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 of arch structures, whether of stone, masonry, or timber.
Early European truss bridges used on King post and Queen post configurations. Some early German bridges included diagonal panel bracing in trusses with parallel top and bottom chords.
Possibly the first covered bridge in the United States was built in Philadelphia in the early 1800s. The investors asked to have it covered in the hopes of extending its life. 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.
Read more about this topic: Covered Bridge
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