A bascule bridge (also referred to as a drawbridge or a lifting bridge) is a moveable bridge with a counterweight that continuously balances a span, or leaf, throughout its upward swing to provide clearance for boat traffic. It may be single- or double-leafed.
|Ancestor||Drawbridge, Plate girder bridge, cantilever bridge|
|Related||Lift bridge, swing bridge|
|Carries||Pedestrian, bicycle, automobile, truck, light rail, heavy rail|
|Falsework required||Site and prefabrication specific|
The name comes from the French term for balance scale, which employs the same principle. Bascule bridges are the most common type of movable span because they open quickly and require relatively little energy to operate, while providing the possibility for unlimited vertical clearance for marine traffic.
Bascule bridges have been in use since ancient times, but until the adoption of steam power in the 1850s, very long, heavy spans could not be moved quickly enough for practical application.
The fixed-Trunnion (sometimes a "Chicago" bascule) rotates around a large axle that raises the span(s). The Chicago bascule name derives from the location where it is widely used, and is a refinement by Joseph Strauss of the fixed-trunnion.
The rolling lift trunnion (sometimes a "Scherzer" rolling lift), raises the span by rolling on a track resembling a rocking-chair base. The "Scherzer" rolling lift is a refinement patented in 1893 by American engineer William Donald Scherzer.
The rarer Rall type combines rolling lift with longitudinal motion on trunnions when opening. It was patented (1901) by Theodor Rall. One of the few surviving examples is the Broadway Bridge (1913), in Portland, Oregon.
- Tower Bridge in London, opened, viewed from the northwest
- Tower Bridge, closed, viewed from the southeast
- Dimensional drawing of Tower Bridge
- White Cart Bridge, Renfrew, Scotland
- The Birkenhead Bridge in Port Adelaide, Australia, fully opened
- Cherry Street Strauss Trunnion Bascule Bridge at Toronto Harbour Shipping Channel, Toronto
- Cherry Street Bridge at Keating Channel in Toronto, Canada
- Crook Point Bascule Bridge, Providence, Rhode Island, USA
- Another Strauss design, the Lefty O'Doul Bridge adjacent to Oracle Park in San Francisco, California
- Mystic River Bascule Bridge, Mystic, Connecticut
- Palace Bridge in Saint Petersburg
- A bascule bridge on the Joensuu Canal of the Pielinen River in Joensuu, Finland
- Pamban Bridge over the Palk Strait in Rameswaram, India
- Rolling lift Pegasus Bridge over the Caen Canal, Normandy, France
- Bascule bridge in Montceau-les-Mines, France
- The Patagones-Viedma Railway Bridge, Argentina. The longest rolling bridge in the world and the only with hydraulic counterweight.
- Railway Rolling lift bridge in Oldenburg, Germany
- Salmon Bay Bridge, a single-leaf through truss with overhead counterweight, Seattle, Washington, US
- Kuala Terengganu Drawbridge in Terengganu, Malaysia
- The Ashtabula lift bridge, a 1925 Strauss bascule built in Ohio, US
- Wabash Avenue Bridge in Chicago, Illinois, US
- Yeongdodaegyo in Busan, South Korea
- Sturgeon Bay Bridge, Sturgeon Bay, Wisconsin
- The Strauss design Johnson Street Bridge across Victoria Harbour, British Columbia, Canada, built in 1924
- The new Johnson Street Bridge in Victoria, British Columbia, Canada
- Lake Shore Lift Bridge, Toledo, Ohio
- Double-beam drawbridge
- List of bascule bridges
- Moveable bridges for a list of other movable bridge types
- Johnson Street Bridge
|Wikimedia Commons has media related to Bascule bridges.|
- Van Zantvliet, P.S. (June 2015). "Analysis of the force distribution on operating mechanisms in a bascule bridge" (PDF).
- Koglin, Terry L. (2003). "4. Bascule Bridges". Movable bridge engineering. John Wiley and Sons. ISBN 978-0-471-41960-0. Retrieved May 25, 2009.
- "Landmark Designation Report: Historic Chicago Bridges" (PDF). Commission on Chicago Landmarks. September 2007 [September 2006]. pp. 12, 15 (pdf pages 14, 17). Retrieved April 21, 2013.
- US grant 511713, Scherzer, William, "Lift-Bridge", issued 26 December 1893
- Wood Wortman, Sharon; Wortman, Ed (2006). The Portland Bridge Book (3rd Edition). Urban Adventure Press. pp. 32, 35. ISBN 0-9787365-1-6.
- "Patent number 669348: T. Rall movable bridge". United States Patent and Trademark Office (referenced online by Google Patents). 1901. Retrieved April 21, 2013.
- Historic American Engineering Record. "Broadway Bridge, Spanning Willamette River at Broadway Street [sic], Portland, Multnomah County, OR". Library of Congress. Retrieved April 21, 2013.