Tied arch bridge

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A tied arch bridge is an arch bridge in which the outward-directed horizontal forces of the arch are borne by the bridge deck, rather than the ground or the bridge foundations. The bridge deck ties the ends of the arch together, and is under tension, much like the string of a bow; therefore, this bridge design is sometimes called a bowstring arch bridge. The elimination of horizontal forces at the abutments allows a tied arch bridge to be constructed with less robust foundations; this bridge type can be easily situated on top of elevated piers or in areas of unstable soil. In addition, since they do not depend on horizontal squeezing forces for their integrity, tied arch bridges can be prefabricated offsite, and subsequently floated, hauled or lifted into place.

[edit] Bridges of this type

16th Street Bridge, Pittsburgh, Pennsylvania.
Abraham Lincoln Memorial Bridge
Big Creek Bridge, Lane County, Oregon
Mississippi River Bridge, La Crosse, Wisconsin
Daniel Carter Beard Bridge
Fort Duquesne Bridge
Fort Pitt Bridge
Fremont Bridge, Portland, Oregon
Hoan Bridge, Milwaukee, Wisconsin
John McLoughlin Bridge
Port Mann Bridge]]]] == == ==

[edit] Gallery of Tied Arch Bridge

Pennybacker Bridge is a traditional arch bridge. Note that the arches terminate at ground-level abutments, which provide the squeezing force which holds the bridge up.

The Fort Pitt Bridge is a tied arch bridge. Note that the arches terminate atop slender raised piers which provide no squeezing force; tension in the road deck holds up the arch.

Portland's Fremont Bridge is the longest tied arch bridge in the world. In this case the half-arches on either end of the bridge terminate atop slender raised piers. The horizontal forces of the main arch and the outer half-arches balance at the ground level foundations.