1609.6.3 Simplified Design Procedure II

Main wind force-resisting systems shall comply with the following:

1. The building shall be designed for the following net lateral wind pressure to be applied to the horizontal projection of the building surfaces:

1.1. From 0 to 100 feet (0 to 30 480 mm) elevation 20 psf (0.96 kN/m²).

1.2. From 100 to 300 feet (30 480 to 91 440 mm) elevation 25 psf (1.2 kN/m²).

2. An importance factor, I, shall be determined in accordance with Section 1609.5 and shall be applied to the pressures indicated above.

The main wind-force-resisting system of buildings, whose wind loads have been determined pursuant to Section 1609.6.3, shall be designed for wind load cases as defined below:

Case 1.
Full design wind pressure acting on the projected area perpendicular to each principal axis of the structure, considered separately along each principal axis.

Case 2.
Seventy-five percent of the design wind pressure acting on the projected area perpendicular to each principal axis of the structure to be applied eccentric to the center of the exposure with eccentricity equal to 15 percent of the exposure width, considered separately for each principal direction.

Case 3.
Wind loading as defined in Case 1 for each orthogonal direction, but considered to act simultaneously at 75 percent of the specified value.

Net design wind positive and negative pressures (pressure and suction) for the components and cladding of buildings represent the net pressures (sum of internal and external) to be applied normal to each building surface. The net design wind positive and negative pressures shall not be less than 30 psf (1.44 kN/m²), except at the corners of the building with a width equivalent to 10 percent of the building's width at its side, the net design wind negative pressure for the components and cladding shall not be less than: (i) 45 psf (2.16 kN/m²) for the portion of the building between 200 feet (60.76 meters) to 300 feet (91.14 meters) height above ground and (ii) 40 psf (1.92 kN/m²) for the portion of the building between 100 feet (30.38 meters) to 199 feet (60.66 meters) in height above ground.

The design pressure and suction acting over the entire roof including purlins, roofing, and other roof elements (including their fastenings) shall not be less than 30 psf (1.44 kN/m²).

The following building elements of buildings whose wind loads have been determined under the provisions of Section 1609.6.3 shall be designed for wind pressures shown in Section 1609.6.3.1 multiplied by the following shape factors given in Table 1609.6.3.5.

TABLE 1609.6.3.5 OTHER BUILDING ELEMENTS

CONSTRUCTION SHAPE FACTOR
Signs (and their supports), or portions thereof, having 70 percent or more of solid surface	1.5
Signs (and their supports), or portions thereof, having less than 70 percent of solid surface	2.0
Tanks, cooling towers, and similar constructions	1.5
Square and rectangular chimneys	1.5

Eaves, cornices, and overhanging elements of the buildings shall be designed for upward pressures twice the values given in Section 1609.6.3.1.