Hadley Parabolic Bridge
Encyclopedia
The Hadley Parabolic Bridge, often referred to locally as the Hadley Bow Bridge, carries Corinth
Road (Saratoga County
Route 1) across the Sacandaga River
in Hadley
, New York, United States. It is an iron bridge dating to the late 19th century.
It is the only surviving iron semi-deck lenticular truss bridge in the state, and the only extant of three known to have been built. In 1977 it was listed on the National Register of Historic Places
. Shortly afterwards it was closed to vehicular traffic, and at some time later to pedestrians as well.
The county had considered demolishing it, but held off after heavy lobbying from local preservation groups. In 2006 it was reconstructed and restored with federal and state grants, and reopened without any load restrictions.
opposite the village of Lake Luzerne
, and just south of the central portions of Hadley. It is within the Adirondack Park's Blue Line
. The river flows rapidly through a deep gorge here, with its sides sloping steeply from the road grade. An abandoned rail bridge is just upstream, and an interpretive panel is located near the bridge.
The bridge is supported by two fieldstone
abutment
s and a pier. Its two spans are identical in construction, with one being much longer than the other. The 45 feet (13.7 m) span at the north end is an end-post three-panel pony truss with both cast
and wrought iron
elements. Its upper chord is a rivet
ed steel girder
supported by lattice-braced members riveted to the flange
s of the plate girder. The lower chord consists of two double wrought iron tension bars. The central panel is cross-braced with wrought-iron tie rod
s. All joints, not just in this span but the main one as well, are secured by threaded
iron pins two inches (5 cm) wide capped with hexagonal nuts
.
The longer span, (136 feet (41.5 m)) uses the same materials but is more intricate. It has nine panels, each 15 feet (4.6 m) wide, creating chords which arch both above and below the deck to the point that they are 22 feet 6 inches (6.9 m) apart at their most distant from each other, in mid-span. The upper chord is made of flanged plate girders riveted together with top and bottom iron cap plates bolted on; the lower of double 1¼-by-3-inch (3.1-by-7.6-cm) wrought iron bars. Both are joined at the span's end with end pins. A lattice-braced system similar to that on the short span supports the lenticular truss, with similar members serving as horizontal braces below the deck. Iron tie rods 1¼ inch wide (3.1 cm) serve as diagonal cross-braces on the panels, and there is a horizontal tension rod at each end of the truss. A set of expansion rollers at the west end, intended to provide additional stability, has since corroded due to road salt and rust.
The deck is composed of rough-cut transverse two-by-fours supported by seven 7 inches (17.8 cm) iron stringers on eight 30-by-¼-inch (760 -by-6 mm) transverse iron I-beams. It is surfaced with asphalt
one inch (25 mm) thick.
, who patent
ed it in 1878. He then assigned the patent to the Berlin Iron Bridge Company in Connecticut, where he had gone to work as an agent, and patented an improved design in 1885.
Berlin manufactured hundreds of these bridges throughout the late 19th century, most of which were installed in New York and New England
. In early 1885 the Hadley Town Board authorized the town's highway commissioner to ask bridge companies for bids for the new bridge over the Sacandaga, replacing one which had been built in 1813 (the abutments are from this bridge). By June several bids had been received, and Berlin's was chosen. The bridge was finished in September at a cost of $6,000 ($ in contemporary dollars). Only three lenticular truss bridges were known to have been built in the "semi-deck" configuration, where the deck was midway between the two chords, and supported by the web posts rather than suspended from the lower chord as is more commonly done with truss bridges. It has been described in lay terms as "a self-anchored suspension bridge
."
The reasons for the use of this design at Hadley are not recorded, but it is likely due to a problem with truss bridges which the design and setting could address. The longer the truss bridge, the deeper the truss itself is required to be, often with lateral bracing to prevent buckling. A medium-length span such as Hadley's is particularly problematic because while it may require bracing as well, the clearance below may not be adequate enough for it to be included. In Hadley's case the bridge is high enough that the parabolic trusses may well have been the least expensive solution.
Many of the lenticular trusses were found to be insufficiently stiff despite the lateral bracing, and the design's popularity waned in the early 20th century. Most were later replaced. Hadley's remained, since in 1907 ownership was taken over by the state when the legislature created the county highway system. In 1926, the construction of the Lake Luzerne bridge on what is today NY 9N
created a newer option for long-distance travel through the region, and ownership reverted to the town.
