Bollman Truss Railroad Bridge

Bollman Truss Railroad Bridge

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The Bollman Truss Railroad Bridge at Savage, Maryland
Savage, Maryland
Savage is a historic town located in Howard County, Maryland, about south of Baltimore and north of Washington, D.C. It is situated close to the city of Laurel and to the planned community of Columbia.A rich vein of American industrial history lies in Savage...

 is the sole surviving example of a revolutionary design in the history of American bridge engineering. The 160 feet (48.8 m) double-span truss bridge
Truss bridge
A truss bridge is a bridge composed of connected elements which may be stressed from tension, compression, or sometimes both in response to dynamic loads. Truss bridges are one of the oldest types of modern bridges...

 is one of the oldest standing iron railroad bridges in the United States
United States
The United States of America is a federal constitutional republic comprising fifty states and a federal district...

. It 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
Wendel Bollman 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...

, a self-educated Baltimore engineer.

History


The bridge was built for an unknown location on the main line of the Baltimore and Ohio Railroad
Baltimore and Ohio Railroad
The Baltimore and Ohio Railroad was one of the oldest railroads in the United States and the first common carrier railroad. It came into being mostly because the city of Baltimore wanted to compete with the newly constructed Erie Canal and another canal being proposed by Pennsylvania, which...

 in 1852, and was moved to its present location, spanning the Little Patuxent River
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 passing through Baltimore, and the Patuxent River between...

 on the spur to the Savage Mill
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 District...

, 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.
1970


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
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

 tension members and cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

 compression members. It was an improvement over wooden structures, as the independent structural units lessened the possibility of structural failure. Patented 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 Wells Creek Bridge
Wells Creek Bollman Bridge
The Wills Creek Bollman Bridge originally served the Baltimore and Ohio Railroad's Pittsburgh Division main line.Designed by the renowned self-taught engineer Wendel Bollman in 1871, this truss bridge is the last remaining span of the Pittsburgh Division line associated with Bollman...

 has also survived, but it employs a different type of truss system.

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
Wrought iron
thumb|The [[Eiffel tower]] is constructed from [[puddle iron]], a form of wrought ironWrought iron is an iron alloy with a very low carbon...

 and cast iron
Cast iron
Cast iron is derived from pig iron, and while it usually refers to gray iron, it also identifies a large group of ferrous alloys which solidify with a eutectic. The color of a fractured surface can be used to identify an alloy. White cast iron is named after its white surface when fractured, due...

. The truss configuration is the design patented by Bollman as the "Bollman suspension truss" in 1852. Each span is 79.5 feet (24.2 m) long, 25.5 feet (7.8 m) wide and about 21 feet (6.4 m) 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.

The truss includes decorative elements, such as Doric
Doric order
The Doric order was one of the three orders or organizational systems of ancient Greek or classical architecture; the other two canonical orders were the Ionic and the Corinthian.-History:...

 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.

Restoration


The bridge was restored by Wallace, Montgomery & Associates, LLP for the Howard County
Howard County, Maryland
-2010:Whereas according to the 2010 U.S. Census Bureau:*62.2% White*17.5% Black*0.3% Native American*14.4% Asian*0.0% Native Hawaiian or Pacific Islander*3.6% Two or more races*2.0% Other races*5.8% Hispanic or Latino -2000:...

 Department of Recreation and Parks in 1983, and more recently underwent additional preservation work and was rededicated on September 16, 2000. Today it receives regular maintenance as part of Savage Park. In 1966, under a new program of the American Society of Civil Engineers
American Society of Civil Engineers
The American Society of Civil Engineers is a professional body founded in 1852 to represent members of the civil engineering profession worldwide. It is the oldest national engineering society in the United States. ASCE's vision is to have engineers positioned as global leaders who strive toward...

, it was designated the first ever Historic Civil Engineering Landmark. The bridge was listed on the National Register of Historic Places
National Register of Historic Places
The National Register of Historic Places is the United States government's official list of districts, sites, buildings, structures, and objects deemed worthy of preservation...

 on December 18, 1972, and was designated a National Historic Landmark
National Historic Landmark
A National Historic Landmark is a building, site, structure, object, or district, that is officially recognized by the United States government for its historical significance...

 on February 16, 2000. Nearby Bollman Bridge Elementary School
Bollman Bridge Elementary School
Bollman Bridge Elementary is an elementary school in the Howard County public school system. It hosts the grades first through fifth, along with full-day kindergarten and pre-school. The school opened in 1988 and is named after the Bollman Truss Railroad Bridge in Savage, Maryland. The mascot was...

 takes its name from the historic bridge.







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