fourth layer to the sheet metal angles at 12 inches on center. Type S screws 2 1/4 inches long shall be used for attaching the third layer of gypsum board or gypsum panel product to the steel studs at 12 inches on center.
Figure 722.5.1(4) Fire Resistance of Structural Steel Columns Protected with Various Thicknesses of Type X Gypsum Wallboard
a
For SI: 1 inch = 25.4 mm, 1 pound per linear foot/inch = 0.059 kg/m/mm.
a. The W/D ratios for typical wide flange columns are listed in Table 722.5.1(1). For other column shapes, the W/D ratios shall be determined in accordance with Section 722.5.1.1.
Figure 722.5.1(5) Wide Flange Structural Steel Columns with Spray-Applied Fire-Resistant Materials
Figure 722.5.1(6) Concrete Protected Structural Steel Columns
a, 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 722.2.1.3).
For SI: 1 inch = 25.4 mm.
Figure 722.5.1(7) Concrete or Clay Masonry Protected Structural Steel Columns
d = Depth of a wide flange column, outside diameter of pipe column, or outside 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).
Table 722.5.1(1) W/D Ratios for Steel Columns
Structural Shape
Contour Profile
Box Profile
Structural Shape
Contour Profile
Box Profile
W14 × 233
2.55
3.65
W10 × 112
1.81
2.57
× 211
2.32
3.35
× 100
1.64
2.33
× 193
2.14
3.09
× 88
1.45
2.08
× 176
1.96
2.85
× 77
1.28
1.85
× 159
1.78
2.60
× 68
1.15
1.66
× 145
1.64
2.39
× 60
1.01
1.48
× 132
1.56
2.25
× 54
0.922
1.34
× 120
1.42
2.06
× 49
0.84
1.23
× 109
1.29
1.88
× 45
0.888
1.24
× 99
1.18
1.72
× 39
0.78
1.09
× 90
1.08
1.58
× 33
0.661
0.93
× 82
1.23
1.68
× 74
1.12
1.53
W8 × 67
1.37
1.94
× 68
1.04
1.41
× 58
1.20
1.71
× 61
0.928
1.28
× 48
1.00
1.44
× 53
0.915
1.21
× 40
0.849
1.23
× 48
0.835
1.10
× 35
0.749
1.08
× 43
0.752
0.99
× 31
0.665
0.97
× 28
0.688
0.96
W12 × 190
2.50
3.51
× 24
0.591
0.83
× 170
2.26
3.20
× 21
0.577
0.77
× 152
2.04
2.90
× 18
0.499
0.67
× 136
1.86
2.63
× 120
1.65
2.36
W6 × 25
0.696
1.00
× 106
1.47
2.11
× 20
0.563
0.82
× 96
1.34
1.93
× 16
0.583
0.78
× 87
1.22
1.76
× 15
0.431
0.63
× 79
1.11
1.61
× 12
0.448
0.60
× 72
1.02
1.48
× 9
0.338
0.46
× 65
0.925
1.35
× 58
0.925
1.31
W5 × 19
0.644
0.93
× 53
0.855
1.20
× 16
0.55
0.80
× 50
0.909
1.23
× 45
0.829
1.12
W4 × 13
0.556
0.79
× 40
0.734
1.00
For SI: 1 pound per linear foot per inch = 0.059 kg/m/mm.
Table 722.5.1(2) Properties of Concrete
Property
Normal Weight Concrete
Structural Lightweight Concrete
Thermal conductivity (k
c
)
0.95 Btu/hr • ft • °F
0.35 Btu/hr • ft • °F
Specific heat (c
c
)
0.20 Btu/lb °F
0.20 Btu/lb °F
Density (P
c
)
145 lb/ft
3
110 lb/ft
3
Equilibrium (free) moisture content (m) by volume
4%
5%
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 lb/ft
3
= 16.0185 kg/m
3
, Btu/hr • ft • °F = 1.731 W/(m • K)
Table 722.5.1(3) Thermal Conductivity of Concrete or Clay Masonry Units
Density (dm) of Units (lb/ft3)
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/m
3
, Btu/hr • ft • °F = 1.731 W/(m • K).
