Seismic P-Delta Stability Coefficient (ASCE 7-22 12.8.7)
theta = Px delta Ie / (Vx hsx Cd): below 0.10 neglect P-delta, up to theta_max = min(0.5/(beta Cd), 0.25) amplify by 1/(1-theta), above it the story is potentially unstable. Px 400 kip, Delta 2.75 in, Vx 80 kip -> theta 0.017, neglect; a soft story at theta 0.19 must be redesigned. A design aid; the engineer of record governs.
Formula and source
theta = Px delta Ie / (Vx hsx Cd); theta_max = min(0.5/(beta Cd), 0.25); neglect <= 0.10, amplify 1/(1-theta) up to theta_max, unstable above.
The ASCE 7-22 12.8.7 P-delta stability coefficient and its limits, by name.
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