{{Short description|Truss design}} {{Use American English|date=August 2022}} {{Use mdy dates|date=August 2022}} {{BridgeTypePix |image=Burr Truss P4230093 Sims Smith.jpg |image_title=Interior structure of a covered bridge utilizing a kingpost with a Burr Arch structure |type_name=Burr bridge |sibling_names=None |descendent_names=None |ancestor_names=Truss bridge, kingpost bridge |carries=Pedestrians, livestock, vehicles |span_range=Short to medium |material=Wood planks |movable=No |design=medium |falsework=}}
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 Burr,<ref name="nyc">{{cite web |title=The Burr Truss |work=Truss Styles of Covered Bridges |publisher=New York State Covered Bridge Society |date=January 2006 |url=https://www.nycoveredbridges.org/page44.html |access-date=September 15, 2006 |url-status=dead |archive-url=https://web.archive.org/web/20060908112144/https://www.nycoveredbridges.org/page44.html |archive-date=September 8, 2006 }}</ref> patented on April 3, 1817,<ref name="uspto">{{cite web | title = Publication Number: X0002769 | work = Publication Images | publisher = United States Patent and Trademark Office | url = https://patimg2.uspto.gov/.piw?Docid=X0002769&idkey=NONE | access-date = September 15, 2006 }}</ref> and used in bridges, usually covered bridges.<ref name="odot">{{cite web | title = Truss Types | work = Covered Bridge Truss Types | publisher = Ohio Department of Transportation Office of Structural Engineering | url = http://www.dot.state.oh.us/se/coveredbridges/truss_types.htm | access-date = September 15, 2006 |archive-url = https://web.archive.org/web/20060904102208/http://www.dot.state.oh.us/se/coveredbridges/truss_types.htm |archive-date = September 4, 2006}}</ref><ref name="tbcbspa">{{cite web | title = Truss Types | publisher = The Theodore Burr Covered Bridge Society of PA, Inc | url = http://www.tbcbspa.com/trusses.htm | access-date = July 28, 2006 }}</ref>
==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.<ref name="calvert">{{cite web | last = Calvert | first = J. B. | title = The Burr Truss | date = October 23, 2000 | url = https://www.du.edu/~jcalvert/tech/burr.htm | access-date = July 28, 2006 | archive-url = https://web.archive.org/web/20060803065121/https://www.du.edu/~jcalvert/tech/burr.htm | archive-date = August 3, 2006 | url-status = dead }}</ref> 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.<ref name="nyc"/> 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.
[[Image:Baumgardener's Covered Bridge Inside Center 3008px.jpg|thumb|center|400px|{{center|Example of a Burr Truss – Baumgardener's Covered Bridge in Lancaster County, Pennsylvania, U.S. }}]]
The U.S. state of Indiana has a large collection of Burr Truss bridges. Of its 92 extant bridges, 53 are Burr Trusses, many of which reside in Parke County. <gallery mode=packed heights=250> File:Burr Truss P4230099 Sims Smith.jpg|'''Sim Smith Covered Bridge''', 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'''. 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''', Jackson County, Indiana. This is the longest covered bridge in Indiana. </gallery>
==Design specification==
thumb|center|500 px|Deer Mills Covered Bridge, Montgomery County, Indiana
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==References== <references/>
==External links== *{{cite web | last = Cummings | first = Hubertis M. | title = Theodore Burr and his bridges across the Susquehanna | url = https://cip.cornell.edu/DPubS/Repository/1.0/Disseminate/psu.ph/1133213421/body/pdf | access-date = July 28, 2006 }} *{{HAER |survey=OH-138 |id=oh2009 |title=Strength of Burr-Arch Trusses |data=108}}
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Category:Truss bridges by type Category:American inventions Category:Trusses Category:Burr Truss bridges