A truss bridge is a
bridge whose load-bearing
superstructure
A superstructure is an upward extension of an existing structure above a baseline. This term is applied to various kinds of physical structures such as buildings, bridges, or ships.
Aboard ships and large boats
On water craft, the superstruct ...
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 sometimes both in response to dynamic loads. The basic types of truss bridges shown in this article have simple designs which could be easily analyzed by 19th and early 20th-century engineers. A truss bridge is economical to construct because it uses materials efficiently.
Design
The nature of a
truss allows the
analysis of its structure using a few assumptions and the application of
Newton's laws of motion according to the branch of
physics known as
statics
Statics is the branch of classical mechanics that is concerned with the analysis of force and torque (also called moment) acting on physical systems that do not experience an acceleration (''a''=0), but rather, are in static equilibrium with ...
. For purposes of analysis, trusses are assumed to be pin jointed where the straight components meet, meaning that taken alone, every joint on the structure is functionally considered to be a flexible joint as opposed to a rigid joint with strength to maintain its own shape, and the resulting shape and strength of the structure is only maintained by the interlocking of the components. This assumption means that members of the truss (chords, verticals and diagonals) will act only in tension or compression. A more complex analysis is required where rigid joints impose significant
bending loads upon the elements, as in a
Vierendeel 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 ...
.
In the bridge illustrated in the
infobox at the top, vertical members are in tension, lower horizontal members in tension,
shear
Shear may refer to:
Textile production
*Animal shearing, the collection of wool from various species
**Sheep shearing
*The removal of nap during wool cloth production
Science and technology Engineering
*Shear strength (soil), the shear strength ...
, and bending, outer diagonal and top members are in compression, while the inner diagonals are in tension. The central vertical member stabilizes the upper compression member, preventing it from
buckling. If the top member is sufficiently stiff then this vertical element may be eliminated. If the lower chord (a horizontal member of a truss) is sufficiently resistant to bending and shear, the outer vertical elements may be eliminated, but with additional strength added to other members in compensation. The ability to distribute the forces in various ways has led to a large variety of truss bridge types. Some types may be more advantageous when wood is employed for compression elements while other types may be easier to erect in particular site conditions, or when the balance between labor, machinery and material costs have certain favorable proportions.
The inclusion of the elements shown is largely an engineering decision based upon economics, being a balance between the costs of raw materials, off-site fabrication, component transportation, on-site erection, the availability of machinery and the cost of labor. In other cases the appearance of the structure may take on greater importance and so influence the design decisions beyond mere matters of economics. Modern materials such as
prestressed concrete and fabrication methods, such as automated
welding, and the changing price of steel relative to that of labor have significantly influenced the design of modern bridges.
Model bridges
A pure truss can be represented as a pin-jointed structure, one where the only forces on the truss members are tension or compression, not bending. This is used in the teaching of statics, by the building of
model bridges from spaghetti. Spaghetti is brittle and although it can carry a modest tension force, it breaks easily if bent. A model spaghetti bridge thus demonstrates the use of a truss structure to produce a usefully strong complete structure from individually weak elements.
History in the United States
Because wood was in abundance, early truss bridges would typically use carefully fitted timbers for members taking compression and iron rods for
tension member
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 tensio ...
s, usually constructed as a
covered bridge to protect the structure. In 1820 a simple form of truss,
Town's lattice truss, was patented, and had the advantage of requiring neither high labor skills nor much metal. Few iron truss bridges were built in the United States before 1850.
Truss bridges became a common type of bridge built from the 1870s through the 1930s. Examples of these bridges still remain across the US, but their numbers are dropping rapidly as they are demolished and replaced with new structures. As metal slowly started to replace timber,
wrought iron bridges in the US started being built on a large scale in the 1870s. Bowstring truss bridges were a common truss design during this time, with their arched top chords. Companies like the
Massillon Bridge Company
The Massillon Bridge Company, most commonly abbreviated Massillon Bridge Co., was located in Massillon, Ohio and founded by Joseph Davenport in 1869. The company became incorporated in 1887 and remained in operation through the early 1900s. Steel ...
of
Massillon, Ohio
Massillon is a city in Stark County, Ohio, Stark County in the U.S. state of Ohio, approximately west of Canton, Ohio, Canton, south of Akron, and south of Cleveland. The population was 32,146 at the 2020 United States Census, 2020 census. Mass ...
, and the
King Bridge Company of
Cleveland, Ohio
Cleveland ( ), officially the City of Cleveland, is a city in the U.S. state of Ohio and the county seat of Cuyahoga County. Located in the northeastern part of the state, it is situated along the southern shore of Lake Erie, across the U.S. ...
, became well-known, as they marketed their designs to cities and townships. The bowstring truss design fell out of favor due to a lack of durability, and gave way to the Pratt truss design, which was stronger. Again, the bridge companies marketed their designs, with the Wrought Iron Bridge Company in the lead. As the 1880s and 1890s progressed,
steel
Steel is an alloy made up of iron with added carbon to improve its strength and fracture resistance compared to other forms of iron. Many other elements may be present or added. Stainless steels that are corrosion- and oxidation-resistant ty ...
began to replace wrought iron as the preferred material. Other truss designs were used during this time, including the camel-back. By the 1910s, many states developed standard plan truss bridges, including steel Warren
pony truss bridges. As the 1920s and 1930s progressed, some states, such as
Pennsylvania, continued to build steel truss bridges, including massive steel through-truss bridges for long spans. Other states, such as
Michigan, used standard plan concrete girder and beam bridges, and only a limited number of truss bridges were built.
