ARE Structural Systems Flashcards
Acceleration
The rate of change of velocity usually expressed as a fraction or percentage of g, the acceleration of gravity
Accelerograph
A seismological instrument that is normally inoperative, but becomes activated when subject to strong earth motion, records teh earth motion, and hten shuts off.
Active Pressure
The pressure exerted by retained earth against a retaining wall.
Admixture
A prepared substance added to concrete to alter or achieve certain characteristics
Aggregate
The chemically inert element of concrete, usually consisting of sand, gravel and/or other granular material.
Air-Supported Structure
A membrane enclosing a pressurized occupied space, which must be held down to its foundation.
Allowable Stress Design
The design method used for most reinforced concrete design until the middle of the 1960s. Still used for steel design. Largely replaced by strength design.
Arch
A curved structure in whic hthe internal stresses are essentially compression.
Axial Load
A longitudinal load that acts as the centroid of a member and perpendicular to its cross section
Balloon Framing
A method of framing wood stud walls, in which the studs are continuous for the full height of the building, which is usually two stories.
Seismic/Base Isolation
A method of isolating a structure from the ground by specially designed bearing and dampers that basorb earthquake forces.
Beam
A structural member that supports loads perpendicular to its longitudinal axis.
Bearing Wall
A wall that supports any vertical load in addition to its own weight.
Bending Moment
The algebraic sum of the moments of all forces that are on one side of a given cross section of a beam.
Braced Frame
A vertical truss used to resist lateral forces.
C
A standard designation for a structural steel American Standard channel
Cable Roof
A curved structure in which the internal stresses are pure tension.
Camber
A curve built into a structural member to compensate for deflection
Cantilever Beam
A beam that is restrained against rotation at one end and free at the other
Cantilever /Strap Footing
An exterior column footing joined by a concrete beam to an interior column footing
Cantilever Wall
A retaining wall in which the stem, heel, and toe act as cantilever slabs.
Catenary
The shape assumed by a cable when the only load acting on it is its own weight
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.
Chord
A perimeter member of a truss
Coefficient of thermal expansion
The ration of unit strain to temperature change, which is constant for a given material.
Collector
A member used to collect seismic load from a diaphragm and deliver it to a shear resisting element.
Column
A member, usually vertical, which is subject primarily to axial compressive load.
Column Footing
A spread footing, generally square or rectangular in plan, used to support a single column.
Combined Footing
A footing supporting two or more columns
Component
One of two or more forces that will produce the same effect on a body as a given force.
Composite Beam
A steel beam and a concrete slab connected so that they act together as a single structural unit to resist bending stresses.
Composite Deck
Steel floor decking with embossed ridges, bonded to a concrete slab so that they act together as a single structural unit.
Compression
Stress that tends to shorten a member to crush it.
Compressive Reinforcement
Reinforcing steel embedded in the compression face of a reinforced concrete beam
Concentrated Load
A load that acts at one point on a structure.
Concrete
A mixture of fine and coarse aggregates, portland cement, and water
Concurrent
Describing the conditions when the lines of action of several forces pass through a common point
Continuous Beam
A beam that rests on more than two supports
Core Test
A compression test of hardened concrete that has been cut from the structure.
Counterfort Wall
A retaining wall in which the stem and base are connected at intervals by transverse walls called counterforts
Couple
Two forces equal in magnitude, but opposite in direction, and acting at some distance from each other.
Creep
Continued deformation of a structural member with time, with no increase of load.
Curing
Maintaing concrete at the proper moisture and temperature after it is cast
Curvature Factor
A factor used to modify the allowable unit stress in bending for the curved portion of glued laminated members.
Cylinder Test
A test to determine the compressive strength of concrete by subjecting a standard cylinder of hardened concrete to compression in a testing machine
Dread Load
The vertical load due to the weight of all permanent structural components of a building, such as walls, floors, roofs, and fixed service equipment
Deflection
The movement of a beam from its original location when load is applied to it
Diaphragm
The horizontal floor or roof system that distributes lateral forces caused by wind or earthquake, by functioning as a horizontal girder
Dome
A roof structure whose shape is that of an arch rotated about its vertical axis to form a curved surface
Drift
The horizontal movement of a structure when subject to wind or earthquake force
Drilled / End-Bearing Caisson
An end-bearing pile, the bottom of which may be belled, which is constructed by pouring concrete into a drilled shaft.
