Structural Systems Flashcards
A drilled pier (caisson) is belled in order to
Increase the bearing area
The most important factor affecting the strength of concrete is the
Water-to-cement ratio
A slump cone is used primarily to provide an indication of which of the following characteristics of concrete?
Strength and workability
Since the 1960’s, thin-shell concrete roof structures have seldom been utilized in the US and Canada primarily because
Formwork is prohibitively expensive
The most frequently used footing type at the exterior wall for load-bearing wall support system is
Continuous wall footings
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.
Inertia
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.
Essential facilities
A method of isolating a structure from the ground by specifically designed bearings and dampers which absorb earthquake forces. Also called seismic isolation.
Base isolation
The boundary element of a diaphragm or shear wall which is assumed to resist axial stresses, analogous to a flange of a beam.
Diaphragm chord
The side of a building facing the direction toward which the wind is blowing.
Leeward side
The projection of the focus, where rock slippage begins, on the ground surface.
Epicenter
Forces acting at the supports of a structure which hold the structure in equilibrium.
Reactions
A force applied to a body.
Load
A reinforced concrete column, usually square or round, containing longitudinal reinforcing bars enclosed by closely spaced continuous steel spiral.
Spiral column
The most commonly used reinforcing steel, rolled from steel billets made by the open-hearth, electric furnace, or acid-bessemer process.
Billet bars
Low-density concrete, usually made with lightweight aggregate.
Lightweight concrete
A state of rest due to balanced forces and balanced moments.
Equilibrium
A reinforced concrete beam consisting of a portion of the slab and the integrally constructed beam, which act together.
T-beam
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 effects of subsoil conditions.
s
A simple structural system consisting of beams simply supported on posts.
Post-and-beam system
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.
Irregular structure
The expected maximum depth of frost penetration in the ground in a given area.
Frost line
A vertical truss used to resist lateral forces.
Braced frame
A device used to measure wind speed.
Anemometer
The speed with which seismic waves move in a given direction, in inches or centimeters per second.
Velocity
Describing the condition when the lines of action of several forces pass through a common point.
Concurrent
The moisture content at which a soil starts to change from plastic to a semi-liquid state.
Liquid limit
A flat slab which is ribbed in two directions, resulting in a waffle-like appearance.
Waffle slab
The level below which the subsoil is completely saturated with water. Also called the water table.
Groundwater level
A structural steel connection using high-strength bolts, in which some slip can occur and bearing stresses are considered.
Bearing-type connection
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.
Stressed skin
A horizontal system which distributes lateral forces, caused by wind or earthquake, to the vertical resisting elements.
Diaphragm
A term used in column design equal to the square root of I/A, where I is the moment of inertia of a member, and A is its cross-sectional area.
Radius of gyration (r)
The location in the earth’s crust where rock slippage begins during an earthquake. Also called the focus.
Hypocenter
In seismic design, a combination of moment-resisting frames and shear wall or braced frames.
Dual system
The load per unit area which can be safely supported by the ground.
Bearing capacity
A member, usually vertical, which is subject primarily to axial compressive load.
Column
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.
Amplification
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.
Resonance
The unit bending stress calculated from the flexure formula, for the maximum bending moment resisted by a beam before rupture.
Modulus of rupture
Pertaining to earthquake and the shock waves within the earth which they produce.
Seismic
Replacing a force with two or more other forces (components) which will produce the same effect on a body as the original force.
Resolving forces
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.
K-bracing
Concrete which is permanently loaded so as to cause stresses opposite in direction from those caused by dead and live loads.
Prestressed concrete
A material which is able to unite nonadhesive substance into a solid mass. The cement most commonly used in concrete construction is Portland cement.
Cement
A continuous spread footing supporting a uniformly loaded wall.
Wall footing
A groove in a concrete structure made to predetermine the location of cracks.
Control joint
A series of trusses which intersect in a consistent grid pattern and are rigidly connected at their points of intersection.
Space frame
A concrete slab designed to span in one direction and whose main reinforcement runs in that direction.
One-way concrete slab
An area where local records and terrain features indicate wind speeds greater than those shown in the building code.
Special wind region
The fasted mile wind speed which has a 2 percent probability of occurring in any one year measured at a point 33 feet (10 meters) above the ground.
Basic wind speed
A steel beam and a concrete slab connected so that they act together as a single structural unit to resist bending stress.
Composite beam
A metal device used for connection members in wood frame construction.
