Page 61

Suggested Citation: "Glossary of Key Terms." National Academies of Sciences, Engineering, and Medicine. 2024. Developing a Guide for On-Bridge Stormwater Treatment Practices. Washington, DC: The National Academies Press. doi: 10.17226/27905.

Glossary of Key Terms

Common Parts of a Bridge
Abutments	The substructure elements at either end of a bridge where the bridge connects to land. A multi-part bridge may have abutments at intermediate points where the bridge connects to land.
Beam	A general term for an approximately horizontal structural element that supports the bridge deck. Girders and cross beams are common types of beams in a bridge design. Note that due to the unique geometries of bridges, it is rare for elements to be truly horizontal. In this report, horizontal refers to a general direction, not a perfect horizontal plane.
Bent cap	A horizontal member that spans the bents and serves as the support for the girders.
Bents (also known as piers)	A vertical part of the substructure located between the ends of a bridge. They are typically made up of two or more columns connected at their topmost ends by a cap.
Cross beam	A horizontal structural element that typically runs between girders to support the bridge deck. These are often parallel or angled relative to the direction of the roadway.
Deck	The structural platform that spans the girders and cross beams and serves as the surface of the bridge. The deck is a structural element. This includes the travel lanes and the shoulders and can also include sidewalks or multi-use paths.
Deck drains	Openings that pass through the bridge deck to convey stormwater runoff.
Edge barrier	A general term used to refer to the barrier(s) at the outer edges of the bridge that help prevent vehicles or pedestrians from going over the sides. This is distinct from a center barrier which separates opposing traffic between two sides of a bridge.
Girders	A horizontal structural element that runs between piers or bents in the direction of the roadway. A girder is a type of beam.
Guard rail	A simple open type of edge barrier.
Lower strand	Refers to the lower edge of the girders.
Parapet (also known as solid barrier)	A railing system made of reinforced concrete along the outside edge of a bridge deck used to help protect vehicles and pedestrians.
Piers (also known as bents)	A type of bent that consists of a single column.
Side drains	Openings that pass through the edge barrier of the bridge to convey stormwater runoff.
Span	Refers to lengths of bridge between substructure elements. Span is also used to refer to specific elements, such as the “center span” of a bridge.
Substructure	A general term referring to the piers and abutments that lie between the bridge foundation and the superstructure.

Page 62

Superstructure	A general term referring to the girders, beams, deck, shoulders, edge barriers, towers (if applicable) other supporting elements above the substructure that support the riding surface of the bridge.
Related Design and O&M Terms
Base flood elevation	Refers to the 100-year peak water surface elevation defined by the Federal Emergency Management Agency (FEMA).
Clogging lifespan	The time that a media filter can operate at or above its design infiltration rate between rehabilitation or media replacement events.
Constructability	Refers to the relative complexity and cost required to construct a design.
Drainage criteria (also known as storm drainage)	A general term referring to the requirements for draining stormwater from a bridge during storms for the purpose of vehicular safety. Drainage criteria typically include the return interval storm event, the allowable lateral spread, and/or other criteria to define the size and spacing of drainage elements.
Floodplain	The floodway and the floodplain fringe that is inundated in the 100-year base flood event.
Floodway	The channel and adjacent overbank areas necessary to effectively convey floodwaters.
Maintenance interval	The time interval at which maintenance activities are required to allow for the ongoing function of a BMP. This includes both routine and rehabilitative maintenance. For a media filtration BMP, this may include sediment removal, debris removal, media replacement, or other activities.
Manual labor	Refers to hand labor, such as the use of shovels, raking of or replacing media, carrying of bags, or other similar activities.
O&M	Operations and maintenance, including inspection, routine maintenance, and major/rehabilitative maintenance.
Structural risks	Refers to the potential for a BMP design to compromise the structural integrity of a bridge.
Traditional hoist	Refers to a truck-mounted boom lift system that can extend over the side of a bridge and lift vertically.
Under-bridge inspection equipment	Refers to a type of lift, boom, or platform truck designed to allow work below the bridge deck via a truck parked on the bridge surface. For example, equipment that allows inspection personnel to ride in a bucket or walk on a temporary walkway below the bridge.
Vacuum truck	A truck with an extendable hose attached to a boom that is designed to pick up and transfer liquids, slurries, and loose aggregates into a tank mounted on the truck.
Vertical clearance	A general term used to refer to the vertical separation between the bottom of the bridge beams and the maximum height that is needed to safely pass vehicles (ships/boats/trains/trucks, etc.) below the bridge. This could be driven by the base flood elevation, navigability requirements, or rail/traffic requirements.
Water quality flows	The flow rate generated from a regulatory water quality treatment event, such as the flow generated from the 85th percentile storm event or the flow required to treat a certain percentage of long-term runoff volume. Water quality flows are nearly always smaller than the storm flows relevant for drainage criteria.

Developing a Guide for On-Bridge Stormwater Treatment Practices (2024)

Chapter: Glossary of Key Terms

Glossary of Key Terms

Publication information

Suggested citation

My Academies

Developing a Guide for On-Bridge Stormwater Treatment Practices (2024)

Chapter: Glossary of Key Terms

Glossary of Key Terms