Structural Engineering Terms: A Plain-Language Glossary

Structural engineering has its own vocabulary. This glossary defines the terms that come up most often in conversations between engineers, architects, contractors, and building owners — in plain language, without unnecessary jargon.

A

Adaptive Reuse The conversion of an existing building to a new use that differs from its original purpose. Structural engineers evaluate whether the existing structure can support the new occupancy loads, seismic requirements, and building code demands, and design the modifications needed to make the building viable for its new use. See also: Old Buildings, New Purpose: The Engineering of Adaptive Reuse

ASCE 7 American Society of Civil Engineers Standard 7 — Minimum Design Loads and Associated Criteria for Buildings and Other Structures. The primary reference standard for structural load determination in the United States, referenced by the International Building Code. Specifies how to calculate dead, live, wind, snow, seismic, and other loads.

Axial Load A force acting along the longitudinal axis of a member — either compression (pushing) or tension (pulling). Columns primarily carry axial compressive loads. Braces carry axial loads in either direction.

B

Beam A horizontal structural member that carries loads perpendicular to its length (primarily bending and shear). Beams transfer floor or roof loads to columns, walls, or other beams.

Bearing Wall A wall that carries load from floors or roofs above and transfers it to the foundation. Removing or modifying a bearing wall requires structural engineering analysis and typically a replacement beam.

Braced Frame A lateral force-resisting system in which diagonal braces are added to a frame to resist wind and seismic forces. The braces carry loads in tension or compression. Braced frames are stiff and efficient but require diagonal members that can conflict with architectural openings.

C

Cantilever A structural member supported at one end only, with the other end free. Cantilevered elements carry loads by bending and must be designed carefully for deflection as well as strength.

Column A vertical structural member that carries compressive axial loads from beams and floors above and transfers them to the foundation.

Construction Administration (CA) The phase of engineering services during which the structural engineer reviews contractor submittals, responds to requests for information (RFIs), and makes site visits to confirm that construction conforms to the structural drawings. See also: Construction Administration: Why the Engineer Should Stay Involved

Core Wall A reinforced concrete wall system, typically surrounding elevators and stairs, that provides lateral resistance in mid- and high-rise buildings. Core walls are efficient because they resist wind and seismic forces from multiple directions.

D

Dead Load The permanent, fixed weight of a structure and its permanent components: concrete, steel, roofing, flooring, mechanical systems. Dead loads do not change over time and are calculated from material weights and dimensions.

Deflection The amount a structural member moves or bends under load. Deflection limits in the building code control how much floors and roofs can move to prevent damage to finishes, cracking of partitions, and serviceability problems. Deflection is often a more controlling design condition than strength.

Design Load The load (or combination of loads) a structural element is designed to resist. Design loads include dead, live, wind, snow, and seismic loads, combined according to the load combinations specified in ASCE 7 and the building code.

Diaphragm A horizontal structural element (typically a floor or roof) that distributes lateral forces (wind, seismic) to the vertical lateral force-resisting elements (shear walls, frames). Diaphragms act like flat beams spanning horizontally.

Drift

1. Snow drift: Accumulation of wind-blown snow at roof level changes in geometry, such as parapet bases, adjacent rooftops, or projections. Drift loads often govern roof structural design. 2. Seismic or wind drift: The lateral displacement of a building floor under wind or seismic load, expressed as an absolute value or as a ratio to story height.

E

Expert Witness A licensed professional engineer who provides technical opinion in legal proceedings, including construction disputes, personal injury cases, and property damage claims. The expert investigates the structure, forms an independent opinion, prepares a report, and may testify at deposition or trial. See also: Engineering Expertise in the Courtroom

F

Forensic Structural Engineering The investigation of structural failures, distress, and disputes by a licensed structural engineer. The forensic engineer identifies the cause of the condition, documents findings, and provides written reports. Forensic work often supports insurance claims, litigation, or building remediation decisions. See also: Forensic Structural Engineering: When You Need an Expert

Foundation The structural element that transfers building loads to the ground. Foundation types include spread footings, continuous footings, grade beams, mat foundations, drilled piers, and driven piles. Foundation selection depends on soil conditions, load magnitude, and building type. See also: Foundation Systems: What’s Under Your Building

Footing A widened base at the bottom of a wall or column that distributes load over a larger area of soil, reducing bearing pressure. Footings are sized based on the loads they carry and the bearing capacity of the soil.

G

Grade Beam A concrete beam at grade level that spans between foundation elements (piers or pilings) or ties spread footings together. Common in construction on expansive soils or uneven terrain.

H

Header A horizontal beam over a door, window, or other opening in a wall. In load-bearing walls, the header carries the loads from the structure above the opening and transfers them to the walls on each side. Header size depends on the span and the load above.