Roadbed types
The truss may carry its
roadbed on top, in the middle, or at the bottom of the truss. Bridges with the roadbed at the top or the bottom are the most common as this allows both the top and bottom to be stiffened, forming a
box truss. When the roadbed is atop the truss it is called a deck truss (an example of this was the
I-35W Mississippi River bridge
The I-35W Mississippi River bridge (officially known as Bridge 9340) was an eight-lane, steel truss arch bridge that carried Interstate 35W across the Mississippi River one-half mile (875 m) downstream from the Saint Anthony Falls in Minneap ...
). When the truss members are both above and below the roadbed it is called a through truss (an example of this application is the
Pulaski Skyway), and where the sides extend above the roadbed but are not connected, a pony truss or
half-through
A plate girder bridge is a bridge supported by two or more plate girders.
Overview
In a plate girder bridge, the plate girders are typically I-beams made up from separate structural steel plates (rather than rolled as a single cross-section), w ...
truss.
Sometimes both the upper and lower chords support roadbeds, forming a
double-decked truss. This can be used to separate rail from road traffic or to separate the two directions of road traffic.
Since through truss bridges have supports located over the bridge deck, they are susceptible to being hit by
overheight loads when used on highways. The
I-5 Skagit River bridge collapsed after such a strike; before the collapse, similar incidents had been common and had necessitated frequent repairs.
Gallery
Image:LittleManateeRiver.jpg, Pratt through truss of the former Seaboard Air Line Railway, located near the village of Willow, Florida; abandoned since the mid-1980s
Image:ErieCanalRRBridge04 1A.jpg, Deck truss railroad bridge over the Erie Canal in Lockport, New York
Image:General Hertzog Bridge over Orange River at Aliwal North.jpg, The four span through truss General Hertzog Bridge over the Orange River at Aliwal North carries vehicular traffic
File:05-23-13 Skagit Bridge Collapse.jpg, The through truss Skagit River bridge on Interstate 5 collapsed after an overhead support was hit by a passing truck
File:Old San Jacinto River Truss Bridge -- Humble, Texas.jpg, Old San Jacinto River truss bridge – Humble, Texas
Image:Puente Tacuarembó 02.jpg, Pony truss bridge of reinforced concrete
Image:Sky gate bridge01s3200.jpg, Sky Gate Bridge R at Kansai International Airport, Osaka, Japan, is the longest double-decked truss bridge in the world. It carries three lanes of automobile traffic on top and two of rail below over nine truss spans.
File:Railroad Truss bridge over trinity river near Goodrich, Texas.jpg, Railroad Truss bridge over Trinity River near Goodrich, Texas
Goodrich is a city in Polk County, Texas, United States. The population was 271 at the 2010 census.
Geography
Goodrich is located at (30.607139, –94.946995).
According to the United States Census Bureau, the city has a total area of , all of ...
Image:HartBridgeJax.jpg, The Hart Bridge spanning the St. Johns River
The St. Johns River ( es, Río San Juan) is the longest river in the U.S. state of Florida and its most significant one for commercial and recreational use. At long, it flows north and winds through or borders twelve counties. The drop in eleva ...
in Jacksonville, Florida, is a continuous, cantilevered truss bridge which combines a suspended road deck on the main span and through truss decks on the adjacent approach spans
File:Columbus and Greenville Railway bridge over Yazoo River.jpg, A railway bridge with a rail track
A railway track (British English and UIC terminology) or railroad track (American English), also known as permanent way or simply track, is the structure on a railway or railroad consisting of the rails, fasteners, railroad ties (sleepers, ...
in Leflore County, Mississippi
Leflore County is a county located in the U.S. state of Mississippi. As of the 2010 census, the population was 32,317. The county seat is Greenwood. The county is named for Choctaw leader Greenwood LeFlore, who signed a treaty to cede his pe ...
File:Chevelon Creek Bridge.jpg, Chevelon Creek Warren Pony Truss Bridge,Chevelon Creek, Navajo County Arizona built 1913
File:Željeznički most, Mursko Središće.3.jpg, Side view of the iron truss railway bridge over Mura River in Mursko Središće
Mursko Središće ( hu, Muraszerdahely, Kajkavian: ''Mursko Središče'') is the northernmost town in Croatia, located at ( alt. 175 m) and one of the oldest localities in Međimurje County.
Mursko Središće has a total population of 6,307, and ...
, Croatia
File:Railroad Truss Drawbridge across Buffalo Bayou -- Houston.jpg, Railroad Truss Drawbridge across Buffalo Bayou—Houston
Multiple spans
Truss bridges consisting of more than one
span
Span may refer to:
Science, technology and engineering
* Span (unit), the width of a human hand
* Span (engineering), a section between two intermediate supports
* Wingspan, the distance between the wingtips of a bird or aircraft
* Sorbitan es ...
may be either a
continuous truss or a series of simple trusses. In the simple truss design, each span is supported only at the ends and is fully independent of any adjacent spans. Each span must fully support the weight of any vehicles traveling over it (the
live load).