Framing anchor
The rate of change of velocity, usually expressed as a fraction or percentage of g, the acceleration of gravity.
Acceleration
A method of isolating a structure from the ground by specially designed bearings and dampers which absorb earthquake forces. Also called base isolation.
Seismic isolation
Uplift of the soil surface or foundations caused by freezing of moisture in the soil.
Frost heave
A short beam passed through a wall to provide temporary support.
Needle beam
The ratio of the lateral unit strain to the longitudinal unit strain, when a member is subject to a uniform longitudinal stress.
Poisson’s ratio (For steel, the value of Poisson’s ratio is about 1/4.)
The assumed distribution of earthquake forces to various levels of a structure.
Triangular distribution
A thin sheet which can resist tension, but cannot resist compression, bending, or shear.
Membrane
The pressure exerted by a liquid against every surface it contacts.
Hydrostatic pressure
The vertical load caused by the use and occupancy of a building, not including wind, earthquake, or dead loads.
Live load
The method generally used for reinforced concrete design, formerly called ultimate strength design.
Strength design
A pile which supports a vertical load.
Bearing pile
The friction between the surface of a pile and the surrounding soil.
Skin friction
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.
Platform framing
In seismic design, a structural system without a complete load-carrying frame. Gravity loads are resisted by bearing walls or bracing systems, and lateral loads are resisted by shear walls or braced frames.
Bearing wall system (designed for relatively high seismic forces)
A type of pile consisting of tapered steel shell which is driven into the ground using a mandrel and then filled with concrete after the mandrel is removed.
Raymond pile
A weld placed in the right angle formed by lapping or intersecting plates and generally subject to shear stress.
Fillet weld
A frame consisting of two columns and two inclined beams which meet at the ridge, in which the joint between column and beam is rigid.
Gabled frame
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.
Method 2 (projected area method)
The time it takes for a structure to go through one complete back-and-forth motion under the action of dynamic loads. Also called fundamental period of vibration or period.
Natural period (t)
Transformation of soil into a liquefied state, similar to quicksand, as a result of earthquake vibrations.
Liquefaction
The horizontal movement of one level of a building relative to the level immediately above or below, caused by wind or earthquake.
Story drift
A localized, violently destructive windstorm characterized by a long funnel-shaped cloud.
Tornado (Building code requirements for wind design do not usually include the effects of tornadoes.)
The effect produced on a structure by earthquake ground motion.
Response
A story whose lateral stiffness is less than 70 percent of the stiffness of the story above. Such an abrupt change of stiffness should be avoided if possible.
Soft story
The side of a building facing the direction from which the wind is blowing
Windward side
The combined height, exposure, and gust factor used in wind design.
ce
A numerical coefficient used in seismic design which depends on the type of lateral force resisting system used.
rw or r
The level below which the subsoil is completely saturated with water. Also called the groundwater level.
Water table
An exterior column footing joined by a concrete beam to an interior column footing. It is also called a strap footing.
Cantilever footing
A membrane enclosing a pressurized occupied space, which must be held down to its foundation.
Air-supported structure
A threaded metal fastener with a pointed end which forms its own matching thread in the wood member into which it is inserted.
Wood screw
A retaining wall in which the stem and base are connected at intervals by transverse walls.
Counterfort wall
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.
Welded wire fabric
A roof structure whose shape is that of an arch rotated about its vertical axis to form a curved surface.
Dome
A retaining wall in which the stem, heel, and toe act as cantilever slabs.
Cantilever wall
A hammer used to drive piles into the ground. Pile hammers may drop by gravity, or may be operated by steam or compressed air.
Pile hammer
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.
Underpinning
The designation of the quality of a manufactured piece of wood.
Grade
Stress which tends to make two members, or parts of a member, slide past each other.
Shear
Another term for bending.
Flexure
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. Also called seismic separation.
Building separation
A jointed structure designed to support vertical or horizontal loads and composed generally of straight members forming a number of triangles.
Truss
A factor used in seismic design which depends on the seismic zone in which a site is located.
Seismic zone factor (z)
The property of a structure which has multiple paths of load resistance, so that if one element fails, the load will be redistributed to other elements. Lateral force resisting systems should be as redundant as possible.
Redundancy
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.
Elastic
An ocean wave produced by displacement of ocean bottom as the result of an earthquake or volcanic activity.
Tsunami ( can affect areas thousands of miles from their origin.)
