FEMA P55 Coastal Construction Manual, Fourth Edition - Mad Cad

8 DETERMINING SITE-SPECIFIC LOADS Volume II
EQUATION 8.16. VERTICAL DISTRIBUTION OF SEISMIC FORCES
The calculated seismic force at each story must be distributed into the building frame. The horizontal shear
forces and related overturning moments are taken into the foundation through a load path of horizontal
floor and roof diaphragms, shear walls, and their connections to supporting structural elements. A complete
seismic analysis includes evaluating the structure for vertical and plan irregularities, designing elements
and their connections in accordance with special seismic detailing, and considering structural system drift
criteria. Example 8.9 illustrates the use of basic seismic calculations.
EXAMPLE 8.9. SEISMIC LOAD
Given:
• S DS for the site = 2/3F a S s , which is determined to be 2/3(1.2)(0.50) = 0.4
• The building structure as shown in Illustration A. Dead load for the building is as follows:
Roof and ceiling = 10 lb/ft 2
Exterior walls = 10 lb/ft 2
Interior Walls = 8 lb/ft 2
Floor = 10 lb/ft 2
Piles = 409 lb each
(Eq. 8.16a)
(Eq. 8.16b)
where:
Fx = lateral seismic force induced at any level
Cvx = vertical distribution factor
V = seismic base shear
wi and wx = portion of the total effective seismic weight of the structure (w) located or
assigned to level i or x
hi and hx = height from the base to Level i or x
k = exponent related to the structure period; for structures having a period of 0.5 sec or
less, k=1
8-70 COASTAL CONSTRUCTION MANUAL