Lateral loads can be applied by any one of the following three methods per Section 3.3.3.2.3 of FEMA 356.

## Method 1

The vertical distribution of the base shear shall be as specified in this section for all buildings. The lateral load applied at any floor level x shall be determined in accordance with equation (1-8-1) and equation (1-8-2):

 Fx = CvxV (1-8-1)

where
Cvx
=
 $w x h x k ∑ i = 1 n w i h i k$ (1-8-2)

## Method 2

A vertical distribution proportional to the shape of the fundamental mode in the direction under consideration is performed. Use of this distribution shall be permitted only when more than 75% of the  total mass participates in the fundamental mode in the direction under consideration, and the uniform distribution is also used.

 $F x = w x ϕ x ∑ i = 1 n w i ϕ i$ (1-8-3)

## Method 3

A vertical distribution is performed consisting of lateral forces at each level proportional to the total mass at each level .

 $F x = w x ∑ i = 1 n w i$ (1-8-4)
where
 Cvx = Vertical distribution factor k = Linear interpolation shall be used to calculate values of for intermediate values of k for intermediate values of T. = 2.0 for T ≥ 2.5 seconds = 1.0 for T ≤ 0.5 seconds V = User-defined base shear wi = Portion of the total building weight W located on or assigned to floor level i wx = Portion of the total building weight W located on or assigned to floor level x hi = Height (in ft) from the base to floor level i hx = Height (in ft) from the base to floor level x Fx = Amplitude of mode a floor level x