L

Lateral Load A horizontal force on a building, typically from wind or earthquake ground motion. Lateral loads must be resisted by a lateral force-resisting system and transferred to the foundation. See also: Lateral Systems: The Part of the Building Most Architects Never See

Lateral System The structural system that resists horizontal (lateral) forces from wind and seismic events. Common lateral systems include shear walls, moment frames, and braced frames. The location of the lateral system significantly affects architectural planning.

Live Load Variable loads from building occupancy: people, furniture, movable equipment, stored materials. Live load magnitudes are specified by occupancy in the building code. Residential floors typically use 40 psf live load; office floors use 50 psf; storage or assembly occupancies are higher.

Load Path The route by which loads travel from their point of application through the structure to the ground. Gravity loads travel from decking to joists to beams to columns to footings to soil. Lateral loads travel from the building skin through diaphragms to lateral force-resisting elements to the foundation. Every element in the load path must be adequate.

M

Mat Foundation A thick concrete slab covering the entire footprint of a building, used when soil bearing capacity is low or loads are high. The mat distributes loads broadly, reducing bearing pressure.

Moment Frame A lateral force-resisting system in which rigid beam-to-column connections allow the frame to resist lateral loads by bending, without diagonal bracing. Moment frames offer architectural flexibility because they do not require diagonal members. See also: Moment Frames and Where They Fit

P

Peer Review An independent review of structural design documents (calculations and drawings) by a licensed engineer not involved in the original design. Peer review catches errors before construction, validates unusual design assumptions, and is required by code in certain jurisdictions for complex structures. See also: Peer Review: What It Is, When to Get One, and What It Protects

Post-Tensioned Concrete Concrete in which high-strength steel tendons are threaded through the member and tensioned after the concrete has cured. Post-tensioning allows longer spans and thinner slabs than conventional reinforced concrete. Common in parking structures, flat-plate floors, and transfer beams. See also: Post-Tensioned Slabs

Professional Engineer (PE) A licensed engineer who has passed the PE examination and is authorized to stamp engineering documents. In Colorado, structural engineering documents submitted for building permits must be stamped by a licensed PE. The PE is legally responsible for the accuracy and adequacy of the stamped design.

R

Reinforced Concrete Concrete that contains embedded steel reinforcing bars (rebar) to resist tensile forces that concrete alone cannot carry. Concrete is strong in compression; steel rebar provides tensile capacity for bending, shear, and seismic resistance.

Rebar (Reinforcing Bar) Steel bars embedded in concrete to provide tensile strength. Specified by diameter (e.g., #4, #5, #8) and grade (yield strength). The size, spacing, and placement of rebar are determined by the structural engineer.

S

Seismic Design Category A classification assigned to a building based on its occupancy and the seismic hazard at its location. Seismic Design Category (SDC) A through F, with F being the most severe. SDC determines which seismic provisions of the building code apply and how detailed the lateral system design must be. See also: Seismic Design in the Mountain West

Shear An internal force in a structural member caused by loads acting perpendicular to the member’s axis. Shear can cause structural failure in concrete beams (diagonal tension cracking), wood members (horizontal splitting), and connections.

Shear Wall A wall designed to resist lateral forces (wind or seismic) in the plane of the wall. Shear walls can be wood-framed (with structural sheathing), reinforced concrete, or reinforced masonry. Their location within the floor plan affects both structural performance and architectural flexibility.

Snow Load The structural load imposed by snow accumulation on roofs. Design snow loads in Colorado are derived from ground snow load maps and converted to roof snow loads using factors for slope, exposure, and thermal conditions. See also: Snow Drift, Unbalanced Load, and Sliding Snow

Spread Footing An individual footing supporting a single column or wall section. The most common foundation type in low- to mid-rise construction where soil bearing capacity is adequate.

Structural Engineer A licensed Professional Engineer with specialized training and experience in the design of load-bearing systems for buildings and other structures. Structural engineers design foundations, framing, lateral systems, and connections, and stamp the structural drawings required for building permits.

T

Tributary Area The portion of a floor, roof, or wall area that contributes loads to a specific structural element. A column supporting a bay of framing has a tributary area equal to half the spans in each direction times the beam spacing.

Transfer Beam A beam that carries loads from columns or walls above and redirects them to columns or walls at a different location below. Transfer beams allow column grids to change between floors — common in mixed-use buildings where parking columns don’t align with residential columns above.

W

Wind Load The force exerted by wind pressure on a building’s exterior surfaces. Wind produces both positive pressure (pushing in) and negative pressure (suction, pulling out) on surfaces, and must be resisted by the lateral force-resisting system and the building skin and connections.

For questions about any of these terms as they apply to your project, contact Frontier Structural Engineering or call 719-247-2928.

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