The highest sustained average wind speed, based on the time required for a mile-long sample of air to pass a fixed joint.
Fastest mile speed
The physical law that states that up to a certain unit stress, called the elastic limit, unit stress is directly proportional to unit strain.
Hooke’s Law
A member which collects seismic load from the diaphragm to which it is attached and delivers it to a shear-resisting element. Also called strut or drag strut.
Collector
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.
Special moment-resisting frame (SMRF)
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.
Richter scale (named after its inventor, Dr. Charles Richter)
A log showing the types of soil encountered in a test boring and other relevant information.
Soil boring log
An analytical method for determining the force in the members of a truss, in which each joint is isolated and the unknown forces determined using the equations of equilibrium.
Methods of joints
An assembly of laminations of lumber in which the grain of all the laminations is approximately parallel longitudinally. The laminations are bonded with adhesive and fabricated in accordance with certain accepted standards.
Glued laminated beam
Concrete made with standard aggregates, usually weighing about 150 pounds per cubic foot.
Normal weight concrete
A large-toothed roller used for the compaction of soil.
Sheepsfoot roller
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.
Tremie
A prepared substance added to concrete to alter or achieve certain characteristics.
Admixture
A concrete slab reinforced in two directions which brings its load directly to supporting columns without any beams, girders, column capital (widened tops of columns), or drop panels (thickened slab around columns).
Flat plate
A flat plate cast at grade around columns and then lifted to position with hydraulic jacks.
Lift slab
A structural steel connection using high-strength bolts, in which no slip can occur.
Slip-critical connection
A horizontal member which extends around the circumference of a dome.
Hoop
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.
Shear plate
A large wood screw with a head similar to that of a bolt and without a nut.
Lag screw
An analytical method for determining the force in the members of a truss, in which the truss is cut by an imaginary section and a free body diagram drawn of the portion of the truss thus isolated.
Method of sections
A roof structure comprising a series of parallel arches, skewed to the axes of the building, which are intersected by another series of skewed arches, so that they interact with each other.
Lamella
An effective length factor used in the design of structural steel columns.
K
A joint formed when a concrete surface hardens before the next batch is placed against it.
Cold joint
A method of prestressing concrete in which the concrete is cast and then the steel tendons are stressed by jacking.
Post tensioning
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.
Catenary
A high-slump concrete, consisting of Portland cement, sand, hydrated lime, water and sometimes pea gravel.
Grout
Reference points offset a given distance from the building line and set prior to excavation.
Batter boards
In wind design, a pressure coefficient for the structure or portion of the structure under consideration.
cq
The chemical reaction which combines cement and water to form a hard, solid mass.
Hydration
One force which will produce the same effect as two or more other forces.
Resultant
The ratio of the ultimate strength of a material to its working stress.
Factor of safety
The part of the structural system assigned to resist lateral forces from wind or earthquake.
Lateral force resisting system
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 percent of that which would produce a balanced design.
Balanced design
A large footing under an entire building, which distributes the building load over the entire area. It is also known as a mat foundation.
Raft foundation
A very lightweight volcanic rock used as an aggregate in lightweight concrete.
Perlite
The chemically inert element of concrete, usually consisting of sand, gravel, and/or other granular material.
Aggregate
A type of cement (ASTM Type III) which provides earlier strength in concrete than ordinary cements. It is used when forms must be removed quickly or when the structure must be put into service quickly.
High-early-strength cement
A reinforced concrete beam cast on or in the ground and used to provide support for the superstructure by spanning between piles or footings.
Grade beam
A short rafter between hip rafter and eave or between valley and ridge.
Jack rafter
A main beam which supports secondary beams.
Girder
A beam that is restrained (fixed) against rotation at both ends.
Fixed end beam
A large footing under an entire building, which distributes the building load over the entire area. It is also known as raft foundation.
Mat foundation
A foundation which spreads the load over a large area of soil. It is also called a spread footing.
Footing
The ease with which concrete can be placed and consolidated in forms.
Workability
A graphical method for determining the forces in the members of a truss. It is also called a Maxwell diagram.
Stress diagram
A device used to support reinforcing bars during the placing of concrete.
Bar chair
In reinforced concrete design, the distance from the extreme compression fiber to the centroid of the tension reinforcement.
Effective depth (d)
The maximum units of stress permissible in a structural member. It is also called working stress.
