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
