220.127.116.11 Story Drift for Moment Frames
The following equation for the drift ratio is applicable only to regular, multistory, multibay frames with columns continuous top and bottom:
Cd = deflection amplification factor from Table 18.104.22.168.
DR = drift ratio = interstory displacement divided by interstory height.
E = modulus of elasticity (ksi).
h = story height (in.).
I = moment of inertia (in.4).
kb = I/L for the beam.
kc = I/h for the column.
L = center-to-center length (in.).
Vc = shear in the column (kips).
For reinforced concrete frames, use appropriate cracked section properties pursuant to ACI 318-95 or later. For other configurations of frames, compute the drift ratio from the principles of structural mechanics.