Allowable stress
The theory used for most reinforced concrete design until the middle 1960s.
Working stress design
Steel floor decking with embossed ridges, bonded to a concrete slab so that they act together as a single structural unit.
Composite deck
In concrete, the cement past in which the aggregate particles are embedded.
Matrix
A mixture of fine and coarse aggregates, Portland cement, and water.
Concrete
The line on a beam cross-section which has zero bending stress when the beam is loaded.
Neutral axis
A basic equation which applies to all columns and gives the maximum stress a slender column can resist without failing by sudden buckling.
Euler’s equation
The resistance to the movement of a retaining wall provided by the earth in front of the wall and its footing.
Passive pressure
Referring to soil which is easily crumbled or reduced to powder.
Friable
An end-bearing pile, the bottom of which may be belled, which is constructed by pouring concrete into a drilled shaft.
Drilled caisson
The point in a beam or other flexural member where the bending moment changes sign and has a value of zero.
Point of inflection
A structural roof system consisting of inclined planes which support each other and function as deep beams.
Folded plate
A laboratory compaction test to determine the optimum moisture content and density for a soil.
Proctor test
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.
Turn-of-net method
A test for mixed concrete to determined consistency and workability.
Slump test
The incorporation of tiny air bubbles into concrete to improve its workability and resistance to frost.
Air entrainment.
The interior members of a truss, which connect the chords.
Web members
Unequal settlement of the various parts of a building which may cause excessive stresses in the structural frame or tilting of the building.
Differential settlement
A curved structure in which the internal stresses are pure tension.
Cable roof
A fine-grained soil, whose particles are larger than clay and smaller than sand.
Silt
To pack a damp concrete mixture into a confined space.
Dry pack
The change in size of a body caused by external forces. It is also called deformation.
Strain
The maximum unit stress that can be developed in a material.
Ultimate strength
The product of an area and the distance from the centroid of the area to a given axis.
Statical moment
The change in size of a body caused by external forces. It is also called strain
Deformation
A prefabricated, lightweight wood truss used to support roof loads and other small structures.
Trussed rafter
A longitudinal load which acts at a distance from a member’s centroid, thereby producing bending moment in addition to axial stress.
Eccentric load
A wall which resists the lateral pressure of retained earth or other material.
Retaining wall
A steel framing system in which beams sit on top of a girder and short lengths of “stub girders” the sasme depth as the floor beams are welded to the top of the girder to provide for composite action.
Stub girder system
A truss with no diagonals
Vierendeel truss
A thin shell saddle-shaped surface formed by moving a vertical parabola with downward curvature along and perpendicular to another parabola with upward curvature.
Hyperbolic paraboloid
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.
Impact hammer test
A load which acts at one point on a structure.
Concentrated load
An abbreviation for pounds per square foot.
psf
Bending moment which produces tension in the upper part of a beam and compression in the lower part.
Negative moment
A test to verify or determine the allowable pile loads used in design.
Pile load test
A symbol for bending moment
M
Temporary support for a portion of a building.
Shoring
A retaining wall which depends entirely on its own weight to resist the pressure of the retained earth and provide stability.
Gravity wall
A curved line on the surface of a dome, usually circular, which is formed by the intersection of a vertical plane with the dome, when the plane passes through the top of the dome.
Meridian
Continued deformation of a structural member with time, with no increase of load.
Creep
The part of a building’s structure which transmits the building’s load to the underlying soil.
Foundation
The tendency of a force to cause rotation about a given point or axis.
Moment
A wall which supports any vertical load in addition to its own weight.
Bearing wall
A reinforced concrete column, usually square or rectangular, containing longitudinal reinforcing bars and separate lateral ties.
Tied column
Vertical members used to temporarily hold the face of an excavation during construction.
Sheeting
A horizontal member supporting joists.
Ledger
A foundation which spreads the load over a large area of soil. It is also called a footing
Spread footing
Any truss member not necessary for stability.
Redundant member
Describing a material or structural system which tends to fail suddenly without warning when subject to high stresses, as opposed to a ductile material or system, which can absorb energy without failure.
Brittle
In seismic design, a structural system with an essentially complete frame which provides support for vertical loads. Lateral loads are resisted by moment-resisting frames.
Moment-resisting-frame system
A scale used to measure the intensity of an earthquake, that is, its effects on people and buildings. The scale varies from I (not felt except under especially favorable circumstances) to XII (damage nearly total).
