Bridge Scour Terminology

The following list defines some of the common terms associated with investigations of bridge erosion concerns. The images at the bottom of this page illustrate examples of many of the terms defined below.

Footers – Footers represent the structural components that bridge piers and abutments rest upon. Most road bridges built over waterways are constructed with pile-supported footers (called pile caps) or spread footers.

Pile Caps – With pile-supported footers, piles are driven into the underlying geologic materials to a specified depth or until refusal. The piles are then cut off at a common elevation and a pile cap is poured which binds them together as a single structural unit. The load-bearing capacity of a pile-supported footer results from the combined skin friction of each of the underlying piles.

Spread Footers – For bridges constructed with spread footers, there are no underlying piles. The load-bearing capacity of the footer is determined by its foot print, structural integrity, and the supporting characteristics of the underlying geologic materials.

Abutments – The structural elements which support the ends of a bridge. Some are vertical and some are sloping (commonly called spill-through abutments).

Piers (or Bents) – The structural elements between the abutments that provide support to the overlying girders and bridge deck.

Girders – Generally horizontal bridge elements that rest upon the abutments and any piers and support the bridge deck.

Bridge Deck – The roadway bed that supports motorized traffic and pedestrians.

Low Steel – The lowest portion of a bridge’s support girders. Significant to the discussion of bridge scour because this feature controls the initiation of pressure flow when flood waters overwhelm a bridge’s conveyance capacity and rise to contact low steel.

Hardened – A term used to describe bridge elements or landform surfaces which have been treated in a way to prevent erosion of the underlying geologic materials.

(Click on any of the images below to enlarge.)

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