Extradosed bridge

Extradosed bridge
Diagram of an extradosed bridge
Diagram of an extradosed bridge
AncestorBox girder bridge, cable-stayed bridge
RelatedLow-tower cable-stayed
Descendantnone
CarriesPedestrians, vehicles, light rail, heavy rail
Span rangeMedium
MaterialConcrete
MovableNo
Design effortHigh
Falsework requiredno

An extradosed bridge employs a structure that combines the main elements of both a prestressed box girder bridge and a cable-stayed bridge.[1][2]: 85 [3] The name comes from the word extrados, the exterior or upper curve of an arch, and refers to how the "stay cables" on an extradosed bridge are not considered as such in the design, but are instead treated as external prestressing tendons deviating upward from the deck. In this concept, they remain part of (and define the upper limit of) the main bridge superstructure.[4]: 1 

Compared to a cable-stayed or cantilever-girder bridge of comparable span, an extradosed bridge uses much shorter stay-towers or pylons than the cable-stayed bridge, and a significantly shallower deck/girder structure than used on the girder bridge.[2]: 85–86  This arrangement results in the typical extradosed "look" of a fan of low, shallow-angle stay cables, usually with a pronounced "open window" region extending from the sides of each tower.[4]

The extradosed bridge form is mostly suited to medium-length spans between 100 m (330 ft) and 250 m (820 ft), and over fifty such bridges had been constructed around the world as of 2012.[4]: 16–26  Whilst incurring many of the construction costs of both the cable-stayed and girder bridge types, extradosed bridges can deliver material savings to offset much of this penalty.[1]: 387–388  They have frequently been adopted when overall height, navigation clearance, or aesthetic requirements have made the cable-stayed or girder alternatives less feasible.[4]: 15, 135–136 

  1. ^ a b Cite error: The named reference Benjumea was invoked but never defined (see the help page).
  2. ^ a b Cite error: The named reference Ikeda was invoked but never defined (see the help page).
  3. ^ Benaim, Robert (2007). The Design of Prestressed Concrete Bridges (Google books (Preview)). Routledge. p. 519. ISBN 978-0-415-23599-0. Retrieved 21 April 2009. Extradosed bridges are transitional between girders and cable-stayed bridges.
  4. ^ a b c d Cite error: The named reference Mermigas was invoked but never defined (see the help page).