A bridge is a support structure that allows an object to travel from one point to another by crossing over some obstacle such as a body of water, valley or road.

The image below illustrates the key bridge components that come together to maintain a safe and stable structure and allow the bridge to support its own weight, traffic and other loads.

Bridge illustration

Illustration: Bridge components

Bridge photo

Photograph: Visual representation of bridge components

A: Deck: the surface of the bridge that allows for the ease of traffic (pedestrian, vehicle, etc.) crossing. It supports the roadway/traffic and transfers the loads into the beams/girders. Decks are typically constructed from reinforced concrete.

B: Beam/Girder: the horizontal structure that spans between two bridge supports, one at each end. Together, these components directly support the downward weight of the bridge and traffic traveling over it.

C: Cap: an intermediate support located between the bridge deck and the column. Bridge caps transfer vertical loads to the column, and resist lateral loads such as wind from the deck and beams/girders.

R: Column: the vertical structure that transfers compressive (vertical) bending loads to the foundation, and lastly, into the soil.

E: Foundation Casing: a large diameter pipe that is assembled and inserted into a drilled section of a borehole. In environments where there is water, the casing acts as a barrier between the water and the concrete being poured for the foundation. It is also used for stability when the soils in the ground are unstable.

F: Drilled Shaft (Foundation): designed to support structures with large vertical and lateral loads and transfer these loads into the soil. This type of foundation is constructed by rotary boring equipment to excavate open shafts to the specified depth, lowering a steel reinforcing cage into the shaft, and then filling the shaft with concrete.