Covered bridge

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A covered bridge is a bridge with enclosed sides and a roof, often accommodating only a single lane of traffic. They have typically been wooden, although some newer ones are concrete or metal with glass sides. Mainly associated with the 19th century, covered bridges often serve as prominent local landmarks and have long attracted the attention of historic preservationists. The Roseman covered bridge from 1883 in Iowa became famous when it was used in R.J.Waller's novel, later filmed, "The Bridges of Madison County".

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Construction details

Early bridges were often made of wood, especially where it was a plentiful resource. Wooden bridges tended to deteriorate rapidly from exposure to the elements, having a useful lifespan of only nine years. Covering them protected their structural members, thus extending their life to 80 years or more.

Most wooden covered bridges employ trusses as their key structural design element. A popular design was the Brown truss, known for its simplicity, but others were also used.

Given the ready availability of steel, concrete, and other modern construction materials, most modern covered bridges are built either for the convenience of the user, rather than to protect the structure itself, or as a statement of style or design.

Many of the oldest bridges were built as post and pile construction. This is commonly seen in stone construction where columns (piles) are used to support spans (posts) covering open spaces. The Kapellbr├╝cke in Lucerne is an example. A modern example is the Covered Bridge, Lovech, which uses stone piers and steel beams. Many older bridges were built using an arch. The Ponte Coperto in Italy and the Ponte Vecchio in Florence, Italy are examples. As bridge needs increased in North America, designs turned to available material, wood. In order to cover the spans needed, truss design was extended and improved. Eleven major trusses were used during the period of wood construction.

Standard Truss Types The earliest covered bridges used the simple King post and Queen post design. These had been traditional truss types for building construction. Older bridges along the east coast are often dominated by King and Queen post designs. Beginning around 1820, new designs were being developed.

  • King Post, most of the remaining covered bridges in Virginia are either King post or Queen post designs. See: List of Virginia covered bridges
    • Curved Multiple Kings Post, an example adopted by local conditions is the Humpback Covered Bridge in Virginia. It is a curved truss using the King post design.
  • Queen post, most Queen posts are in New England, with a few on the west coast. It is also a common design used for non-covered steel bridges.[1]

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