Concrete double arch bridge is the first segmentally constructed concrete arch bridge in the United States
General Information
Scenic overlooks and viewpoints are generally accessible year-round, subject to maintenance and construction closures.
Nashville, Tennessee (approximately 20 mi)
How to Get There
From Franklin (10 mi): Take TN-96 West toward the Natchez Trace Parkway, enter the Parkway heading south, and continue to the iconic Double Arch Bridge (Birdsong Hollow Bridge) near Milepost 438.
Overview
The Natchez Trace Parkway Bridge is a concrete double arch bridge located in Williamson County, Tennessee, 8.7 mi (14.0 km) from the northern terminus of the Natchez Trace Parkway. It is 1,572 ft (479 m) long and carries the two-lane Natchez Trace Parkway 145 ft (44 m) over State Route 96 and a heavily wooded valley.
The bridge, also known as the Natchez Trace Parkway Arches, is the first segmentally constructed concrete arch bridge in the United States. The arches comprise 122 hollow box segments precast in nearby Franklin, each of which was about 9.8 ft (3.0 m) long and weighed between 29 and 45 short tons. The deck consists of 196 precast post-tensioned trapezoidal box girder segments, each typically 8.5 ft (2.6 m) long. The sections atop the crown of the arch are 13 ft (4.0 m) deep. The foundations and piers of the bridge were cast in place.
The 582 ft (177 m) long main span is symmetrical, while the 462 ft (141 m) long second arch is not, due to the slope of the valley at the southern end of the bridge. 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. This procedure was chosen in place of conventional shoring towers so that environmental damage to the valley would be minimized. The bridge was officially opened on March 22, 1994.
The bridge has won many awards for its design, including a Presidential Award for Design Excellence in 1995, and an Award of Merit from the Federal Highway Administration in 1996. The Eleventh International Bridge Conference named it the single most outstanding achievement in the bridge industry for 1994.
This article uses material from the Wikipedia article "Natchez Trace Parkway Bridge" which is released under the Creative Commons Attribution-Share-Alike License 3.0
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