Bollman Truss Bridge
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The Bollman Truss Railroad Bridge across the
Little Patuxent River The Patuxent River is a tributary of the Chesapeake Bay in the state of Maryland. There are three main river drainages for central Maryland: the Potomac River to the west passing through Washington, D.C., the Patapsco River to the northeast ...
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 ...
, is one of the oldest standing iron railroad bridges in the
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and the sole surviving example of a revolutionary design in the history of American bridge engineering. The double-span was built in 1852 at an unknown location on the main line of 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 ...
. 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. The Bollman design, a
suspension Suspension or suspended may refer to: Science and engineering * Suspension (topology), in mathematics * Suspension (dynamical systems), in mathematics * Suspension of a ring, in mathematics * Suspension (chemistry), small solid particles suspend ...
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 ...
bridge, was the first successful all-metal bridge design to be adopted and consistently used on a railroad. 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 List of municipalities in Maryland, most populous city in the U.S. state of Maryland, fourth most populous city in the Mid-Atlantic (United States), Mid-Atlantic, and List of United States cities by popula ...
civil engineer A civil engineer is a person who practices civil engineering – the application of planning, designing, constructing, maintaining, and operating infrastructure while protecting the public and environmental health, as well as improving existing ...
. Bollman formed two companies in Baltimore, the W. Bollman and Company and the Patapsco Bridge Company, to market the bridge in North and South America. In 1966, the
American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
designated the bridge as the first
National Historic Civil Engineering Landmark __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United State ...
. The bridge was listed on the
National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic v ...
on December 18, 1972, and was designated a
National Historic Landmark A National Historic Landmark (NHL) is a building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance. Only some 2,500 (~3%) of over 90,000 places listed ...
on February 16, 2000.


History

The bridge was built for an unknown location on the main line of 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 ...
in 1852, and was moved to its present location, spanning the
Little Patuxent River The Patuxent River is a tributary of the Chesapeake Bay in the state of Maryland. There are three main river drainages for central Maryland: the Potomac River to the west passing through Washington, D.C., the Patapsco River to the northeast ...
on the spur to the
Savage Mill The Savage Mill is a historic cotton mill complex in Savage, Maryland, which has been turned into a complex of shops and restaurants. It was placed on the National Register of Historic Places in 1974. It is located in the Savage Mill Historic Dis ...
, in 1887. This spur line dates to around 1840 and originally crossed the river on a stone arch bridge; however, due to alterations to the mill in the 1880s and topographical restrictions, a replacement bridge was needed. The bridge remained in service until the mill closed in 1947; switching crews used additional cars in order to avoid crossing the bridge with locomotives, and thus there was never a need for a more substantial structure. A smaller, narrower example was installed next to the railroad bridge for road traffic, which was torn down after World War I. It was the first successful all-metal bridge design to be adopted and consistently used on a railroad. The design employs
wrought iron Wrought iron is an iron alloy with a very low carbon content (less than 0.08%) in contrast to that of cast iron (2.1% to 4%). It is a semi-fused mass of iron with fibrous slag Inclusion (mineral), inclusions (up to 2% by weight), which give it a ...
tension members and
cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
compression members. It was an improvement over wooden structures, as the independent structural units lessened the possibility of structural failure. After receiving a patent on January 6, 1852, the company built about a hundred of these bridges through 1873. Their durability and ease of assembly greatly facilitated expansion of American railroads in this period. Bollman's Wills Creek Bridge has also survived, but it employs a different type of truss system.


Restoration

In 1966, the
American Society of Civil Engineers American(s) may refer to: * American, something of, from, or related to the United States of America, commonly known as the "United States" or "America" ** Americans, citizens and nationals of the United States of America ** American ancestry, pe ...
introduced its
National Historic Civil Engineering Landmark __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United State ...
program, and designating the bridge as the first landmark. The bridge was listed on the
National Register of Historic Places The National Register of Historic Places (NRHP) is the United States federal government's official list of districts, sites, buildings, structures and objects deemed worthy of preservation for their historical significance or "great artistic v ...
on December 18, 1972, and was designated a
National Historic Landmark A National Historic Landmark (NHL) is a building, district, object, site, or structure that is officially recognized by the United States government for its outstanding historical significance. Only some 2,500 (~3%) of over 90,000 places listed ...
on February 16, 2000. The bridge was surveyed for restoration in 1978 by Modjeski and Masters, which noted deterioration of the floor trusses. A $214,200 restoration contract was let to Dewey-Jordan of Frederick in September 1982. The bridge was restored by Wallace, Montgomery & Associates, LLP, for the Howard County Department of Recreation and Parks in 1983. In 2000, it received additional preservation work and was rededicated on September 16. Today it receives regular maintenance as part of Savage Park. Nearby
Bollman Bridge Elementary School The Howard County Public School System (HCPSS) is the school district that manages and runs the public schools of Howard County, Maryland. It operates under the supervision of an elected, eight-member Board of Education. Antonia Watts is the chai ...
takes its name from the historic bridge.


