Natchez Trace Parkway Bridge

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Natchez Trace Parkway Bridge
Natchez Trace Parkway Bridge.jpg
The Natchez Trace Parkway Bridge, viewed from the north
Coordinates35°59′12″N 86°59′32″W / 35.9866°N 86.9923°W / 35.9866; -86.9923
Carries Natchez Trace Parkway
Crosses SR 96
LocaleWilliamson County, Tennessee
Maintained byNational Park Service[1]
ID number5570463P0000000
Characteristics
DesignArch
Total length479.1 m (1,572 ft)[1]
Width11.3 m (37 ft)[2]
Height44.2 m (145 ft)[2]
Longest span177.4 m (582 ft)[1]
Clearance below32.7 m (107 ft)[1]
History
OpenedMarch 22, 1994
Statistics
Daily traffic210 (in 1997)[1]
Tollnone

The Natchez Trace Parkway Bridge is a concrete double arch bridge located in Williamson County, Tennessee, 14 km (8.7 mi) from the northern terminus of the Natchez Trace Parkway. It is 479.1 m (1,572 ft) long and carries the two-lane Natchez Trace Parkway 44.2 m (145 ft) over State Route 96 and a heavily wooded valley.

Background[edit]

The bridge, also known as the Natchez Trace Parkway Arches, is the first segmentally constructed concrete arch bridge in the United States.[2] The arches comprise 122 hollow box segments precast in nearby Franklin, each of which was about 3 m (9.8 ft) long and weighed between 26 and 41 metric tons (29 and 45 short tons) .[2] The deck consists of 196 precast post-tensioned trapezoidal box girder segments, each typically 2.6 m (8.5 ft) long. The sections atop the crown of the arch are 3.9 m (13 ft) deep.[2] The foundations and piers of the bridge were cast in place.[2]

The 177.4 m (582 ft) long main span is symmetrical, while the 140.8 m (462 ft) long second arch is not, due to the slope of the valley at the southern end of the bridge.[2] The bridge is rare in that it does not use spandrel columns to support the deck from the arch. Rather than being evenly distributed along the arch's length, the weight of the bridge is concentrated at the crown of the arch. The lack of spandrel columns results in a clean, unencumbered appearance: it is termed a cathedral arch bridge.

The bridge was designed by Figg Engineering Group and built by PCL Civil Constructors Inc., a subsidiary of PCL Constructors Inc. The arches and deck were constructed using a balanced cantilever method. Each arch was supported by temporary cable stays anchored from the top of the piers and the valley sides until it was fully built.[2] This procedure was chosen in place of conventional shoring towers so that environmental damage to the valley would be minimized.[3] The bridge cost US$11.3 million to build,[4] and was completed in October 1993.[2] It was officially opened on March 22, 1994.[5]

The bridge has won many awards for its design, including a Presidential Award for Design Excellence in 1995,[6] and an Award of Merit from the Federal Highway Administration in 1996.[7] The Eleventh International Bridge Conference named it the single most outstanding achievement in the bridge industry for 1994.[8] The bridge "impressed the... jury with its aesthetically striking double-arch design, which shows exceptional sensitivity to the historical context of the site."[9]

Suicide Bridge[edit]

Since its construction, the Natchez Trace Parkway Bridge has become known locally as a "suicide bridge".[10] Suicide prevention signs were posted in 2011 but the deaths continue as the bridge’s 32-inch railings[11] do not deter jumpers. According to the Williamson County Sheriff, at least 32 people have successfully committed suicide by jumping from the bridge as of December 2018.[12][13] The Natchez Trace Bridge Barrier Coalition was formed in September 2018 to work with federal congressional delegates and the National Park Service to install a suicide prevention barrier.[14] Studies have shown that curbing access to impulsive and lethal means of suicide is a successful method of prevention. [15][16]

See also[edit]

Gallery[edit]

References[edit]

  1. ^ a b c d e "National Bridge Inventory Database".
  2. ^ a b c d e f g h i Corven, John A.; John W. Jordan Jr. (November 1993). "Arches for a parkway". Civil Engineering. American Society of Civil Engineers. 63 (11): 44–47.
  3. ^ "Natchez Trace Parkway Bridge over Tennessee Route 96". Archived from the original on 2006-03-11.
  4. ^ Natchez Trace Parkway Arches at Structurae
  5. ^ "Finley McNary Bridge Engineering Projects". Archived from the original on 2003-08-23.
  6. ^ "Figg Engineering Group". Archived from the original on 2003-12-13.
  7. ^ "Excellence in Highway Design 1997". Federal Highway Administration, U.S. Department of Transportation.
  8. ^ "International Bridge Conference: Bridge Awards". Archived from the original on 2010-07-30.
  9. ^ Goldstein, Harry (July 1995). "Triumphant Arches". Civil Engineering. American Society of Civil Engineers. 65 (7): 48–49. Retrieved 2011-03-15.
  10. ^ [1]
  11. ^ Natchez Trace Bridge: Resolution recognizing suicides moves to full committee
  12. ^ Natchez Trace Bridge: Resolution recognizing suicides moves to full committee
  13. ^ They lost loved ones to suicide on the Natchez Trace Bridge. They say better barriers could prevent more tragedies.
  14. ^ Natchez Trace Bridge Barrier Coalition
  15. ^ Means restriction for suicide prevention
  16. ^ Tennessee Is Home To One Of The Deadliest National Parks In The Nation: Here's How We Change That, by Bill Frist