Minimum Design Loads for Buildings and
Other Structures
1.0 GENERAL uncertainties in the analysis that transforms the load
into a load effect, and for the probability that more
than one extreme load will occur simultaneously.
1.1 SCOPE Loads: Forces or other actions that result from
the weight of all building materials, occupants and
This standard provides minimum load require- their possessions, environmental effects, differential
ments for the design of buildings and other structures movement, and restrained dimensional changes. Per-
that are subject to building code requirements. Loads manent loads are those loads in which variations over
and appropriate load combinations, which have been time are rare or of small magnitude. All other loads
developed to be used together, are set forth for are variable loads. (See also nominal loads.)
strength design and allowable stress design. For de- Nominal loads: The magnitudes of the loads
sign strengths and allowable stress limits, design specified in Sections 3 through 9 (dead, live, soil,
specifications for conventional structural materials wind, snow, rain, flood and earthquake) of this
used in buildings and modifications contained in this standard.
standard shall be followed. Nominal strength: The capacity of a structure or
member to resist the effects of loads, as determined
by computations using specified material strengths
1.2 DEFINITIONS and dimensions and formulas derived from accepted
principles of structural mechanics or by field tests or
The following definitions apply to the provisions laboratory tests of scaled models, allowing for mod-
of the entire standard. eling effects and differences between laboratory and
field conditions.
Allowable stress design: A method of propor-
Occupancy: The purpose for which a building
tioning structural members such that elastically com-
or other structure, or part thereof, is used or intended
puted stresses produced in the members by nominal
to be used.
loads do not exceed specified allowable stresses (also
Other structures: Structures, other than build-
called working stress design).
ings, for which loads are specified in this standard.
Authority having jurisdiction: The organiza-
P-delta effect: The second order effect on shears
tion, political subdivision, office or individual
and moments of frame members induced by axial
charged with the responsibility of administering and
loads on a laterally displaced building frame.
enforcing the provisions of this standard.
Resistance factor: A factor that accounts for de-
Buildings: Structures, usually enclosed by walls
viations of the actual strength from the nominal
and a roof, constructed to provide support or shelter
strength and the manner and consequences of failure
for an intended occupancy.
(also called strength reduction factor).
Design strength: The product of the nominal
Strength design: A method of proportioning
strength and a resistance factor.
structural members such that the computed forces
Essential facilities: Buildings and other struc-
produced in the members by the factored loads do
tures that are intended to remain operational in the
not exceed the member design strength (also called
event of extreme environmental loading from wind,
load and resistance factor design).
snow or earthquakes.
Temporary facilities: Buildings or other struc-
Factored load: The product of the nominal load
tures that are to be in service for a limited time and
and a load factor.
have a limited exposure period for environmental
Limit state: A condition beyond which a struc-
loadings.
ture or member becomes unfit for service and is
judged either to be no longer useful for its intended
function (serviceability limit state) or to be unsafe
(strength limit state). 1.3 BASIC REQUIREMENTS
Load effects: Forces and deformations produced
in structural members by the applied loads. 1.3.1 Strength
Load factor: A factor that accounts for devia- Buildings and other structures, and all parts
tions of the actual load from the nominal load, for thereof, shall be designed and constructed to support
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MINIMUM DESIGN LOADS FOR BUILDINGS AND OTHER STRUCTURES
safely the factored loads in load combinations defined 1.4 GENERAL STRUCTURAL INTEGRITY
in this document without exceeding the appropriate
strength limit states for the materials of construction. Buildings and other structures shall be designed
Alternatively, buildings and other structures, and all to sustain local damage with the structural system as
parts thereof, shall be designed and constructed to a whole remaining stable and not being damaged to
support safely the nominal loads in load combina- an extent disproportionate to the original local dam-
tions defined in this document without exceeding the age. This shall be achieved through an arrangement
appropriate specified allowable stresses for the mate- of the structural elements that provides stability to
rials of construction. the entire structural system by transferring loads from
any locally damaged region to adjacent regions capa-
1.3.2 Serviceability ble of resisting those loads without collapse. This
Structural systems and members thereof shall be shall be accomplished by providing sufficient conti-
designed to have adequate stiffness to limit deflec- nuity, redundancy, or energy-dissipating capacity
tions, lateral drift, vibration, or any other deforma- (ductility), or a combination thereof, in the members
tions that adversely affect the intended use and per- of the structure.
formance of buildings and other structures.
