Depends upon length, materials, and degree of prefabrication
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 sometimes both in response to dynamic loads. There are several types of truss bridges, including some with simple designs that were among the first bridges designed in the 19th and early 20th centuries. A truss bridge is economical to construct primarily because it uses materials efficiently.
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. 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 the strength to maintain its shape, and the resulting shape and strength of the structure are 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.
In the bridge illustrated in the infobox at the top, vertical members are in tension, lower horizontal members in tension, shear, 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 the 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 has 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.
United States
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 members, 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 of Massillon, Ohio, and the King Bridge Company of Cleveland, 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 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.
In the 1920s and 1930s, Pennsylvania and several states continued to build steel truss bridges, using 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 a deck truss; an example of this was the I-35W Mississippi River bridge. When the truss members are both above and below the roadbed it is called a through truss; an example of this is the Pulaski Skyway, and where the sides extend above the roadbed but are not connected, a pony truss or half-through 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.[2]
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.
Railroad Truss bridge over Trinity River near Goodrich, Texas
The Hart Bridge spanning the St. Johns River in Jacksonville, Florida, is a continuous, cantilevered truss bridge which combines a suspended road deck on the 332-metre (1,088ft) main span and through truss decks on the adjacent approach spans
Railroad Truss Drawbridge across Buffalo Bayou—Houston
Multiple spans
Truss bridges consisting of more than one span 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.[3]:168 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.[3]:169–170 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.
It has been suggested that this section be split out into another article. (Discuss) (February 2023)
Bridges are the most widely known examples of truss use. There are many types,[4] some of them dating back hundreds of years. Below are some of the more common designs.
Allan truss
An Allan truss
The Allan truss, designed by Percy Allan, is partly based on the Howe truss. 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.[5][6] Completed in March 1895, the Tharwa Bridge located at Tharwa, Australian Capital Territory, 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.[7][8][9] 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.[10] In his design, Allan used Australian ironbark for its strength.[11] A similar bridge also designed by Percy Allen is the Victoria Bridge on Prince Street, Picton, New South Wales. Also constructed of ironbark, the bridge is still in use today for pedestrian and light traffic.[12]
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.
The Bollman Truss Railroad Bridge at Savage, Maryland, United States is the only surviving example of a revolutionary design in the history of American bridge engineering. The type was named after its inventor, Wendel Bollman, a self-educated Baltimore 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.
Wells Creek Bollman Bridge is the only other bridge designed by Wendel Bollman still in existence, but it is a Warren truss configuration.
Bowstring truss
Bowstring trussA bowstring truss bridge, in London, Ontario, Canada
The bowstring truss bridge was patented in 1841[13] by Squire Whipple.[14] While similar in appearance to a tied-arch bridge, 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.
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.
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.
The K-truss is named after the K formed in each panel by the vertical member and two oblique members. Examples include the Südbrücke rail bridge over the River Rhine, Mainz, Germany,[16] the bridge on I-895 (Baltimore Harbor Tunnel Thruway) in Baltimore, Maryland, the Long–Allen Bridge in Morgan City, Louisiana (Morgan City Bridge) with three 600-foot-long spans, and the Wax Lake Outlet bridge in Calumet, Louisiana[17]
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.
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.[19] 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.[19]
One type of lenticular truss consists of arcuate upper compression chords and lower eyebar chain tension links. Brunel'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,[20] 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.
The old Großhesselohe bridge before 1905, designed by Friedrich von Pauli
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."[19] It is named after Friedrich Augustus von Pauli[de], whose 1857 railway bridge (the Großhesseloher Brücke[de]) spanned the Isar near Munich. (See also Grosshesselohe Isartal station.) 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.[19]
The Long truss was designed by Stephen H. Long in 1830. The design resembles a Howe truss, but is entirely made of wood instead of a combination of wood and metal.[21] The longest surviving example is the Eldean Covered Bridge north of Troy, Ohio, spanning 224 feet (68m).[22] One of the earliest examples is the Old Blenheim Bridge, which with a span of 210 feet (64m) and a total length of 232 feet (71m) 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.[23]
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 in Saskatoon, Canada. An example of a camelback truss is the Woolsey Bridge near Woolsey, Arkansas.
Partridge truss
Partridge truss design
Designed and patented in 1872 by Reuben Partridge, after local bridge designs proved ineffective against road traffic and heavy rains.[24] It became the standard for covered bridges built in central Ohio in the late 1800s and early 1900s.
