Wood Shear Wall Deflection (SDPWS Eq 4.3-1)
How far the top of a wood shear wall drifts, from the SDPWS three-term equation: end-post bending 8vh^3/(EAb), panel shear plus nail slip vh/(1000 Ga) with the tabulated apparent stiffness, and anchorage rotation h da/b from the holdown slack -- in the equation's own calibrated units. A 10 x 8 ft wall at 400 plf on 4x4 posts deflects 0.47 in (0.40% drift), the shear and anchorage terms carrying nearly all of it; double the height and the h^3 bending term wakes up. Checked against the ASCE 7 story-drift limit -- the reason a tall narrow wall can pass strength and fail stiffness. A design aid, not a substitute for the engineer of record's stamped lateral design.
Formula and source
delta = 8 v h^3 / (E A b) + v h / (1000 Ga) + h da / b (unit-specific: v plf, h/b ft, E psi, A in^2, Ga kips/in, da/delta in).
The AWC SDPWS Equation 4.3-1 three-term shear-wall deflection (the apparent-shear-stiffness Ga linearization of the legacy four-term form), as compiled in the AWC/APA wood-frame shear-wall design guides, by name.
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