A Brown truss is a type of
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 somethi ...
truss
A truss is an assembly of ''members'' such as beams, connected by ''nodes'', that creates a rigid structure.
In engineering, a truss is a structure that "consists of two-force members only, where the members are organized so that the assembl ...
, used in
covered bridges
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 ...
. It is noted for its economical use of materials and is named after the inventor, Josiah Brown Jr., of
Buffalo,
New York
New York most commonly refers to:
* New York City, the most populous city in the United States, located in the state of New York
* New York (state), a state in the northeastern United States
New York may also refer to:
Film and television
* '' ...
, who
patent
A patent is a type of intellectual property that gives its owner the legal right to exclude others from making, using, or selling an invention for a limited period of time in exchange for publishing an enabling disclosure of the invention."A p ...
ed it July 7, 1857, as
US patent
Under United States law, a patent is a right granted to the inventor of a (1) process, machine, article of manufacture, or composition of matter, (2) that is new, useful, and non-obvious. A patent is the right to exclude others, for a limited ...
17,722.
Description
The Brown truss is a
box truss
A box truss is a structure composed of three or more ''chords'' connected by transverse and/or diagonal structural elements.
Application
Box trusses are commonly used in certain types of aircraft fuselages, electric power pylons, large radio ant ...
that is a
through truss
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or ...
(as contrasted with a
deck truss
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or ...
) and consists of diagonal cross
compression member
Compression members are structural elements that are pushed together or carry a load; more technically, they are subjected only to axial compressive forces. That is, the loads are applied on the longitudinal axis through the centroid of the mem ...
s connected to horizontal top and bottom stringers.
There may be vertical or almost vertical
tension members (the diagram shows these members, while the patent application diagram does not) but there are no vertical members in compression. In practice, when used in a
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 ...
, the most common application, the truss is protected with outside sheathing.
The floor and roof are also trusses, but are horizontal and serve to give the truss rigidity. The bottoms of the diagonals tend to protrude below the sheathing. The Brown truss is noted for economy of materials as it can be built with very little metal.
Patent
Brown's patent claims did not actually address the economy afforded by lack of vertical members ("braces"). Instead he focused on the improved strength over previous trusses that had members ("braces" in his terminology) come to the horizontal chord near to each other but not exactly together (at "gains" in his terminology), by having several members come together in the same place. From the patent text:
I do not claim broadly furnishing the main or counter braces with gains and passing them between the timbers of the chords;
What I do claim as my invention, and desire to secure by letters Patent, is— Providing each of the main and counter braces with two gains at top and bottom, and each of the timbers of the chord with a gain at the point where the braces are applied corresponding with the gains in the braces, and the braces thus formed up between the timber, with the gains of the braces in such relation to the gains of the timbers that when the timbers of the chords are brought together they are combined and become, as it were, only one piece, no part of which can be operated upon or affected independently of the other by the downward and upward thrusts common to truss bridges, even if the bolt which passes laterally through and intersects each set of braces and the timbers of the chord were removed.[ OCRed and hand corrected to match image.]
History
The Brown truss enjoyed a brief period of favor in the 1860s, and is known to have been used in four covered bridges in Michigan, the
Ada Covered Bridge, the
Fallasburg Bridge,
Whites Bridge and one other. The design did not appear to gain wide acceptance as modern bridges tend to be
Howe
Howe may refer to:
People and fictional characters
* Howe (surname), including a list of people and fictional characters
* Howe Browne, 2nd Marquess of Sligo (1788–1845), Irish peer and colonial governor
Titles
* Earl Howe, two titles, an ext ...
,
Pratt
Pratt is an English surname. Notable people with the surname include:
A–F
* Abner Pratt (1801–1863), American diplomat, jurist, politician, lawyer
* Al Pratt (baseball) (1847–1937), American baseball player
* Andy Pratt (baseball) (bor ...
,
bowstring or
Warren
A warren is a network of wild rodent or lagomorph, typically rabbit burrows. Domestic warrens are artificial, enclosed establishment of animal husbandry dedicated to the raising of rabbits for meat and fur. The term evolved from the medieval A ...
trusses.
Image:FallasburgBridge Overall DownstreamApproachDSCN9984.JPG, Fallasburg Bridge, a Brown truss 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 ...
Image:WhitesBridge FlatRiver InteriorTrussDetail DSCN9947.JPG, Whites Bridge interior showing diagonal members on sides and horizontal diagonal roof support, forming the top of the box truss
Image:WhitesBridge FlatRiver FloorTrussDetail DSCN9961.JPG, Whites Bridge underside, showing floor supports pinned to side (diagonal) truss members. Bottom of diagonal truss members protrude below the sheathing.
Image:Ada Michigan Covered Bridge downstream underside DSCN9708.JPG, Ada Covered Bridge looking upward. Truss member ends can be seen protruding below sheathing. Very top of truss is visible above sheathing gap below roofline. This gap admitted light, making the bridge interior usable, if somewhat dark.
Image:FallasburgBridge InteriorFloorDetailDSCN9995.JPG, Bottom of diagonal truss members interlock with floor (Fallasburg Bridge)
Image:FallasburgBridge InteriorSnowProtectionDSCN9996.JPG, The truss ends are special, additional material may be present for rigidity or to protect the structure from snow. (Fallasburg Bridge)
Image:ADU-1000-5.JPG, The steerable frames of Deep Space Communication Complex constructed from battleship gun turrets and railway bridge trusses.
See also
*
Truss bridge
A truss bridge is a bridge whose load-bearing superstructure is composed of a truss, a structure of connected elements, usually forming triangular units. The connected elements (typically straight) may be stressed from tension, compression, or ...
for bridges employing various truss types
References
{{DEFAULTSORT:Brown Truss
Truss bridges by type
American inventions
Trusses