Simplified Frame Analysis - Simplified Design of Reinforced Concrete Buildings - page 23

Design live loads will depend on the intended use and occupancy of the portion or portions of the building
being designed. Live loads include loads due to movable objects and movable partitions temporarily supported
by the building during maintenance. In ASCE Table 4-1, uniformly distributed live loads range from 40 psf
for residential use to 250 psf for heavy manufacturing and warehouse storage. Portions of buildings, such
as library floors and file rooms, require substantially heavier live loads. Live loads on a roof include
maintenance equipment, workers, and materials. Also, snow loads, ponding of water, and special features, such
as landscaping, must be included where applicable.

Occasionally, concentrated live loads must be included; however, they are more likely to affect individual
supporting members and usually will not be included in the frame analysis (see ASCE 4.3).

2.2.2 Wind Loads

Wind pressure occurs as a result of transformation of the kinetic energy of the moving air when it is obstructed
by a building. The magnitude of pressure at a point depends on the velocity of the wind, the shape of the
building and the angle of incidence of the wind. Wind load effects on buildings are dynamic in nature. In case
of tall buildings, the dynamic nature of wind loads cannot be neglected. Tall buildings tend to deflect
appreciably and oscillate under wind effects. If a tall building is not properly designed for wind, the
oscillations may increase continuously leading to destruction. However, in many situations, such as buildings
of medium height and without irregularities, the dynamic nature of wind effects may be neglected. This allows
the designer to consider wind loads as statically applied pressure.

Design wind loads and procedures for design are usually given in the general building code having jurisdiction.
The calculation of wind loads in this publication is based on the procedure presented in ASCE/SEI 7-05 Standard,
Minimum Design Loads for Buildings and Other Structures 2.1 . The ASCE/SEI 7-05 Standard provides three
methods to account for wind effects on buildings; simplified procedure (ASCE/SEI Sec. 6.4), analytical
procedure (ASCE/SEI Sec. 6.5) and wind tunnel procedure (ASCE/SEI Sec. 6.6). For the scope of buildings
covered in this publication, the analytical procedure is used.

In the ASCE/SE 7-05 analytical procedure the wind load is treated as static pressure. The calculations of the
pressure depend on the building size, geometry, importance, location, and openness. The magnitude of the
pressure varies with the height above ground. The procedure requires the determination of basic wind speed,
wind directionality factor, velocity pressure coefficient, gust effect factor and velocity pressure coefficient.
Table 2-1 summarizes ASCE/SEI 7-05 wind pressure parameters and the relevant Section in the Standard.