Table 722.5.1(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
2.50
3.33
W24 × 68
0.942
1.21
× 280
2.35
3.12
× 62
0.934
1.14
× 260
2.18
2.92
× 55
0.828
1.02
× 245
2.08
2.76
× 230
1.95
2.61
W21 × 147
1.87
2.60
× 210
1.96
2.45
× 132
1.68
2.35
× 194
1.81
2.28
× 122
1.57
2.19
× 182
1.72
2.15
× 111
1.43
2.01
× 170
1.60
2.01
× 101
1.30
1.84
× 160
1.51
1.90
× 93
1.40
1.80
× 150
1.43
1.79
× 83
1.26
1.62
× 135
1.29
1.63
× 73
1.11
1.44
× 68
1.04
1.35
W33 × 241
2.13
2.86
W21 × 62
0.952
1.23
× 221
1.97
2.64
× 57
0.952
1.17
× 201
1.79
2.42
× 50
0.838
1.04
× 152
1.53
1.94
× 44
0.746
0.92
× 141
1.43
1.80
× 130
1.32
1.67
W18 × 119
1.72
2.42
× 118
1.21
1.53
× 106
1.55
2.18
× 97
1.42
2.01
W30 × 211
2.01
2.74
× 86
1.27
1.80
× 191
1.85
2.50
× 76
1.13
1.60
× 173
1.66
2.28
× 71
1.22
1.59
× 132
1.47
1.85
× 65
1.13
1.47
× 124
1.39
1.75
× 60
1.04
1.36
× 116
1.30
1.65
× 55
0.963
1.26
× 108
1.21
1.54
× 50
0.88
1.15
× 99
1.12
1.42
× 46
0.878
1.09
× 40
0.768
0.96
W27 × 178
1.87
2.55
× 35
0.672
0.85
× 161
1.70
2.33
× 146
1.55
2.12
W16 × 100
1.59
2.25
× 114
1.39
1.76
× 89
1.43
2.03
× 102
1.24
1.59
× 77
1.25
1.78
× 94
1.15
1.47
× 67
1.09
1.56
× 84
1.03
1.33
× 57
1.09
1.43
× 50
0.962
1.26
× 45
0.870
1.15
W24 × 162
1.88
2.57
× 40
0.780
1.03
× 146
1.70
2.34
× 36
0.702
0.93
× 131
1.54
2.12
× 31
0.661
0.83
× 117
1.38
1.91
× 26
0.558
0.70
× 104
1.24
1.71
× 94
1.28
1.63
W14 × 132
1.89
3.00
x 84
1.15
1.47
x 120
1.71
2.75
× 76
1.05
1.34
× 109
1.57
2.52
W14 × 99
1.43
2.31
W10 × 30
0.806
1.12
× 90
1.31
2.11
× 26
1.708
0.98
× 82
1.45
2.12
× 22
0.606
0.84
× 74
1.32
1.93
× 19
0.607
0.78
× 68
1.22
1.78
× 17
0.543
0.70
× 61
1.10
1.61
× 15
0.484
0.63
× 53
1.06
1.48
× 12
0.392
0.51
× 48
0.970
1.35
W14 × 43
0.874
1.22
W8 × 67
1.65
2.55
× 38
0.809
1.09
× 58
1.44
2.26
× 34
0.725
0.98
× 48
1.21
1.91
× 30
0.644
0.87
× 40
1.03
1.63
× 26
0.628
0.79
× 35
0.907
1.44
× 22
0.534
0.68
× 31
0.803
1.29
× 28
0.819
1.24
W12 × 87
1.47
2.34
× 24
0.704
1.07
× 79
1.34
2.14
× 21
0.675
0.96
× 72
1.23
1.97
× 18
0.583
0.84
× 65
1.11
1.79
× 15
0.551
0.74
× 58
1.10
1.69
× 13
0.483
0.65
× 53
1.02
1.55
× 10
0.375
0.51
× 50
1.06
1.54
× 45
0.974
1.40
W6 × 25
0.839
1.33
× 40
0.860
1.25
× 20
0.678
1.09
× 35
0.810
1.11
× 16
