Covered bridges

Covered Bridge
Cogan House Covered Bridge, U.S.A.
Ancestor Truss bridge, others
Related Tubular bridge, Skyway, Jetway
Descendant None
Carries Pedestrians, livestock, vehicles
Span range Short
Material Typically wood beams with iron fittings and iron rods in tension
Movable No
Design effort Low
Falsework required Determined by enclosed bridge structure, site conditions, and degree of prefabrication

A covered bridge is a timber-truss bridge with a roof and siding which, in most covered bridges, create an almost complete enclosure.[1] The purpose of the covering is to protect the wooden structural members from the weather. Uncovered wooden bridges have a life span of only 10 to 15 years because of the effects of rain and sun.[2]

Bridges having covers for reasons other than protecting wood trusses, such as for protecting pedestrians, are also sometimes called covered bridges.

History and development


Early timber covered bridges consisted of horizontal beams laid on top of piles driven into the riverbed. The problem is that the length between spans is limited by the maximum length of each beam. The development of the timber truss allowed bridges to span greater distances than those with beam-only structures or arch structures, whether of stone, masonry, or timber.[3]

Early European truss bridges used king post and queen post configurations. Some early German bridges included diagonal panel bracing in trusses with parallel top and bottom chords.[3]

At least two covered bridges make the claim of being the first built in the United States. Town records for Swanzey, New Hampshire, indicate their Carleton Bridge was built in 1789, but this remains unverified.[4] Philadelphia, however, claims a bridge built in the early 1800s on 30th Street and over the Schuylkill River was the first, noting that investors wanted it covered to extend its life.[5] Beginning around 1820, new designs were developed, such as the Burr, Lattice, and Brown trusses.

In the mid-1800s, the development of cheaper wrought iron and cast iron led to metal rather than timber trusses, except in those areas of plentiful large timber.[3]

Examples of covered bridges

There are about 1600 covered bridges in the world.[6]

Other covered bridges

The term covered bridge is also use to describe any bridge-like structure that is covered. For example

Covered bridges in fiction

Covered bridges are popular in folklore[21] and fiction.

North American covered bridges received much recognition as a result of the success of the novel, The Bridges of Madison County written by Robert James Waller and made into a Hollywood motion picture starring Meryl Streep and Clint Eastwood. The Roseman Covered Bridge from 1883 in Iowa became famous when it was featured in both the novel and the film. A covered bridge is also prominently featured in the story Never Bet the Devil Your Head by Edgar Allan Poe, and covered bridges serve as plot points in the 1988 comedy films Beetlejuice and Funny Farm.

Gallery

References

External links

  • "Covered Spans of Yesteryear", documenting the current and former covered bridges of the United States and Canada
  • National Society for the Preservation of Covered Bridges
  • Covered Bridge Map, an interactive map showing locations of covered bridges in the United States and Canada
  • (French) "Les ponts couverts au Québec, héritage précieux", an article on covered bridges in Quebec
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