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A406.3.1 Horizontal Wood Diaphragms
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Allowable shear values for existing horizontal wood diaphragms that require analysis under Section A403.10 are permitted to be taken from Table A4-A. The values in Table A4-A shall be used for allowable stress design. Design forces based on strength design shall be reduced to allowable stress levels before comparison with the limiting values in the table.
EXISTING MATERIALS OR CONFIGURATIONS OF MATERIALSa |
ALLOWABLE VALUES |
´ 14.594 for N/m | |
1. Horizontal diaphragmsb 1.1. Roofs with straight sheathing and roofing applied directly to the sheathing 1.2. Roofs with diagonal sheathing and roofing applied directly to the sheathing 1.3. Floors with straight tongue-and-groove sheathing 1.4. Floors with straight sheathing and finished wood flooring with board edges offset or perpendicular 1.5. Floors with diagonal sheathing and finished wood flooring |
-100 lbs. per ft. for seismic shear 250 lbs. per ft. for seismic shear 100 lbs. per ft. for seismic shear 500 lbs. per ft. for seismic shear 600 lbs. per ft. for seismic shear |
2. Crosswallsb, c 2.1. Plaster on wood or metal lath 2.2. Plaster on gypsum lath 2.3. Gypsum wallboard, unblocked edges 2.4. Gypsum wallboard, blocked edges | Per side: 200 lbs. per ft. for seismic shear 175 lbs. per ft. for seismic shear 75 lbs. per ft. for seismic shear 125 lbs. per ft. for seismic shear |
3. Existing footings, wood framing, structural steel and reinforced steel 3.1. Plain concrete footings 3.2. Douglas fir wood 3.3. Reinforcing steel 3.4. Structural steel | f 'c = 1,500 psi (10.3 MPa) unless otherwise shown by testsd Allowable stress same as D.F. No. 1d fs = 18,000 psi (124 MPa) maximumd fs = 20,000 psi (138 MPa) maximumd |
For SI: 1 foot = 304.8 mm.
- Material must be sound and in good condition.
- A one-third increase in allowable stress is not allowed.
- Shear values of these materials may be combined, except the total combined value shall not exceed 300 pounds per foot.
- Stresses given may be increased for combination of loads as specified in the building code.
Related Code Sections
A406.3.1 Earthquake Hazard Reduction in Existing Woodframe Residential Buildings With Soft, Weak or Openfront Walls, Horizontal Wood Diaphragms
Allowable shear values for existing horizontal wood diaphragms that require analysis under Section A403.10 are permitted to be taken from Table A4-A ...
A403.8 Earthquake Risk Reduction in Wood-Frame Residential Buildings With Soft, Weak or Open Front Walls, Horizontal Diaphragms
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A403.10 Earthquake Hazard Reduction in Existing Woodframe Residential Buildings With Soft, Weak or Openfront Walls, Horizontal Diaphragms
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2508.5 Gypsum Board and Plaster, Horizontal Gypsum Board Diaphragm Ceilings
Gypsum board shall be permitted to be used on wood joists to create a horizontal diaphragm ceiling in accordance with Table 2508.5.
TABLE 2508.5 ...
2508.6 Gypsum Board, Gypsum Panel Products and Plaster, Horizontal Gypsum Board or Gypsum Panel Product Diaphragm Ceilings
Gypsum board or gypsum panel products shall be permitted to be used on wood joists to create a horizontal diaphragm ceiling in accordance with Table ...