Drilled/Friction Pile
A vertical shaft drilled into the ground and filled with concrete, which supports building loads by skin friction
Ductility
As used in earthquake design, the ability of structural systems and materials to deform and absorb energy, without failure or collapse
E
A symbol for modulus of elasticity
Eccentric Load
A longitudinal load that acts at a distance from a member’s centroid, thereby producing bending moment in additional to axial stress
Elastic Limit
The unit stress for a material, below which Hooke’s Law applies
Engineering News Formula
A dynamic formula used to determine the capacity of driven piles
Epicenter
The projection of the focus on the ground surface
Equillibrant
A force equal in magnitude to the resultant, but opposite in direction and on the same line of action as the resultant.
Equilibrium
A state of rest due to balanced forces and balanced moments
Euler’s Equation
A basic equation that applies to all columns and gives the maximum stress a slender column can resist without failing by sudden buckling.
Expansive Soil
A fine-grained cohesive soil which undergoes large volume changes with changes in moisture content
Factor of Safety
The ratio of the ultimate strength of a material to its working stress.
Fault
The boundary between adjacent rock plates along which movement may take place during an earthquake
Fillet Weld
A weld placed in the right angle formed by lapping or intersecting plates and generally subject to shear stress
Fixed End Beam
A beam that is restrained (fixed) against rotation at both ends
Flat Plate
A concrete slab reinforced in two directions which brings its load directly to supporting columns without any beams, girders, column capitals (widened tops of columns), or drop panels (thickened slab around columns). A flat slab without column capitals or drop panels
Flat Slab
A concrete slab reinforced in two directions that brings its load directly to supporting columns without any beams or girders, usually requiring column capitals (widened tops or columns) and drop panels (thickened slab around columns).
Flexure
Bending
Focus/Hypocenter
The location in the earth’s crust where rock slippage begins during an earthquake
Folded Plate
A structural roof system consisting of inclined planes that support each other and function as deep beams
Force
A push or pull exerted on an object. The description of a force includes its magnitude, direction, and point of application
Frost Line
The maximum depth of frost penetration in the ground expected in a given area
Gabled Frame
A frame consisting of two columns and two inclined beams that meet at the ridge, in which the joint between each column and beam is rigid.
Girder
A main beam that supports secondary beams.
Glued Laminated Beam
An assembly of laminations of lumber in which the grain of all the laminations is approximately parallel longitudinally and fabricated in accordance with certain accepted standards.
Gravity Wall
A retaining wall that depends entirely on its own weight to resist the pressure of the retained earth and provide stability.
Groove Weld
A weld placed between two butting pieces of metal to be joined.
Grout
A high slump concrete, consisting of portland cement, sand, hydrated lime, water, and sometimes pea gravel.
Hooke’s Law
The physical law that states that up to a certain unit stress, called the elastic limit, unit stress is directly proportional to unit strain.
Hoop
A horizontal member that extends around the circumference of a dome.
Hydrostatic Pressure
The pressure exerted by a liquid against every surface it contacts
Hyperbolic Paraboloid
A thin shell saddle-shaped surface formed by moving a vertical parabola with downward curvature along and perpendicular to another parabola with upward curvature
I
- A symbol for moment of inertia
- The importance factor used in earthquake or wind design
Impact Hammer Test
A nondestructive test to determine the strength of hardened concrete, by measuring the rebound of a plunger after striking the concrete surface. This test is not accurate enough to be a substitute for standard compression tests.
Joist
One of a series of small, closely-spaced beams used to support floor, ceiling, or roof loads
Joist Girder
A shop-fabricated steel truss that supports evenly-spaced steel joists along its top chord
K
An effective length factor used in the design of structural steel columns
Kelly Ball Test
A method of measuring the workability to fresh concrete
Kip
A unit of force or weight equal to 1,000 pounds
Ksi
An abbreviation for kips per square inch
L
A standard designation for a structural steel angle
Lamella
A roof structure comprising a series of parallel arches, skewed to the axes fo the building, which are intersected by another series of skewed arches, so that they interact with each other
Lateral Load
Any horizontal load on a building, including the load from wind or earthquake
Lift Slab
A flat plate cast at grade around columns and then lifted to position with hydraulic jacks
Line of Action
A line parallel to and in line with a force
Lintel
A structural member placed over an opening and supporting construction above.
