Shear-Wall Cantilever Deflection (SDPWS)
Wood shear-wall deflection per the AWC SDPWS three-term equation — bending, panel shear via Ga, and anchorage slip, with drift ratio.
Your recent runs (stored only in your browser)
No calculations yet — results land here so you can compare runs.
The engineering
A wood-frame shear wall deflects like a cantilever with three softness sources: chord bending (the end studs stretching and shortening), panel shear distortion plus nail slip (lumped into the apparent shear stiffness Ga from SDPWS Table 4.3A), and rigid-body rotation from hold-down and anchorage slip. This card evaluates the SDPWS 4.3-1 three-term equation exactly as written — it is unit-locked to plf, feet, psi, in², and kips/in, so keep inputs in those units.
On real walls the shear and anchorage terms dominate; chord bending is usually a rounding error until h/b climbs past 2. If your drift looks bad, the cheapest fixes are a stiffer hold-down (Δa) and tighter nailing (higher Ga) — not bigger chords. Δa must include device slip, shrinkage, and crushing, elongated to the load level, and remember SDPWS caps WSP wall aspect ratio at 3.5:1 with a stiffness penalty above 2:1.
Where this math comes from
The classic four-term shear-wall deflection equation came out of racking tests run by the Douglas Fir Plywood Association (later APA) in the 1950s, where engineers separated the measured deflection into chord bending, panel shear, nail slip, and anchorage rotation so each could be predicted from first principles. That four-term form was eventually codified in the Uniform Building Code, complete with the awkward nail-slip term e_n that required table lookups per nail type and load.
When AF&PA (now the American Wood Council) published the first Special Design Provisions for Wind and Seismic in 2005, it folded panel shear and nail slip into a single tabulated apparent shear stiffness Ga, producing the three-term equation this card computes. It gives the same answer as the four-term version at design shear levels and is what IBC-referenced SDPWS editions require today.
- 1955Douglas Fir Plywood Association / APARacking-test programs decompose shear-wall deflection into bending, shear, nail-slip, and anchorage terms.
- 1997ICBO Uniform Building CodeCodifies the four-term deflection equation with the e_n nail-slip term in UBC Standard 23-2.
- 2005AF&PAFirst SDPWS edition introduces apparent shear stiffness Ga and the three-term equation 4.3-1.
- 2021American Wood CouncilSDPWS 2021, referenced by the IBC, carries the three-term equation with updated Ga tables.
See the full timeline of the math behind every calculator →
Runs entirely in your browser — nothing you enter leaves this page. Your recent runs are stored only on your device.