In 1972 the Hadley Bridge, stressed by increased traffic caused by the closure of the Route 9N bridge to Lake Luzerne, was closed for a while so that its structure could be strengthened. The cross braces were supplemented with a series of steel cable braces tightened with turnbuckle
s. The deck support system was changed from timber to iron, and the roadway itself was narrowed by 18 inches (45.7 cm) with a wooden curb so that it would only have enough room for one vehicle at a time, with a speed limit of 10 mph (16 km/h), thereby further reducing loads.
It was restricted to loads of 3 tons (2.7 metric tons) or less afterwards, but it continued to deteriorate. In 1983 it was closed to vehicles, effectively bisecting the Town of Hadley. In 1994 it was surveyed for the Historic American Engineering Record. The town transferred ownership to the county in 1999, and the next year the deck had to be removed as well, closing it even to pedestrians. The county was planning to dismantle the remaining structural components, but delayed that at the request of some local historic preservation
groups.
In 2000 the county's Board of Supervisors
committed up to $350,000 in matching funds
to restore the bridge. Those funds were more than matched with a $1.38 million combined federal and state transportation enhancement grant
the next year. A Mechanicville
company was awarded the contract in 2005 and finished the bridge the next year. It is now open again, without load restriction, as a single-lane bridge.
Corinth, New York
Corinth is the name of three places in the state of New York:*Corinth , New York, a town*Corinth , New York, located in the Town of Corinth...
Road (Saratoga County
Saratoga County, New York
Saratoga County is a county located in the U.S. state of New York. As of the 2010 census, the population was 219,607. It is part of the Albany-Schenectady-Troy Metropolitan Statistical Area. The county seat is Ballston Spa...
Route 1) across the Sacandaga River
Sacandaga River
The Sacandaga River is a river in the northern part of New York in the United States. Its name comes from the Native American Sa-chen-da'-ga, meaning "overflowed lands"....
in Hadley
Hadley, New York
Hadley is a town in Saratoga County, New York, United States. The population was 1,971 at the 2000 census. The town was named after Hadley, Massachusetts.The Town of Hadley is in the northern part of the county and is west of Glens Falls....
, New York, United States. It is an iron bridge dating to the late 19th century.
It is the only surviving iron semi-deck lenticular truss bridge in the state, and the only extant of three known to have been built. In 1977 it 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...
. Shortly afterwards it was closed to vehicular traffic, and at some time later to pedestrians as well.
The county had considered demolishing it, but held off after heavy lobbying from local preservation groups. In 2006 it was reconstructed and restored with federal and state grants, and reopened without any load restrictions.
Structure
The bridge is located just above where the Sacandaga flows into the Hudson RiverHudson River
The Hudson is a river that flows from north to south through eastern New York. The highest official source is at Lake Tear of the Clouds, on the slopes of Mount Marcy in the Adirondack Mountains. The river itself officially begins in Henderson Lake in Newcomb, New York...
opposite the village of Lake Luzerne
Lake Luzerne, New York
Lake Luzerne is a town in southern Warren County, New York, United States. The town is located within the Adirondack Park. The town is part of the Glens Falls Metropolitan Statistical Area. Lake Luzerne is west of the city of Glens Falls. The town population was 3,219 at the 2000 census.- History...
, and just south of the central portions of Hadley. It is within the Adirondack Park's Blue Line
Blue Line (New York State)
The Blue Line is the term used in New York state for the boundaries of the Adirondack and Catskill parks, within which can be found the state's Forest Preserve...
. The river flows rapidly through a deep gorge here, with its sides sloping steeply from the road grade. An abandoned rail bridge is just upstream, and an interpretive panel is located near the bridge.