In contrast, a continuous truss functions as a single rigid structure over multiple supports. This means that the live load on one span is partially supported by the other spans, and consequently it is possible to use less material in the truss.
Continuous truss bridges were not very common before the mid-20th century because they are
statically indeterminate, which makes them difficult to design without the
use of computers.
A multi-span truss bridge may also be constructed using
cantilever spans, which are supported at only one end rather than both ends like other types of trusses. Unlike a continuous truss, a cantilever truss does not need to be connected rigidly, or indeed at all, at the center.
[ Many cantilever bridges, like the Quebec Bridge shown below, have two cantilever spans supporting a simple truss in the center. The bridge would remain standing if the simple truss section were removed.
File:Bally Bridge.jpg, A multi-span simple truss bridge, Vivekananda Setu over the ]Hooghly River
The Bhagirathi Hooghly River (Anglicized alternatively spelled ''Hoogli'' or ''Hugli'') or the 'Bhāgirathi-Hooghly', called the Ganga or the Kati-Ganga in mythological texts, is the eastern distributary of the Ganges River in West Bengal, Indi ...
in Kolkata, India.
File:Kingston-Rhinecliff Bridge2.JPG, A continuous truss bridge, Kingston–Rhinecliff Bridge
The George Clinton Kingston–Rhinecliff Bridge is a continuous under-deck truss toll bridge that carries NY 199 across the Hudson River in New York State north of the City of Kingston and the hamlet of Rhinecliff. It was opened to traffic o ...
over the Hudson River in 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
* '' ...
, United States.
File:Le pont de Québec, de l'embouchure de la rivière Chaudière.jpg, A cantilever truss bridge, Quebec Bridge over the Saint Lawrence River in Quebec, Canada.
Truss types used in bridges
Bridges are the most widely known examples of truss use. There are many types, some of them dating back hundreds of years. Below are some of the more common designs.
Allan truss
The Allan truss, designed by Percy Allan, is partly based on the Howe truss
A Howe truss is a truss bridge consisting of chords, verticals, and diagonals whose vertical members are in tension and whose diagonal members are in compression. The Howe truss was invented by William Howe in 1840, and was widely used as a bridg ...
. The first Allan truss was completed on 13 August 1894 over Glennies Creek at Camberwell, New South Wales and the last Allan truss bridge was built over Mill Creek near Wisemans Ferry in 1929. Completed in March 1895, the Tharwa Bridge located at Tharwa, Australian Capital Territory
Tharwa (postcode 2620) is a township within the District of Paddys River, Australian Capital Territory, south of Canberra, the capital city of Australia. At the , Tharwa had a population of 81.
The village is located on the banks of the Murr ...
, was the second Allan truss bridge to be built, the oldest surviving bridge in the Australian Capital Territory and the oldest, longest continuously used Allan truss bridge. Completed in November 1895, the Hampden Bridge in Wagga Wagga, New South Wales, Australia, the first of the Allan truss bridges with overhead bracing, was originally designed as a steel bridge but was constructed with timber to reduce cost. In his design, Allan used Australian ironbark for its strength. A similar bridge also designed by Percy Allen is the Victoria Bridge Victoria Bridge may be a reference to:
Bridges
;Australia
* Victoria Bridge, Brisbane, a road bridge across the Brisbane River in Brisbane
* Victoria Bridge, Devonport a road ridge across the Mersey River in Devonport, Tasmania
* Victoria Bridge, M ...
on Prince Street, Picton, New South Wales. Also constructed of ironbark, the bridge is still in use today for pedestrian and light traffic.
Bailey truss
The Bailey truss was designed by the British in 1940-1941 for military uses during World War II. A short selection of prefabricated modular components could be easily and speedily combined on land in various configurations to adapt to the needs at the site and allow rapid deployment of completed trusses. In the image, note the use of pairs of doubled trusses to adapt to the span and load requirements. In other applications the trusses may be stacked vertically, and doubled as necessary.
Baltimore truss
The Baltimore truss is a subclass of the Pratt truss. A Baltimore truss has additional bracing in the lower section of the truss to prevent buckling in the compression members and to control deflection. It is mainly used for rail bridges, showing off a simple and very strong design. In the Pratt truss the intersection of the verticals and the lower horizontal tension members are used to anchor the supports for the short-span girders under the tracks (among other things). With the Baltimore truss, there are almost twice as many points for this to happen because the short verticals will also be used to anchor the supports. Thus the short-span girders can be made lighter because their span is shorter. A good example of the Baltimore truss is the Amtrak Old Saybrook – Old Lyme Bridge in Connecticut, United States.
Bollman truss
The Bollman Truss Railroad Bridge at Savage, Maryland
Savage is an unincorporated community and census-designated place located in Howard County, Maryland, United States, approximately south of Baltimore and north of Washington, D.C. It is situated close to the city of Laurel and to the planned co ...
