what about bowstring bridge?

Question

in bridge construction

Answer 1

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 sqeezing forces for their integrity, tied arch bridges can be prefabricated offsite, and subsequently floated, hauled or lifted into place.
http://en.wikipedia.org/wiki/Tied_arch_bridge

More info can be found here:
http://www.matsuo-bridge.co.jp/english/bridges/basics/arch.shtm