Liquefaction
Transformation of soil into a liquefied state, similar to quicksand, as a result of earthquake vibrations
Live Load
The vertical load caused by the use and occupancy of a building, not including wind, earthquake or dead loads
Load
A force applied to a body
M
A symbol for bending moment
Mat Foundation
A large footing under an entire building, which distributes the building load over the entire area.
Membrane
A thin sheet that can resist tension, but cannot resist compression, bending, or shear
Meridian
A curved line on the surface of a dome, usually circular, which is formed by intersection of a vertical plane with the dome when the plane passes through the top of the dome
Method of Joints
An analytical method for determining the forces in the members of a truss
Method of Sections
An analytical method for determining the forces in the members of a truss
Modified Mercalli Scale
A scale used to measure the intensity of an earthquake
Modulus of Elasticity
Within the elastic limit, the constant ratio of the unit stress in a material to the corresponding unit strain
Modulus of Rupture
The unit bending stress calculated from the flexure formula, for the maximum bending moment resisted by a beam before rupture.
Moment
The tendency of a force to cause rotation about a given point or axis
Moment Diagram
A graphic representation of the value of the bending moment at any point along a beam
Moment of Inertia
The sum of the products obtained by multiplying each unit of area by the square of its distance to the neutral axis
Rigid/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
Natural Period of Vibration
The time it takes for a structure to go through one complete back and forth motion under the action of dynamic loads
Negative Moment
Bending moment that produces tension in the upper part of a beam and compression in the lower part
Neutral Axis
The line on a beam cross section that has zero bending stress when the beam in loaded
Nonbearing Wall
A wall that supports no vertical load other htan its own weight
Open Web Steel Joist
A shop-fabricated, lightweight steel truss used to span between main members or bearing walls and support roof or floor loads
Overhanging Beam
A beam that rests on two or more supports and has one or both ends projecting beyond the support
P-Delta Effect
The secondary effect on frame members produced by vertical loads acting on a building frame that is laterally displaced by earthquake loads
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 or plates and angles which are fastened together to form an integral member
Plate Tectonics
The theory that explains earthquake phenomena
Platform Framing
A method of framing wood stud walls in which the studs are one story in height and the floor joists bear on the top plates of the wall below.
Point of Inflection
The point in a beam or other flexural member where the bending moment changes sign and has a value of zero
Portland Cement
The finely-ground material used as a binder for structural concrete
Positive Moment
Bending moment that produces compression in the upper part of a beam and tension in the lower part
Posttensioning
A method of prestressing concrete in which the concrete is cast and then the steel tendons stressed by jacking
Prestressed Concrete
Concrete that is permanently loaded so as to cause stresses opposite in direction from those caused by dead and live loads
Pretensioning
A method of prestressing concrete in which the tensile force is put into high strength steel wires before the concrete is cast
Proctor Test
A laboratory compaction test to determine the optimum moisture content and density for a soil
Psf
An abbreviation for pounds per square foot
Psi
An abbreviation for pounds per square inch
Punching Shear
Two-way shear that occurs in a flat slab, spread footing, or pile cap
Purlin
A regularly spaced roof beam that spans between girders or trusses
r
A symbol for radius of gyration
R
A numerical coefficient used in earthquake design
Radiographic Inspection
Nondestructive testing of welded joints using x-rays and gamma rays
Radius of Gyration
A term used in column design equal to, where I is the moment of inertia of a member and A is its cross-sectional area
Reactions
Forces acting at the supports of a structure that hold the structure in equilibrium
Redundancy
The ability of part of a structural system to redistribute loads to other parts of the system. Lateral force resisting systems should be as redundant as possible.
Redundant Member
Any truss member not necessary for stability
Reinforced Brick Masonry
A type of wall construction consisting of brick units, usually two tiers, with a solidly grouted space between in which vertical and horizontal reinforcing bars are placed
Reinforced Concrete Block Masonry
A type of wall construction consisting of hollow concrete masonry units, with certain cells continuously filled with grout in which reinforcing bars are embedded
Resolving Forces
Replacing a force with two or more other forces (components) that will produce the same effect on a body as the original force
Response Spectrum
A curve that shows the maximum acceleration of a series of idealized structures when subject to an earthquake
Resultant
One force that will produce the same effect as two or more other forces
Retaining Wall
A wall that resists the lateral pressure of retained earth or other material
Richter Scale
A logarithmic scale used to measure earthquake magnitudes
Rigidity
Stiffness, resistance to deformation
S
- A symbol for section modulus
- A standard designation for a structural steel I beam, also known as American Standard beam
Section Modulus
The ratio of the moment of inertia of a beam (I) to the distance from its neutral axis to the most remote fiber (c). Thus, section modulus (S)=I/c
Shear
Stress that tends to make two members, or two parts of a member, slide past each other
Shear Diagram
A graphic representation of the value of the vertical shear at any point along a beam
Shear Wall
A wall designed to resist lateral forces parallel to itself cause by wind or earthquake
Simple Beam
A beam that rest on a support at each end.