0.684
0.96
× 30
0.699
0.96
× 15
0.521
0.83
× 26
0.612
0.84
× 12
0.526
0.75
× 22
0.623
0.77
× 9
0.398
0.57
× 19
0.540
0.67
× 16
0.457
0.57
W5 × 19
0.776
1.24
× 14
0.405
0.50
× 16
0.664
1.07
W10 × 112
2.17
3.38
W4 × 13
0.670
1.05
× 100
1.97
3.07
× 88
1.74
2.75
× 77
1.54
2.45
× 68
1.38
2.20
× 60
1.22
1.97
× 54
1.11
1.79
× 49
1.01
1.64
× 45
1.06
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 722.5.1(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 hours
3 hours
4 hours
1 hour
2 hours
3 hours
4 hours
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/m
3
.
Note: Tabulated values assume 1-inch air gap between masonry and steel section.
Table 722.5.1(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 hours
3 hours
4 hours
1 hour
2 hours
3 hours
4 hours
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
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 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)
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 foot = 16.02 kg/m
3
.
Table 722.5.1(7) Minimum Cover (inch) for Steel Columns Encased in Normal-Weight Concrete
a
Figure 722.5.1(6)(c)
Structural Shape
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
W14 × 233
1
1
1
1 1/2
2
× 176
2 1/2
× 132
2
× 90
1 1/2
× 61
× 48
1 1/2
2 1/2
× 43
W12 × 152
1
1
1
2
2 1/2
× 96
× 65
1 1/2
1 1/2
3
× 50
2 1/2
× 40
W10 × 88
1
1 1/2
1 1/2
2
3
× 49
1
2 1/2
× 45
× 39
3 1/2
× 33
2
W8 × 67
1
1
1 1/2
2 1/2
3
× 58
× 48
1 1/2
3 1/2
× 31
2
3
× 21
× 18
4
W6 × 25
1
1 1/2
2
3
3 1/2
× 20
2
2 1/2
4
× 16
3 1/2
× 15
1 1/2
× 9
For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of normal-weight concrete given in Table 722.5.1(2).
Table 722.5.1(8) Minimum Cover (inch) for Steel Columns Encased in Structural Lightweight Concrete
a
Figure 722.5.1(6)(c)
Structural Shape
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
W14 × 233
1
1
1
1
1 1/2
× 193
1 1/2
× 74
2
× 61
2 1/2
× 43
11 /2
2
W12 × 65
1
1
1
1 1/2
2
× 53
2
2 1/2
× 40
1 1/2
W10 × 112
1
1
1
1 1/2
2
× 88
× 60
2
2 1/2
× 33
1 1/2
W8 × 35
1
1
1 1/2
2
2 1/2
× 28
3
× 24
2 1/2
× 18
1 1/2
For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of structural lightweight concrete given in Table 722.5.1(2).