The bridge is supported by two fieldstone
Fieldstone
Fieldstone is a building construction material. Strictly speaking, it is stone collected from the surface of fields where it occurs naturally...
abutment
Abutment
An abutment is, generally, the point where two structures or objects meet. This word comes from the verb abut, which means adjoin or having common boundary. An abutment is an engineering term that describes a structure located at the ends of a bridge, where the bridge slab adjoins the approaching...
s and a pier. Its two spans are identical in construction, with one being much longer than the other. The 45 feet (13.7 m) span at the north end is an end-post three-panel pony truss with both cast
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...
and 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...
elements. Its upper chord is a rivet
Rivet
A rivet is a permanent mechanical fastener. Before being installed a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite the head is called the buck-tail. On installation the rivet is placed in a punched or pre-drilled hole, and the tail is upset, or bucked A rivet...
ed steel girder
Girder
A girder is a support beam used in construction. Girders often have an I-beam cross section for strength, but may also have a box shape, Z shape or other forms. Girder is the term used to denote the main horizontal support of a structure which supports smaller beams...
supported by lattice-braced members riveted to the flange
Flange
A flange is an external or internal ridge, or rim , for strength, as the flange of an iron beam such as an I-beam or a T-beam; or for attachment to another object, as the flange on the end of a pipe, steam cylinder, etc., or on the lens mount of a camera; or for a flange of a rail car or tram wheel...
s of the plate girder. The lower chord consists of two double wrought iron tension bars. The central panel is cross-braced with wrought-iron tie rod
Tie rod
A tie rod is a slender structural unit used as a tie and capable of carrying tensile loads only.- Subtypes and examples of applications :* In airplane structures, tie rods are sometimes used in the fuselage or wings....
s. All joints, not just in this span but the main one as well, are secured by threaded
Screw thread
A screw thread, often shortened to thread, is a helical structure used to convert between rotational and linear movement or force. A screw thread is a ridge wrapped around a cylinder or cone in the form of a helix, with the former being called a straight thread and the latter called a tapered thread...
iron pins two inches (5 cm) wide capped with hexagonal nuts
Nut (hardware)
A nut is a type of hardware fastener with a threaded hole. Nuts are almost always used opposite a mating bolt to fasten a stack of parts together. The two partners are kept together by a combination of their threads' friction, a slight stretch of the bolt, and compression of the parts...
.
The longer span, (136 feet (41.5 m)) uses the same materials but is more intricate. It has nine panels, each 15 feet (4.6 m) wide, creating chords which arch both above and below the deck to the point that they are 22 feet 6 inches (6.9 m) apart at their most distant from each other, in mid-span. The upper chord is made of flanged plate girders riveted together with top and bottom iron cap plates bolted on; the lower of double 1¼-by-3-inch (3.1-by-7.6-cm) wrought iron bars. Both are joined at the span's end with end pins. A lattice-braced system similar to that on the short span supports the lenticular truss, with similar members serving as horizontal braces below the deck. Iron tie rods 1¼ inch wide (3.1 cm) serve as diagonal cross-braces on the panels, and there is a horizontal tension rod at each end of the truss. A set of expansion rollers at the west end, intended to provide additional stability, has since corroded due to road salt and rust.
The deck is composed of rough-cut transverse two-by-fours supported by seven 7 inches (17.8 cm) iron stringers on eight 30-by-¼-inch (760 -by-6 mm) transverse iron I-beams. It is surfaced with asphalt
Asphalt
Asphalt or , also known as bitumen, is a sticky, black and highly viscous liquid or semi-solid that is present in most crude petroleums and in some natural deposits, it is a substance classed as a pitch...
one inch (25 mm) thick.
History
The lenticular truss bridge design was developed by engineer William O. Douglas of BinghamtonBinghamton, New York
Binghamton is a city in the Southern Tier of New York in the United States. It is near the Pennsylvania border, in a bowl-shaped valley at the confluence of the Susquehanna and Chenango Rivers...
, who patent
Patent
A patent is a form of intellectual property. It consists of a set of exclusive rights granted by a sovereign state to an inventor or their assignee for a limited period of time in exchange for the public disclosure of an invention....
ed it in 1878. He then assigned the patent to the Berlin Iron Bridge Company in Connecticut, where he had gone to work as an agent, and patented an improved design in 1885.
Berlin manufactured hundreds of these bridges throughout the late 19th century, most of which were installed in New York and New England
New England
New England is a region in the northeastern corner of the United States consisting of the six states of Maine, New Hampshire, Vermont, Massachusetts, Rhode Island, and Connecticut...
