The Tyngsborough Bridge is a steel

tied-arch bridge A tied-arch bridge is an arch bridge in which the outward horizontal forces of the arch(es) caused by tension at the arch ends to a foundation are countered by equal tension of its own gravity plus any element of the total deck structure such grea ...

located in

Tyngsborough, Massachusetts Tyngsborough (also spelled Tyngsboro) is a town in northern Middlesex County, Massachusetts, United States. Tyngsborough is from Boston along the Route 3 corridor, and located on the New Hampshire state line. At the 2020 census, the town popula ...

and carries Route 113 over the

Merrimack River The Merrimack River (or Merrimac River, an occasional earlier spelling) is a river in the northeastern United States. It rises at the confluence of the Pemigewasset and Winnipesaukee rivers in Franklin, New Hampshire, flows southward into M ...

. With a span of 547 feet, it has the longest span of any steel rib through arch bridges in Massachusetts. It is also the 2nd oldest steel rib through arch bridge in the state. The bridge is center hinged and features pratt-type trussing.

History

The Tyngsborough Bridge was constructed in 1931 to replace the wooden Whipple truss bridge. The new bridge was sited alongside but not parallel to the older, starting close the old structure on the eastern side of the river but reaching the western side well both of the old bridge. The Tyngsboro Bridge shares its open, braced rib design with the

Boston University Bridge The Boston University Bridge, originally the Cottage Farm Bridge and commonly referred to as the BU Bridge, is a steel truss through arch bridge with a suspended deck carrying Route 2 over the Charles River, connecting the Boston University ca ...

. Starting in 1975 the bridge was rebuilt, but the cost of the construction generated controversy. Tyngsborough Bridge

In November 2005, the bridge was closed again for repairs following reports of structural deficiency. The temporary Mabey Panel Bridge was constructed alongside of the main bridge and repairs on the main bridge began in 2009. The repair operation was contracted out to S & R Corp. for $16.4 million, but eventually cost $19 million by the completion of the project. This was partially due to delays with steel girders failing stress tests, which required re-engineering, and the discovery that the original bridge had been constructed with

lead paint Lead paint or lead-based paint is paint containing lead. As pigment, lead(II) chromate (, "chrome yellow"), lead(II,IV) oxide, (, "red lead"), and lead(II) carbonate (, "white lead") are the most common forms.. Lead is added to paint to accele ...

which required S & R Corp. to take measures to ensure that the paint chips did not fall into the river below. The repairs took three years to complete with the bridge reopening in 2012.

References

{{Reflist, 2 ;Additional sources * Peter M. Millot, ''The Lower Merrimack River Valley: an inventory of historic engineering and industrial sites'' (North Andover, Massachusetts: Merrimack Valley Textile Museum, 1978)

External links

Photographs, 1931-1932
Bridges in Middlesex County, Massachusetts Bridges completed in 1930 Bridges over the Merrimack River Steel bridges in the United States Through arch bridges in the United States Road bridges in Massachusetts