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definitions index
ALLOWABLE
STRESS DESIGN.
A
method of proportioning structural members, such that elastically
computed stresses produced in the members by nominal loads
do not exceed specified allowable stresses (also called “working
stress design”).
BALCONY, EXTERIOR.
An exterior floor
projecting from and supported by a structure without additional
independent supports.
DEAD LOADS.
The weight of materials
of construction incorporated into the building, including
but not limited to walls, floors, roofs, ceilings, stairways,
built-in partitions, finishes, cladding and other similarly
incorporated architectural and structural items, and the weight
of fixed service equipment, such as cranes, plumbing stacks
and risers, electrical feeders, heating, ventilating and air-conditioning
systems and fire sprinkler systems.
DECK.
An exterior floor
supported on at least two opposing sides by an adjacent structure,
and/or posts, piers or other independent supports.
DESIGN STRENGTH.
The product of the
nominal strength and a resistance factor (or strength reduction
factor).
DIAPHRAGM.
A horizontal or sloped
system acting to transmit lateral forces to the vertical-resisting
elements. When the term “diaphragm” is used, it
shall include horizontal bracing systems.
Diaphragm,
blocked. In
light-frame construction, a diaphragm in which all sheathing
edges not occurring on a framing member are supported on and
fastened to blocking.
Diaphragm
boundary. In
light-frame construction, a location where shear is transferred
into or out of the diaphragm sheathing. Transfer is either
to a boundary element or to another force-resisting element.
Diaphragm
chord. A diaphragm
boundary element perpendicular to the applied load that is
assumed to take axial stresses due to the diaphragm moment.
Diaphragm
flexible.
A
diaphragm is flexible for the purpose of distribution of story
shear and torsional moment where so indicated in Section 12.3.1
of ASCE7, as modified in
Section 1613.6.1.
Diaphragm,
rigid. A
diaphragm is rigid for the purpose of distribution of story
shear and torsional moment when the lateral deformation of
the diaphragm is less than or equal to two times the average
story drift.
DURATION OF
LOAD. The
period of continuous application of a given load, or the aggregate
of periods of intermittent applications of the same load.
ESSENTIAL
FACILITIES. Buildings
and other structures that are intended to remain operational
in the event of extreme environmental loading from flood,
wind, snowor earthquakes.
FABRIC PARTITIONS.
A partition consisting
of a finished surface made of fabric, without a continuous
rigid backing, that is directly attached to a framing system
in which the vertical framing members are spaced greater than
4 feet (1219 mm) on center.
FACTORED LOAD.
The product of a
nominal load and a load factor.
GUARD.
See Section
1002.1.
IMPACT LOAD.
The load resulting
from moving machinery, elevators, craneways, vehicles and
other similar forces and kinetic loads, pressure and possible
surcharge from fixed or moving loads.
LIMIT STATE.
A condition beyond
which a structure or member becomes unfit for service and
is judged to be no longer useful for its intended function
(serviceability limit state) or to be unsafe (strength limit
state).
LIVE LOADS.
Those loads produced
by the use and occupancy of the building or other structure
and do not include construction or environmental loads such
as wind load, snow load, rain load, earthquake load, flood
load or dead load.
LIVE LOADS
(ROOF). Those
loads produced:
(1) during maintenance
by workers, equipment and materials; and
(2) during the
life of the structure by movable objects such as planters
and by people.
LOAD AND RESISTANCE
FACTOR DESIGN (LRFD).
A method of proportioning
structural members and their connections using load and resistance
factors such that no applicable limit state is reached when
the structure is subjected to appropriate load combinations.
The term “LRFD” is used in the design of steel and
wood structures.
LOAD EFFECTS.
Forces and deformations
produced in structural members by the applied loads.
LOAD FACTOR.
A factor that accounts
for deviations of the actual load from the nominal load, for
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.
LOADS.
Forces
or other actions that result from the weight of building materials,
occupants and their possessions, environmental effects, differential
movement and restrained dimensional changes. Permanent loads
are those loads in which variations over time are rare or
of small magnitude, such as dead loads. All other loads are
variable loads (see also “Nominal
loads”).
NOMINAL LOADS.
The magnitudes of
the loads specified in this chapter (dead, live, soil, wind,
snow, rain, flood and earthquake).
OCCUPANCY
CATEGORY. A
category used to determine structural requirements based on
occupancy.
OTHER STRUCTURES.
Structures, other
than buildings, for which loads are specified in this chapter.
PANEL (PART
OF A STRUCTURE). The
section of a floor, wall or roof comprised between the supporting
frame of two adjacent rows of columns and girders or column
bands of floor or roof construction.
RESISTANCE
FACTOR. A
factor that accounts for deviations of the actual strength
from the nominal strength and the manner and consequences
of failure (also called “strength reduction factor”).
STRENGTH,
NOMINAL. The capacity
of a structure or member to resist the effects of loads, as
determined by computations using specified material strengths
and dimensions and equations derived from accepted principles
of structural mechanics or by field tests or laboratory tests
of scaled models, allowing for modeling effects and differences
between laboratory and field conditions.
STRENGTH,
REQUIRED. Strength
of a member, cross section or connection required to resist
factored loads or related internal moments and forces in such
combinations as stipulated by these provisions.
STRENGTH DESIGN.
A method of proportioning
structural members such that the computed forces produced
in the members by factored loads do not exceed the member
design strength [also called “load and resistance factor
design” (LRFD)]. The term “strength design”
is used in the design of concrete and masonry structural elements.
VEHICLE BARRIER
SYSTEM. A
system of building components near open sides of a garage
floor or ramp or building walls that act as restraints for
vehicles.
NOTATIONS.
D
=
Dead load.
E
=
Combined effect of horizontal and vertical earthquake induced
forces as defined in Section 12.4.2 of ASCE 7.
Em
= Maximum seismic
load effect of horizontal and vertical seismic forces as
set forth in Section 12.4.3 of ASCE 7.
F
=
Load due to fluids with well-defined pressures and maximum
heights.
Fa
= Flood load.
H
=
Load due to lateral earth pressures, ground water pressure
or pressure of bulk materials.
L
=
Live load, except roof live load, including any permitted
live load reduction.
Lr
= Roof live
load including any permitted live load reduction.
R
=
Rain load.
S
=
Snow load.
T
=
Self-straining force arising from contraction or expansion
resulting from temperature change, shrinkage, moisture change,
creep in component materials, movement due to differential
settlement or combinations thereof.
W
=
Load due to wind pressure.
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