Wood Shear Wall Unit Shear and Holdown (SDPWS / ASD)
The two numbers a wood shear wall is detailed for.
Example
You enter
- ASD story shear V on the wall (lb; 0.7 x strength-level seismic or 0.6 x wind) 8000
- Shear-wall length b (ft) 8
- Shear-wall height h (ft) 10
- Tributary dead load W (lb) 3000
You get
- Unit shear v = V/b 1,000 plf
- Mot (ft-lb) 80000
- Mr (ft-lb) 7200
- T (lb) 9100
No published worked example is on file for this calculation. It is checked against a hand-worked derivation of its method and an independent reference test.
Details, formula, and sources
ScopeThe 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 for wind, or (0.6 - 0.14 SDS) times it for seismic, where the vertical quake effect lightens the wall (the ASD combinations). 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 holdown 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 or tablev = V / b; Mot = V h; Mr = k W (b/2), k = 0.6 - 0.14 SDS (seismic; 0.6 for wind, SDS = 0); T = max((Mot - Mr) / b, 0).
Source and editionThe AWC SDPWS segmented shear-wall model with the ASCE 7 / IBC allowable-stress overturning check ((0.6 - 0.14 SDS)D seismic, 0.6D wind), as compiled in the AWC/APA wood-frame shear-wall design guides, by name.
Free accessAWC SDPWS is viewable free of charge through AWC's online reader; the unit-shear and overturning-couple arithmetic is public.
What governsEstimate. AHJ and licensed professional govern.
API field namesv_lb, b_ft, h_ft, w_lb, v_plf, mot_ftlb, mr_ftlb, t_lb
- Resisting dead load (0.6 - 0.14 SDS)D in the ASD seismic combination (Ev = 0.2 SDS D subtracts), 0.6D with wind (SDS entered as 0)ASCE 7-22 §2.4.5; ASCE 7-16 §12.4.2.3
- Segmented wall a single fully sheathed segment with the holdown at its end; perforated and force-transfer-around-openings walls distribute differentlyAWC SDPWS §4.3
- Companion checks separate sill anchor-bolt shear, compression-chord bearing, and the sheathing nailing selection are separate checksAWC/APA design guides