Section R608 Exterior Concrete Wall Construction
These provisions are based on the assumption that interior walls and partitions, both load-bearing and nonload-bearing, floors and roof/ceiling assemblies are constructed of light-framed construction complying with the limitations of this code and the additional limitations of Section R608.2. Design and construction of light-framed assemblies shall be in accordance with the applicable provisions of this code. Where second-story exterior walls are of light-framed construction, they shall be designed and constructed as required by this code.
The provisions of this section shall apply to the construction of exterior concrete walls for buildings not greater than 60 feet (18 288 mm) in plan dimensions, floors with clear spans not greater than 32 feet (9754 mm) and roofs with clear spans not greater than 40 feet (12 192 mm). Buildings shall not exceed 35 feet (10 668 mm) in mean roof height or two stories in height above grade. Floor/ceiling dead loads shall not exceed 10 pounds per square foot (479 Pa), roof/ceiling dead loads shall not exceed 15 pounds per square foot (718 Pa) and attic live loads shall not exceed 20 pounds per square foot (958 Pa). Roof overhangs shall not exceed 2 feet (610 mm) of horizontal projection beyond the exterior wall and the dead load of the overhangs shall not exceed 8 pounds per square foot (383 Pa).
Walls constructed in accordance with the provisions of this section shall be limited to buildings subjected to a maximum design wind speed of 160 mph (72 m/s) Exposure B, 136 mph (61 m/s) Exposure C and 125 mph (56 m/s) Exposure D. Walls constructed in accordance with the provisions of this section shall be limited to detached one- and two-family dwellings and townhouses assigned to Seismic Design Category A or B, and detached one- and two-family dwellings assigned to Seismic Design Category C.
Buildings that are not within the scope of this section shall be designed in accordance with PCA 100 or ACI 318.
DIMENSIONAL REQUIREMENTS FOR WALLSa, b
|WALL TYPE |
WIDTH, W, OF
THICKNESS, T, OF
|MINIMUM WEB |
For SI: 1 inch = 25.4 mm; 1 pound per square foot = 0.0479 kPa, 1 pound per cubic foot = 2402.77 kg/m3, 1 square inch = 645.16 mm2, 1 inch4 = 42 cm4.
- Width "W," thickness "T," spacing and web thickness, refer to Figures R608.3(2) and R608.3(3).
- N/A indicates not applicable.
- Wall weight is based on a unit weight of concrete of 150 pcf. For flat walls the weight is based on the nominal thickness. The tabulated values do not include any allowance for interior and exterior finishes.
- Nominal wall thickness. The actual as-built thickness of a flat wall shall not be more than 1/2 inch less or more than 1/4 inch more than the nominal dimension indicated.
- Vertical core is assumed to be elliptical-shaped. Another shape core is permitted provided the minimum thickness is 5 inches, the moment of inertia, I, about the centerline of the wall (ignoring the web) is not less than 65 inch4, and the area, A, is not less than 31.25 square inches. The width used to calculate A and I shall not exceed 8 inches.
- Vertical core is assumed to be circular. Another shape core is permitted provided the minimum thickness is 7 inches, the moment of inertia, I, about the centerline of the wall (ignoring the web) is not less than 200 inch4, and the area, A, is not less than 49 square inches. The width used to calculate A and I shall not exceed 8 inches.
- Vertical core is assumed to be circular. Another shape core is permitted provided the minimum thickness is 5.5 inches, the moment of inertia, I, about the centerline of the wall is not less than 76 inch4, and the area, A, is not less than 30.25 square inches. The width used to calculate A and I shall not exceed 6.25 inches.
Stay-in-place forms constructed of rigid foam plastics shall be protected from sunlight and physical damage by the application of an approved exterior wall covering complying with this code. Exterior surfaces of other stay-in-place forming systems shall be protected in accordance with this code.
Requirements for installation of masonry veneer, stucco and other finishes on the exterior of concrete walls and other construction details not covered in this section shall comply with the requirements of this code.
The following standards as referenced in Chapter 46 shall be permitted to be used.
- ASTM C150
- ASTM C595
- ASTM C1157
The nominal maximum size of coarse aggregate shall not exceed onefifth the narrowest distance between sides of forms, or three-fourths the clear spacing between reinforcing bars or between a bar and the side of the form.
Proportions of materials for concrete shall be established to provide workability and consistency to permit concrete to be worked readily into forms and around reinforcement under conditions of placement to be employed, without segregation or excessive bleeding. Slump of concrete placed in removable forms shall not exceed 6 inches (152 mm).
Exception:When approved, the slump is permitted to exceed 6 inches (152 mm) for concrete mixtures that are resistant to segregation, and are in accordance with the form manufacturer's recommendations.
Concrete shall be consolidated by suitable means during placement and shall be worked around embedded items and reinforcement and into corners of forms. Where stay-in-place forms are used, concrete shall be consolidated by internal vibration.
Exception:When approved, self-consolidating concrete mixtures with slumps equal to or greater than 8 inches (203 mm) that are specifically designed for placement without internal vibration need not be internally vibrated.
Forms shall be made of wood, steel, aluminum, plastic, a composite of cement and foam insulation, a composite of cement and wood chips, or other approved material suitable for supporting and containing concrete. Forms shall provide sufficient strength to contain concrete during the concrete placement operation.
Form ties shall be steel, solid plastic, foam plastic, a composite of cement and wood chips, a composite of cement and foam plastic, or other suitable material capable of resisting the forces created by fluid pressure of fresh concrete.
LAP SPLICE AND TENSION DEVELOPMENT LENGTHS
|BAR SIZE |
|YIELD STRENGTH OF STEEL, fy- psi (MPa)|
|40,000 (280)||60,000 (420)|
|Splice length or tension development length |
|Lap splice length-tension||4||20||30|
|Tension development length for straight bar||4||15||23|
|Tension development length for: ||4||6||9|
|Tension development length for bar with 90-degree or 180-degree standard |
hook having less cover than required above.
For SI: 1 inch = 25.4 mm.
MAXIMUM SPACING FOR ALTERNATIVE BAR SIZE AND/OR ALTERNATIVE GRADE OF STEELa, b, c
|BAR SPACING FROM |
APPLICABLE TABLE IN
|BAR SIZE FROM APPLICABLE TABLE IN SECTION R608.6|
|Alternate bar size and/or alternate grade of steel desired|
|Grade 60||Grade 40||Grade 60||Grade 40||Grade 60||Grade 40|
|Maximum spacing for alternate bar size and/or alternate grade of steel (inches)|
For SI: 1 inch = 25.4 mm.
- This table is for use with tables in Section R608.6 that specify the minimum bar size and maximum spacing of vertical wall reinforcement for foundation walls and above-grade walls. Reinforcement specified in tables in Section R608.6 is based on Grade 60 (420 MPa) steel reinforcement.
- Bar spacing shall not exceed 48 inches on center and shall be not less than one-half the nominal wall thickness.
- For Grade 50 (350 MPa) steel bars (ASTM A996, Type R), use spacing for Grade 40 (280 MPa) bars or interpolate between Grade 40 (280 MPa) and Grade 60 (420 MPa).