Modified Mercalli scale
An exterior column footing joined by a concrete beam to an interior column footing. It is also called a cantilever footing.
Strap footing
A compression test of hardened concrete which has been cut from the structure.
Core test
The steepest angle with the horizontal at which a pile of loose earth will stand without sliding.
Angle of repose
A ratio used to determine the bearing capacity of a soil, based on a standard test.
California bearing ration (CBR)
The unit stress for a material, below which Hooke’s Law applies.
Elastic limit
The total design lateral force or shear at the base of a structure.
Base shear (v)
A member which collects seismic load from the diaphragm to which it is attached and delivers it to a shear-resisting element. Also called a collector or drag strut.
Strut
An inside corner which occurs in buildings with L-, 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.
Reentrant corner
Any horizontal load on a building, including the load from wind or earthquake.
Lateral load
The separation of lamination of a glued laminated beam caused by failure of the adhesive.
Delamination
The ratio of water to cement in a concrete mix, the main factor which determines concrete strength.
Water-cement ratio
A factor used to reduce the capacity of reinforced concrete members to account for possible variations in quality control.
Strength reduction factor
Increased earth pressure against a retaining wall caused by vertical load behind the wall or sloping ground surface.
Surcharge
A structural member which supports loads perpendicular to its longitudinal axis.
Beam
Two-way shear which occurs in a flat, slab, spread footing, or pile cap.
Punching shear
The moisture content at which a soil starts to change from a semisolid to a plastic state.
Plastic limit
A high strength timber connector used in wood-to-wood joints.
Split ring
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.
Regular structure
A horizontal truss system which distributes lateral forces, caused by wind or earthquake, to the vertical resisting elements.
Horizontal bracing system
The moment, caused by wind or earthquake, which tends to overturn a structure.
Overturning moment
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 wall.
Weep hole
A perimeter member of a truss.
Chord
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).
Timber connector
Cross braces used between joists to stabilize them.
Bridging
A medium carbon steel, rolled in a variety of shapes and sizes for use as load-bearing structural members.
Structural steel
A regularly spaced roof beam which spans between girders or trusses.
Purlin
The floor or roof area supported by an individual structural member.
Tributary area
A structural steel pile whose cross-section is H-shaped.
H-pile
Nondestructive testing of welded testing joints using x-rays and gamma rays.
Radiographic inspection
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. The S-value of beam is a measure of its ability to resist bending moment.
Section modulus (s)
Map contours connecting points of equal intensity for a given earthquake.
Isoseismals
A standard designation for structural steel angle.
L
A seismological instrument which is normally inoperative, but becomes activated when subject to strong earth motion, records the earth motion, and then shuts off.
Accelerograph
A test to determine the compressive strength of concrete by subjecting a standard cylinder of hardened concrete to compression in a testing machine.
Cylinder test
A graphic representation of the value of the vertical shear at any point along the beam.
Shear diagram
The most widely used fastener for structural steel connections made in the field. A very 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.
High-strength bolt
The ability of a material to undergo large deformations without fracture.
Ductility
The arbitrary limits which define the boundaries between the different states of rigidity or fluidity of fine-grained soils
Atterberg limits
The sudden application of load from a moving object, such as a crane or elevator, which causes stresses much greater than those caused by static load.
Impact load
In wind design, the nature of the terrain at a given site, varying from B (the least severe exposure) to D (the most sever exposure)
Exposure
An internal force in a body which resists an external force.
Stress
The time it takes for a structure to go through one complete back-and-forth motion under the action of dynamic loads. Also called fundamental period of vibration or natural period.
Period (t)
A story whose strength is less than 80 percent of that of the story above. Such an abrupt change of strength should be avoided if possible.
Weak story
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.
Fundamental period of vibration (t)
The test to determine the workability of fresh concrete.
Kelly ball test
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.
Thin shell
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.
Free body diagram
Factor used to increase loads, shears, and moments to their ultimate values in reinforced concrete design.
Ultimate load factor (u)
A machine used primarily for the compaction of a granular soils, such as sands.
Vibratory compactor
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.
Magnitude
The theory which explains earthquake phenomena.
Plate tectonics
The ratio I/r o r Kl/r used in column design, where l is the length, r is the radius of gyration, and K is an effective length factor.
Slenderness ratio
A graphic representation of the value of the bending moment at any point along a beam.
Moment diagram
A horizontal tie beam connecting two opposing rafters at a level above the wall plates.
