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# 2305.3 Design of Wood Shear Walls

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Wood shear walls are permitted to resist horizontal forces in vertical distributing or resisting elements, provided the deflection in the plane of the shear wall, as determined by calculations, tests or analogies drawn therefrom, does not exceed the more restrictive of the permissible deflection of attached distributing or resisting elements or the drift limits of Section 12.12.1 of ASCE 7. Shear wall sheathing other than wood structural panels shall not be permitted in Seismic Design Category E or F (see Section 1613).

Permissible deflection shall be that deflection up to which the shear wall and any attached distributing or resisting element will maintain its structural integrity under design load conditions, i.e., continue to support design loads without danger to occupants of the structure.

The deflection (Δ) of a blocked wood structural panel shear wall uniformly fastened throughout is permitted to be calculated by the use of the following equation:

where:

v = Maximum shear due to design loads at the top of the wall, in pounds per linear foot (N/mm).

Δ = The calculated deflection, in inches (mm).

The deflection (Δ) of a blocked wood structural panel shear wall uniformly fastened throughout is permitted to be calculated by the use of the following equation:

(Equation 23-2)

For SI:

where:

*= Area of boundary element cross section in square inches (mm*

AA

^{2}) (vertical member at shear wall boundary).*= Wall width, in feet (mm).*

bb

*= Vertical elongation of overturning anchorage (including fastener slip, device elongation, anchor rod elongation, etc.) at the design shear load (*

dd

_{a}*v*).*= Elastic modulus of boundary element (vertical member at shear wall boundary), in pounds per square inch (N/mm*

EE

^{2}).*= Nail or staple deformation, in inches (mm) [see Table 2305.2.2(1)].*

ee

_{n}*Panel rigidity through the thickness, in pounds per inch (N/mm) of panel width or depth [see Table 2305.2.2(2)].*

Gt =Gt =

*= Wall height, in feet (mm).*

hh

v = Maximum shear due to design loads at the top of the wall, in pounds per linear foot (N/mm).

Δ = The calculated deflection, in inches (mm).

Wood shear walls shall be constructed of wood structural panels manufactured with exterior glue and not less than 4 feet by 8 feet (1219 mm by 2438 mm), except at boundaries and at changes in framing. All edges of all panels shall be supported by and fastened to framing members or blocking. Wood structural panel thickness for shear walls shall not be less than set forth in Table 2304.6.1 for corresponding framing spacing and loads, except that

^{1}/_{4}inch (6.4 mm) is permitted to be used where perpendicular loads permit.Size and shape of shear walls, perforated shear wall segments within perforated shear walls and wall piers within shear walls that are designed for force transfer around openings shall be limited as set forth in Table 2305.3.4. The height,

*h*, and the width,*w*, shall be determined in accordance with Sections 2305.3.5 through 2305.3.5.2 and 2305.3.6 through 2305.3.6.2, respectively. TYPE | MAXIMUM HEIGHT-WIDTH RATIO |

Wood structural panels or particleboard, nailed edges | For other than seismic: 3^{1}/_{2}:1 For seismic: 2:1^{a} |

Diagonal sheathing, single | 2:1 |

Fiberboard | 1^{1}/_{2}:1 |

Gypsum board, gypsum lath, cement plaster | 1^{1}/_{2}:1^{b} |

- For design to resist seismic forces, shear wall height-width ratios greater than 2:1, but not exceeding 3
^{1}/_{2}:1, are permitted provided the allowable shear values in Table 2306.4.1 are multiplied by 2*w/h*. - Ratio shown is for unblocked construction. Height-to-width ratio is permitted to be 2:1 where the wall is installed as blocked construction in accordance with Section 2306.4.5.1.2.

The height of a shear wall,

*h*, shall be defined as:- The maximum clear height from the top of the foundation to the bottom of the diaphragm framing above; or
- The maximum clear height from the top of the diaphragm to the bottom of the diaphragm framing above [see Figure 2305.3.5(a)].

