Allowable Strength

Nominal strength divided by the safety factor.

ASD

Allowable Strength Design. A method of designing structural elements such that the allowable strength is greater than or equal to the strength necessary to support the required load combinations.

Axial Force

A force that acts along the longitudinal axis of a structural member. Axial tension causes elongation of the member. Axial compression causes shortening of the member.

Beam

A structural member, usually horizontal, that carries a load that is applied transverse to its length.

Beam Analysis

The use of physical laws and mathematics to compute internal forces, stresses, and deformations.

Caisson

A long cylindrical reinforced concrete foundation element formed by drilling into firm soil and pouring concrete into the hole.

Column

An upright structural member acting primarily in compression.

Continuous Beam

A single beam that is supported by more than two supports such that it has at least two distinct spans.

Dead Load

The weight of the building or building components.

Deep Foundation

A foundation that transfers building loads into the earth well below the building structure.

Deflection

The distance a beam or structure deforms under loading, typically due to bending in a beam.

Deformation

A change in the shape of a structure or structural member caused by a load or force acting on the structure.

Design Load

Equilibrium

The state of a body such that the sum of all the external forces acting on the body equals zero and the sum of all external moments acting on the body equals zero.

Fixed Support

A support condition in which translation of a structural member is restricted in two perpendicular directions and rotation is restricted. A fixed support provides two perpendicular reaction forces and a reaction moment when the member is loaded.

Footing

The lowest, widest part of the foundation that distributes the load over a broad area of the soil.

Force

Foundation

The lower part of a building, which transfers structural loads from the building to the soil.

Free-body Diagram

A diagram used to isolate a body from its environment, showing all external constraints and forces acting upon it and all geometric measurements necessary to model the body.

Girder

A horizontal beam that supports other beams; a very large beam, especially one that is built up from other sections.

Grade Beam

A reinforced concrete beam that transmits the load from a bearing wall into a spaced foundation such as pile caps or caissons.

Internal Force

A force that is internal to structural elements and is needed to determine the material stress and strain.

Kip

A unit of weight equal to 1000 pounds.

Lateral Load

A force acting generally in a horizontal direction, such as wind, earthquake, and soil pressure against a structure.

Live Load

The weight of movable objects such as people, furnishings, machines, vehicles, and goods in or on a building.

Load

 Forces or other actions that result from the weight of building materials, occupants and their possessions, and environmental effects.

Load Path

A continuous system of structural elements that transfer an applied load to the supporting soil.

Mat (Raft) Foundation

A single concrete footing that is essentially equal in area to the area of ground covered by the supported structure.

Moment

(about a point P)

The tendency of a force to rotate an object about point P. It is equal to the product of the magnitude of the force acting on the object and the perpendicular distance from the point P to the force.

Moment Arm

The perpendicular distance from a reference point to the line of action of the force.

Moment Diagram

A plot of the internal moment in a beam versus position along the axis of the beam.

Nominal Strength

The load carrying capacity of a structural member.

Occupancy Category

A category used to determine structural requirements based on occupancy of the building.

Pile

A long slender piece of material driven or drilled into the ground to act as an element of a foundation.

Pin Support

A support condition in which translation of a structural member is restricted in two directions but rotation is not restricted. A pin support provides two perpendicular reaction forces when the member is loaded.

Roller (Rocker) Support

A support condition in which translation of a structural member is restricted in only one direction and rotation is not restricted. A roller support provides one reaction force when the member is loaded.

Safety Factor

A factor intended to compensate for uncertainties in design and analysis by reducing the theoretical strength of a member for use in design.

Seismic Load

A load on a structure caused by movement of the Earth relative to the structure during an earthquake.

Serviceability

The ability of a structure to maintain its appearance, durability, comfort for occupants, proper function of equipment, and ease of maintenance.

Shallow Foundation

A foundation that transfers building loads into the Earth at the base of a column or bearing wall.

Shear Diagram

A plot of the shear force in a beam versus the position along the axis of the beam.

Shear Force

The internal force, usually in a beam, which acts in the plane of the cross-section of the beam.

Simple Beam

A beam that is supported on one end by a pin support and supported on the other end by a roller support.

Span

The distance between supports for a beam, girder, truss, or other horizontal structural member; to carry a load between supports.

Spread Footing

A wide shallow footing usually constructed of reinforced concrete.

Stability

A condition of a frame or structure in which a slight disturbance in the loads or geometry of the structure does not produce large displacements or failure.

Statically Determinate Beam

A beam which is supported such that the number of unknown reaction forces is equal to the number of equilibrium equations.

Statically Indeterminate Beam

A beam which is supported such that the number of unknown reaction forces is greater than the number of equilibrium equations.

Strain

Deformation under stress.

Stress

Force per unit area.

Structural Engineer

An engineer that is licensed to design the structural systems for a building.

Tributary Area

Tributary Width

The width of floor or roof along the length of a beam, measured perpendicular to the beam, representing the portion of surface from which an applied uniform load is assumed to transfer to that beam.

Truss

An assembly of structural members joined to form a rigid framework, usually connected to form triangles..

Weight

The force exerted upon a body due to gravitational attraction to a planet.

Wind Load

Pressure from the wind that can cause lateral loads as well as uplift on the roof or downward pressure.

Yield Stress

The stress at which a material begins to deform plastically.