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The minimum thickness of concrete cover over reinforcement in concrete slabs, reinforced beams and prestressed beams shall comply with this section.
COVER THICKNESS FOR REINFORCED CONCRETE FLOOR OR ROOF SLABS (inches)
CONCRETE AGGREGATE TYPE FIRE-RESISTANCE RATING (hours)
Restrained Unrestrained
1 11/2 2 3 4 1 11/2 2 3 4
Siliceous 3/4 3/4 3/4 3/4 3/4 3/4 3/4 1 11/4 15/8
Carbonate 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 11/4 11/4
Sand-lightweight or lightweight 3/4 3/4 3/4 3/4 3/4 3/4 3/4 3/4 11/4 11/4
For SI: 1 inch = 25.4 mm.
COVER THICKNESS FOR PRESTRESSED CONCRETE FLOOR OR ROOF SLABS (inches)
CONCRETE AGGREGATE TYPE FIRE-RESISTANCE RATING (hours)
Restrained Unrestrained
1 11/2 2 3 4 1 11/2 2 3 4
Siliceous 3/4 3/4 3/4 3/4 3/4 11/8 11/2 13/4 23/8 23/4
Carbonate 3/4 3/4 3/4 3/4 3/4 1 13/8 15/8 21/8 21/4
Sand-lightweight or lightweight 3/4 3/4 3/4 3/4 3/4 1 13/8 11/2 2 21/4
For SI: 1 inch = 25.4 mm.
MINIMUM COVER FOR MAIN REINFORCING BARS OF REINFORCED CONCRETE BEAMSc (APPLICABLE TO ALL TYPES OF STRUCTURAL CONCRETE)
RESTRAINED OR UNRESTRAINEDa BEAM WIDTHb (inches) FIRE-RESISTANCE RATING (hours)
1 11/2 2 3 4
Restrained 5 3/4 3/4 3/4 1a 11/4a
7
3/4 3/4 3/4 3/4 3/4
≥10 3/4 3/4 3/4 3/4 3/4
Unrestrained 5 3/4 1 11/4
7 3/4 3/4 3/4 13/4 3
≥ 10 3/4 3/4 3/4 1 13/4
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
  1. 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.
  2. For beam widths between the tabulated values, the minimum cover thickness can be determined by direct interpolation.
  3. 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.
MINIMUM COVER FOR PRESTRESSED CONCRETE BEAMS 8 INCHES OR GREATER IN WIDTHb
RESTRAINED OR UNRESTRAINEDa CONCRETE AGGREGATE TYPE BEAM WIDTH (inches) FIRE-RESISTANCE RATING (hours)
1 11/2 2 3 4
Restrained Carbonate or siliceous
8
11/2
11/2
11/2
13/4a
21/2a
Carbonate or siliceous
≥ 12
11/2
11/2
11/2
11/2
17/8a
Sand lightweight
8
11/2
11/2
11/2
11/2
2a
Sand lightweight
≥ 12
11/2
11/2
11/2
11/2
15/8a
Unrestrained Carbonate or siliceous
8
11/2
13/4
21/2
5c
Carbonate or siliceous
≥ 12
11/2
11/2
17/8a
21/2
3
Sand lightweight
8
11/2
11/2
2
31/4
Sand lightweight
≥ 12
11/2
11/2
15/8
2
21/2
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.
  1. 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.
  2. For beam widths between 8 inches and 12 inches, minimum cover thickness can be determined by direct interpolation.
  3. Not practical for 8-inch-wide beam but shown for purposes of interpolation.
MINIMUM COVER FOR PRESTRESSED CONCRETE BEAMS OF ALL WIDTHS
RESTRAINED OR UNRESTRAINEDa CONCRETE AGGREGATE TYPE BEAM AREAb A (square inches) FIRE-RESISTANCE RATING (hours)
1 11/2 2 3 4
Restrained All 40 ≤ A ≤ 150 11/2 11/2 2 21/2
Carbonate or siliceous 150 < A ≤ 300 11/2 11/2 11/2 13/4 21/2
300 < A 11/2 11/2 11/2 11/2 2
Sand lightweight 150 < A 11/2 11/2 11/2 11/2 2
Unrestrained All 40 ≤ A ≤ 150 2 21/2
Carbonate or siliceous 150 < A ≤ 300 11/2 13/4 21/2
300 < A 11/2 11/2 2 3c 4c
Sand lightweight 150 < A 11/2 11/2 2 3c 4c
For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm, 1 square inch = 645.2 mm2.
  1. 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.
  2. The cross-sectional area of a stem is permitted to include a portion of the area in the flange, provided that the width of the flange used in the calculation does not exceed three times the average width of the stem.
  3. 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.
722.2.3.1 Slab Cover
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 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 mm) or greater in width. Values in Table 722.2.3(5) apply to beams or stems of any width, provided that the cross-section area is not less than 40 square inches (25 806 mm2). 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 mm), whichever is greater.

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