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Table of Contents

Bridge Terms


Supports at both ends of bridge. A retaining wall holding roadway fill material and supporting bridge beams.

Approach Fill

Manmade compacted earth that supports road ramps leading to the ends of the bridge.

Approach Spans

Short spans over land leading to the main spans.


Thin horizontal members of the bridge that support the deck


General name for vertical support elements of the bridge; may be a column, pier, or abutment.


In a truss, the upper and lower horizontal (or arched) members of the frame.


Diagonal bracing that resists wind, earthquake or other forces on beams and trusses.


A diagramatic view of a roadway or bridge that "cuts" through the roadway like a a knife cutting thru a sausage and looks at the cut end to examine the width of the road; the lanes, the sidewalk, and other features.

Dead Load

Self-weight of bridge that must be considered during design.


Slab of concrete or steel that rests on the floor support system that is supported by beams. Traffic moves on the deck.


Separation of concrete from steel reinforcement bars; weakens the strength of the concrete member.


Outside beam or girder; also, non-structural decorative elements on the exterior.


Deck support beams perpendicular to the centerline of the roadway.


"At the bottom of a column or bent. A spread footing distributes a heavy load onto the soil. A pilecap footing distributes the load to piling that penetrates the soil down to bedrock."


The lowest support of the structure, usually the soil and/or bedrock beneath the footing.


A structural skeleton designed to resist collapse due to the joint angles being fixed.


Main load-carrying horizontal member of a span.


Rate of change in elevation of road surface.

Horizontal Curve

Left or right curve in the roadway.

Live Load

Weight of traffic on the bridge, e.g. trucks, buses, cars, pedestrians.


Parallel to the direction of traffic and the centerline of the bridge.

Main Spans

Differ from approach spans. Usually larger, longer, stronger and over water or primary obstacle.


An area in roadway or barrier between opposing travel lanes; minimize head-on collisions.


Structural pieces that compose a bridge: beams, columns, floorbeams, girders, for example.


Mathematical representation of a real world problem for analysis purposes. Traffic and structural models are used on the Sellwood Bridge Project.

Multi-Use Path

For use by bicyclists and pedestrians; may be two way for bicyclists.

Seismic Retrofit (Phase I)

Methods to upgrade an existing bridge that involve tying the horizontal span members to the vertical supports (bents), to prevent the deck from falling.

Seismic Retrofit (Phase II)

Methods to upgrade an existing bridge that involve strengthening the footings and foundation to prevent them from settling during an earthquake. Roughly equivalent to new bridge in earthquake performance.


Similar to bent or column when it is located in water.


Strengthening a structural member by adding cables and shortening them, forcing the member into compression. Post-tensioning is done after the structural member is built and is in place.


Strengthening a structural member by adding cables and shortening them during the fabrication process. Structural members are delivered and installed in the compressed condition.

Reinforced Concrete

Concrete members made by forming a shape and installing a reinforcing steel cage before placing the concrete. Reinforced concrete is stronger, more elastic, cracks less, and can be used in tension as well as compression.


Forces pertaining to earthquakes and earth vibrations.

Sight Distance

Distance of clear vision ahead required to stop if there is an blockage in the road. Related to speed of vehicle, horizontal and vertical curvature, or trees and signs that could obstruct vision.


Numbered segments of the bridge between vertical supports (bents). Spans over land are generally shorter than over water because the supports are more difficult to build in water.


Curve with a changing radius. Spirals smooth out the transition between straightaways and currves.


Supports, e.g. bents and footings.


Cross-slope in a road curves, designed in to prevent vehicles from rolling.


Part of bridge that rests on supports, e.g. beams, truss, deck, sidewalks.


Perpendicular to the direction of traffic or centerline of the bridge.


Jointed open structure; the frame is divided into a series of triangular figures for rigidity and strength. Elements include upper and lower chords, verticals and diagonals.

Vertical Curve

Curve in the roadway in the vertical plane; either a crest (hill) or sag (valley).

Environmental Process Terms

Affected Environment

A description of the existing environment to be affected by the proposed action (40 CFR 1502.15).


A reasonable way to fix the identified problem or satisfy the stated need (40 CFR 1502.4).

American Recovery and Reinvestment Act of 2009 (ARRA)

ARRA is commonly referred to as the Stimulus or Recovery Act. It is an economic stimulus package passed by Congress in February 2009. The stimulus was intended to create new jobs and spur economic activity during the recession.

Categorical Exclusion (CX)

A category of actions that do not individually or cumulatively have a significant effect on the human environment and have been found to have no such effect in procedures adopted by a Federal agency pursuant to NEPA (40 CFR 1508.4).

Council on Environmental Quality (CEQ)

Established under Title II of NEPA to develop Federal agency-wide policy and regulations for implementing the procedural provisions of NEPA, resolve interagency disagreements concerning proposed major Federal actions, and to ensure that Federal agency programs and procedures are in compliance with NEPA.

