The Cogan House Covered Bridge, Pennsylvania | |
Ancestor | Truss bridge, others |
---|---|
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, decking, 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 typically have a lifespan of only 20 years because of the effects of rain and sun, but a covered bridge can last over 100 years.[2] In the United States, only about 1 in 10 survived the 20th century.[3] The relatively small number of surviving bridges is due to deliberate replacement, neglect, and the high cost of restoration.[4]
Surviving covered bridges often attract touristic attention due to their rarity, quaint appearance, and bucolic settings. Many are considered historic and have been the subject of historic preservation campaigns.