Chapter 6WIND LOADS6.1 GENERAL6.1.1

Chapter 6
WIND LOADS
6.1 GENERAL
6.1.1 Scope.Buildings and other structures, including the Main
Wind-Force Resisting System (MWFRS) and all components and
cladding thereof, shall be designed and constructed to resist wind
loads as specified herein.
6.1.2 Allowed Procedures.The design wind loads for buildings
and other structures, including the MWFRS and component and
cladding elements thereof, shall be determined using one of the
following procedures: (1) Method 1—Simplified Procedure as
specified in Section 6.4 for buildings meeting the requirements
specified therein; (2) Method 2—Analytical Procedure as specified in Section 6.5 for buildings meeting the requirements specified therein; (3) Method 3—Wind Tunnel Procedure as specified
in Section 6.6.
6.1.3 Wind Pressures Acting on Opposite Faces of Each
Building Surface.In the calculation of design wind loads for
the MWFRS and for components and cladding for buildings, the
algebraic sum of the pressures acting on opposite faces of each
building surface shall be taken into account.
6.1.4 Minimum Design Wind Loading.The design wind load,
determined by any one of the procedures specified in Section 6.1.2, shall be not less than specified in this section.
6.1.4.1 Main Wind-Force Resisting System.The wind load to
be used in the design of the MWFRS for an enclosed or partially
enclosed building or other structure shall not be less than 10 lb/ft
2
(0.48 kN/m
2
)multiplied by the area of the building or structure
projected onto a vertical plane normal to the assumed wind direction. The design wind force for open buildings and other structures shall be not less than 10 lb/ft
2(0.48 kN/m
2
)multiplied by the
areaAf
.
6.1.4.2 Components and Cladding.The design wind pressure
for components and cladding of buildings shall not be less than
anet pressure of 10 lb/ft
2(0.48 kN/m
2
)acting in either direction
normal to the surface.
6.2 DEFINITIONS
The following definitions apply only to the provisions of
Chapter 6:
APPROVED:Acceptable to the authority having jurisdiction.
BASIC WIND SPEED,V:Three-second gust speed at 33 ft
(10 m) above the ground in Exposure C (see Section 6.5.6.3) as
determined in accordance with Section 6.5.4.
BUILDING, ENCLOSED:Abuilding that does not comply
with the requirements for open or partially enclosed buildings.
BUILDING ENVELOPE:Cladding, roofing, exterior walls,
glazing, door assemblies, window assemblies, skylight assemblies, and other components enclosing the building.
BUILDING AND OTHER STRUCTURE, FLEXIBLE:
Slender buildings and other structures that have a fundamental
natural frequency less than 1 Hz.
BUILDING, LOW-RISE: Enclosed or partially enclosed
buildings that comply with the following conditions:
1. Mean roof heighthless than or equal to 60 ft (18 m).
2. Mean roof heighthdoes not exceed least horizontal dimension.
BUILDING, OPEN: Abuilding having each wall at least
80 percent open. This condition is expressed for each wall by
the equation Ao≥0.8Agwhere
Ao=total area of openings in a wall that receives positive
external pressure, in ft
2(m
2
)
Ag=the gross area of that wall in which Ao is identified, in
ft
2(m
2
)
BUILDING, PARTIALLY ENCLOSED: Abuilding that
complies with both of the following conditions:
1. The total area of openings in a wall that receives positive
external pressure exceeds the sum of the areas of openings
in the balance of the building envelope (walls and roof ) by
more than 10 percent.
2. The total area of openings in a wall that receives positive
external pressure exceeds 4 ft
2(0.37 m
2
)or1percent of the
area of that wall, whichever is smaller, and the percentage
of openings in the balance of the building envelope does not
exceed 20 percent.
These conditions are expressed by the following equations:
1. Ao>1.10Aoi
2. Ao>4sqft (0.37 m
2
)or>0.01Ag, whichever is smaller,
andAoi/Agi≤0.20
where
Ao, Agare as defined for Open Building
Aoi =the sum of the areas of openings in the building envelope (walls and roof) not includingAo,inft
2(m
2
)
Agi=the sum of the gross surface areas of the building envelope (walls and roof) not includingAg,inft
2(m
2
)
BUILDING OR OTHER STRUCTURE, REGULARSHAPED:Abuilding or other structure having no unusual geometrical irregularity in spatial form.
BUILDING OR OTHER STRUCTURES, RIGID:Abuilding or other structure whose fundamental frequency is greater
than or equal to 1 Hz.
BUILDING, SIMPLE DIAPHRAGM:Abuilding in which
both windward and leeward wind loads are transmitted through
floor and roof diaphragms to the same vertical MWFRS (e.g., no
structural separations).
COMPONENTS AND CLADDING:Elements of the building envelope that do not qualify as part of the MWFRS.
Minimum Design Loads for Buildings and Other Structures 21