Seismic Design Story Drift and Allowable Limit (ASCE 7-22 12.8.6 / 12.12)
Amplified drift delta_x = Cd delta_xe / Ie against the allowable delta_a = drift coefficient x story height (commonly 0.020 hsx). Cd 5.5, delta_xe 0.5 in, 144 in story -> 2.75 in vs 2.88 in allowable, OK at 0.955 utilization; a softer frame at 0.6 in fails. A design aid; the engineer of record governs.
Formula and source
delta_x = Cd delta_xe / Ie; delta_a = drift_ratio x hsx; util = delta_x / delta_a.
The ASCE 7-22 12.8.6 amplified design story drift and the 12.12 allowable story-drift limit, by name.
Audience
This tile is built for trades and the adjacent professions in the Carpentry and Construction group. The interactive calculator runs entirely in your browser. No account, no fee, no advertising, no tracking.
Related tools
Posture
Rough Logic answers the math question the working professional asks on the job. The site is a calm, fast, ad-free, account-free, ever-free reference. It does not interpret code. It does not replace the licensed professional. It does not store your inputs. The Authority Having Jurisdiction governs all installations and inspections.