A bridge deck or road bed is the roadway, or the pedestrian walkway, surface of a bridge, and is one structural element of the superstructure of a bridge. It is not to be confused with any deck of a ship. The deck may be constructed of concrete, steel, open grating, or wood. Sometimes the deck is covered with asphalt concrete or other pavement. The concrete deck may be an integral part of the bridge structure (T-beam or double tee structure) or it may be supported with I-beams or steel girders.
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When a bridge deck is installed in a through truss, it is sometimes called a floor system. A suspended bridge deck will be suspended from the main structural elements on a suspension or arch bridge. On some bridges, such as a tied-arch or a cable-stayed, the deck is a primary structural element, carrying tension or compression to support the span.
Structural analysis
Structural engineers have several principal categories of bridge decks, for the purposes of analytic techniques. A beam deck is one where the deck and any supporting structure act together as a single beam. A grid deck uses beams and diaphragms as the supporting structure. The supporting system of a grid deck is analyzed using a grillage analysis. A slab deck is one where the deck is analyzed as a plate. If the slab has a stiffness that is different in two directions (at right angles), then the deck is known and analyzed as an orthotropic deck. A beam and slab deck is one where the beams may deflect somewhat independently, and any transverse forces are carried in the deck. A cellular deck is one where a number of thin slabs and webs will enclose cells within the deck. A boxgirder deck is one where the deck forms the top of the box girder during analysis.
Railway bridge decks
In the case of a railway bridge, when the railway track and ties are supported on load carrying elements of the superstructure (floor beams, stringers or girders), it is called an open deck. When the track rests upon ballast, which is then carried by the superstructure of the bridge, it is called a ballasted deck. A third type of rail support is direct fixation, where ties are not used and the rails are anchored directly to the superstructure of the bridge.
