Design Notes

Specify:
The Designer will need to determine the holdown loads required at each floor. Use the charts provided to pick the appropriate Anchor Tiedown System (ATS) run based on the number of floors and the capacity. The ATS will provide only the tension part of the shearwall; the Designer will need to determine the compression shear edge nailing schedule, horizontal drift, and meet all other requirements in accordance with the applicable building code.

For simplicity during installation the Designer may want to designate and group similar runs.

Given Overturning (OT) Forces


Example for Derivation of Forces at Level 1:

1. Note that Moment Arm, M, is the distance between the centerline of compression members to centerline of tension members.
2. Cumulative OT Tension Force at level 1 =
   T₁= [S₁ (H₁) + S₂ (H₁ + H₂) + S₃ (H₁ + H₂ + H₃)] / M
   Cumulative OT Tension Force at level 2 =
   T₂= [S₂ (H₂) + S₃ (H₂ + H₃)] / M
   Cumulative OT Tension Force at level 3 =
   T₃= [S₃ (H₃)] / M
3. The incremental OT Forces are the difference between the cumulative OT Forces at each level. Incremental OT Force T₁ = 8,000 lbs. T₂ = 7,000 lbs. T₃ = 6,000 lbs. The incremental OT Forces are typically the incremental bearing forces.
4. See sketch at right for additional information.
5. Cumulative OT Compression Forces are higher than Cumulative OT Tension Forces due to the addition of code required dead loads.

topStep 1: Check Incremental and Cumulative ASD OT Forces against capacities.

1. The Designer is responsible for verifying that the building drift is within acceptable limitations and code limitations.

topStep 2: Use Compression Member Selection Tables to Select Compression Members

1. See 8-foot D.Fir-L compression capacity.
2. 8'-0" plate height and 1.33 load duration factor used.
3. Calculations based on 2005 NDS.
4. Example only reviews compression case for the lumber species, plate height, and loads provided. Designer must review compression post and size for any additional loads, load combinations, variation in species, variation in lumber grade, or unsupported heights as specified in the code.

topStep 3: The Solution

CTDS33 AND COMPRESSION MEMBERS SHOWN.

Typical CTDS33 Run