The height of a perforated shear wall segment,

*h*, shall be defined as specified in Section 2305.3.5 for shear walls.The height,

*h*, of a wall pier in a shear wall with openings designed for force transfer around openings shall be defined as the clear height of the pier at the side of an opening [see Figure 2305.3.5(b)].The width of a shear wall,

*w*, shall be defined as the sheathed dimension of the shear wall in the direction of application of force [see Figure 2305.3.5(a)].The width of a perforated shear wall segment,

*w*, shall be defined as the width of full-height sheathing adjacent to openings in the perforated shear wall [see Figure 2305.3.5(a)].The width,

*w*, of a wall pier in a shear wall with openings designed for force transfer around openings shall be defined as the sheathed width of the pier at the side of an opening [see Figure 2305.3.5(b)].Where the dead load stabilizing moment in accordance with Chapter 16 allowable stress design load combinations is not sufficient to prevent uplift due to overturning moments on the wall, an anchoring device shall be provided. Anchoring devices shall maintain a continuous load path to the foundation. Wood structural panel sheathing and fastening designed to transfer resultant forces across horizontal framing joints shall constitute an acceptable continuous load path as an alternative to the use of anchorage devices when calculated by principles of mechanics using values of fastener strength and sheathing shear resistance.

The provisions of this section shall apply to the design of shear walls with openings. Where framing and connections around the openings are designed for force transfer around the openings, the provisions of Section 2305.3.8.1 shall apply. Where framing and connections around the openings are not designed for force transfer around the openings, the provisions of Section 2305.3.8.2 shall apply.

Where shear walls with openings are designed for force transfer around the openings, the limitations of Table 2305.3.4 shall apply to the overall shear wall, including openings, and to each wall pier at the side of an opening. Design for force transfer shall be based on a rational analysis. Detailing of boundary elements around the opening shall be provided in accordance with the provisions of this section[see Figure 2305.3.5(b)].

The provisions of Section 2305.3.8.2 shall be permitted to be used for the design of perforated shear walls. For the determination of the height and width of perforated shear wall segments, see Sections 2305.3.5.1 and 2305.3.6.1, respectively.

For SI: 1 inch = 25.4 mm, 1 foot = 304.8 mm.

WALL HEIGHT, H | MAXIMUM OPENING HEIGHT ^{a} | ||||

H/3 | H/2 | 2H/3 | 5H/6 | H | |

8' wall | 2'- 8" | 4'- 0" | 5'- 4" | 6'- 8" | 8'- 0" |

10' wall | 3'- 4" | 5'- 0" | 6'- 8" | 8'- 4" | 10'- 0" |

Percentage of full-height sheathing ^{b} | Shear resistance adjustment factor | ||||

10% | 1.00 | 0.69 | 0.53 | 0.43 | 0.36 |

20% | 1.00 | 0.71 | 0.56 | 0.45 | 0.38 |

30% | 1.00 | 0.74 | 0.59 | 0.49 | 0.42 |

40% | 1.00 | 0.77 | 0.63 | 0.53 | 0.45 |

50% | 1.00 | 0.80 | 0.67 | 0.57 | 0.50 |

60% | 1.00 | 0.83 | 0.71 | 0.63 | 0.56 |

70% | 1.00 | 0.87 | 0.77 | 0.69 | 0.63 |

80% | 1.00 | 0.91 | 0.83 | 0.77 | 0.71 |

90% | 1.00 | 0.95 | 0.91 | 0.87 | 0.83 |

100% | 1.00 | 1.00 | 1.00 | 1.00 | 1.00 |

- See Section 2305.3.8.2.2, Item 2.
- See Section 2305.3.8.2.2, Item 1.

The following limitations shall apply to the use of Section 2305.3.8.2:

- A perforated shear wall segment shall be located at each end of a perforated shear wall. Openings shall be permitted to occur beyond the ends of the perforated shear wall, provided the width of such openings is not be included in the width of the perforated shear wall.
- The allowable shear set forth in Table 2306.4.1 shall not exceed 490 plf (7150 N/m).
- Where out-of-plane offsets occur, portions of the wall on each side of the offset shall be considered as separate perforated shear walls.
- Collectors for shear transfer shall be provided through the full length of the perforated shear wall.
- A perforated shear wall shall have uniform top of wall and bottom of wall elevations. Perforated shear walls not having uniform elevations shall be designed by other methods.
- Perforated shear wall height,
*h*, shall not exceed 20 feet (6096 mm).