, United States is the only surviving example of a revolutionary design in the history of American bridge engineering. The type was named for its inventor, Wendel Bollman
Wendel Bollman (January 21, 1814 – 1884) was an American self-taught civil engineer, best known for his iron railway bridges. Only one of his patented "Bollman truss" bridges survives, the Bollman Truss Railroad Bridge in Savage, Maryland. Th ...
, a self-educated Baltimore
Baltimore ( , locally: or ) is the most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic, and the 30th most populous city in the United States with a population of 585,708 in 2020. Baltimore was d ...
engineer. It was the first successful all-metal bridge design (patented in 1852) to be adopted and consistently used on a railroad. The design employs wrought iron tension members and cast iron compression members. The use of multiple independent tension elements reduces the likelihood of catastrophic failure. The structure was also easy to assemble.
The Wells Creek Bollman Bridge
The Wills Creek Bollman Bridge originally served the Baltimore and Ohio Railroad's Pittsburgh Division main line.
Designed by the self-taught civil engineer Wendel Bollman in 1871, this truss bridge is the last remaining span of the Pittsburgh Div ...
is the only other bridge designed by Wendel Bollman still in existence, but it is a Warren truss configuration.
Bowstring truss
The bowstring truss bridge was patented in 1841 by Squire Whipple
Squire Whipple (September 16, 1804 – March 15, 1888) was an American civil engineer.
Biography
Squire Whipple was born in Hardwick, Massachusetts on September 16, 1804. His family moved to New York when he was thirteen. He received his seco ...
. While similar in appearance to a tied-arch bridge
A tied-arch bridge is an arch bridge in which the outward horizontal forces of the arch(es) caused by tension at the arch ends to a foundation are countered by equal tension of its own gravity plus any element of the total deck structure such grea ...
, a bowstring truss has diagonal load-bearing members: these diagonals result in a structure that more closely matches a Parker truss or Pratt truss than a true arch.
Brown truss
In the Brown truss all vertical elements are under tension, with exception of the end posts. This type of truss is particularly suited for timber structures that use iron rods as tension members.
Brunel truss
See Lenticular 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 assembla ...
below.
Burr arch truss
This combines an arch with a truss to form a structure both strong and rigid.
Cantilever truss
Most trusses have the lower chord under tension and the upper chord under compression. In a cantilever truss the situation is reversed, at least over a portion of the span. The typical cantilever truss bridge is a "balanced cantilever", which enables the construction to proceed outward from a central vertical spar in each direction. Usually these are built in pairs until the outer sections may be anchored to footings. A central gap, if present, can then be filled by lifting a conventional truss into place or by building it in place using a "traveling support". In another method of construction, one outboard half of each balanced truss is built upon temporary falsework. When the outboard halves are completed and anchored the inboard halves may then be constructed and the center section completed as described above.
Fink truss
The Fink truss was designed by Albert Fink
Albert Fink (October 27, 1827 – April 3, 1897) was a German-born civil engineer who worked in the United States. He is best known for his railroad bridge designs, which helped revolutionize the use of iron for American railroad bridge constructio ...
of Germany in 1854. This type of bridge was popular with the Baltimore and Ohio Railroad
The Baltimore and Ohio Railroad was the first common carrier railroad and the oldest railroad in the United States, with its first section opening in 1830. Merchants from Baltimore, which had benefited to some extent from the construction of ...
. The Appomattox High Bridge on the Norfolk and Western Railway
The Norfolk and Western Railway , commonly called the N&W, was a US class I railroad, formed by more than 200 railroad mergers between 1838 and 1982. It was headquartered in Roanoke, Virginia, for most of its existence. Its motto was "Precisio ...
included 21 Fink deck truss spans from 1869 until their replacement in 1886.
There are also inverted Fink truss bridges such as the Moody Pedestrian Bridge in Austin, Texas.
Howe truss
The Howe truss, patented in 1840 by Massachusetts millwright
A millwright is a craftsperson or skilled tradesperson who installs, dismantles, maintains, repairs, reassembles, and moves machinery in factories, power plants, and construction sites.
The term ''millwright'' (also known as ''industrial mecha ...
William Howe, includes vertical members and diagonals that slope up towards the center, the opposite of the Pratt truss.[Matsuo Bridge Company]
Bridge Types – Truss
, accessed September 2007
In contrast to the Pratt truss, the diagonal web members are in compression and the vertical web members are in tension. Few of these bridges remain standing. Examples include Jay Bridge
Jay Bridge is a wooden covered bridge that spans the east branch of the Ausable River in Jay, Essex County, New York, USA. It is eligible to be listed in the National Register of Historic Places. Of the 29 covered bridges in New York State, it a ...
in Jay, New York
Jay is a town in Essex County, New York, United States. The population was 2,506 at the 2010 census. The town is named after John Jay, governor of New York when the town was formed.
The town is on the northern border of Essex County and is sout ...