Size Factor
A factor used to reduce the allowable bending stress for wood beams deeper than 12 inches
Slenderness Ratio
The ratio l/r used in column design, where l is the length and r i s the radius of gyration
Slump Test
A test for mixed concrete to determine consistency and workability
Space Frame
A series of trusses that intersect in a consistent grid pattern and are rigidly connected at their points of intersection.
Spiral Column
A reinforced concrete column, usually square or round, containing longitudinal reinforcing bars enclosed by a closely-spaced continuous steel spiral.
Statical Moment
The product of an area and the distance from the centroid of the area to a given axis
Statically Determinate
Describing a structure whose reactions cannot be found from the equations of equilibrium only, but requires additional equations
Stiffness
Resistance to deformation
Stirrup
A vertical steel bar, usually U-shaped, used to reinforce a reinforced concrete beam where the shear stresses are excessive
Strain
The deformation (change in size) of a body caused by external forces.
Strength Design
The method generally used for reinforced concrete design, formerly called quake, when the center of mass does not coincide with the center of rigidity
Tributary Area
The floor or roof area supported by an individual structural member
Truss
A jointed structure designed to support vertical or horizontal loads and composed generally of straight members forming a number of triangles
Trussed Rafter
A prefabricated lightweight wood truss used to support roof loads for dwellings and other small structures
Tsunami
An ocean wave produced by displacements of the ocean bottom as a result of earthquake or volcanic activity. Can affect areas thousands of miles from their origin
Tubular System
A structural system used in tall buildings, consisting of closely-spaced columns at the perimeter connected by deep spandrel beams, which acts like a tube that cantilevers from the ground when subject to lateral wind or earthquake loads.
Ultimate Strength
The maximum unit stress that can be developed in a material
Ultrasonic Testing
Nondestructive testing of welded joints using high-frequency sound waves
Uniformly Distributed Load
A beam loading of constant magnitude per unit of length
V
- A symbol for vertical shear
- The total lateral earthquake force at the base of a structure
Vault
A series of arches placed side-by-side to forma a continuous structure
Vertical Shear
The algebraic sum of the forces that are on one side of a given cross-section of a beam
Vibratory Compactor
A machine used primarily for the compaction of granular soils, such as sands
Vierendeel Truss
A truss with no diagonals
Volume Factor
A factor used to reduce the allowable bending stress for glued laminated beams, based on width, depth, and span
W
- The total dead load used in earthquake design
- A standard designation for a structural steel wide flange shape
Wall Footing
A continuous spread footing supporting a uniformly loaded wall
Water-Cement Ratio
The ratio of water to cement in a concrete mix, the main factor that determines concrete strength
Web Members
The interior members of a truss, which connect the chords.
Wind Bent
A frame used to resist lateral forces from wind.
Workability
The ease with which concrete can be placed and consolidated in the forms.
Allowable/Working Stress
The maximum unit stress permissible in a structural member
Yield Point
The unit stress at which a material deforms with no increase in load
Z
Plastic section modulus of a structural steel section
Web
The portion of a truss between the chords, or the portion of a beam between the flanges.
Control Joint
A groove in a concrete structure made to predetermine the location of cracks
Cement
A material which is able to unite nonadhesive substances into a solid mass.
Gravel
A coarse granular material, with particles varying from about 3 inches to 3/16 inch
belled caisson
An end-bearing pile constructed by pouring concrete into a drilled shaft, the bottom of which is enlarged (belled) to provide a larger bearing area
Underpinning
Deepening an existing foundation or building a new foundation for an existing building. Underpinning is usually required when excavation for a new building is adjacent to and deeper than an existing foundation.
Structural Steel
A medium carbon steel, rolled in a variety of shapes and sizes for use as load-bearing structural members.
Welding
A method of joining two pieces of metal by heating their surfaces until they are molten or plastic, with or without applying pressure, and with or without the use of additional filler material.
Sleeper
A horizontal wood member used to support a structure above, such as one of the wood strips between a concrete slab and a finished wood floor.
