The three-term deflection combines the shear and nail slip terms
with
where the formula for Ga is adapted from the American Wood Council's Special Design Provisions from Wind and Seismic (SDPWS), Equation C4.2.2-3 as
where vCAP is the force using serviceability load combinations (SLS) at the point where the shear wall is at capacity using ultimate limit state combinations (ULS). For wind design
where
For seismic design, it is
where IE is the ULS importance factor for wind design.