Wood Shear Wall Unit Shear and Holdown (SDPWS / ASD)
The two numbers a wood shear wall is detailed for: the unit shear v = V/b checked against the SDPWS nailing schedule, and the net holdown tension T = (V h - 0.6 W b/2)/b once the story shear tries to overturn the wall and only 0.6 times the tributary dead load resists it (the ASD combination). An 8 ft wall taking 8 kip at 10 ft with 3,000 lb of dead load runs 1,000 plf and a 9.1 kip holdown; load the wall to 20,000 lb and gravity cuts the holdown to 4.0 kip, and past the balance point the tile clamps to zero. Segmented wall; sill anchorage and chord bearing are separate. A design aid, not a substitute for the engineer of record's stamped lateral design.
Formula and source
v = V / b; Mot = V h; Mr = 0.6 W (b/2); T = max((Mot - Mr) / b, 0).
The AWC SDPWS segmented shear-wall model with the ASCE 7 / IBC 0.6D allowable-stress overturning check, as compiled in the AWC/APA wood-frame shear-wall design guides, by name.
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