3 Flashcards
Unified Soil Classification System
The most widely used system for classifying soils. In this system, the soils are primarily classed as coarse-grained (gravels and sands), fine-grained (silts and clays), and highly organic.
precast concrete
A concrete element cast in a location other than its final position. After curing, it is moved to its final location and installed.
coefficient of thermal expansion
The ratio of unit strain to temperature change, which is constant for a given material.
concentric braced frame
A braced frame in which the center lines of intersecting members meet at a point and whose members are therefore subjected primarily to axial forces.
coefficient of friction
The ratio of the maximum frictional force between two bodies to the normal (perpendicular) for pressing the surfaces together.
moment
The tendency of a force to cause rotation about a given point or axis.
working stress
The maximum unit stress permissible in a structural member. It is also called allowable stress.
clay
A fine-grained, cohesive, inorganic soil.
volume factor
A factor used to reduce the allowable bending stress for glued, laminated beams, based on width, depth, and span.
thrust
The horizontal reaction at the base of an arch.
fill
A manmade deposit of soil.
caisson
A waterproof box-like structure in which construction work can be performed underwater. Also a pile constructed by pouring concrete into a drilled shaft.
construction joint
The joint between two successive concrete pours. Construction joints are usually located where the shear is minimum, such as at the midspan of beams.
rigid frame
A frame with rigid joints, in which members and joints are capable of resisting vertical and horizontal forces primarily by flexure. It is also called a moment/resisting frame.
p-delta effect
The secondary effect on frame members produced by vertical loads acting on a building frame which is laterally displaced by earthquake loads.
deflection
The movement of a beam from its original location when load is applied to it.
centroid
The point in a cross-section where all of the area may be considered concentrated without affecting the moment of the area about any axis. For symmetrical shapes, the centroid is the geometric center of the shape.
vertical shear (v)
The algebraic sum of the forces that are on one side of a given cross-section of a beam.
component
One of two or more forces which will produce the same effect on a body as a given force.
in situ
In place.
pile cap
A thick, reinforced concrete slab placed over a group of piles and used to distribute the structural load to all the piles in a group.
continuous beam
A beam that rests on more than two supports.
compression
Stress which tends to shorten a member or crush it.
column
A member, usually vertical, which is subject primarily to axial compressive load.
amplification
An increase in a building’s response to earthquake ground motion, resulting from the building’s period coinciding with that of the ground shaking, or other causes.
resonance
The condition that occurs when a building’s period is close to that of the predominant period of the earthquake ground shaking. Resonance causes the building’s response to be amplified, and the resulting increases in the buildings earthquake-induced forces and deformations must be considered in the design.
bearing capacity
The load per unit area which can be safely supported by the ground.
spiral column
A reinforced concrete column, usually square or round, containing longitudinal reinforcing bars enclosed by a closely spaced continuous steel spiral.
billet bars
The most commonly used reinforcing steel, rolled from steel billets made by open-hearth, electric furnace, or acid-bessemer process.
load
A force applied to a body.
reactions
Forces acting at the supports of a structure which hold the structure in equilibrium.
epicenter
The projection of the focus, where rock slippage begins, on the ground surface.
windward side
The side of a building facing the direction from which the wind is blowing.
diaphragm chord
The boundary element of a diaphragm or shear wall which is assumed to resist axial stresses, analogous to a flange of a beam.
base isolation
A method of isolating a structure from the ground by specially designed bearings and dampers which absorb earthquake forces. Also called seismic isolation.
essential facilities
Structures or buildings which must be safe and usable for emergency purposes after an earthquake or severe windstorm. Such facilities include hospitals and fire and police stations.
dynamic lateral force procedure
A method for determining earthquake forces in which a mathematical model of the structure is developed and then subjected to appropriate ground motions. This procedure is always acceptable for design.
tension
Stress which tends to stretch a member or pull it apart.
seismicity
A measure of the frequency, intensity, and distribution of earthquakes in a given area.
suction
Negative pressure.
response spectrum
A curve which shows the maximum acceleration of a series of idealized structures when subject to an earthquake.
curing
Maintaining concrete at the proper moisture and temperature after it is cast.
equilibrant
A force equal in magnitude to the resultant, but opposite in direction and on the same line of action as the resultant.
three-hinged arch
An arch with a hinge at each support and at the high point, or crown; the only type of arch which is statically determinate.
laitance
A low-strength layer of fine particles that floats to the surface of wet concrete.
cluster
A group of piles.
arch
A curved structure in which the internal stresses are essentially compression.
cantilever beam
A beam that is restrained against rotation at one end and free at the other.
purlin
A regularly spaced roof beam which spans between girders or trusses.
structural steel
A medium carbon steel, rolled in a variety of shapes and sizes for use as load-bearing structural members.
fundamental period of vibration (t)
The time it takes for a structure to go through one complete back-and-forth motion under the action of dynamic loads. Also called period or natural period.
weak story
A story whose strength is less than 80% of that of the story above. Such an abrupt change of strength should be avoided if possible.
stress
An internal force in a body which resists an external force.
exposure
In wind design, the nature of the terrain at a given site, varying from B (the least severe exposure) to D (the most severe exposure).
