Various Types of Bridges

Also known as: Girder bridge

Description: Beam bridges are the most common type of bridge. They consist of one or more beams supported underneath at their ends.

Description: Truss bridges utilize horizontal beams at two different heights. The bottom and top beams are connected by a series of vertical and angled beams. The top beam and the vertical connections to the bottom beam are in compression (being pressed inward from the ends) while the bottom beam and the angled beams connected to the top beam are in tension (the ends of the beams are being pulled away from each other). The two level structure gives the bridge rigidity that a single level beam bridge does not have, and thus truss bridges can have longer spans than simple beam bridges when using the same type of material to construct the bridge.

Description: The main supporting structure of an arch bridge is an arch that spans from a foundation on one side of the bridge to a foundation on the other side of the bridge. The foundations experience both vertical and horizontal loads, so more care is needed when engineering these types of supports. This type of structure generally requires less material than a beam bridge would for the same span.

Description: Suspension bridges feature one or more towers that are connected to each other and to anchorages at either end of the bridge by arching cables. The deck of the bridge is located below the top of the tower or towers and is supported by additional cables attached to the main cables.

Description: To be cantilevered means to project outward, supported only at one end (like a diving board). Cantilever bridges consist of one or more beams that are supported from underneath in the middle, and the ends of the beams extend outward.

Facts:

• The foundations on either end of the bridge can be made more simply than in other bridge types because they are not the main support of the bridge.
• This type of bridge does not require extensive "falsework" (used to support the bridge during construction) but can be built outward from the center in a balanced fashion.

Description: Cable-stay bridges are similar to suspension bridges in that they have one or more towers that support the deck of the bridge by cables. However, the cables in cable-stay bridges are attached directly from the top of the tower to the deck in straight lines.

Facts: Unlike suspension bridges, cable-stay bridges do not require anchorages for the cables on the shore at the ends of the bridge.