1.5 CLASSIFICATION OF BUILDINGS AND
1.3.3 Self-Straining Forces
OTHER STRUCTURES
Provision shall be made for anticipated self-
straining forces arising from differential settlements
Buildings and other structures shall be classified,
of foundations and from restrained dimensional
based on the nature of occupancy, according to Table
changes due to temperature, moisture, shrinkage,
1-1 for the purposes of applying flood, wind, snow,
creep, and similar effects.
and earthquake provisions. The categories range from
I to IV, where Category I represents buildings and
1.3.4 Analysis other structures with a low hazard to human life in
Load effects on individual structural members the event of failure and Category IV represents es-
shall be determined by methods of structural analysis sential facilities. Each building or other structure
that take into account equilibrium, general stability, shall be assigned to the highest applicable category
geometric compatibility, and both short- and long- or categories. Assignment of the same structure to
term material properties. Members that tend to accu- multiple categories, based on use and the type of
mulate residual deformations under repeated service load condition being evaluated (e.g. wind, seismic,
loads shall have included in their analysis the added etc.), shall be permissible.
eccentricities expected to occur during their service When buildings or other structures have multiple
life. uses (occupancies), the relationship between the uses
of various parts of the building or other structure and
1.3.5 Counteracting Structural Actions the independence of the structural systems for those
All structural members and systems, and all various parts shall be examined. The classification for
components and cladding in a building or other struc- each independent structural system of a multiple use
ture, shall be designed to resist forces due to earth- building or other structure shall be that of the highest
quake and wind, with consideration of overturning, usage group in any part of the building or other
sliding, and uplift, and continuous load paths shall be structure which is dependent on that basic structural
provided for transmitting these forces to the founda- system.
tion. Where sliding is used to isolate the elements,
the effects of friction between sliding elements shall
be included as a force. Where all or a portion of the 1.6 ADDITIONS AND ALTERATIONS TO
resistance to these forces is provided by dead load, EXISTING STRUCTURES
the dead load shall be taken as the minimum dead
load likely to be in place during the event causing When an existing building or other structure is
the considered forces. Consideration shall be given to enlarged or otherwise altered, structural members af-
the effects of vertical and horizontal deflections re- fected shall be strengthened if necessary so that the
sulting from such forces. factored loads defined in this document will be sup-
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ASCE 7-98
ported without exceeding the specified design 1.7 LOAD TESTS
strength for the materials of construction. When using
allowable stress design, strengthening is required A load test of any construction shall be con-
when the stresses due to nominal loads exceed the ducted when required by the authority having juris-
specified allowable stresses for the materials of diction whenever there is reason to question its safety
construction. for the intended occupancy or use.
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MINIMUM DESIGN LOADS FOR BUILDINGS AND OTHER STRUCTURES
TABLE 1-1. Classification of Buildings and Other Structures for Flood, Wind, Snow, and
Earthquake Loads
Nature of Occupancy Category
Buildings and other structures that represent a low hazard to human life in the event of failure including, I
but not limited to:
• Agricultural facilities
• Certain temporary facilities
• Minor storage facilities
All buildings and other structures except those listed in Categories I, III and IV II
Buildings and other structures that represent a substantial hazard to human life in the event of failure III
including, but not limited to:
• Buildings and other structures where more than 300 people congregate in one area
• Buildings and other structures with day-care facilities with capacity greater than 150
• Buildings and other structures with elementary or secondary school facilities with capacity greater
than 150
• Buildings and other structures with a capacity greater than 500 for colleges or adult education
facilities
• Health care facilities with a capacity of 50 or more resident patients but not having surgery or
emergency treatment facilities
• Jails and detention facilities
• Power generating stations and other public utility facilities not included in Category IV
Buildings and other structures containing sufficient quantities of toxic, explosive or other hazardous
substances to be dangerous to the public if released including, but not limited to:
• Petrochemical facilities
• Fuel storage facilities
• Manufacturing or storage facilities for hazardous chemicals
• Manufacturing or storage facilities for explosives
Buildings and other structures that are equipped with secondary containment of toxic, explosive or other IV
hazardous substances (including, but not limited to double wall tank, dike of sufficient size to
contain a spill, or other means to contain a spill or a blast within the property boundary of the
facility and prevent release of harmful quantities of contaminants to the air, soil, ground water, or
surface water) or atmosphere (where appropriate) shall be eligible for classification as a Category II
structure.
In hurricane prone regions, buildings and other structures that contain toxic, explosive, or other
hazardous substances and do not qualify as Category IV structures shall be eligible for classification
as Category II structures for wind loads if these structures are operated in accordance with
mandatory procedures that are acceptable to the authority having jurisdiction and which effectively
diminish the effects of wind on critical structural elements or which alternatively protect against
harmful releases during and after hurricanes.
Buildings and other structures designated as essential facilities including, but not limited to:
• Hospitals and other health care facilities having surgery or emergency treatment facilities
• Fire, rescue and police stations and emergency vehicle garages
• Designated earthquake, hurricane, or other emergency shelters
• Communications centers and other facilities required for emergency response
• Power generating stations and other public utility facilities required in an emergency
• Ancillary structures (including, but not limited to communication towers, fuel storage tanks, cooling
towers, electrical substation structures, fire water storage tanks or other structures housing or
supporting water or other fire-suppression material or equipment) required for operation of Category
IV structures during an emergency
• Aviation control towers, air traffic control centers and emergency aircraft hangars
• Water storage facilities and pump structures required to maintain water pressure for fire suppression
• Buildings and other structures having critical national defense functions
