G.17.4.1.8 Lateral Load Distribution
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):
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.
Method 3
A vertical distribution is performed consisting of lateral forces at each level proportional to the total mass at each level .
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