Lowry Avenue Bridge
Encyclopedia
The Lowry Avenue Bridge is a steel
tied-arch bridge under construction over the Mississippi River
in Minneapolis, Minnesota
since 2010. It is expected to be completed in 2012.
design. This bridge lasted 51 years until it became too weak to carry traffic.
In 1958, five new truss spans were built in this location, using the same piers but raised 20 feet to allow navigation on the upper Mississippi River. This bridge was notable in that it had a steel grid deck where the river was visible directly through the mesh, as opposed to the (currently) more common concrete deck.
Lead-based paint was removed from the bridge during a 2004 repainting effort and the steel grid deck was replaced in 2003. At this time, the bridge was expected to be replaced in the mid-2010s, and community meetings were held in 2007 to choose a design for the new span. However, the timetable to replace the bridge was accelerated as the condition of the 100-year-old piers deteriorated.
During the 2004 repainting, engineers discovered that the pier 3 bearings (east side of navigation channel) had displaced roughly 11 inches east of their original location as a result of unexpected movement of that pier (west) towards the main river channel. Hennepin County contracted with Wiss, Janey, Elstner and Associates (WJE) to investigate and report on the cause and extent of damage. The consultant's report concluded that evidence suggested the pier underwent many years, perhaps 50, of creep deflection due to sustained lateral earth pressure at the foundation which was held in check by the bearing assemblies. The bearing assemblies ultimate strength was finally overcome sometime in 2004 which allowed the unrestrained and rapid movement of the pier. The structural engineers at WJE were unable to predict the magnitude of future pier displacements.
Hennepin County
, which owns and maintains the bridge, closed the bridge at 10:00 AM on April 25, 2008 due to safety concerns. Controlled explosions were used to demolish the bridge spans 14 months later on the morning of June 21, 2009.
Construction of the $80 million replacement bridge began early 2010 and is expected to be completed by late 2012.
Steel
Steel is an alloy that consists mostly of iron and has a carbon content between 0.2% and 2.1% by weight, depending on the grade. Carbon is the most common alloying material for iron, but various other alloying elements are used, such as manganese, chromium, vanadium, and tungsten...
tied-arch bridge under construction over the Mississippi River
Mississippi River
The Mississippi River is the largest river system in North America. Flowing entirely in the United States, this river rises in western Minnesota and meanders slowly southwards for to the Mississippi River Delta at the Gulf of Mexico. With its many tributaries, the Mississippi's watershed drains...
in Minneapolis, Minnesota
Minneapolis, Minnesota
Minneapolis , nicknamed "City of Lakes" and the "Mill City," is the county seat of Hennepin County, the largest city in the U.S. state of Minnesota, and the 48th largest in the United States...
since 2010. It is expected to be completed in 2012.
History
The original structure was built in 1905 and utilized a 5-span truss bridgeTruss bridge
A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...
design. This bridge lasted 51 years until it became too weak to carry traffic.
In 1958, five new truss spans were built in this location, using the same piers but raised 20 feet to allow navigation on the upper Mississippi River. This bridge was notable in that it had a steel grid deck where the river was visible directly through the mesh, as opposed to the (currently) more common concrete deck.
Lead-based paint was removed from the bridge during a 2004 repainting effort and the steel grid deck was replaced in 2003. At this time, the bridge was expected to be replaced in the mid-2010s, and community meetings were held in 2007 to choose a design for the new span. However, the timetable to replace the bridge was accelerated as the condition of the 100-year-old piers deteriorated.
During the 2004 repainting, engineers discovered that the pier 3 bearings (east side of navigation channel) had displaced roughly 11 inches east of their original location as a result of unexpected movement of that pier (west) towards the main river channel. Hennepin County contracted with Wiss, Janey, Elstner and Associates (WJE) to investigate and report on the cause and extent of damage. The consultant's report concluded that evidence suggested the pier underwent many years, perhaps 50, of creep deflection due to sustained lateral earth pressure at the foundation which was held in check by the bearing assemblies. The bearing assemblies ultimate strength was finally overcome sometime in 2004 which allowed the unrestrained and rapid movement of the pier. The structural engineers at WJE were unable to predict the magnitude of future pier displacements.
Hennepin County
Hennepin County, Minnesota
Hennepin County is a county located in the U.S. state of Minnesota, named in honor of the 17th-century explorer Father Louis Hennepin. As of 2010 the population was 1,152,425. Its county seat is Minneapolis. It is by far the most populous county in Minnesota; more than one in five Minnesotans live...
, which owns and maintains the bridge, closed the bridge at 10:00 AM on April 25, 2008 due to safety concerns. Controlled explosions were used to demolish the bridge spans 14 months later on the morning of June 21, 2009.
Construction of the $80 million replacement bridge began early 2010 and is expected to be completed by late 2012.