. In early 1885 the Hadley Town Board authorized the town's highway commissioner to ask bridge companies for bids for the new bridge over the Sacandaga, replacing one which had been built in 1813 (the abutments are from this bridge). By June several bids had been received, and Berlin's was chosen. The bridge was finished in September at a cost of $6,000 ($ in contemporary dollars). Only three lenticular truss bridges were known to have been built in the "semi-deck" configuration, where the deck was midway between the two chords, and supported by the web posts rather than suspended from the lower chord as is more commonly done with truss bridges. It has been described in lay terms as "a self-anchored suspension bridge
Suspension bridge
A suspension bridge is a type of bridge in which the deck is hung below suspension cables on vertical suspenders. Outside Tibet and Bhutan, where the first examples of this type of bridge were built in the 15th century, this type of bridge dates from the early 19th century...
."
The reasons for the use of this design at Hadley are not recorded, but it is likely due to a problem with truss bridges which the design and setting could address. The longer the truss bridge, the deeper the truss itself is required to be, often with lateral bracing to prevent buckling. A medium-length span such as Hadley's is particularly problematic because while it may require bracing as well, the clearance below may not be adequate enough for it to be included. In Hadley's case the bridge is high enough that the parabolic trusses may well have been the least expensive solution.
Many of the lenticular trusses were found to be insufficiently stiff despite the lateral bracing, and the design's popularity waned in the early 20th century. Most were later replaced. Hadley's remained, since in 1907 ownership was taken over by the state when the legislature created the county highway system. In 1926, the construction of the Lake Luzerne bridge on what is today NY 9N
New York State Route 9N
New York State Route 9N is a north–south state highway in northeastern New York, United States. It extends from an intersection with U.S. Route 9 , NY 29, and NY 50 in the city of Saratoga Springs to a junction with US 9 and NY 22 in the Clinton County village of...
created a newer option for long-distance travel through the region, and ownership reverted to the town.
In 1972 the Hadley Bridge, stressed by increased traffic caused by the closure of the Route 9N bridge to Lake Luzerne, was closed for a while so that its structure could be strengthened. The cross braces were supplemented with a series of steel cable braces tightened with turnbuckle
Turnbuckle
A turnbuckle, stretching screw or bottlescrew is a device for adjusting the tension or length of ropes, cables, tie rods, and other tensioning systems. It normally consists of two threaded eyelets, one screwed into each end of a small metal frame, one with a left-hand thread and the other with a...
s. The deck support system was changed from timber to iron, and the roadway itself was narrowed by 18 inches (45.7 cm) with a wooden curb so that it would only have enough room for one vehicle at a time, with a speed limit of 10 mph (16 km/h), thereby further reducing loads.
It was restricted to loads of 3 tons (2.7 metric tons) or less afterwards, but it continued to deteriorate. In 1983 it was closed to vehicles, effectively bisecting the Town of Hadley. In 1994 it was surveyed for the Historic American Engineering Record. The town transferred ownership to the county in 1999, and the next year the deck had to be removed as well, closing it even to pedestrians. The county was planning to dismantle the remaining structural components, but delayed that at the request of some local historic preservation
Historic preservation
Historic preservation is an endeavor that seeks to preserve, conserve and protect buildings, objects, landscapes or other artifacts of historical significance...
groups.
In 2000 the county's Board of Supervisors
Town supervisor
Town Supervisor is an elective legislative position in New York towns. Supervisors sit on the town board, where they preside over town board meetings and vote on all matters with no more legal weight than that of any other board member .Towns may adopt local laws that allow them to provide for an...
committed up to $350,000 in matching funds
Matching funds
Matching funds, a term used to describe the requirement or condition that a generally minimal amount of money or services-in-kind originate from the beneficiaries of financial amounts, usually for a purpose of charitable or public good.-Charitable causes:...
to restore the bridge. Those funds were more than matched with a $1.38 million combined federal and state transportation enhancement grant
Grant (money)
Grants are funds disbursed by one party , often a Government Department, Corporation, Foundation or Trust, to a recipient, often a nonprofit entity, educational institution, business or an individual. In order to receive a grant, some form of "Grant Writing" often referred to as either a proposal...
the next year. A Mechanicville
Mechanicville, New York
Mechanicville is a city in Saratoga County, New York, United States. The population is 5,196 as of the 2010 census. It is the smallest city by area in the state. The name is derived from the occupations of early residents....
company was awarded the contract in 2005 and finished the bridge the next year. It is now open again, without load restriction, as a single-lane bridge.
See also
- List of bridges on the National Register of Historic Places in New York
- National Register of Historic Places listings in Saratoga County, New York
External links
- Old Corinth Road Bridge at Historic American Engineering Record.