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 someth ...

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 wo ...

. 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 ...

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 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, o ...

(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 memb ...

s connected to horizontal top and bottom stringers. There may be vertical or almost vertical

tension members Tension members are structural elements that are subjected to axial tensile forces. Examples of tension members are bracing for buildings and bridges, truss members, and cables in suspended roof systems. Calculation In an axially loaded ten ...

(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 Ada Covered Bridge is a span Brown truss covered bridge erected in 1867 in Ada, Michigan, United States. Carrying Bronson Street across the Thornapple River, it is located just south of where the Thornapple enters the Grand River, in tu ...

, the

Fallasburg Bridge Fallasburg Bridge (alternatively Fallassburgh Bridge) is a span Brown truss covered bridge, erected in 1871 in Vergennes Township, Michigan, United States, north of Lowell on the Flat River. Carrying Covered Bridge Road across the Flat, it is ...

Whites Bridge __NOTOC__ Whites Bridge (alternatively White's Bridge) is a Brown truss covered bridge, originally erected in 1869 in Keene Township, Michigan, United States, near Smyrna on the Flat River. Carrying Whites Bridge Road across the Flat River, ...

and one other. The design did not appear to gain wide acceptance as modern bridges tend to be Howe,

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) (born 19 ...

bowstring A bowstring joins the two ends of the bow stave and launches the arrow. Desirable properties include light weight, strength, resistance to abrasion, and resistance to water. Mass has most effect at the center of the string; of extra mass in th ...

or Warren trusses. Image:FallasburgBridge Overall DownstreamApproachDSCN9984.JPG,

, a Brown truss

Image:WhitesBridge FlatRiver InteriorTrussDetail DSCN9947.JPG,

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,

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.

References

{{DEFAULTSORT:Brown Truss Truss bridges by type American inventions Trusses

Description

Patent

History

See also

References