30 November 1998
C8. PERIOD DETERMINATION. The fundamental period of the building, T in the direction under
consideration shall be defined using the structural properties and deformational characteristics of the
resisting elements in a properly substantiated analysis (FEMA 302, 5.3.3). Alternatively, T is permitted
to be taken as the approximate fundamental period, Ta determined in accordance with the following
requirements. The fundamental period, T shall not exceed the product of the coefficient for upper limit
on calculated period, Cu from Table C-4 and the approximate fundamental period, Ta determined as
Ta = CThn
CT = constant = 0.0731 metric, (0.030 English) for cold-formed steel shear panels with
hn = the height in meters (ft - English) above the base to the highest level in the structure.
Table C-4 Coefficient for Upper Limit on Calculated Period
Design Spectral Response
SD1 < 0.1g
0.1g ≤ SD1 < 0.15g
0.15g ≤ SD1 < 0.2g
0.2g ≤ SD1 < 0.3g
0.3g ≤ SD1 < 0.4g
0.4g ≤ SD1
C9. VERTICAL DISTRIBUTION OF LATERAL SEISMIC FORCES. The vertical distribution of lateral
seismic forces, Fx (kN or kip), induced at any level shall be determined from the following equations
(FEMA 302, 5.3.4):
Fx = C vx V
Wx h x
C vx =
Cvx = the vertical distribution factor.
V = the total design lateral force or shear at the base of the structure (kN or kip).
wi and wx = the portion of the total gravity load of the structure, W located or assigned to level i
hi and hx = the height (m or ft) from the base to level i or x.
The horizontal distribution of seismic story shear in any story, Vx (kN or kips) shall be determined from
the following equation (FEMA 302, 5.3.5):
Vx = ∑ Fi
Fi = the portion of the seismic base shear, V (kN or kips) induced at level i.