Table 722.5.1(9) Minimum Cover (inch) for Steel Columns in Normal-Weight Precast Covers
a
Figure 722.5.1(6)(a)
Structural Shape
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
W14 × 233
1 1/2
1 1/2
1 1/2
2 1/2
3
× 211
3 1/2
× 176
2
× 145
3
× 109
2
2 1/2
× 99
4
× 61
3 1/2
× 43
4 1/2
W12 × 190
1 1/2
1 1/2
1 1/2
2 1/2
3 1/2
× 152
2
× 120
3
4
× 96
× 87
2
2 1/2
3 1/2
× 58
4 1/2
× 40
W10 × 112
1 1/2
1 1/2
2
3
3 1/2
× 88
4
× 77
2
2 1/2
× 54
3 1/2
× 33
4 1/2
W8 × 67
1 1/2
1 1/2
2
3
4
× 58
2
2 1/2
3 1/2
× 48
× 28
4 1/2
× 21
2 1/2
3
× 18
4
W6 × 25
1 1/2
2
2 1/2
3 1/2
4 1/2
× 20
2 1/2
3
× 16
4
× 12
2
× 9
5
For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of normal-weight concrete given in Table 722.5.1(2).
Table 722.5.1(10) Minimum Cover (inch) for Steel Columns in Structural Lightweight Precast Covers
a
Figure 722.5.1(6)(a)
Structural Shape
Fire-Resistance Rating (hours)
1
1 1/2
2
3
4
W14 × 233
1 1/2
1 1/2
1 1/2
2
2 1/2
× 176
3
× 145
2 1/2
× 132
× 109
× 99
2
× 68
3 1/2
× 43
3
W12 × 190
1 1/2
1 1/2
1 1/2
2
2 1/2
× 152
× 136
3
× 106
2 1/2
× 96
3 1/2
× 87
× 65
2
× 40
3
W10 × 112
1 1/2
1 1/2
1 1/2
2
3
× 100
2 1/2
× 88
× 77
2
3 1/2
× 60
× 39
3
× 33
2
W8 × 67
1 1/2
1 1/2
1 1/2
2 1/2
3
× 48
2
3
3 1/2
× 35
× 28
2
× 18
2 1/2
4
W6 × 25
1 1/2
2
2
3
3 1/2
× 15
2 1/2
4
× 9
3 1/2
For SI: 1 inch = 25.4 mm.
a. The tabulated thicknesses are based upon the assumed properties of structural lightweight concrete given in Table 722.5.1(2).
722.5.1.1 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 structural 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 722.5.1(1).
722.5.1.1.1 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.
722.5.1.1.2 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.
722.5.1.1.3 Weight-to-perimeter ratio.
Table 722.5.1(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.
722.5.1.2 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 that are protected with Type X gypsum wallboard shall be permitted to be determined from the following expression:
(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.
722.5.1.2.1 Attachment.
The gypsum board or gypsum panel products shall be supported as illustrated in either Figure 722.5.1(2) for fire-resistance ratings of 4 hours or less, or Figure 722.5.1(3) for fire-resistance ratings of 3 hours or less.
722.5.1.2.2 Gypsum wallboard equivalent to concrete.
The determination of the fire resistance of structural steel columns from Figure 722.5.1(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 x 233 wide flange shape.
722.5.1.3 Spray-applied fire-resistant materials.
The fire resistance of wide-flange structural steel columns protected with spray-applied fire-resistant materials, as illustrated in Figure 722.5.1(5), shall be permitted to be determined from the following expression:
R = [C
1
(W/D) + C
2
] 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).
C
1
and C
2
= Material-dependent constants.
W = Weight of structural steel column (pounds per linear foot).
Exception: 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.
722.5.1.3.1 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-resistance tests in accordance with Section 703.2. Unless evidence is submitted to the commissioner 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.
722.5.1.3.2 Identification.
Spray-applied fire-resistant materials shall be identified by density and thickness required for a given fire-resistance rating.
722.5.1.4 Concrete-protected columns.
The fire resistance of structural steel columns protected with concrete, as illustrated in Figure 722.5.1(6)(a) and (b), shall be permitted to be determined from the following expression:
R = R
0
(1 + 0.03m)
(Equation 7-14)
where:
R
0
= 10 (W/D)
0.7
+ 17(h
1.6
/k
c
0.2
) × (1 + 26 (h/p
c
c
c
h (L + h))
0.8
)
As used in these expressions:
R = Fire endurance at equilibrium moisture conditions (minutes).
