Title: Shear Walls
1Shear Walls
2Typical Shear Wall
3Location of Shear Walls
- Create box structure
- Equal length symmetrical
Even Distribution of Shear Walls
4Break in Load Path
Exterior Shear Wall
Interior Partition
Interior Shear Wall
Cripple Wall
Continuous Load Path
Floor Must Support Shear Wall
5Vertical Offset of Shear Wall
6Shear Wall OverFloor Beam
7Horizontal Shear Forces
8Uplift Forces OnShear Wall
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10Two Functions of a Shear Wall
STIFFNESS Control Sidesway
Earthquake Force
STRENGTH
Resist Shear
Connection For Uplift Resistance
Connection For Sliding Resistance
11What Provides Shear Wall Strength?
- Lumber
- Sheathing
- Fasteners
12LumberStrengthFailure
13Sheathing Strength Failure
14FastenerStrengthFailure
15Combining Different Material Strengths
- Different sheathing materials DO NOT combine
strength - Sheathing materials reach ultimate strength at
different wall displacements
16Sheathing Material Strengths
17C
T
Earthquake Force
End Stud in Tension
Earthquake Force
End Stud in Compression
C
T
Resisting Force from Connection
18Most Important Factors
Height
Weight
ARE STIFFER THAN
Tall Narrow Walls
Long Short Walls
19Allowable Aspect Ratios
20Northridge EarthquakeShowed Us
- Most materials did NOT do as well as predicted
- More material and wider walls needed
21Reduced Code Values
22Drywall Failure
23Stucco Failure
24NarrowPanelFailure
25Successful Plywood Coverage
26Wood Structural Panel Shear Walls
- Lumber type
- Lumber size
- Condition of existing wood
27Douglas Fir-Larch
Stronger
Weaker
Hem Fir
28Effect Of Lumber Species On Strength
Allowable Shears (lbs/ft) Based on Lumber Species
Nail Spacing at Panel Edges
Common Nail Sizes
Wood Structural Panel
Redwood Open Grain
Hem- Fir
Douglas Fir-Larch
Thickness
Panel Grade
15/32 in
Structural 1
8d
4
430
355
280
15/32 in
Structural 1
8d
3
550
450
360
Structural 1
15/32 in
10d
3
665
545
430
29Use Proper Size Stud
- Framing members split at ultimate loads when
sheathing nails are closely spaced - Shear Walls 17 stronger when 3 framing used
throughout
302 Adjoining Stud
31Install Proper Size Blocking
- Fasten all edges to framing members or blocking
- Provide blocking if panel members are unsupported
between framing members
32Cripple Wall Blocking
333 Flat Blocking
34Reinforced Window Opening in Shear Wall
35Blocking For Opening Reinforcement
36How is the Length ofShear Wall Measured?
- Horizontally along sheathing between wall ends
with hold-downs - NOT length of plywood
- IS measured by hold-down location
37Whats Wrong?
Too close to end wall countersunk
38Whats Wrong?
Too far from shear wall end
39Acceptable Hold-Down Location
40Lumber Grade
41Effect of Lumber Grade onHold-Down Capacity
42Penetration Through Shear Wall
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45Wood Decay
46Termite Damage
47Crawl Space Ventilation
48Installing the Sheathing
- Use specified wood structural panel
- OSB
- Plywood
49Construction of Oriented Strand Board Panel
50Construction of Plywood
3 ply 3 layer panel
4 ply 3 layer panel
5 ply 5 layer panel
51Minimum Recommended Thickness
- 15/32
- Both 4-ply and 5-ply
- More plies ð stronger sheathing
52Use Correct Panel Grade
53Sheathing Orientation
54- Use proper size panel
- 21 aspect ratio
- 4 x 8 panel minimum
- Mark stud locations on panels
- Avoid improper fastening
- Maintain fire resistive and sound-rated
construction - Dont change anything!
55Cripple Wall Ventilation
56Shear WallFasteners
57Use Common Nails
58Use ProperNail LengthandHead Size
59Performance Losses for Nail Substitutions
60Nail Gun With Flush Attachment
61Round-Head Nails(P-Nails)
ModifiedRound-Head Nails (P-Nails)
62Clipped Nail Head
Smaller nail head areas è smaller shear wall
strengths
631994 UBC
Nail should not fracture the surface of the
sheathing
1997 UBC
The head or crown of the nail is flush with the
surface of the sheathing
Overdriven nails reduce shear wall strength
64Overdriven Nails
Improper Edge Distance
65Important
- Install nails flush to sheathing
- Maintain proper sheathing edge distance
- Check for splitting
- Remove improperly installed nails
- Provide proper edge nailing
66OOPS!
67How to Nail a Shear Wall
- Edge nail
- hold-down stud(s)
- upper top plate
- sill or sole plate
- blocking for individual panel edges
- blocking for opening reinforcement
- Field nail the studs between the panel edges