Bascule bridge

Bascule bridge
	This animation shows the movement of a double-leaf bascule.
Ancestor	Drawbridge, Plate girder bridge, cantilever bridge
Related	Lift bridge, swing bridge
Descendant	None
Carries	Pedestrian, bicycle, automobile, truck, light rail, heavy rail
Span range	Short
Material	Steel
Movable	Yes
Design effort	Medium
Falsework required	Site and prefabrication specific

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.

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.

History

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.

Types

There are three types of bascule bridge^[1] and the counterweights to the span may be located above or below the bridge deck.

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.^[2]

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.^[3]

The rarer Rall type combines rolling lift with longitudinal motion on trunnions when opening.^[4] It was patented (1901) by Theodor Rall.^[2]^[4]^[5] One of the few surviving examples is the Broadway Bridge (1913), in Portland, Oregon.^[4]^[6]

The counterweight is often hidden below the road surface in the bridge abutment.^[7]
Animation of a double-leaf Strauss fixed-trunnion bridge (based on engineering drawings from the Henry Ford Bridge)
Animation of a rolling lift bridge (such as the Pegasus Bridge)
Bascule bridge in the down position

References

^ Koglin, Terry L. (2003). "4. Bascule Bridges". Movable bridge engineering. John Wiley and Sons. ISBN 978-0-471-41960-0. Retrieved May 25, 2009.
^ ^a ^b "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
^ ^a ^b ^c Wood Wortman, Sharon; Wortman, Ed (2006). The Portland Bridge Book (3rd ed.). 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.
^ Van Zantvliet, P. S. (June 2015). "Analysis of the force distribution on operating mechanisms in a bascule bridge" (PDF). Archived (PDF) from the original on 2021-09-21.

External links

Media related to Bascule bridges at Wikimedia Commons

[1] Koglin, Terry L. (2003). "4. Bascule Bridges". Movable bridge engineering. John Wiley and Sons. ISBN 978-0-471-41960-0. Retrieved May 25, 2009.

[chicago_landmarks-2] "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.

[3] US grant 511713, Scherzer, William, "Lift-Bridge", issued 26 December 1893

[wood-wortman-4] Wood Wortman, Sharon; Wortman, Ed (2006). The Portland Bridge Book (3rd ed.). Urban Adventure Press. pp. 32, 35. ISBN 0-9787365-1-6.

[Rall_patent-5] "Patent number 669348: T. Rall movable bridge". United States Patent and Trademark Office (referenced online by Google Patents). 1901. Retrieved April 21, 2013.

[haer-broadwaybridge-6] Historic American Engineering Record. "Broadway Bridge, Spanning Willamette River at Broadway Street [sic], Portland, Multnomah County, OR". Library of Congress. Retrieved April 21, 2013.

[7] Van Zantvliet, P. S. (June 2015). "Analysis of the force distribution on operating mechanisms in a bascule bridge" (PDF). Archived (PDF) from the original on 2021-09-21.

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Structural types	Arch Beam Box girder Bridge–tunnel Burr Truss Cable-stayed Canopy Cantilever Cantilever spar cable-stayed Covered Crib Double-beam drawbridge Extradosed Jet Log Moon Moveable Bascule Drawbridge Folding Retractable Rolling Rolling bascule Submersible Swing Table Tilt Transporter Vertical-lift Multi-way Navigable aqueduct Pile Pontoon Vlotbrug Suspension types Timber Through arch Trestle Truss Tubular Viaduct Visual index to various types
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See also

References

External links