; McConnell's Mill Covered Bridge in Slippery Rock Township, Lawrence County, Pennsylvania; Sandy Creek Covered Bridge
Sandy Creek Covered Bridge State Historic Site is a publicly owned property in Jefferson County, Missouri, administered by the Missouri Department of Natural Resources, preserving the Sandy Creek Covered Bridge. The bridge is one of four remaini ...
in Jefferson County, Missouri; and Westham Island Bridge in Delta, British Columbia, Canada.
Image:Large Timber Howe Truss.jpg, A large timber Howe truss in a commercial building.
Image:Jay Bridge interior.jpg, Jay Bridge
Jay Bridge is a wooden covered bridge that spans the east branch of the Ausable River in Jay, Essex County, New York, USA. It is eligible to be listed in the National Register of Historic Places. Of the 29 covered bridges in New York State, it a ...
showing the truss design.
Image:Westham island bridge.jpg, Westham Island Bridge showing its wooden truss design.
K-truss
The K-truss is named after the ''K'' formed in each panel by the vertical member and two oblique members. Examples are the Südbrücke rail bridge over the River Rhine, Mainz, Germany, the bridge on I-895 (Baltimore Harbor Tunnel Thruway) in Baltimore, Maryland, the Long–Allen Bridge in Morgan City, Louisiana
Morgan City is a small city in St. Mary and lower St. Martin parishes in the U.S. State of Louisiana. The population was 12,404 at the 2010 census. Known for being “right in the middle of everywhere”, Morgan City is located 68 miles (109&nb ...
(Morgan City Bridge) with three 600-foot-long spans, and the Wax Lake Outlet bridge in Calumet, Louisiana
Kingpost truss
One of the simplest truss styles to implement, the king post consists of two angled supports leaning into a common vertical support.
Lattice truss (Town's lattice truss)
This type of bridge uses a substantial number of lightweight elements, easing the task of construction. Truss elements are usually of wood, iron, or steel.
Lenticular truss
A lenticular truss bridge includes a lens-shape truss, with trusses between an upper chord (functioning as an arch) that curves up and then down to end points, and a lower chord (functioning as a suspension cable) that curves down and then up to meet at the same end points. Where the arches extend above and below the roadbed, it is called a lenticular pony truss bridge. The Pauli truss bridge is a specific variant of the lenticular truss, but the terms are not interchangeable.
One type of lenticular truss consists of arcuate upper compression chords and lower eyebar chain tension links. Brunel
Isambard Kingdom Brunel (; 9 April 1806 – 15 September 1859) was a British civil engineer who is considered "one of the most ingenious and prolific figures in engineering history," "one of the 19th-century engineering giants," and "one ...
's Royal Albert Bridge over the River Tamar between Devon and Cornwall uses a single tubular upper chord. As the horizontal tension and compression forces are balanced these horizontal forces are not transferred to the supporting pylons (as is the case with most arch types). This in turn enables the truss to be fabricated on the ground and then to be raised by jacking as supporting masonry pylons are constructed. This truss has been used in the construction of a stadium, with the upper chords of parallel trusses supporting a roof that may be rolled back. The Smithfield Street Bridge in Pittsburgh, Pennsylvania, is another example of this type.
An example of a lenticular pony truss bridge that uses regular spans of iron is the Turn-of-River Bridge
The Turn-of-River Bridge, also known as Old North Stamford Road Bridge, is a single-span lenticular pony truss bridge built by the Berlin Iron Bridge Company in 1892. It was listed on the National Register of Historic Places in 1987. It formerly br ...
designed and manufactured by the Berlin Iron Bridge Co.
The Berlin Iron Bridge Company was a Berlin, Connecticut company that built iron bridges and buildings that were supported by iron. It is credited as the architect of numerous bridges and buildings now listed on the U.S. National Register of His ...
The Pauli truss is a variant of the lenticular truss, "with the top chord carefully shaped so that it has a constant force along the entire length of the truss." It is named after , whose 1857 railway bridge (the ) spanned the Isar
The Isar is a river in Tyrol, Austria, and Bavaria, Germany, which is not navigable for watercraft above raft size. Its source is in the Karwendel range of the Alps in Tyrol; it enters Germany near Mittenwald and flows through Bad Tölz, Munic ...
near Munich. (''See also Grosshesselohe Isartal station
Großhesselohe Isartalbahn station (german: Großhesselohe Isartalbahnhof) is a station on the Isar Valley Railway from Munich to Bichl in the German state of Bavaria. Since 1981, it has been a station of the Munich S-Bahn. The station is located ...
''.) The term Pauli truss is not interchangeable with the term lenticular truss and, according to Thomas Boothby, the casual use of the term has clouded the literature.
Long truss
The Long truss was designed by Stephen H. Long in 1830. The design resembles a Howe truss
A Howe truss is a truss bridge consisting of chords, verticals, and diagonals whose vertical members are in tension and whose diagonal members are in compression. The Howe truss was invented by William Howe in 1840, and was widely used as a bridg ...
, but is entirely made of wood instead of a combination of wood and metal. The longest surviving example is the Eldean Covered Bridge
The Eldean Covered Bridge is a historic covered bridge spanning the Great Miami River in Miami County, Ohio north of Troy, Ohio, Troy. Built in 1860, it is one of the nation's finest surviving examples of a Long truss, patented in 1830 by engineer ...
north of Troy, Ohio, spanning . One of the earliest examples is the Old Blenheim Bridge, which with a span of and a total length of long was the second-longest covered bridge in the United States, until its destruction from flooding in 2011.