R
0
= 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).
k
c
= 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).
p
c
= Concrete density (pounds per cubic foot).
c
c
= Ambient temperature specific heat of concrete (Btu/lb °F).
L = Interior dimension of one side of a square concrete box protection (inches).
722.5.1.4.1 Reentrant space filled.
For wide-flange structural steel columns completely encased in concrete with all reentrant spaces filled (Figure 722.5.1(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 + (p
c
c
c
/144) (b
f
d-A
s
)
(Equation 7-15)
where:
b
f
= Flange width of the steel column (inches).
d = Depth of the steel column (inches).
A
s
= Cross-sectional area of the steel column (square inches).
722.5.1.4.2 Concrete properties unknown.
If specific data on the properties of concrete are not available, the values given in Table 722.5.1(2) are permitted.
722.5.1.4.3 Minimum concrete cover.
For structural steel column encased in concrete with all reentrant spaces filled, Figure 722.5.1(6)(c) and Tables 722.5.1(7) and 722.5.1(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 apply to structural steel columns larger than those listed.
722.5.1.4.4 Minimum precast concrete cover.
For structural steel columns protected with precast concrete column covers as shown in Figure 722.5.1(6)(a), Tables 722.5.1(9) and 722.5.1(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 apply to structural steel columns larger than those listed.
722.5.1.4.5 Masonry protection.
The fire resistance of structural steel columns protected with concrete masonry units or clay masonry units as illustrated in Figure 722.5.1(7), shall be permitted to be determined from the following expression:
R = 0.17 (W/D)
0.7
+ [0.285 (T
e
1.6
/K
0.2
)][1.0 + 42.7 {(A
s
/d
m
T
e
)/(0.25p + T
e
)}
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 the steel column (inches) (see Figure 722.5.1(7)).
T
e
= Equivalent thickness of concrete or clay masonry unit (inches) (see Table 722.3.2 Note a or Section 722.4.1).
K = Thermal conductivity of concrete or clay masonry unit (Btu/hr ft °F) (see Table 722.5.1(3)).
A
s
= Cross-sectional area of steel column (square inches).
d
m
= Density of the concrete or clay masonry unit (pounds per cubic foot).
p = Inner perimeter of concrete or clay masonry protection (inches) (see Figure 722.5.1(7)).
722.5.1.4.6 Equivalent concrete masonry thickness.
For structural steel columns protected with concrete masonry, Table 722.5.1(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 722.5.1(6) gives the equivalent thickness of concrete masonry required for various fire-resistance ratings for typical column shapes.
722.5.2 Structural steel beams and girders.
The fire-resistance ratings of structural 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 722.5.2 Determination of the Heated Perimeter of Structural Steel Beams and Girders
722.5.2.1 Determination of fire resistance.
These procedures establish a basis for determining resistance of structural steel beams and girders that differ in size from that specified in approved fire-resistant 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 element 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 722.5.2.
722.5.2.1.1 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 722.5.1(4). For different shapes, the weight-to-heated-perimeter ratios (W/D) shall be determined in accordance with the definitions given in this section.
722.5.2.1.2 Beam and girder substitutions.
Except as provided for in Section 722.5.2.2, 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.
722.5.2.2 Spray-applied fire-resistant materials.
The provisions in this section apply to structural steel beams and girders protected with spray-applied 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-resistant-rated assemblies, provided that the thickness of the fire-resistant material is adjusted in accordance with the following expression:
h
2
= {[W
1
/D
1
) + 0.60]/[(W
2
/D
2
) + 0.60]} h
1
(Equation 7-17)
where:
h = Thickness of spray-applied 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 or girder in inches.
Subscript 1 refers to the beam and fire-resistant material thickness in the fire-resistance-rated assembly.
Subscript 2 refers to the substitute beam or girder and the required thickness of fire-resistant material.
