Retractable bridge
Lift bridge, submersible bridge, folding bridge | |
Descendant | None |
---|---|
Carries | Automobile, pedestrians |
Span range | Short |
Material | Steel |
Movable | Yes |
Design effort | Medium |
Falsework required | No |
A retractable bridge is a type of
![](http://upload.wikimedia.org/wikipedia/commons/thumb/0/0e/Uppsala_Ultunabron01_2005-06-16.jpg/220px-Uppsala_Ultunabron01_2005-06-16.jpg)
![](http://upload.wikimedia.org/wikipedia/commons/thumb/8/8f/Borden_Avenue_Bridge_over_Dutch_Kills_slide_tracks_jeh.jpg/220px-Borden_Avenue_Bridge_over_Dutch_Kills_slide_tracks_jeh.jpg)
Retractable bridges date back to medieval times. Due to the large dedicated area required for this type of bridge, this design is not common. A retractable design may be considered when the maximum horizontal clearance is required (for example, over a canal).
Two remaining examples exist in New York City: the
Some retractable bridges are also floating bridges, such as the Hood Canal Bridge. Two other floating bridges in Washington state used to have retractable spans but were replaced with new floating bridges without retractable spans: the Evergreen Point Floating Bridge (replaced in 2016) and Lacey V. Murrow Memorial Bridge (replaced after it accidentally sank in 1990). This design is popular in Guyana, which has the Demerara Harbour Bridge and the Berbice Bridge.
Historical examples of designs for retractable bridges include those by Leonardo da Vinci[2] and Agostino Ramelli.[3]
In the Netherlands, especially in the province of North Holland, a vlotbrug is a design of retractable bridge across a canal in which the roadway floats and can be retracted under fixed structures on the canal banks.
See also
![](http://upload.wikimedia.org/wikipedia/commons/thumb/b/b1/MovableBridge_thrust.gif/220px-MovableBridge_thrust.gif)
- Guthrie rolling bridge
- Moveable bridges for a list of other movable bridge types
References
- ^ "Helix Bridge (City of Westminster, 2004)". Structurae. Retrieved Sep 18, 2019.
- ^ "Leonardo and the Engineers of the Renaissance". brunelleschi.imss.fi.it. Retrieved Sep 18, 2019.
- ^ "Image of retractable bridge for crossing a moat, 1588. by Science & Society Picture Library". www.scienceandsociety.co.uk. Retrieved Sep 18, 2019.