Old wooden covered bridges in the Northeast states of America are a remarkable example of the 19th century engineering. Blenheim Bridge over Schoharie Creek in the New York state had been considered one of the longest clear span wooden bridges in the world until the August 28, 2011, when it was washed out by a disastrous flood, caused by the Hurricane Irene. Current research paper investigates the historic and engineering aspects of the Blenheim Bridge construction and suggests the possible ways of its renovation. The problem remains urgent for Blenheim people and all those who are concerned with historical landmarks of America.
Covered Bridges in North America
Covered wooden bridges present an example of the nineteenth century engineering art. The idea of covered bridges originates from Europe, presumably, Switzerland, (Comwill 9). First covered bridges appeared there in the late Middle Ages period. Building of such structures was rational in the areas where timber was easy to procure. Structurally covered bridge is a combination of wooden arches and trusses or just arches. Inner beams made of timber let the construction span a long way between two supports. The number of spans can vary, but the history records prove examples of building long single span covered bridges, which is conditioned by truss engineering possibilities.
The first American covered bridges appeared at the beginning of the nineteenth century and served as important routes and roads in urban districts. Then people started building covered bridges in rural areas and by the times of the Civil War they were a common feature of the North American landscape. Beginning of the twentieth century is marked as the era of steel bridges while the old wooden structures seemed to be old-fashioned obstacles on the way of progress. Today, covered wooden bridges are mostly associated with America’s rural past. They look like old barns over the quick waters of North American rivers and creeks.
Those, who are interested in history, can still find old covered bridges in on the territories of the Northeastern States and in Canada. According to a research, (Conwill, 6), approximately 750 covered bridges still exist in the lands of Pennsylvania, Ohio, Vermont, Indiana, Oregon and New Hampshire. About 150 covered bridges are located on the territory of Canada. Wooden covered bridges are still a peculiar attraction for historians and a tourist destination for travelers.
As the territory was covered with forests, timber was the most appropriate material to use for building purposes. It was cheap and abundant to be used in large amounts for creation of new engineering constructions.
Why did the builders choose covered rather than bridges without roof? The answer lies in weather peculiarities and conditions of the region. Regular rains and severe frosty winters stipulated the necessity to protect wooden surface from wet and moisture. The cover sheltered the tracking surface and prevented it from quick rotting. There still remain a lot of decently preserved examples which prove efficiency of the idea.
The problem of the covered bridges preservation remains urgent with the course of time. Since 1960’s authorities have supported any measures, which might prolong the actual existence of theses historic relics. No one dares to suggest the question of their replacement. Though different measures are taken to protect these structures from destruction, every year some of them are lost in natural disasters, overloading or inappropriate maintenance. Nothing can last forever with this notion being especially true for old wooden bridges. State and local authorities take part in protection and promotion of these old relics. Nevertheless, the twenty first century climate changes and natural disasters have turned out to be too merciless to vulnerable wooden structures. A remarkable example of the nineteenth century engineering, the Blenheim Bridge in New York State, was lost during the Hurricane Irene in 2011.
Description of The Blenheim Bridge
The Blenheim Bridge was constructed out of necessity to cross the Schoharie Creek in North Blenheim, New York. It was a double-barrel covered bridge made of local types of wood. White pine was used for the main framing white oak became the material for splice, pre-stressing wedges and shear blocks. Cast iron and wrought iron was used for making tie rods, bolts and washers.
As it has been mentioned above the amount of a cover bridge spans can vary. The Blenheim Bridge was unique and precious as the longest survived single-span bridge. Its total length was 232 feet and the length of the open span was 210 feet. (Bennett, 2022). The height of the construction from the deck up to the highest point of the arch measured 24 feet. The total width of the bridge was 26’-3 feet with width of every of the two barrels of approximately 10’-2 feet between the trusses. (Bennett 4).
The trusses were designed in accordance with the engineering drafts of Col. Stephen Harriman Long , who patented the idea in 1830. Four parallel lines of timber planks made up the upper chord to which splices were bolted at the end and mid points. The lower chord presented the same four planks joint. Paired timber braces and single counter braces were adjusted to the posts. The lower chord fastened the posts with large steel bolts ¾” in diameter. Timber wedges were used for connection of the bottom of counter braces to the posts. According to Colonel Long’s patent, the wedges were necessary to prestress the truss during the construction process (Bennett 4).
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The arch of Blenheim Bridge was made of three wooden plys measuring 9 ½ *10 ½ each.. The height of the arch was about 30 feet to the top ridge and the length was 210 feet. The arch was made from different types of timber: spruce and white oak.
