A bascule bridge (sometimes referred to as a drawbridge) 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.
This animation shows the movement of a double-leaf bascule.
|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|
Bascule bridges have been in use since ancient times. However, it was not until the adoption of steam power in the 1850s that very long, heavy spans could 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 the 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.
The Broadway Bridge is a Rall-type bascule bridge spanning the Willamette River in Portland, Oregon, United States, built in 1913. It was Portland's first bascule bridge, and it continues to hold the distinction of being the longest span of its bascule design type in the world. It was added to the National Register of Historic Places in November 2012.Cheboygan Bascule Bridge
The Cheboygan Bascule Bridge, also known as the State Street Bridge, is a double-leaf bascule bridge in Cheboygan, Michigan, carrying U.S. Highway 23 (State Street) across the Cheboygan River. Built in 1940, it was the last bascule bridge constructed in the state of Michigan prior to the end of World War II. It replaced an aging swing bridge built in 1877. The bridge is listed on the National Register of Historic Places.Cherry Street Strauss Trunnion Bascule Bridge
The Cherry Street Strauss Trunnion Bascule Bridge is a bascule bridge and Warren truss in Toronto, Ontario, Canada. Located in the industrial Port Lands area, it carries Cherry Street over the Toronto Harbour Ship Channel and opens to allow ships to access the channel and the turning basin beyond. There are two bascule bridges on Cherry Street. The other, smaller bridge, crosses the Keating Channel, while this bridge crosses the Ship Channel.
The bridge was built in 1930 by the company of Joseph Strauss and the Dominion Bridge Company. The north side of the bridge has 750-ton concrete counterweights that allow the bridge to pivot to open. The bridge uses 500 tons of steel in its construction. The bridge is designed to carry two lanes of traffic. It cost CA$500,000 ($8.13 million in 2018 dollars) to build. It was officially opened on June 29, 1931 by Toronto Mayor William Stewart. The bridge was listed under the Ontario Heritage Act by the City of Toronto in 1992 as architecturally historical.
The city spent CA$2.5 million to refurbish the bridge in 2007. The Toronto Port Authority made further repairs from December 2012 to September 2013 at a cost of CA$2 million.Crook Point Bascule Bridge
The Crook Point Bascule Bridge (or the Seekonk River Drawbridge) is a defunct Scherzer rolling lift railway bridge which spans the Seekonk River, connecting the city of Providence, Rhode Island, to the city of East Providence. Stuck in the open position since its abandonment in 1976, it is known to nearby residents as the "Stuck-Up Bridge" and has become somewhat of a local icon of urban decay.Erasmusbrug
Erasmusbrug (English: "Erasmus Bridge") is a combined cable-stayed and bascule bridge in the centre of Rotterdam, connecting the north and south parts of this city, second largest in the Netherlands. The bridge was named after Desiderius Erasmus, a prominent Christian renaissance humanist also known as Erasmus of Rotterdam.FEC Strauss Trunnion Bascule Bridge
The FEC Strauss Trunnion Bascule Bridge is a double track railroad bridge spanning the St. Johns River in Jacksonville, Florida.
Completed in 1925 by the Florida East Coast Railway, this structure replaced a single-track swing bridge which opened on January 5, 1890. The current structure is a simple truss bridge with plate girder approaches and a bascule lift allowing ships to pass. It is adjacent to the Acosta Bridge.Fruitvale Bridge
The Fruitvale Bridge and the Fruitvale Avenue Bridge (the latter officially the Miller-Sweeney Bridge at Fruitvale Avenue) are parallel bridges that cross the Oakland Estuary, linking the cities of Oakland and Alameda in California. The Fruitvale Bridge is a vertical-lift railroad moveable bridge, while the Fruitvale Avenue Bridge is a road bascule bridge that connects Fruitvale Avenue in Oakland with Tilden Avenue in Alameda.Joseph Strauss (engineer)
Joseph Baermann Strauss (January 9, 1870 – May 16, 1938) was an American structural engineer German descent, who revolutionized the design of bascule bridges. He was the chief engineer of the Golden Gate Bridge, a suspension bridge.Kinzie Street railroad bridge
The Chicago and North Western Railway's Kinzie Street railroad bridge (also known as the Carroll Avenue bridge) is a single leaf bascule bridge across the north branch of the Chicago River in downtown Chicago, Illinois. At the time of its opening in 1908 it was the world's longest and heaviest bascule bridge. Previous bridges on the same site included the first bridge to cross the Chicago River, Chicago's first railroad bridge, and one of the first all-steel bridges in the United States.
The Chicago Sun-Times, the last railroad customer to the east of the bridge, moved their printing plant out of downtown Chicago in 2000, and the bridge has been unused since. It was designated a Chicago Landmark in 2007. The bridge is lowered once a year and inspected by crew driving a Hi-Rail truck, and is still in "active" status.Lafayette Avenue Bridge
The Lafayette Avenue Bridge, formerly listed on the National Register of Historic Places as the Bay City Bascule Bridge, is a set of three bridges located in Bay City, Michigan. It carries M-13 and M-84 over the Saginaw River. It is maintained by the Michigan Department of Transportation, and is currently the oldest of Bay City's four modern drawbridges. It was listed on the National Register of Historic Places on November 30, 1999, but was removed from the Register in 2015.Martin Luther King Bridge (Toledo, Ohio)
The Martin Luther King Memorial Bridge (formerly Cherry Street Bridge) is a double-leaf bascule bridge adjacent to downtown Toledo, Ohio, where Cherry Street crosses the Maumee River to become Main Street on the east side of the city. The structure opened to traffic in 1914.Michigan Avenue Bridge
The Michigan Avenue Bridge (officially DuSable Bridge) is a bascule bridge that carries Michigan Avenue across the main stem of the Chicago River in downtown Chicago, Illinois, United States. The bridge was proposed in the early 20th century as part of a plan to link Chicago's south side and north side parks with a grand boulevard. Construction of the bridge started in 1918, it opened to traffic in 1920, and decorative work was completed in 1928. The bridge provides passage for vehicles and pedestrians on two levels; it is an example of a fixed trunnion bascule bridge, which is also known as a "Chicago style bascule bridge". The bridge is included in the Michigan–Wacker Historic District and has been designated as a Chicago Landmark.