The Busching bridge, often erroneously used as an example of a Long truss, is an example of a Howe truss, as the verticals are metal rods.
Parker (camelback) truss
A Parker truss bridge is a Pratt truss design with a polygonal upper chord. A "camelback" is a subset of the Parker type, where the upper chord consists of exactly five segments. An example of a Parker truss is the Traffic Bridge
The Traffic Bridge is the name given to two truss bridges constructed across the South Saskatchewan River, connecting Victoria Avenue to 3rd Avenue South and Spadina Crescent in Saskatoon, Saskatchewan, Canada. The original bridge opened on Oc ...
in Saskatoon, Canada. An example of a camelback truss is the Woolsey Bridge
Woolsey Bridge (NRHP listed as Washington County Road 35 Bridge) was a truss bridge built in 1925, formerly located near West Fork, Arkansas. It carried County Route 35 over the West Fork of the White River for . It is listed on the National Regis ...
near Woolsey, Arkansas
Woolsey, Arkansas (formerly Woolseys, Arkansas) is an unincorporated community in Crawford Township, Washington County, Arkansas, United States."Feature Detail Report for: Woolsey, Arkansas." USGS. Retrieved October 5, 2010. It is located on U.S ...
.
Partridge truss
Designed and patented in 1872 by Reuben Partridge
Reuben L. Partridge (September 10, 1823 – July 17, 1900) was an American pioneer and engineer in Union County, Ohio, known locally as "The Bridge Builder".
Early life
Reuben Partridge was born September 10, 1823, in Wilmington, New York, to Cy ...
, after local bridge designs proved ineffective against road traffic and heavy rains.[Kennedy, Willella Shearer. "Heritage: Being Little Stories of Union County". ''Union County Historical Society'', Printed by The Marysville Journal Tribune. 1963. Pg. 48.] It became the standard for covered bridges built in central Ohio in the late 1800s and early 1900s.
Pegram truss
The Pegram truss is a hybrid between the Warren and Parker trusses where the upper chords are all of equal length and the lower chords are longer than the corresponding upper chord. Because of the difference in upper and lower chord length, each panel is not square. The members which would be vertical in a Parker truss vary from near vertical in the center of the span to diagonal near each end (like a Warren truss). George H. Pegram
George Herndon Pegram (1855–1937), most commonly known as George H. Pegram, was an engineer who patented the Pegram truss.
Biography
George H. Pegram was born in Council Bluffs, Iowa, on December 29, 1855. He completed a civil engineering de ...
, while the chief engineer of Edge Moor Iron Company in Wilmington, Delaware, patented this truss design in 1885.
The Pegram truss consists of a Parker type design with the vertical posts leaning towards the center at an angle between 60 and 75°. The variable post angle and constant chord length allowed steel in existing bridges to be recycled into a new span using the Pegram truss design. This design also facilitated reassembly and permitted a bridge to be adjusted to fit different span lengths. There are twelve known remaining Pegram span bridges in the United States with seven in Idaho, two in Kansas, and one each in California, Washington, and Utah.
Pennsylvania (Petit) truss
The Pennsylvania (Petit) truss is a variation on the Pratt truss. The Pratt truss includes braced diagonal members in all panels; the Pennsylvania truss adds to this design half-length struts or ties in the top, bottom, or both parts of the panels. It is named after the Pennsylvania Railroad
The Pennsylvania Railroad (reporting mark PRR), legal name The Pennsylvania Railroad Company also known as the "Pennsy", was an American Class I railroad that was established in 1846 and headquartered in Philadelphia, Pennsylvania. It was named ...
, which pioneered this design. It was once used for hundreds of bridges in the United States, but fell out of favor in the 1930s, and very few bridges of this design remain. Examples of this truss type include the Lower Trenton Bridge
The Lower Trenton Toll Supported Bridge, commonly called the Lower Free Bridge, Warren Street Bridge or Trenton Makes Bridge, is a two-lane Pennsylvania (Petit) through truss bridge over the Delaware River between Trenton, New Jersey and Mor ...
in Trenton, New Jersey, the Fort Wayne Street Bridge
Fort Wayne Street Bridge, also known as the County Bridge #403 and Indiana Avenue Bridge, is a historic Pennsylvania truss bridge located at Goshen, Elkhart County, Indiana. It was built in 1896 by the Bellefontaine Bridge & Iron Co. and spans ...
in Goshen, Indiana, the Schell Bridge
The Schell Memorial Bridge is a steel cantilever Pennsylvania (Petit) truss bridge spanning the Connecticut River in the town of Northfield, Massachusetts. Designed by Edward S. Shaw, the bridge abutments and piers were built by the firm of Elli ...
in Northfield, Massachusetts, the Inclined Plane Bridge
The Inclined Plane Bridge is a , Pennsylvania through truss bridge that spans Stonycreek River in Johnstown, Cambria County, in the U.S. state of Pennsylvania. It connects the city to the lower station of the Johnstown Inclined Plane. The bridge w ...