Collar beam
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.
Arc welding
Reinforcing steel embedded in the compression face of a reinforced concrete beam.
Compressive reinforcement
A pile whose load is supported by a firm soil or rock under the pile tip.
End-bearing pile
A standard designation for a structural steel America Standard channel.
C
A framework of horizontal members used to spread a structural load over a larger area.
Grillage
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.
Reinforced concrete
Describing a structure whose reactions can be determined from the equation of equilibrium. Examples are simple beams, cantilever beams, and overhanging beams that rest on the two supports.
Statically determinate
An end-bearing pile constructed by pouring concrete into a drilled shaft, the bottom of which is enlarged (belled) to provide a large bearing area.
Belled caisson
Wood that has been sawn into construction members.
Lumber
The pressure exerted by retained earth against a retaining wall.
Active pressure
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.
Moment-resisting frame
Describing a bolted joint which has two shearing planes through the bolts.
Double shear
A shop-fabricated steel truss that supports evenly-spaced steel joist along its top chord.
Joist girder
A unit of force or weight equal to 1,000 pounds.
Kip
The rotation caused in the 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.
Torsion
A type of wall construction consisting of hollow concrete masonry units, with certain cells continuously filled with grout in which reinforcing bars are embedded.
Reinforced concrete block masonry
An alloy of iron and carbon with a carbon content between 0.1 and 1.7 percent (more than that of wrought iron and less than that of cast iron).
Steel
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 measure of its stiffness, or resistance to deflection.
Moment of inertia (I)
A spread footing, generally square or rectangular in plan, used to support a single column.
Column footing
The ability of a material or structure to resist stresses.
Strength
A wind design method in which the wind pressures are assumed to act simultaneously normal (perpendicular) to all exterior surfaces.
Method 1 (normal force method)
A wall consisting of small, closely spaced members usually sheathed on both faces with a wall material.
Stud wall
The decrease of vibration caused by the absorption of energy. Building contain a number of elements, both structural and nonstructural, which absorb energy during an earthquake and thereby diminish the earthquake-induced vibrations.
Damping
To crush and spread the head of a wood pile by driving with a hammer.
Broom
A series of arches placed side-by-side to form a continuous structure.
Vault
A method of placing piles using high-pressure water jets.
Jetting
A horizontal reinforced masonry beam, usually built integrally with masonry wall.
Bond beam
A smooth dense concrete surface, produced by steel troweling after the concrete has partially hardened.
Trowel finish
The movement of water to the surface of freshly cast concrete.
Bleeding
A standard designation for a structural steel, wide, flange shape. Also, the total dead load used in earthquake design.
W
A symbol for either base shear or vertical shear
v
A wall which supports no vertical load other than its own weight.
Nonbearing wall
An abbreviation for kips per square inch
Ksi
The horizontal movement of structure when subject to wind or earthquake forces.
Drift
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.
Vibration
A method of joining two pieces of metal by heating their surface until they are molten or plastic, with or without applying pressure, and with or without the use of additional filler material.
Welding
A factor used to modify the allowable unit stress in bending for the curved portion of glued laminated members.
Curvature factor
The finely ground material used as the binder for structural concrete.
Portland cement
A diagram used to graphically determine the resultant of two or more forces.
Force polygon
A wide, flat reinforced concrete member, usually horizontal, which is supported by beams or walls.
Structural slab
A beam loading of constant magnitude per unit of length.
Uniformly distributed load
A beam that rests on a support at each end.
Simple beam
An assembly of steel plates, or plates and angles, which are fastened together to form an integral member.
Plate girder
An underground wood, concrete, or steel member, usually vertical, and usually driven into place, which is used to support building loads.
Pile
The stress diagram used in the graphical solution of a truss, which consists of the combined force polygons for all the truss joints.
Maxwell diagram
A lightweight aggregate used in lightweight concrete
Vermiculite
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.
Sleeper
The most common accelerating admixture used for concrete. It can be used in amounts up to 2 percent of the Portland cement weight.
Calcium chloride
A concrete slab in which the main reinforcement runs in two directions, generally perpendicular to each other.
Two-way concrete slab
A frame used to resist lateral forces from wind.
Wind bent
The boundary between adjacent rock plates along which movement may take place during an earthquake, such as the San Andreas fault in California.
Fault
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.
Aftershocks
An instrument which makes a continuous permanent record of earth motion, called a seismogram.