Pegram truss
Pegramtruss
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, similar to a Warren truss. George H. Pegram, while the chief engineer of Edge Moor Iron Company in Wilmington, Delaware, patented this truss design in 1885.[25]
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.[citation needed]
Pennsylvania (Petit) truss
The Fair Oaks Bridge is an example of Pennsylvania Petit truss bridge.
A Post truss is a hybrid between a Warren truss and a double-intersection Pratt truss. Invented in 1863 by Simeon S. Post, it is occasionally referred to as a Post patent truss although he never received a patent for it.[27] The Ponakin Bridge and the Bell Ford Bridge are two examples of this truss.
Pratt truss
A Pratt trussGatton Railway Bridge showing the Pratt truss designMacleay River Railway Bridge, a Pratt truss design at Kempsey in NSW, Australia
A Pratt truss includes vertical members and diagonals that slope down towards the center, the opposite of the Howe truss.[15] The interior diagonals are under tension under balanced loading and vertical elements under compression. If pure tension elements (such as eyebars) are used in the diagonals, 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.[28] This truss is practical for use with spans up to 250 feet (76m) and was a common configuration for railroad bridges as truss bridges moved from wood to metal. They are statically determinate bridges, which lend themselves well to long spans. They were common in the United States between 1844 and the early 20th century.[28]
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 action to provide mechanical stability. This truss style is only suitable for relatively short spans.[29]
Smith truss
Smith truss
The Smith truss, patented by Robert W Smith on July 16, 1867,[30] 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 is the last known surviving example in the state.[31]
Thacher truss
A Thacher truss bridge
The Thacher truss[32] combines some of the characteristics of a Pratt truss with diagonals under tension and of a Howe truss with diagonals under compression, which is rare.
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.
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.
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 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.
A Whipple truss, named after its inventor Squire Whipple, 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).
The Wichert truss is a modified type of continuous truss which is statically determinate and helps avoid some of the other shortcomings of continuous trusses.[33] It was patented in 1930 by Pittsburgh-based civil engineer Edward Martin Wichert (1883–1955).[34][35]
The defining feature of this truss type is a hinged kite-shaped section above each intermediate support.[citation needed] 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 in Pittsburgh.[36]
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. The bridge features three simply supported Parker Truss spans.
Related Research Articles
A truss is an assembly of members such as beams, connected by nodes, that creates a rigid structure.
A cantilever bridge is a bridge built using structures that project horizontally into space, supported on only one end. For small footbridges, the cantilevers may be simple beams; however, large cantilever bridges designed to handle road or rail traffic use trusses built from structural steel, or box girders built from prestressed concrete.
A lattice truss bridge is a form of truss bridge that uses many small, closely spaced diagonal elements forming a lattice. The design was patented in 1820 by architect Ithiel Town.
A tied-arch bridge is an arch bridge in which the outward-directed horizontal forces of the arch(es) are borne as tension by a chord tying the arch ends rather than by the ground or the bridge foundations. This strengthened chord may be the deck structure itself or consist of separate, independent tie-rods.
The Bollman Truss Railroad Bridge across the Little Patuxent River at Savage, Maryland, is one of the oldest standing iron railroad bridges in the United States and the sole surviving example of a revolutionary design in the history of American bridge engineering. The 160-foot (48.8 m) double-span was built in 1852 at an unknown location on the main line of the Baltimore and Ohio Railroad. It was moved 35 years later to its present location, where it replaced the very first Bollman bridge. Today, it carries the Savage Mill Trail.
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 bridge in the mid to late 1800s.
A Brown truss is a type of bridge truss, used in covered bridges. It is noted for its economical use of materials and is named after the inventor, Josiah Brown Jr., of Buffalo, New York, who patented it July 7, 1857, as US patent 17,722.
Blackfriars Bridge in London, Ontario, Canada is a wrought iron bowstring arch through truss bridge, crossing the North Thames River. The bridge was constructed in 1875 and carries single-lane vehicles, bicycles and pedestrians from Blackfriars Street to Ridout Street North.
In structural engineering, a Warren truss or equilateral truss is a type of truss employing a weight-saving design based upon equilateral triangles. It is named after the British engineer James Warren, who patented it in 1848.
The Hadley Parabolic Bridge, often referred to locally as the Hadley Bow Bridge, carries Corinth Road across the Sacandaga River in Hadley, New York, United States. It is an iron bridge dating from the late 19th century.