in Johnstown, Pennsylvania, the Easton–Phillipsburg Toll Bridge
The Easton–Phillipsburg Toll Bridge is a modified Truss bridge#Pennsylvania (Petit) truss, Pennsylvania (Petit) through truss bridge that carries U.S. Route 22 over the Delaware River. The bridge is located between Easton, Pennsylvania and Phil ...
in Easton, Pennsylvania, the Connecticut River Bridge
This is a list of bridges and other crossings of the Connecticut River from its mouth at Long Island Sound upstream to its source at the Connecticut Lakes. The list includes current road and rail crossings, as well as ferries carrying a state high ...
in Brattleboro, Vermont, the Metropolis Bridge
The Metropolis Bridge is a railroad bridge which spans the Ohio River at Metropolis, Illinois. Originally built for the Chicago, Burlington and Quincy Railroad, construction began in 1914 under the direction of engineer Ralph Modjeski.
The brid ...
in Metropolis, Illinois, and the Healdsburg Memorial Bridge
The Healdsburg Memorial Bridge is a steel truss bridge across the Russian River in Healdsburg, California, listed in the National Register of Historic Places. in Healdsburg, California.
Post truss
A Post truss is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post
Simeon () is a given name, from the Hebrew ( Biblical ''Šimʿon'', Tiberian ''Šimʿôn''), usually transliterated as Shimon. In Greek it is written Συμεών, hence the Latinized spelling Symeon.
Meaning
The name is derived from Simeon, son ...
, it is occasionally referred to as a ''Post patent truss'' although he never received a patent for it. The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss.
Pratt truss
A Pratt truss includes vertical members and diagonals that slope down towards the center, the opposite of the Howe truss
A Howe truss is a truss bridge consisting of chords, verticals, and diagonals whose vertical members are in tension and whose diagonal members are in compression. The Howe truss was invented by William Howe in 1840, and was widely used as a bridg ...
. The interior diagonals are under tension under balanced loading and vertical elements under compression. If pure tension elements are used in the diagonals (such as eyebars) then crossing elements may be needed near the center to accept concentrated live loads as they traverse the span. It can be subdivided, creating Y- and K-shaped patterns. The Pratt truss was invented in 1844 by Thomas and Caleb Pratt.[ This truss is practical for use with spans up to and was a common configuration for railroad bridges as truss bridges moved from wood to metal. They are ]statically determinate
In statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations force and moment equilibrium conditions are insufficient for determining the internal forces and Reaction (physics), reactions on tha ...
bridges, which lend themselves well to long spans. They were common in the United States between 1844 and the early 20th century.[
Examples of Pratt truss bridges are the Governor's Bridge in Maryland,] Dearborn River High Bridge
The Dearborn River High Bridge is a Pratt half-deck truss bridge built in 1897, and has been placed on the National Register of Historic Places as it is one of the few bridges of its type left standing in the United States. On a half-deck bridge, ...
near Augusta, Montana, built in 1897, and the Fair Oaks Bridge
The Fair Oaks Bridge is a truss bridge over the lower banks of the American River, connecting Fair Oaks, California, Fair Oaks to the greater Sacramento, California region. The current bridge, built 1907-1909 at a cost of $63,000, is the third b ...
in Fair Oaks, California, built 1907–09.
The Scenic Bridge near Tarkio, Montana, is an example of a Pratt deck truss bridge, where the roadway is on top of the truss.
Queenpost truss
The queenpost truss, sometimes called "queen post" or "queenspost", is similar to a king post truss in that the outer supports are angled towards the center of the structure. The primary difference is the horizontal extension at the center which relies on beam
Beam may refer to:
Streams of particles or energy
*Light beam, or beam of light, a directional projection of light energy
**Laser beam
*Particle beam, a stream of charged or neutral particles
**Charged particle beam, a spatially localized grou ...
action to provide mechanical stability. This truss style is only suitable for relatively short spans.
Smith truss
The Smith truss, patented by Robert W Smith on July 16, 1867, has mostly diagonal criss-crossed supports. Smith's company used many variations of this pattern in the wooden covered bridges it built.
While most all of the bridges built in the 19th century in the Jackson County, Ohio, area used the Smith truss design, the Johnson Road Covered Bridge
The Johnson Road Covered Bridge is a covered bridge located near Petersburg, Jackson County, Ohio, United States.
It was built around 1870 by Robert W. Smith, using his 1867 patent for the Smith truss design. While most all of the covered bridge ...
is the last known surviving example in the state.
Thacher truss
The Thacher truss combines some of the characteristics of a Pratt truss with diagonals under tension and of a Howe truss
A Howe truss is a truss bridge consisting of chords, verticals, and diagonals whose vertical members are in tension and whose diagonal members are in compression. The Howe truss was invented by William Howe in 1840, and was widely used as a bridg ...
with diagonals under compression. It is quite rare.
Truss arch
A truss arch may contain all horizontal forces within the arch itself, or alternatively may be either a thrust arch consisting of a truss, or of two arcuate sections pinned at the apex. The latter form is common when the bridge is constructed as cantilever segments from each side as in the Navajo Bridge
Navajo Bridge is the name of twin steel spandrel arch bridges that cross the Colorado River in the Grand Canyon National Park (near Lee's Ferry, Lees Ferry) in northern Coconino County, Arizona, Coconino County, Arizona, United States. The newer ...