Seismograph
Seismic coefficient based on the building’s seismic zone factor and soil type.
ca and cv
A short-fabricated lightweight steel truss used to span between main members or bearing walls and support roof or floor loads.
Open web steel joist
A curve built into a structural member to compensate for defection.
Camber
The collision between two adjacent buildings which move differently during an earthquake.
Pounding
A member which collects seismic load from the diaphragm to which it is attached and delivers it to a shear resisting element. Also called a collector or strut.
Drag strut
The unit stress at which a material deforms with no increase in load.
Yield point
The direct wind pressure on a vertical surface, in pounds per square foot.
Stagnation pressure (qs)
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 which cantilevers from the ground when subject to lateral wind or earthquake loads.
Tubular system
A method of seismic design in which static horizontal forces 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.
Static lateral force procedure
The algebraic sum of the moments of all forces that are on one side of a given cross-section of a beam.
Bending moment
A solid core is used in driving a shell pile into the ground. When driving is complete, the mandrel is removed and the shell is filled with concrete.
Mandrel
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.
Plywood
A line parallel to and aligned with a force.
Line of action
With the elastic limit, the constant ratio of the unit stress in a material to the corresponding unit strain. The modulus of elasticity of a material is a measure of its stiffness.
Modulus of elasticity (e)
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.
Inelastic
Nondestructive testing of welded joints using high frequency sound waves.
Ultrasonic testing
A symbol for modulus of elasticity.
e
Bending moment which produces compression in the upper part of a beam and tension in the lower part.
Positive moment
A method of prestressing concrete in which the tensile force is put into high-strength steel wires before the concrete is cast.
Pretensioning
A method for solving for the bending moments in statically indeterminate structures, such as rigid frames and continuous beams, by successive approximation.
Moment distribution
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.
Balloon framing
A beam that rests on two or more supports and has one or both ends projecting beyond the support.
Overhanging beam
A footing supporting two or more columns.
Combined footing
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.
Gunite
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.
Precast pile
A fine-grained cohesive soil which undergoes large volume changes with changes in moisture content.
Expansive soil
A push or pull exerted on an object. The description of a force includes its magnitude, direction, and point of application.
Force
Resistance to deformation, also known as rigidity.
Stiffness
A pile whose load is supported by friction between the pile surface and the surrounding soil.
Friction pile
Resistance to deformation, also known as stiffness
Rigidity
A symbol for moment of inertia.
I
A plate girder having a tapered profile, usually varying from minimum depth at the supports to maximum depth at midspan.
Tapered girder
Soil with a high organic content (decomposed vegetable or animal matter). Organic soils are usually very compressible and have very low bearing capacities.
Organic soil
Stress which tends to shorten a member or crush it.
Compression
A beam that rests on more than two supports.
Continuous beam
A thick, reinforced concrete slab placed over a group of piles and used to distribute the structural load to all piles in the group.
Pile cap
In place.
In situ
One of two or more forces which will produce the same effect on a body as given force.
Component
The algebraic sum of the forces that are on one side of a given cross-section of a beam.
Vertical shear (v)
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 controid is the geometric center of the shape.
Centroid
The movement of a beam from its original location when load is applied to it.
Deflection
The secondary effect on frame members produced by vertical loads acting on a building frame which is laterally displaced by earthquake loads.
P-delta effect
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.
Rigid frame
The joint between two successive concrete pours. Construction joints are usually located where the shear is minimum, such as at the midspan of beams.
Construction joint
A waterproof box-like structure in which construction work can be performed underwater. Also a pile constructed by pouring concrete into a drilled shaft.
Caisson
A manmade deposit of soil.
Fill
The horizontal reaction at the base of an arch.
Thrust
A factor used to reduce the allowable bending stress for glued, laminated beams, based on width, depth, and span.
Volume factor
A fine-grained, cohesive, inorganic soil.
Clay
The maximum unit stress permissible in a structural member. It is also called allowable stress.
Working stress
The tendency of a force to cause rotation about a given point or axis.
Moment
The ratio of the minimum frictional force between two bodies to the normal (perpendicular) for pressing the surface together.
Coefficient of friction
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.
Concentric braced frame
The ratio of unit strain to temperature change, which is constant for a given material.
Coefficient of thermal expansion
A concrete element cast in a location other than its final position. After curing, it is moved to its final location and installed.