Exception: 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.
722.5.2.2.1 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 (W
2
/D
2
) shall be not less than 0.37.
2. The thickness of fire protection materials for the substitute beam or girder (T
1
) shall be not less than 3/8 inch (9.5 mm).
3. The unrestrained or restrained beam rating shall be not less than 1 hour.
4. Where used to adjust the material thickness for a restrained beam, the use of this procedure is limited to structural steel sections classified as compact in accordance with AISC 360.
722.5.2.3 Structural steel trusses.
The fire resistance of structural steel trusses protected with fire-resistant materials spray applied 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 722.5.1.3. The weight-to-heated-perimeter ratio (W/D) of truss elements which can be simultaneously exposed to fire on all sides shall be determined on the same basis as columns, as specified in Section 722.5.1.1. The weight-to-heated-perimeter ratio (W/D) of truss elements which directly support floor or roof assembly shall be determined on the same basis as beams and girders, as specified in Section 722.5.2.1.
Exception: 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.
722.6 Wood assemblies.
The provisions of this section contain procedures by which the fire-resistance ratings of wood assemblies are established by calculations.
722.6.1 General.
This section contains procedures for calculating the fire-resistance ratings of walls, floor/ceiling and roof/ceiling assemblies based in part on the standard method of testing referenced in Section 703.2.
722.6.1.1 Maximum fire-resistance rating.
Fire-resistance ratings calculated for assemblies using the methods in Section 722.6 shall be limited to a maximum of 1 hour.
722.6.1.2 Dissimilar membranes.
Where dissimilar membranes are used on a wall assembly that requires consideration of fire exposure from both sides, the calculation shall be made from the least fire-resistant (weaker) side.
722.6.2 Walls, floors and roofs.
These procedures apply to both load-bearing and nonload-bearing assemblies.
Table 722.6.2(1) Time Assigned to Wallboard Membranes
a, b, c, d
Description of Finish
Time
e
(minutes)
3/8-inch wood structural panel bonded with exterior glue
5
15/32-inch wood structural panel bonded with exterior glue
10
19/32-inch wood structural panel bonded with exterior glue
15
3/8-inch gypsum wallboard
10
1/2-inch gypsum wallboard
15
5/8-inch gypsum wallboard
30
1/2-inch Type X gypsum wallboard
25
5/8-inch Type X gypsum wallboard
40
Double 3/8-inch gypsum wallboard
25
1/2- + 3/8-inch gypsum wallboard
35
Double 1/2-inch gypsum wallboard
40
For SI: 1 inch = 25.4 mm.
a. These values apply only where membranes are installed on framing members that are spaced 16 inches o.c or less.
b. Gypsum wallboard installed over framing or furring shall be installed so that all edges are supported, except 5/8-inch Type X gypsum wallboard shall be permitted to be installed horizontally with the horizontal joints staggered 24 inches each side and unsupported but finished.
c. On wood frame floor/ceiling or roof/ceiling assemblies, gypsum board shall be installed with the long dimension perpendicular to framing members and shall have all joints finished.
d. The membrane on the unexposed side shall not be included in determining the fire resistance of the assembly. Where dissimilar membranes are used on a wall assembly, the calculation shall be made from the least fire-resistant (weaker) side.
e. The time assigned is not a finished rating.
Table 722.6.2(2) Time Assigned for Contribution of Wood Frame
a, b, c
Description
Time Assigned to Frame (minutes)
Wood studs 16 inches o.c.
20
Wood floor and roof joists 16 inches o.c
10
For SI: 1 inch = 25.4 mm.
a. This table does not apply to studs or joists spaced more than 16 inches o.c.
b. All studs shall be nominal 2 × 4 and all joists shall have a nominal thickness of not less than 2 inches.
c. Allowable spans for joists shall be determined in accordance with Sections 2308.4.2.1, 2308.7.1 and 2308.7.2.