Atterberg limits
The arbitrary limits which define the boundaries between the different states of rigidity or fluidity of fine-grained soils.
ductility
The ability of a material to undergo large deformations without without fracture.
high-strength bolt
The most widely used fastener for structural steel connections made in the field. A very high tensile stress is developed in the bolt, thus tightly clamping together the connects parts. The resulting friction between the clamped parts resists the applied loads.
shear diagram
A graphic representation of the value of the vertical shear at any point along the beam.
statically determinate
Describing a structure whose reactions can be determined from the equations of equilibrium. Examples are simple beams, cantilever beams, and overhanging beams that rest on two supports.
grillage
A framework of horizontal members used to spread a structural load over a larger area.
C
A standard designation for a structural steel American Standard channel.
compressive reinforcement
Reinforcing steel embedded in the compression face of a reinforced concrete beam.
collar beam
A horizontal tie beam connecting two opposing rafters at a level above the wall plates.
moment diagram
A graphic representation of the value of the bending moment at any point along a beam.
slenderness ratio
The ratio l/r or Kl/r used in column design, where l is the length, r is the radius of gyration, and K is an effective length factor.
magnitude
The amount of energy released by an earthquake, as measured by the Richter scale. Magnitude refers to an earthquake’s energy, while intensity refers to an earthquake’s effects.
ultimate load factor (u)
A factor used to increase loads, shears, and moments to their ultimate values in reinforced concrete design.
free body diagram
A diagram obtained by making an imaginary cut through a structure and applying the equations of equilibrium to the remaining portion, called the “free body”. By this means, the internal forces of a structure may be determined.
thin shell
A structure with a curved surface that supports load by tension, compression, and shear in the plane of its surface, but which is too thin to resist bending stresses.
Kelly ball test
A test to determine the workability of fresh concrete.
strength
The ability of a material or a structure to resist stresses.
moment of inertia (I)
The sum of the products obtained by multiplying each unit of area by the square of its distance to the neutral axis. Moment of inertia of a beam is a measure of its stiffness, or resistance to deflection.
steel
An alloy of iron and carbon, with a carbon content between 0.1 and 1.7% (more than that of wrought iron and less than that of cast iron).
torsion
The rotation caused in a diaphragm by lateral load from wind or earthquake, when the center of mass does not coincide with the center of rigidity. Torsional effects are most significant in unsymmetrical buildings.
joist girder
A shop-fabricated steel truss that supports evenly-spaced steel joists along its top chord.
double-shear
Describing a bolted joint which has two shearing planes through the bolts.
moment-resisting frame
A frame with rigid joints, in which the members and joints are capable of resisting vertical and horizontal forces primarily by flexure. It is also called a rigid frame.
calcium chloride
The most common accelerating admixture used for concrete. It can be used safely in amounts up to 2% of the Portland cement weight.
vermiculite
A lightweight aggregate used in lightweight concrete.
Maxwell diagram
The stress diagram used in the graphical solution of a truss, which consists of the combined force polygons for all the trust joints.
pile
An underground wood, concrete, or steel member, usually vertical, and usually driven into place, which is used to support building loads.
plate girder
An assembly of steel plates, plates and angles, which are fastened together to form an integral member.
ground shaking
The principal cause of structural damage, injury, and loss of life during an earthquake. The provisions of the Uniform Building Code provide resistance to earthquake ground shaking, without settlement, slides, subsidence, or faulting in the immediate vicinity of the structure.
force polygon
A diagram used to graphically determine the resultant of two or more forces.
curvature factor
A factor used to modify the allowable unit stress in bending for the curved portion of glue laminated members.
vibration
Consolidating freshly poured concrete by using an oscillating vibrator. Immersion-type (spud) vibrators are lowered into the concrete, while form vibrators are attached to the exterior of forms.
drift
The horizontal movement of a structure when subject to wind or earthquake forces.
eccentric braced frame (EBF)
A braced frame in which at least one end of each brace is eccentric to the beam-column joint or the opposing brace. The intent is to make the braced frame more ductile and therefore able to absorb a significant amount of energy without buckling the braces.
building frame system
In seismic design, a structural system with an essentially complete frame providing support for gravity loads. Lateral loads are resisted by shear walls or braced frames. Building frame systems are designed for seismic forces which are lower than those for bearing wall systems.
chevron bracing
A type of diagonal bracing in which one end of each brace frames into a beam-column joint and the other end frames into a beam. There are two configurations, V-bracing and inverted-V-bracing. Because of various potential problems with chevron bracing, the bracing members must be designed for increased seismic loads.
intensity
The effects of an earthquake on people and structures at a particular place, as measured by the Modified Mercalli scale. Intensity refers to an earthquake’s effects, while magnitude refers to an earthquake’s energy.
W
A standard designation for a structural steel, wide flange shape. Also, the total dead load used in earthquake design.
bond beam
A horizontal reinforced masonry beam, usually built integrally with a masonry wall.
jetting
A method of placing piles using high-pressure water jets.
vault
A series of arches placed side-by-side to form a continuous structure.
broom
To crush and spread the head of a wood pile by driving it with a hammer.
damping
The decrease of vibration caused by the absorption of energy. Buildings contain a number of elements, both structural and nonstructural, which absorb energy during an earthquake and thereby diminish the earthquake-induced vibrations.
Method 1
normal force method
A wind design method in which the wind pressures are assumed to act simultaneously normal (perpendicular) to all exterior surfaces.
shear wall
A wall designed to resist lateral forces parallel to itself caused by wind or earthquake.
s
A symbol for section modulus, also a standard designation for a structural steel I-beam (American Standard beam), also a factor used in earthquake design which takes into account the effect of subsoil conditions.