Precast concrete
The most widely used system for classifying soils. In this system, the soil are primarily classed as coarse-grained (gravels and sands), fine-grained (silts and clays), and highly organic.
Unified Soil Classification System
A reinforced concrete wall which is precast at the job site, usually in a flat position, and later tilted up and set into place.
Tilt-up wall
Granular material, ranging from about 3/8 inch to 0.005 inch.
Sand
A factor used to reduce the allowable bending stress for wood beams deeper than 12 inches.
Size factor
Referring to construction in which fire resistance is obtained by using wood structural members of specified minimum sizes.
Heavy timber
A structural member placed over an opening and supporting construction above.
Lintel
Horizontal or vertical movement of a structural element resulting from applied seismic or other load.
Displacement
The location in the earth’s crust where rock slippage begins during an earthquake. Also called the hypocenter.
Focus
Round steel bars with surface deformations which are placed in the forms prior to casting of concrete, and which primarily resist tension.
Reinforcing steel
A symbol for bending moment.
m
A longitudinal load which acts at the centroid of a member and perpendicular to its cross-section, thereby producing uniform tensile or compressive stress without any bending.
Axial load
A wall designed to resist lateral forces parallel to itself caused by wind or earthquake.
Shear wall
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.
Ground shaking
A watertight, temporary structure used under water, in which construction work can be performed.
Cofferdam
A substance, such as calcium chloride, added to concrete mix to speed up its setting and strength development.
Accelerator
A vertical steel bar, usually U-shaped, used to reinforce a reinforced concrete beam where the shear stresses are excessive.
Stirrup
The portion of a truss between the chords, or the portion of a beam between flanges.
Web
A vertical shaft drilled into the ground and filled with concrete, which supports building loads by skin friction.
Drilled pile
A metal fastener with a head at one end and external thread at the other end to receive a nut.
Bolt
A weld placed between two butting pieces of metal to be joined.
Groove weld
A coarse granular material, with particles varying from about 3 inches to 3/16 inch.
Gravel
Two forces equal in magnitude, but opposite in direction, and acting at some distance from each other. The moment produced by a couple is equal to the value of one force multiplied by the distance between the two forces.
Couple
The group of piles.
Cluster
A low-strength layer of fine particles that floats to the surface of wet concrete.
Laitance
An arch with a hinge at each support and at the high point, or crown; the only type of arch which is statically determinate.
Three-hinged arch
A force equal in magnitude to the resultant, but opposite in direction and on the same line of action as the resultant.
Equilibrant
Maintaining concrete at the proper moisture and temperature after it is cast.
Curing
A curve which shows the maximum acceleration of a series of idealized structures when subject to an earthquake.
Response spectrum
Negative pressure.
Suction
A measure of the frequency, intensity, and distribution of earthquakes in a given area.
Seismicity
Stress which tends to stretch a member or pull it apart.
Tension
One of a series of small, closely spaced beams used to support floor, ceiling, or roof loads.
Joist
A type of wall construction consisting of brick units, usually two tiers, with a solidly grouted space between each in which vertical and horizontal reinforcing bars are placed.
Reinforced brick masonry
Describing a bolted joint which has one shearing plane through the bolts.
Single-shear
An abbreviation for pounds per square inch.
psi
A concrete slab reinforced in two directions which brings its load directly to supporting columns without any beams or girders, usually requiring column capitals (widened tops of columns) and drop panels (thickened slab around columns).
Flat slab
A dynamic formula used to determine the capacity of driven piles.
Engineering news formula
A beam that is restrained against rotation at one end and free at the other.
Cantilever beam
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. Also called building separation.
Seismic separation
A curved structure in which the internal stresses are essentially compression.
Arch
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.
Statically indeterminate
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.
Dynamic lateral force procedure
Fill which has been densified by the application of pressure, usually by mechanical equipment, in order to increase its strength and stability and reduce its settlement. Properly compacted fill is often suitable for the support of building footings.
Compacted fill
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.
Eccentric braced frame (EBF)
In seismic design, a structural system with and essentially complete frame providing support for gravity 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.
Building frame system
A severe tropical storm which occurs mainly along the coast 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.
Hurricane
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.
Chevron bracing
The vertical load dues to the weight of all permanent structural and nonstructural components of a building, such as walls, floors, roofs, and fixed service equipment.
Dead load
The effect 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.
Intensity
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.
Importance factor (i)
The 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.
Test boring
