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The Burr Arch Truss—or, simply, Burr Truss or Burr Arch—is a combination of an
File:Burr Truss P4230099 Sims Smith.jpg,
arch
An arch is a vertical curved structure that spans an elevated space and may or may not support the weight above it, or in case of a horizontal arch like an arch dam, the hydrostatic pressure against it.
Arches may be synonymous with vau ...
and a ''multiple kingpost'' truss design. It was invented in 1804 by Theodore Burr, patented on April 3, 1817, and used in bridge
A bridge is a structure built to span a physical obstacle (such as a body of water, valley, road, or rail) without blocking the way underneath. It is constructed for the purpose of providing passage over the obstacle, which is usually someth ...
s, usually covered bridge
A covered bridge is a timber-truss bridge with a roof, decking, and siding, which in most covered bridges create an almost complete enclosure. The purpose of the covering is to protect the wooden structural members from the weather. Uncovered woo ...
s.
Design
The design principle behind the Burr arch truss is that the arch should be capable of bearing the entire load on the bridge while the truss keeps the bridge rigid. Even though the kingpost truss alone is capable of bearing a load, this was done because it is impossible to evenly balance a dynamic load crossing the bridge between the two parts. The opposite view is also held, based on computer models, that the truss performs the majority of the load bearing and the arch provides the stability. Either way, the combination of the arch and the truss provides a more stable bridge capable of supporting greater weight than either the arch or truss alone.Gallery
TheU.S. state
In the United States, a state is a constituent political entity, of which there are 50. Bound together in a political union, each state holds governmental jurisdiction over a separate and defined geographic territory where it shares its sove ...
of Indiana
Indiana () is a U.S. state in the Midwestern United States. It is the 38th-largest by area and the 17th-most populous of the 50 States. Its capital and largest city is Indianapolis. Indiana was admitted to the United States as the 19th ...
has a large collection of Burr Truss bridges. Of its 92 extant bridges, 53 are Burr Trusses, many of which reside in Parke County.
Sim Smith Covered Bridge
The Sim Smith Covered Bridge is east of Montezuma, Indiana. The single span Burr Truss
The Burr Arch Truss—or, simply, Burr Truss or Burr Arch—is a combination of an arch and a ''multiple kingpost'' truss design. It was invented in 180 ...
, Parke County, Indiana. Notice the arch projects below the lower chords of the bridge.
File:Burr Truss (2 span) P4230017 Mansfield CB (Parke Cty).jpg, Mansfield Covered Bridge, Parke County, Indiana. The roof was missing after a major storm and the interior design was easier to see.
File:Burr Truss (2 span) P4230125 Mansfield CB (Parke Cty).jpg, Mansfield Covered Bridge
The Mansfield Covered Bridge is a Double Burr Arch double span truss bridge located on Mansfield Road (historic) and Big Raccoon Creek in Mansfield southeast of Rockville in Parke County, Indiana. Built by Joseph J. Daniels in 1867 at a cost of ...
. Spans could be added to extend the bridge further than bridges of similar design.
File:Burr Truss (3 span) 011 09A (Medora, Jackson Cty).jpg, Medora Covered Bridge
The Medora Covered Bridge was the longest covered bridge in the United states with the entire original historic truss still in place with some repairs but no structural changes. Measuring the clear span (abutment face to abutment face) of 431'10", ...
, Jackson County, Indiana. This is the longest covered bridge in Indiana.
Design specification
References
External links
* * {{Bridge footer Truss bridges by type American inventions Trusses