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 1804 by Theodore Burrcite web
title = The Burr Truss
work = Truss Styles of Covered Bridges
publisher = New York State Covered Bridge Society
date = 2006-01
url = http://www.nycoveredbridges.org/page44.html
accessdate = 2006-09-15] , patented on April 3, 1817cite web
title = Publication Number: X0002769
work = Publication Images
publisher = United States Patent and Trademark Office
url = http://patimg2.uspto.gov/.piw?Docid=X0002769&idkey=NONE
accessdate = 2006-09-15 ] , and used in bridges, usually covered bridges.cite web
title = Truss Types
work = Covered Bridge Truss Types
publisher = Ohio Department of Transportation Office of Structural Engineering
date =
url = http://www.dot.state.oh.us/se/coveredbridges/truss_types.htm
accessdate = 2006-09-15 ] cite web
title = Truss Types
publisher = The Theodore Burr Covered Bridge Society of PA, Inc
url = http://www.tbcbspa.com/trusses.htm
accessdate = 2006-07-28 ]

Design

The design principle behind the Burr arch truss was that the arch should be capable of holding the entire load on the bridge while the truss was used to keep the bridge rigid. Even though the kingpost truss alone was 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.cite web
last = Calvert
first = J. B.
title = The Burr Truss
date = 2000-10-23
url = http://www.du.edu/~jcalvert/tech/burr.htm
accessdate = 2006-07-28 ] 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 . Regardless, the combination of the arch with the truss provides a more stable bridge capable of carrying greater weight than with the either the truss or arch alone.

References

*cite web
last = Cummings
first = Hubertis M.
title = Theodore Burr and his bridges across the Susquehanna
url = http://cip.cornell.edu/DPubS/Repository/1.0/Disseminate/psu.ph/1133213421/body/pdf
accessdate = 2006-07-28