.
Vierendeel truss
The Vierendeel truss, unlike common pin-jointed trusses, imposes significant bending forces upon its members—but this in turn allows the elimination of many diagonal elements. It is a structure where the members are not triangulated but form rectangular openings, and is a frame with fixed joints that are capable of transferring and resisting bending moments. While rare as a bridge type due to higher costs compared to a triangulated truss, it is commonly employed in modern building construction as it allows the resolution of gross shear forces against the frame elements while retaining rectangular openings between columns. This is advantageous both in allowing flexibility in the use of the building space and freedom in selection of the building's outer curtain wall, which affects both interior and exterior styling aspects.
Waddell truss
Patented 1894 (); its simplicity eases erection at the site. It was intended to be used as a railroad bridge.
One example was the Waddell "A" Truss Bridge (Parkville, Missouri).
Warren truss
The Warren truss was patented in 1848 by James Warren and Willoughby Theobald Monzani, and consists of longitudinal members joined only by angled cross-members, forming alternately inverted equilateral triangle-shaped spaces along its length, ensuring that no individual strut, beam, or tie
Tie has two principal meanings:
* Tie (draw), a finish to a competition with identical results, particularly sports
* Necktie, a long piece of cloth worn around the neck or shoulders
Tie or TIE may also refer to:
Engineering and technology
* Ti ...
is subject to bending or torsional straining forces, but only to tension or compression. Loads on the diagonals alternate between compression and tension (approaching the center), with no vertical elements, while elements near the center must support both tension and compression in response to live loads. This configuration combines strength with economy of materials and can therefore be relatively light. The girders being of equal length, it is ideal for use in prefabricated modular bridges. It is an improvement over the Neville truss which uses a spacing configuration of isosceles triangles.
Whipple truss
A Whipple truss, named after its inventor Squire Whipple
Squire Whipple (September 16, 1804 – March 15, 1888) was an American civil engineer.
Biography
Squire Whipple was born in Hardwick, Massachusetts on September 16, 1804. His family moved to New York when he was thirteen. He received his seco ...
, is usually considered a subclass of the Pratt truss because the diagonal members are designed to work in tension. The main characteristic of a Whipple truss is that the tension members are elongated, usually thin, and at a shallow angle, and cross two or more bays (rectangular sections defined by the vertical members).
Wichert truss
The Wichert truss is a modified type of continuous truss which is statically determinate
In statics and structural mechanics, a structure is statically indeterminate when the static equilibrium equations force and moment equilibrium conditions are insufficient for determining the internal forces and Reaction (physics), reactions on tha ...
and helps avoid some of the other shortcomings of continuous trusses. It was patented in 1930 by Pittsburgh-based civil engineer Edward Martin Wichert (1883–1955). The defining feature of this truss type is a hinged kite-shaped section above each intermediate support. Only about ten Wichert truss bridges were ever built, mostly in Pennsylvania and Maryland. Of these, one of the best known is the Homestead Grays Bridge
The Homestead Grays Bridge, also known as the (Homestead) High Level Bridge, was built in 1936 and spans the Monongahela River between Homestead Borough and the southernmost tip of Pittsburgh's Squirrel Hill neighborhood. It is notable as the fir ...
in Pittsburgh.
Truss bridge video
Driving across a truss bridge: The video shows the roadway perspective of a through truss bridge over the Willamette River in Harrisburg, Oregon, USA. The bridge features three simply supported Parker Truss spans.
References
*
Footnotes
External links
Bridge Basics – A Spotter's Guide to Bridge Design
– from Pghbridges.com – Illustrates many of the various types of truss arrangements used in bridges.
Historic Bridges of Michigan and Elsewhere
– Many photos of truss bridges are available on this informative and mainly truss-focused bridge website.
Historic Bridges of Iowa
– An illustrated list of different architectural bridge types found in Iowa, USA. Many of these are truss bridges.
Historic Bridges of the U.S.
– An enormous database of historic bridges. Over 17,400 truss bridges are listed here.
Iron and Early Steel Bridges of Ohio
A comprehensive inventory of all remaining truss bridges in Ohio. Includes maps, photos, and invites visitor assistance in identifying extant or demolished bridges.
Matsuo Bridge Company: Bridge Types – Truss
Management Plan for Historic Bridges in Virginia: The 2017 Update
Virginia Department of Transportation's plan for managing its historic bridges, including metal truss bridges. The update includes sections on study findings such as "General Issues Regarding Metal and Metal Truss Bridges (Including Potential Life Span)," "Coatings Issues for Metal Truss Bridges: Painting, Metallizing, and Galvanizing," and "Truss Bridge Capacity and Overloading Potential."
structurae.de
The Structurae
Structurae is an online database containing pictures and information about structural engineering, structural and civil engineering works, and their associated engineers, architects, and builders. Its entries are user-generated content, contribu ...
database on bridges.
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Bridges by structural type
Articles containing video clips