The location is significant in the early history of Chicago. Events from the city's past are commemorated with sculptures and plaques on the bridge, and exhibits in the McCormick Bridgehouse & Chicago River Museum—housed in one of the bridge tender houses—detail the history of the Chicago River.Montlake Bridge
The Montlake Bridge is a double-leaf bascule bridge that carries State Route 513 (Montlake Boulevard) over Seattle's Montlake Cut—part of the Lake Washington Ship Canal—connecting Montlake and the University District.
It is the easternmost bridge spanning the canal. The bridge is 344 ft (105 m) long, and was designed by Carl F. Gould, one of the original architects of the University of Washington campus. The bridge and its control towers were designed in conjunction with the university's Collegiate Gothic style. It provides a clearance of 46 ft (14 m) and is reported as providing 48 ft (15 m) of vertical clearance above the mean regulated level of Lake Washington for the central 100 ft (30 m) of the bascule span. It is one of four original bascule-type drawbridges over the Ship Canal, the others being the Ballard, Fremont, and University Bridges. It was the last one to be completed, has the highest clearance of the four, and is the only one that is part of the state highway system. It is also one of six bascule bridges based on a design derived from the Chicago bascule bridge, but is unique because of its trunnion supports, employed to avoid a patent infringement lawsuit by the Strauss Bascule Bridge Company.
Piers and abutments for a permanent bridge were built in 1914 as part of construction for the Ship Canal, but a serious proposal for a bridge at Montlake didn't come until 1916. The first bridge in its place was a makeshift walkway made from a series of barges, set up by graduate manager Dar Meisnest to allow football fans to cross for the Washington/Dartmouth game in 1920. The temporary bridge was so heavily traveled, it demonstrated the need for a permanent structure, which was finished in June 1925.
A report from 1993 states that the Montlake Bridge averaged a volume of 60,900 vehicles each weekday, while another report from 2001 puts normal weekend traffic across the bridge at about 40,000 vehicles each day. In addition to the vehicular traffic, the bridge conveys pedestrians and bicyclists across the canal by way of sidewalks on each side of the roadway. The bridge does not open during morning and evening rush hours. It opens at designated times (usually on the hour and half-hour) during the hours just prior to and after rush periods, and on demand at other times. The bridge openings last for an average of four minutes from when traffic stops to when it resumes again. Most of the openings are for sailboats, as most of the tugs that operate this far east are able to pass under the bridge in its closed position. The bridge creates a bottleneck for traffic heading to and from State Route 520 (SR-520), and the creation of alternate routes has been proposed multiple times over the years. Traffic can become backed up for more than a mile when the bridge is open, as can be seen in aerial photographs. Plans to replace SR-520 include adding a second bascule bridge across the Montlake Cut next to the current Montlake Bridge.Mystic River Bascule Bridge
The Mystic River Bascule Bridge is a bascule bridge spanning the Mystic River in Mystic, Connecticut in the United States. It carries vehicle and foot traffic directly into the tourist district of town via 33 ft-wide (10 m) Main Street (U.S. Route 1).Pero's Bridge
Pero's Bridge (grid reference ST585726) is a pedestrian bascule bridge that spans St Augustine's Reach in Bristol Harbour, Bristol, England. It links Queen Square and Millennium Square.Salmon Bay Bridge
The Salmon Bay Bridge, also known as Bridge No. 4, is a single-leaf bascule bridge spanning across Salmon Bay and connecting Magnolia/Interbay to Ballard in Seattle, Washington. The bridge is located just west of Commodore Park. It carries the main line of the BNSF Railway on its way north to Everett and south to King Street Station and Seattle's Industrial District.
The Salmon Bay Bridge, which is located west of the Hiram M. Chittenden Locks, is the last bridge to span the Lake Washington Ship Canal before it becomes Puget Sound. Built in 1914 by the Great Northern Railway, it has an opening span of 61 meters (200 feet) and has two tracks. Additionally, vessel clearance when lowered is 13.1 meters (43 feet) at mean high tide, and up to 15.3 meters (50 feet) at low tide.
A project to replace the current single-leaf bascule bridge with a vertical-lift bridge is currently being planned by BNSF Railway.Seekonk River
The Seekonk River is a tidal extension of the Providence River in the U.S. state of Rhode Island. It flows approximately 8 km (5 mi). Most historical scholars agree that the name is derived from two Native American words, sucki (meaning black) and honc (meaning goose). The river is home to the Brown University men's rowing team, India Point Park, Blackstone Park, Crook Point Bascule Bridge, Narragansett Boat Club (the oldest rowing club in the country), Swan Point Cemetery, and the Bucklin Point waste-water treatment facility. The River is listed by RIDEM as an impaired waterway.Teglværksbroen
Teglværksbroen is a bascule bridge which connects Sluseholmen to Teglholmen in the South Harbour of Copenhagen, Denmark. It crosses the entrance to the Teglværkshavnen (em. Tileworks Dock) from which it takes its name.
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