![]() ![]() Like the simple case it exclusively places vertical loads on all ground-bound supports.Īn example is the Fremont Bridge in Portland, Oregon which is the second-longest tied-arch bridge in the world and also classifies as a through arch bridge. The supporting piers at this point may be slender, because the outward-directed horizontal forces of main and auxiliary arch ends counterbalance. The latter usually support the deck from below and join their bottom feet to those of the main arch(es). Some tied-arch bridges only tie a segment of the main arch directly and prolong the strengthened chord to tie to the top ends of auxiliary (half-)arches. ![]() Hoge Brug (or Passerelle Céramique) in Maastricht. īoth the tied-arch bridge and the self-anchored suspension bridge place only vertical loads on the anchorage, and so are suitable where large horizontal forces are difficult to anchor. Notable bridges of this type include the Fremont Bridge in Portland, Oregon as well as the first "computer designed" bridge of this type the Fort Pitt Bridge in Pittsburgh, Pennsylvania. ![]() In addition, since they do not depend on horizontal compression forces for their integrity, tied-arch bridges can be prefabricated offsite, and subsequently floated, hauled or lifted into place. The elimination of horizontal forces at the abutments allows tied-arch bridges to be constructed with less robust foundations thus they can be situated atop elevated piers or in areas of unstable soil. Therefore, the design is also called a bowstring-arch or bowstring-girder bridge. However, in a tied-arch or bowstring bridge, these movements are restrained not by the abutments but by the strengthened chord, which ties these tips together, taking the thrusts as tension, rather like the string of a bow that is being flattened. Thrusts downwards on a tied-arch bridge deck are translated, as tension, by vertical ties between the deck and the arch, tending to flatten it and thereby to push its tips outward into the abutments, like for other arch bridges. ![]()
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