Table 722.6.2(3) Membrane
a
on Exterior Face of Wood Stud Walls
Sheathing
Paper
Exterior Finish
5/8-inch T & G lumber 5/16-inch exterior glue plywood 1/2-inch gypsum wallboard 5/8-inch gypsum wallboard 1/2-inch fiberboard
Sheathing paper
Lumber siding Wood shingles and shakes 1/4-inch fiber-cement lap, panel or shingle siding 1/4-inch wood structural panels-exterior type 1/4-inch hardboard Metal siding Stucco on metal lath Masonry veneer Vinyl siding
None
–
3/8-inch exterior-grade wood structural panels
For SI: 1 inch = 25.4 mm.
a. Any combination of sheathing, paper, and exterior finish is permitted.
Table 722.6.2(4) Flooring or Roofing over Wood Framing
a
Assembly
Structural Members
Subfloor or Roof Deck
Finished Flooring or Roofing
Floor
Wood
15/32-inch wood structural panels or 11/16 inch T & G softwood
Hardwood or softwood flooring on building paper resilient flooring, parquet floor felted-synthetic fiber floor coverings, carpeting, or ceramic tile on 1/4-inch-thick fiber-cement underlayment or 3/8-inch-thick panel-type underlay
Ceramic tile on 1 1/4-inch mortar bed
Roof
Wood
15/32-inch wood structural panels or 11/16 inch T & G softwood
Finished roofing material with or without insulation
For SI: 1 inch = 25.4 mm.
a. This table applies only to wood joist construction. It is not applicable to wood truss construction.
Table 722.6.2(5) Time Assigned for Additional Protection
Description of Additional Protection
Fire Resistance (minutes)
Add to the fire-resistance rating of wood stud walls if the spaces between the studs are completely filled with glass fiber mineral wool batts weighing not less than 2 pounds per cubic foot (0.6 pound per square foot of wall surface) or rockwool or slag material wool batts weighing not less than 3.3 pounds per cubic foot (1 pound per square foot of wall surface), or cellulose insulation having a nominal density not less than 2.6 pounds per cubic foot.
15
For SI: 1 pound/cubic foot = 16.0185 kg/m
3
.
722.6.2.1 Fire-resistance rating of wood frame assemblies.
The fire-resistance rating of a wood frame assembly is equal to the sum of the time assigned to the membrane on the fire-exposed side, the time assigned to the framing members and the time assigned for additional contribution by other protective measures such as insulation. The membrane on the unexposed side shall not be included in determining the fire resistance of the assembly.
722.6.2.2 Time assigned to membranes.
Table 722.6.2(1) indicates the time assigned to membranes on the fire-exposed side.
722.6.2.3 Exterior walls.
For an exterior wall with a fire separation distance greater than 5 feet (1524 mm), the wall is assigned a rating dependent on the interior membrane and the framing as described in Tables 722.6.2(1) and 722.6.2(2). The membrane on the outside of the nonfire-exposed side of exterior walls with a fire separation distance greater than 5 feet (1524 mm) shall consist of sheathing, sheathing paper and siding as described in Table 722.6.2(3).
722.6.2.4 Floors and roofs.
In the case of a floor or roof, the standard test provides only for testing for fire exposure from below. Except as noted in Section 703.3, Item 5, floor or roof assemblies of wood framing shall have an upper membrane consisting of a subfloor and finished floor conforming to Table 722.6.2(4) or any other membrane that has a contribution to fire resistance of not less than 15 minutes in Table 722.6.2(1).
722.6.2.5 Additional protection.
Table 722.6.2(5) indicates the time increments to be added to the fire resistance where glass fiber, rock wool, slag mineral wool or cellulose insulation is incorporated in the assembly.
722.6.2.6 Fastening.
Fastening of wood frame assemblies and the fastening of membranes to the wood framing members shall be done in accordance with Chapter 23.
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