The Dodd Ford Bridge is a bridge spanning the Blue Earth River about 1 mile (2 km) southwest of Amboy, Minnesota, in Blue Earth County, Minnesota.
The AJX Bridge is a historic Pratt truss bridge in southwestern Johnson County, Wyoming. The bridge was built in 1931 across the South Fork of the Powder River near Kaycee, Wyoming. AJX Bridge was built to provide a river crossing for U.S. Route 87. It was placed on the National Register of Historic Places in 1985 as part of a Multiple Property Submission devoted to historic bridges in Wyoming.
Gaunless Bridge was a railway bridge on the Stockton and Darlington Railway. It was completed in 1823 and is one of the first railway bridges to be constructed of iron and the first to use an iron truss. It is also of an unusual lenticular truss design.
The Bethanga Bridge is a steel truss road bridge that carries the Riverina Highway across Lake Hume, an artificial lake on the Murray River in Australia. The dual heritage-listed bridge crosses the border between the Australian states of New South Wales and Victoria, linking the Victorian towns of Bellbridge and Bethanga with the regional New South Wales city of Albury.
Sadliers Crossing Railway Bridge is a heritage-listed railway bridge at over Bremer River between Tallon Street, Sadliers Crossing and Dixon Street, Wulkuraka, Queensland, Australia on the Main Line (this section is now the Ipswich and Rosewood railway line. It was added to the Queensland Heritage Register on 13 November 2008.
The bridge is significant locally as the only Pratt through-truss bridge remaining in Kosciusko County, and is important regionally as one of the few surviving spans built by the Bellefontaine Bridge and Iron Company.
Starke County Bridge No. 39 is a single span Warren Pony Truss structure. The bridge is located on the northern outskirts of the small town of Knox, Indiana, where Main and Water Streets terminate at the former Penn Central Railroad cut. The bridge spans the rail cut in a northwest–southeast direction, allowing access to Wythougan Park.
The Lincoln Covered Bridge is a historic covered bridge, just south of U.S. Route 4 in West Woodstock, Vermont. Built in 1877, it is one of the only known examples of a wooden Pratt truss bridge in the United States. It was listed on the National Register of Historic Places in 1973.
The Straight Street Bridge is a vehicular bridge over the Passaic River in Paterson, New Jersey, that is listed on the National Register of Historic Places.
Old Cobram-Barooga Bridge is a heritage-listed former road bridge and now footbridge over the Murray River at Barooga-Cobram Road, Barooga, New South Wales, Australia. The bridge links Barooga with Cobram, its sister town in Victoria. It was designed by Ernest de Burgh (engineer) and the New South Wales Department of Public Works and built from 1900 to 1902. It is also known as RMS Bridge No 3247. It is owned by Transport for NSW. It was added to the New South Wales State Heritage Register on 1 April 2016.
↑ Science and IndustryArchived 2017-02-15 at the Wayback Machine , Members of a Truss Bridge by Benj. F. La Rue, Home Study Magazine, Published by the Colliery Engineer Company, Vol 3, No. 2, March 1898, pages 67-68.
1 2 Adams, Charles Kendall, ed. (1909). "Bridges". Universal Cyclopædia and Atlas. New York: D. Appleton and Company. pp.161–174. Retrieved September 1, 2022.
↑ Kirsanov, M. (2019). Planar Trusses: Schemes and Formulas. GB: Cambridge Scholars Publishing. p.206. ISBN978-1-5275-3531-2.
↑ "Timber Truss Bridges"(PDF). McMillan Britton & Kell Pty Limited. Roads and Traffic Authority. December 1998. Archived(PDF) from the original on 19 March 2011. Retrieved 23 November 2010.
↑ "Busching Bridge". CLR Inc. Construction and Transportation. Archived from the original on August 20, 2011. Retrieved June 25, 2012.
↑ Kennedy, Willella Shearer. "Heritage: Being Little Stories of Union County". Union County Historical Society, Printed by The Marysville Journal Tribune. 1963. Pg. 48.
↑ US 314262,Pegram, George H.,"Truss for Roofs and Bridges",published 10-24-1881,issued 03-24-1885
↑ "R.W. Smith Truss Patent 66,900". United States Patent Office. United States of America. July 16, 1867. Archived from the original on 11 November 2018. Retrieved 10 November 2018.
Historic Bridges of Iowa – An illustrated list of different architectural bridge types found in Iowa, US. 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.
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."
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