Vertical Distribution of Seismic Forces (Section 12.8.3)

The vertical seismic force,. F_x, (kip) at a story level is calculated according to the following equation:

F_x = C_vxV

(12.8-11)

C_{v x} = \frac{w_{x} h_{x}^{k}}{\sum_{i = 1}^{n} w_{i} h_{i}^{k}}

where

C_vx	=	vertical distribution factor
V	=	Base shear (kip)
w_i & w_x	=	effective seismic weight (kip) at story i or x
h_i & h_x	=	height from base to level i or x
k	=	${\begin{matrix} 1.0 & T \leq 0.5 \\ 2.0 & T \geq 2.5 \end{matrix}$ Note: For structure with 0.5 < T < 2.5, a linear interpolation is permitted between 1 and 2.

For structures in Seismic Design Category A, the lateral seismic force for level x is calculated according to the following equation (see Sections 11.7 and 1.4):

F_x = 0.01W_x

(1.4-1)

where

W_x

dead load of structure at story x

Equation (1.4-1) is enforced within this implementation.