Cumulative Effect

The incremental environmental impact or effect of the proposed action, together with impacts of past, present, and reasonably foreseeable future actions, regardless of what agency (Federal or non-Federal) or person undertakes such other actions. Cumulative effects can result from individually minor but collectively significant actions taking place over a period of time (40 CFR 1508.7).

Environmental Consequences

Environmental effects of project alternatives, including the proposed action, any adverse environmental effects which cannot be avoided, the relationship between short-term uses of the human environment, and any irreversible or irretrievable commitments of resources which would be involved if the proposal should be implemented (40 CFR 1502.16).

Environmental Action Statement (EAS)

A Service-required document prepared to improve the Service's administrative record for categorically excluded actions that may be controversial, emergency actions under CEQ's NEPA regulations (40 CFR 1506.1 1), decisions based on EAs to prepare an EIS, and any decision where improved documentation of the administrative record is desirable, and to facilitate internal program review and final approval when a FONSI is to be signed at the FWS-WO and FWS-RO level (550 FW).

Environmental Impact Statement (EIS)

A detailed written statement required by section 102(2)(C) of NEPA, analyzing the environmental impacts of a proposed action, adverse effects of the project that cannot be avoided, alternative courses of action, short-term uses of the environment versus the maintenance and enhancement of long-term productivity, and any irreversible and irretrievable commitment of resources (40 CFR 1508.1 1).

Environmental Assessment (EA)

A concise public document, prepared in compliance with NEPA, that briefly discusses the purpose and need for an action, alternatives to such action, and provides sufficient evidence and analysis of impacts to determine whether to prepare an environmental impact statement or finding of no significant impact (40 CFR 1508.9).

Finding of No Significant Impact (FONSI)

A document prepared in compliance with NEPA, supported by an environmental assessment, which analyzes whether a Federal action will have no significant effect on the human environment and for which an environmental impact statement, therefore, will not be prepared (40 CFR 1508.13).

Human Environment

Includes the natural and physical environment and the relationship of people with the environment (40 CFR 1508.14).

Impact (Effect)

A direct result of an action which occurs at the same time and place; or an indirect result of an action which occurs later in time or in a different place and is reasonably foreseeable; or the cumulative results from the incremental impact of the action when added to other past, present, and reasonably foreseeable future actions regardless of what agency or person undertakes such other actions (40 CFR 1508.8).

Lead Agency

The agency or agencies responsible for preparing the environmental impact statement (40 CFR 1508.16).

Major Federal Action

Actions with effects that may be major and which are potentially subject to Federal control and responsibility (40 CFR 1508.18).

Memorandum of Agreement (MOA)

Once mitigation measures are decided by project leaders, a document called a "Memorandum of Agreement," or MOA, is drafted which stipulates the particulars of mitigation. The MOA represent a legally binding commitment to implement the mitigation included in the MOA.


Planning actions taken to avoid an impact altogether to minimize the degree or magnitude of the impact, reduce the impact over time, rectify the impact, or compensate for the impact (40 CFR 1508.20)

National Environmental Policy Act of 1969 (NEPA)

Requires all agencies, including the Service, to examine the environmental impacts of their actions, incorporate environmental information, and utilize public participation in the planning and implementation of all actions. Federal agencies must integrate NEPA with other planning requirements and prepare appropriate NEPA documents to facilitate better environmental decision making. NEPA requires Federal agencies to review and comment on Federal agency environmental plans/documents when the agency has jurisdiction by law or special expertise with respect to any environmental impacts involved. (42 U.S.C. 4321- 4327) (40 CFR 1500-1508).

Notice of Intent (NOI)

A notice that an environmental impact statement will be prepared and considered (40 CFR 1508.22).

No Action Alternative

The alternative where current conditions and trends are projected into the future without another proposed action (40 CFR 1502.14(d)).

Proposed Action

A plan that contains sufficient details about the intended actions to be taken, or that will result, to allow alternatives to be developed and its environmental impacts analyzed (40 CFR 1508.23).

Record of Decision (ROD)

A concise public record of decision prepared by the Federal agency, pursuant to NEPA that contains a statement of the decision, identification of all alternatives considered, identification of the environmentally preferable alternative, a statement as to whether all practical means to avoid or minimize environmental harm from the alternative selected have been adopted (and if not, why they were not), and a summary of monitoring and enforcement where applicable for any mitigation (40 CFR 1505.2).

Relationship of Short-Term Uses and Long-Term Productivity

The balance or trade-off between short-term uses and long-term productivity need to be defined in relation to the proposed activity in question. Each resource, of necessity, has to be provided with its own definitions of short- term and long-term (40 CFR 1502.16).


The range of actions, alternatives, and impacts to be considered in an environmental impact statement (40 CFR 1508.25).


The coverage of general matters in broader environmental impact statements with subsequent narrower statements of environmental analysis, incorporating by reference, the general discussions and concentrating on specific issues (40 CFR 1508.28).

Unavoidable Adverse Effects

Effects that can not be avoided due to constraints in alternatives. These effects do not have to be avoided by the planning agency, but they must be disclosed, discussed, and mitigated, if possible (40 CFR 1500.2(e).