Description

The Bollman Bridge is a two-span through-truss, resting on granite abutments at each end and a granite pier in the middle of the river. The truss structure is a mixture of wrought and
cast iron Cast iron is a class of iron–carbon alloys with a carbon content more than 2%. Its usefulness derives from its relatively low melting temperature. The alloy constituents affect its color when fractured: white cast iron has carbide impuriti ...
. The truss configuration is the design patented by Bollman as the "Bollman suspension truss" in 1852. Each span is long, wide and about tall. The Bollman truss suspends the deck from a network of tension members, while the top chord resists compressive forces. The system is therefore referred to as a suspension truss. Bollman published a booklet describing the Harpers Ferry bridge and the system in general as a “suspension and trussed bridge” which is accurate as the design lacks an active lower chord required of a strict truss bridge. Later descriptions used "suspension truss" for the design. The truss includes decorative elements, such as
Doric Doric may refer to: * Doric, of or relating to the Dorians of ancient Greece ** Doric Greek, the dialects of the Dorians * Doric order, a style of ancient Greek architecture * Doric mode, a synonym of Dorian mode * Doric dialect (Scotland) * Doric ...
styled vertical members. The cast iron end towers, which bear transfer the weight of the structure to the abutments and pier, are also detailed. A decorative and protective metal enclosure at the top of the towers was lost to vandalism, but was replaced during the restoration work. Metal strips at each portal read "W. BOLLMAN, PATENTEE", "BALTIMORE, MD.", "BUILT BY B&O R.R. CO.", "1869" AND "RENEWED 1866". Replicas of the original strips were installed during the restoration. The bridge was brightly painted, using red oxide for the towers and the heavier compression members and an ivory color for the lighter tension members. The bridge was originally painted in a three-color scheme, documented in black-and-white photography, with specific shades unknown. Image:ExistingBridgeElevation.jpg, Savage, Md - Existing bridge, 1982 (prior to 1983-84 rehabilitation work by WM&A) Image:ExistingBridgeUpperCords.jpg, Savage, Md - Upper cords of the existing structure, 1982 Image:ExistingBridgeThruView.jpg, Savage, Md - View through the existing bridge, 1982 Image:NewBridgeElevation.jpg, Savage, Md - Elevation of The Bollman Truss following rehabilitation by WM&A, 1984 Image:NewBridgePartialElevation.jpg, Savage, Md - Partial elevation, 1984 Image:NewBridgePier.jpg, Savage, Md - Pier elevation, 1984 Image:NewBridgeLowerCords.jpg, Savage, Md - Lower cords, 1984.


Other Bollman Truss-type bridges

* Built in 1869 in Ilchester, Maryland, for the B & O Railroad to replace the stone Patterson Viaduct which was destroyed by flood in 1868.


See also

*
List of bridges documented by the Historic American Engineering Record in Maryland __NOTOC__ This is a list of bridges documented by the Historic American Engineering Record in the US state of Maryland. Bridges See also * List of bridges on the National Register of Historic Places in Maryland * List of covered bridges in Maryl ...
*
List of Historic Civil Engineering Landmarks __NOTOC__ The following is a list of Historic Civil Engineering Landmarks as designated by the American Society of Civil Engineers since it began the program in 1964. The designation is granted to projects, structures, and sites in the United State ...
*
List of bridges on the National Register of Historic Places in Maryland This is a list of bridges and tunnels on the National Register of Historic Places in the U.S. state of Maryland. References

{{NRHP bridges Bridges on the National Register of Historic Places in Maryland, Lists of bridges on the Nationa ...
*
List of Howard County properties in the Maryland Historical Trust The Maryland Historical Trust serves as the central historic preservation office in Maryland. The properties listed reside within the boundaries of modern Howard County. Prior to 1851, sites would have been part of Anne Arundel County. Sites settle ...
*
List of National Historic Landmarks in Maryland This is a List of National Historic Landmarks in Maryland. There are currently 76 National Historic Landmarks (NHLs) in Maryland. Also included are short lists of former NHLs and of other historic sites of national importance administered by the ...
* National Register of Historic Places listings in Howard County, Maryland


References


External links


Color images of the Bollman Bridge after preservation workNational Historic Landmark informationAmerican Society of Civil Engineers - Bollman Truss Bridge
*

*, including photo in 1985, at Maryland Historical Trust * {{NRHP bridges Baltimore and Ohio Railroad bridges Bridges in Howard County, Maryland Railroad bridges in Maryland Truss bridges in the United States Bridges completed in 1869 Historic Civil Engineering Landmarks Railroad bridges on the National Register of Historic Places in Maryland Railroad-related National Historic Landmarks National Historic Landmarks in Maryland Historic American Engineering Record in Maryland 1852 establishments in Maryland Relocated buildings and structures in Maryland National Register of Historic Places in Howard County, Maryland Wrought iron bridges in the United States Iron bridges in the United States Suspension bridges in Maryland