Hurricane
A severe tropical storm which occurs mainly along the coasts of the Gulf of Mexico and the South Atlantic. The design of buildings to resist wind in accordance with building code requirements includes the effects of hurricanes.
Bond Beam
A horizontal reinforced masonry beam, usually built integrally with a masonry wall.
Angle of Repose
The steepest angle with the horizontal at which a pile of loose earth will stand without sliding
Cold Joint
A joint formed when a concrete surface hardens before the next batch is placed against it
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.
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 connected parts. The resulting friction between the clamped parts resists the applied load.
Stress
An internal force in a body which resists an external force
Impact Load
The sudden application of load from a moving object, such as a crane or elevator, which causes stresses much greater than those caused by a static load
Reinforced concrete
Concrete containing adequate reinforcing steel and designed on the basis that the concrete and steel act together in resisting forces. The concrete is usually assumed to resist compression, while the reinforcing steel is assumed to resist tension.
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.
Structural Slab
A wide, flat reinforced concrete member, usually horizontal, which is supported by beams or walls.
Test Boring
A hole drilled into the ground at the site of a proposed structure in order to obtain samples of the subsurface soil for examination and testing in a laboratory. Based on these tests, the soils engineer recommends the type of foundation and the allowable soil bearing pressure.
T-beam
A reinforced concrete beam consisting of a portion of the slab and integrally constructed beam, which act together
Leeward Side
The side of a building facing the direction toward which the wind is blowing
Lightweight Concrete
Low-density concrete, usually made with lightweight aggregate.
Frost Heave
Uplift of the soil surface or foundations caused by freezing of moisture in the soil
Needle Beam
A short beam passed through a wall to provide temporary support.
Clay
A fine-grained, cohesive, inorganic soil.
Construction joint
The joint between the two successive concrete pours. Construction joints are usually located where the shear is minimum, such as at the midspan of beams.
Reinforcing Steel
Round steel bars with surface deformation which are placed in the forms prior to casting of concrete, and which primarily resist tension.
Bearing capacity
The load per unit area which can be safely supported by the ground
Aftershocks
Earthquakes following the occurrence of a large earthquake, or main shock. The magnitude of an aftershock is usually less than that of the main shock.
Precast Pile
A reinforced concrete pile cast in other than its final location. After curing, it is moved to its final location and driven into place. Precast piles are square, round, or octagonal, and are frequently prestressed.
Lumber
Wood that has been sawn into construction members.
Steel
An alloy of iron and carbon, with a carbon content between 0.1-1.7% (more than wrought iron, less than cast iron)
Coefficient of Friction
The ratio of the maximum frictional force between two bodies to the normal (perpendicular) for pressing the surfaces together.
Caisson
A waterproof box-like structure in which construction work can be performed underwater. Also a pile constructed by pouring
Elastic
Describing a material which returns to its original size and shape when load is removed. Also describes structural behavior in which members are stressed below the yield point
Dead Load
The vertical load due to the weight of all permanent structural and nonstructural components of a building, such as walls, floors, roofs and fixed service equipment
Plywood
A laminated panel of thin wood veneers, or plies, permanently bonded together with an adhesive. The grain of the adjacent plies is usually placed at right angles.
Tension
Stress which tends to stretch a member or pull it apart
Story Drift
The horizontal movement of one level of a building relative to the level immediately above or below caused by wind or earthquake
Wood Screw
A threaded metal fastener with a pointed end which forms its own matching thread in the wood member into which it is inserted
Pile Hammer
A hammer used to drive piles into the ground. Pile hammers may drop by gravity, or may be operated by steam or compressed air
Grade
The designation of the quality of a manufactured piece of wood
Welded Wire Fabric
A type of reinforcement used in reinforced concrete, consisting of a grid of steel wires perpendicular to each other and welded at all points of intersection
arc welding
The most usual welding process used in building construction, in which intense heat is produced by an electric arc between the members to be joined and a metal wire or rod, called the electrode.
Atterberg limits
The arbitrary limits which define the boundaries between the different states of rigidity or fluidity of fine-grained soils
Balanced Design
Reinforced concrete design in which there is simultaneous crushing of concrete and yielding of the reinforcing steel. To assure that yielding of the steel occurs before crushing of the concrete, the amount of reinforcing is limited to 75% of that which would produce a balanced design.
Base shear (v)
The total design lateral force or shear at the base of a structure.
