Design of timber shear walls
1. Determine the seismic load at each floor/roof level
2. Determine the design actions on the shear wall at each level,
T*,C*, and V*.
3. Design the sheathing to framing nail connections
4. From the previous step, determine the strength of the wall
5. Apply an overstrength factor of 2, and then calculate the
overstrength design actions for the chords and sheathing
6. Design the chords for tension and compression
7. Design the sheathing to resist shear
(note: figures and tables in this handout from NZS3603)
Sheathing to framing nail connections
First find the shear flow:
q* = V* / B, where B is the width of the wall.
Select a nail size, and obtain the design strengths Qn from Table 3 of the handout. Also
decide on spacings s, so that:
𝑞 ∗ ≤ ∅𝑄𝑛 /𝑠
Use a strength reduction factor, Ø, of 0.8
The yield strength of the wall Vy is then:
𝑉𝑦 = 𝐵 ∅𝑄𝑛 /𝑠
Design of end chords for tension and compression
Modification factors:
Duration of load factor: k1
Parallel support factor: k4
Stability factor: k8
First find the slenderness ratio for the appropriate axis of bending, S 2 or S3:
S2 = Lax / d
S3 = Lay / b
Then find the value of K8 from the figure below:
Example:
From http://www.timberdesign.org.nz/design.cfm/view/103/parent/26
Design of sheathing
Assume K8 = 1
t = thickness, d is panel thickness
Class exercise:
1. For the five storey wall below, draw the shear force and bending moment diagrams (lateral forces are in kN).
2. Determine the design actions for the 1st, 3rd and 5th floors (that is the tension and compression forces on the
end chords, and the shear resisted by the sheathing).
3. Design the 2nd floor shear wall, using VSG8 for the chords, and F11 plywood for the sheathing.