The resistance of a perforated shear wall shall be calculated in accordance with the following:

- The percentage of full-height sheathing shall be calculated as the sum of the widths of perforated shear wall segments divided by the total width of the perforated shear wall, including openings.
- The maximum opening height shall be taken as the maximum opening clear height. Where areas above and below an opening remain unsheathed, the height of the opening shall be defined as the height of the wall.
- The unadjusted shear resistance shall be the allowable shear set forth in Table 2306.4.1 for height-to-width ratios of perforated shear wall segments that do not exceed 2:1 for seismic forces and 3
^{1}/_{2}:1 for other than seismic forces. For seismic forces, where the height-to-width ratio of any perforated shear wall segment used in the calculation of the sum of the widths of perforated shear wall segments, Σ*L*, is greater than 2:1 but does not exceed 3_{i}^{1}/_{2}:1, the unadjusted shear resistance shall be multiplied by 2*w/h*. - The adjusted shear resistance shall be calculated by multiplying the unadjusted shear resistance by the shear resistance adjustment factors of Table 2305.3.8.2. For intermediate percentages of full-height sheathing, the values in Table 2305.3.8.2 are permitted to be interpolated.
- The perforated shear wall resistance shall be equal to the adjusted shear resistance times the sum of the widths of the perforated shear wall segments.

Design of perforated shear wall anchorage and load path shall conform to the requirements of Sections 2305.3.8.2.4 through 2305.3.8.2.8, or shall be calculated using principles of mechanics. Except as modified by these sections, wall framing, sheathing, sheathing attachment and fastener schedules shall conform to the requirements of Section 2305.2.4 and Table 2306.4.1.

Anchorage for uplift forces due to overturning shall be provided at each end of the perforated shear wall. The uplift anchorage shall conform to the requirements of Section 2305.3.7, except that for each story the minimum tension chord uplift force,

Σ

*T*, shall be calculated in accordance with the following: (Equation 23-3)

where: *= Tension chord uplift force, pounds (N).*

TT

*= Shear force in perforated shear wall, pounds (N).*

VV

*= Perforated shear wall height, feet (mm).*

hh

CC

_{o}= Shear resistance adjustment factor from Table 2305.3.8.2.Σ

*L*_{i}= Sum of widths of perforated shear wall segments, feet (mm).The unit shear force,

where:

v

S

*v*, transmitted into the top of a perforated shear wall, out of the base of the perforated shear wall at full height sheathing and into collectors connecting shear wall segments shall be calculated in accordance with the following: (Equation 23-4) |

where:

v

*=*Unit shear force, pounds per lineal feet (N/m).*= Shear force in perforated shear wall, pounds (N).*

VV

CC

_{o}= Shear resistance adjustment factor from Table 2305.3.8.2.S

*L*_{i }= Sum of widths of perforated shear wall segments, feet (mm).In addition to the requirements of Section 2305.3.8.2.4, perforated shear wall bottom plates at full-height sheathing shall be anchored for a uniform uplift force,

*t*, equal to the unit shear force,*v*, determined in Section 2305.3.8.2.5.Each end of each perforated shear wall segment shall be designed for a compression chord force,

*C*, equal to the tension chord uplift force,*T*, calculated in Section 2305.3.8.2.4.A load path to the foundation shall be provided for each uplift force, T and t, for each shear force, V and v, and for each compression chord force, C. Elements resisting shear wall forces contributed by multiple stories shall be designed for the sum of forces contributed by each story. Wood structural panel sheathing and fastening designed to transfer resultant forces across horizontal framing joints shall constitute an acceptable continuous load path as an alternative to the use of anchorage devices when calculated by principles of mechanics using values of fastener strength and sheathing shear resistance.

The controlling deflection of a blocked shear wall with openings uniformly fastened throughout shall be taken as the maximum individual deflection of the shear wall segments calculated in accordance with Section 2305.3.2, divided by the appropriate shear resistance adjustment factors of Table 2305.3.8.2.

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