Bearing-type Connection
A structural steel connection using high-strength bolts, in which some slip can occur and bearing stresses are considered.
ca and cv
Seismic coefficients based on the buildings’s seismic zone factor and soil type
ce
The combined height, exposure, and gust factor used in wind design.
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
Groove Weld
A weld placed between two butting pieces of metal to be joined.
Method 1 (Projected area Method)
A wind design method in which the wind pressures are assumed to act simultaneously normal (perpendicular) to all exterior surfaces
Method 2 (Normal Force Method)
A wind design method in which the horizontal pressures are assumed to act on the full vertical projected area of the structure, and the vertical pressures are assumed to act simultaneously on the full horizontal projected area.
Moment Distribution
A method for solving for the bending moments in statically indeterminate structures, such as rigid frames and continuous beams, by successive approximation
Plastic Limit
The moisture content at which a soil starts to change from a semisolid to a plastic state
Seismic Zone Factor (z)
A factor used in seismic design which depends on the seismic zone in which a site is located
Shear Plate
A high-strength timber connector used in wood to steel connections (using one shear plate) or wood-to-wood connections (using two shear plates), where demountability is desired.
Slip-critical Connection
A structural steel connection using high-strength bolts, in which no slip can occur
Split Ring
A high-strength timber connector used in wood-to-wood joints
Stagnation Pressure (qs)
The direct wind pressure on a vertical surface, in pounds per square foot
Strength Reduction Factor
A factor used to reduce the capacity of reinforced concrete members to account for possible variations in quality control.
Timber Connector
A high-strength connector used for wood-to-wood or wood-to-steel joints. Types include one split ring (wood-to-wood), two shear plates (wood-to-wood), and one shear plate (wood-to-steel)
Triangular Distribution
The assumed distribution of earthquake forces at various levels of a structure
Building/Seismic Separation
The separation between two adjoining buildings, or parts of the same building, to permit these adjoining elements to move independently when subject to earthquake motion. The amount of separation should be sufficient to prevent the adjoining elements from battering each other during an earthquake
Catenary
The curve assumed by a cable hung between two supports, when the only load acting on it is its own weight. The stresses in the cable are pure tension
Composite Deck
Steel floor decking with embossed ridges, bonded to a concrete slab so that they act together as a single structural unit.
Core Test
A compression test of hardened concrete which has been cut from the structure.
Grade Bream
A reinforced concrete beam cast on or in the ground and used to provide support for the superstructure by spanning between piles or footings
Lag Screw
A large wood screw with a head similar to that of a bold and without a nut
Tornado
A localized, violently destructive windstorm characterized by a long funnel-shaped could. Building code requirements fro wind design do not usually include the effects of tornadoes
Shoring
Temporary support for a portion of a building
Hyperbolic Paraboloid
A thin shell saddle-shaped surface formed by moving a vertical parabola with downward curvature along and perpendicular to another parabola with upward curvature
Weep Hole
A small hole near the bottom of a retaining wall, usually backfilled with gravel, to allow water to drain to the outside of the wall and thus avoid hydrostatic pressure against the wall
Spread Footing
A foundation which spreads the load over a large area of soil
Foundation
The part of a building’s structure which transmits the building’s load to the underlying soil
Silt
A fine-grained soil, whose particles are larger than clay and smaller than sand
Richter Scale
A logarithmic scale used to measure the magnitude of an earthquake (the amount of energy it releases). The largest earthquake ever recorded had a magnitude of about 8.9. The scale is named after its inventor, Dr. Charles Richter.
Friable
Referring to soil which is easily crumbled or reduced to powder
Liquid Limit
The moisture content at which a soil starts to change from a plastic to a semiliquid state
Pile Load Test
A test to verify or determine the allowable pile loads used in design
Thrust
The horizontal reaction at the base of an arch
response
The effect produced on a structure by earthquake ground motion
inertia
The physical property which causes the superstructure of a building to remain in its original position while the base is moved by an earthquake’s ground motion
Isoseismals
Map contours connection points of equal intensity for a given earthquake
rw or r
A numerical coefficient used in seismic design which depends on the type of lateral force resisting system used
cq
In wind design, a pressure coefficient for the structure or portion of the structure under consideration
Effective Depth (d)
In reinforced concrete design, the distance from the extreme compression fiber to the centroid of the tension reinforcement
matrix
In concrete, the cement past in which the aggregate particles are embedded.
Modified Mercalli Scale
A scale used to measure the intensity of an earthquake, that is, its effects on people and buildings. The scale varies from 1 (not felt except under especially favorable circumstances) to XII (damage nearly total)
Elastic Limit
The unit stress for a material, below which Hooke’s Law applies
Perlite
A very lightweight volcanic rock used as an aggregate in lightweight concrete
Collar Beam
A horizontal tie beam connection two opposing rafters at a level above the wall plates
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
Working Stress Design
The theory used for most reinforced concrete design until the middle 1960s
Stressed Skin
A structural system consisting of spaced members solidly sheathed on one or both sides, in which the sheathing forms the flanges and resists flexure while the spaced members comprise the webs and resist shear
Dual System
In seismic design, a combination of moment resisting frames and shear walls or braced frames
Single-Shear
Describing a bolted joint which has one shearing plan through the bolts
Method of Joints
An analytical method for determining the force in the members of a truss, in which each joint is isolated and unknown forces determined using the equations of equilibrium
Strut
A member which collects seismic load from the diaphragm to which it is attached and delivers it to shear-resisting element. AKA Collector or Drag Strut
Organic Soil
Soil with a high organic content (decomposed vegetable or animal matter). Organic soils are usually very compressible and have very low bearing capacities.
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.
Waffle Slab
A flat slab which is ribbed in two directions, resulting in a waffle-like appearance
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
irregular structure
In seismic design, a structure which has significant physical discontinuities in plan or vertical configuration or in its lateral force resisting system. Since irregular structures have less favorable and predictable seismic response characteristics than regular structures, specific design requirements are prescribed for each type of irregularity
Overturning Moment
The moment caused by wind or earthquake, which tends to overturn a structure
Coefficient of Thermal Expansion
The ratio of unit strain to temperature change, which is constant for a given material
Poisson’s ratio
The ratio of the lateral unit strain to the longitudinal unit strain, when a member is subject to a uniform longitudinal stress. For steel, the value of Poisson’s ratio is about 1/4
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
Inelastic
Describing a material which does not return to its original size and shape when load is removed, but retains permanent deformation. Also describes structural behavior in which members are stressed above the yield point.
Period (t)
The time it takes for a structure to go through one complete back and fourth motion under the action of dynamic loads. Also called fundamental period of vibration or natural period
pounding
The collision between two adjacent buildings which move differently during an earthquake
Static lateral force procedure
A method of seismic design in which static horizontal force which produce internal forces similar to those that would be induced by an actual earthquake motion are applied to a structure. This procedure is allowed only under certain conditions of building regularity, occupancy, and height
Building Frame System
In seismic design, a structural system with and 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
Modulus of Elasticity (e)
Within the elastic limit, the constant ratio of the unit stress in a material to the corresponding unit strain. Measure of a materials stiffness
Dynamic Lateral force procedure
A method of 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.
Ultimate Load Factor (u)
Factor used to increase loads, shears, and moments to their ultimate values in reinforced concrete design
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
Special Wind Region
An area where local records and terrain features indicate wind speeds greater than those shown in the building code
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
Displacement
Horizontal or vertical movement of a structural element resulting from applied seismic or other load
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
Statically Indeterminate
Describing a structure whose reactions cannot be found from the equations of equilibrium only, but requires additional equations. Examples are continuous beams, fixed end beams, and most rigid frames
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 building’s earthquake induced forces and deformations must be considered in the design
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
Double-Shear
Describing a bolted joint which has 2 shearing planes through the bolts
Importance Factor (i)
A factor used in earthquake and wind design, whose value varies between 1.0 and 1.5. This provides that certain essential facilities, such as hospitals and fire and police stations, be designed for seismic and wind forces greater than normal. In this way, such emergency facilities are expected to be safe and usable following an earthquake or severe windstorm.
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.
Laitance
A low-strength layer of fine particles that floats to the surface of wet concrete.
Framing Anchor
A metal device used for connection members in wood frame construction.
Essential Facilities
Structures of 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.
Regular Structure
In seismic design, a structure which has no significant physical discontinuities in plan or vertical configuration or in its lateral force resisting system. Regular structures exhibit more favorable and predictable seismic response characteristics than irregular structures.
Brittle
Describing a material or structural system which tends to fail suddenly without warning when subject to high stresses, as opposed to a ductile material system, which can absorb energy without failure.
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.
Ledger
A horizontal member supporting joists.
Tied Column
A reinforced concrete column, usually square or rectangular, containing longitudinal reinforcing bars and separate lateral ties
Mandrel
A solid core is used in driving a shell pile into the ground. When the driving is complete, the mandrel is removed and the shell is filled with concrete
Bleeding
The movement of water to the surface of freshly cast concrete.
Passive Pressure
The resistance to the movement of a retaining wall provided by the earth in front of the wall and its footing.
Jack Rafter
A short rafter between hip rafter and eave or between valley and ridge.
Turn-of-Net-Method
A method used to provide the bolt tension specified for high-strength-bolts, in which the bolts are first brought to a “snug tight” condition and then tightened additionally by a specified amount of nut rotation
Basic Wind Speed
The fastest mile wind speed which has a 2% probability of occurring in any one year measured at a point 33 feet (10 meters) above the ground.
K-Bracing
A type of diagonal bracing in which each end of each brace frames into a beam or column, not a beam-column joint. K-bracing is considered undesirable for seismic resistance and is generally prohibited.
Jetting
A method of placing piles using high-pressure water jets.
Tapered Girder
A plate girder having a tapered profile, usually varying from minimum depth at the supports to maximum depth at midspan.
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.
Horizontal Bracing System
A horizontal truss system which distributes lateral forces, caused by wind or earthquake, to the vertical resisting elements.
Tremie
A pipe for placing concrete under water. A hopper for filling is provided at the top, while the lower end is kept submerged in fresh concrete.
Stub Girder System
A steel framing system in which beams sit on top of a girder and short lengths of “stub girders” the same depth as the floor beams are welded to the top of the girder to provide for composite action.
Broom
To crush and spread the head of a wood pile by driving with a hammer
Grillage
A framework of horizontal members used to spread a structural load over a larger area
Maxwell Diagram
The stress diagram used in the graphical solution of a truss, which consists of the combined force polygons for all the truss joints.
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.
Exposure
In wind design, the nature of the terrain at a given site, varying from B (the least sever exposure) to D (the most severe exposure).
Stress Diagram
A graphical method for determining the forces in the members of a truss. It is also called a Maxwell Diagram
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 the group
Gunite
Pneumatically applied concrete shot into place by means of compressed air. This method may be used for both repair work and new construction, especially in difficult locations or where thin sections occur
Sand
Granular material, ranging from about 3/8” to .005”
Billet Bars
The most commonly used reinforcing steel, rolled from stell billets made by the open-hearth, electric furnace, or acid-bessermer process.
Fastest Mile Speed
The highest sustained average wind speed, based on the time required for a mile-long sample of air to pass a fixed joint.
Dry Pack
To pack a damp concrete mixture into a confined space.
Cluster
A group of piles
Surcharge
Increased earth pressure against a retaining wall caused by vertical load behind the wall or a sloping ground surface
Cofferdam
A watertight, temporary structure used under water, in which construction work can be performed
Seismograph
An instrument which makes a continuous permanent record of earth motion, called a seismogram
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. Beacause of various potential problems with chevron bracing, the bracing members must be designed for increased seismic loads
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
Force Polygon
A diagram used to graphically determine the resultant of two or more forces
Special Moment Resisting Frame (SMRF)
As used in earthquake design, a moment-resisting frame made of structural steel or reinforced concrete which has the ability to absorb a large amount of energy in the inelastic range, that is, when the material is stressed above its yield point, without failure and without deforming unacceptably.
Vermiculite
A lightweight aggregate used in lightweight concrete
Raymond Pile
A type of pile consisting of a tapered steel shell which is driven into the ground using a mandrel and then filled with concrete after the mandrel is removed
Anemometer
A device used to measure wind speed
Skin Friction
The friction between the surface of a pile and the surrounding soil
Reentrant Corner
An inside corner which occurs in buildings with :-, T-, U- and cross shaped plans. Reentrant corners cause high stress concentration during an earthquake unless they are strengthened or a seismic separation is provided.
Soft Story
A story whose lateral stiffness is less than 70% of the stiffness of the story above. Such an abrupt change of stiffness should be avoided if possible.
Weak Story
A story whose strength is <80% of that of the story above. Such an abrupt change of strength should be avoided if possible
Trowel Finish
A smooth dense concrete surface, produced by steel troweling after the concrete has partially hardened
Suction
Negative Pressure
Seismicity
A measure of the frequency, intensity and distribution of earthquakes in a given area.
Sheeting
Vertical members used to temporarily hold the face of an excavation during construction.
Bridging
Cross braces used between joists to stabilize them