Beams measuring 4 ½ *10 feet, which rested on the lower chord were used for the floor of the construction. The beams also served as a support to the deck. Tie rods fastened each panel point; lateral bracing was used to fix the lower chord. The upper chord was notched and bolted with tie beams in the similar way. Sway braces connected the tie beams and posts in the upper lateral bracing. The rafters rose up diagonally to the top of the roof. The outer surface was covered with galvanized steel, which was fastened to purlins on the top of the arch.
Outer board and batten siding planks, measuring 1*12 feet, covered the bridge walls down to approximately 2 feet below the chord. Wooden nails fastened the sheathing to the truss on the outer surface. The entrances were corbelled and had peaked openings of a triangular shape (Bennett 5).
Artificially cut stones with mortared joints were used as abutments for the bridge. The lower chords of the bridge were set into a concrete cap on the top of walls abutment. The eastern end of the bridge was closed after the bridge stopped functioning. Since 1932, the Blenheim Bridge retired and served as a holiday and tourist destination. A small picnic area was arranged near the western end of the bridge.
History of Creation
As Richard Sanders Allen states in his book “Covered bridges of the Northeast”, Theodore Burr was the pioneer of bridge building in New York, (Allen). He built his first arch-truss bridge across Hudson in Waterford in 1804. The first covered bridge appeared in 1807 in Bridgeville, New York. Maj.Salmon Weat led the project of an arched double-barrel structure with a span of 160 feet. Four years later Burr built a covered bridge with three wooden arches in Esperance, Schoharie County. Those examples could influence the design and construction of the Blenheim Bridge, whose unique peculiarity lies rather in the length of its single span than in its design.
The total amount of covered bridges, built on the New York State territory is over 250 (Conwill, 2004). In the middle of the twentieth century, only forty six of them remained. Nowadays, most of the preserved bridges are located around the Catskills and their total amount is less than thirty constructions. The building binge of covered bridges dates back to the period from 1850 to 1880. The Blenheim Bridge represented a unique example of a covered bridge with secondary arch.
Another name of North Blenheim, the place of location of the Blenheim Bridge is Patchin Hollow. The settlement was located on the western side of the Schoharie Creek and was divided by a steep hill.
In 1828, the New York state authorities passed the Act which incorporated establishment of the Blenheim Bridge Company. Nevertheless, the building did not start until 1854.
In 1850, a tannery appeared in the area, and the owner Maj. Hezekiah Dickerman raised the question of building again. Hemlock bark was used in the production process. The trees grew on the other side of the creek only, so the necessity of the bridge became commercially stipulated. After being elected to the town board of Supervisors in 1854, Mr. Dickerman led the project of building a new bridge. (Bennett).
In 1854, a prominent architect of that time, Nicholas Powers, was invited to complete the job. The engineer was engaged in repairing another covered bridge. Hence, the local authorities offered him to lead the build of a new bridge in North Blenheim. With Nicholas Power at the head, Blenheim Bridge Company managed to create a long trussed span with an arch within one year period. The new double barrel bridge was finished in 1855. Nickolas Powers was paid two thousand dollars for his work and the workers’ daily salary amounted one dollar. The total cost of the project is estimated to be $ 6,000.
Concerns were voiced that the Blenheim Bridge might ruin when the building works would be removed. Powers was so sure of his calculations that on the opening day climbed the roof of the bridge and ordered to take off the building works. He said: “If the bridge goes down, I never want to see the sunrise again!” (Bennett 7). There were assumptions that the bridge might sag and become inappropriate for loading transportation over the river. Nevertheless all anticipations were dissolved, when after removal of the building works the bridge sagged even less than Power’s calculations supposed.
The bridge was opened and functioned as a privately-owned structure, and a toll was taken for its crossing. A toll-keeper lived not far from the bridge and took charge of 1 cent from a foot passer and 12 cents from a group. In 1860, Mr. Dickerman purchased the bridge as the Blenheim Bridge Company went into liquidation. He passed the ownership on the bridge to his daughter, Mrs. Charles Waite. Moses Hubert bought the bridge for $2,000 in 1871. After the rent expired, in 1891, the Blenheim Bridge came to be in the possession of the State of New York. In 1930, numerous programs of replacement of old wooden bridges due to their shabby conditions and danger of exploitation were introduced. There was a plan to build a new steel bridge on the place, but in 1931, the County Board of Supervisors voted to preserve the span as a historic relic. The county received the ownership on the Blenheim Bridge.
In 1932, Blenheim Bridge was closed for crossing and the approach span from the western side was removed. In 1964, the bridge was designated as a National Historic Landmark and in 1984 it was proclaimed a National Historic Civil Engineering Landmark. Though a lot of effort was put by the authorities to preserve and save Blenheim Bridge it could not survive the natural disasters of the twenty first century and the tropical storm Irene removed and destroyed it completely (Bennett).
The usual width of the Schoharie Creek is no more than 100 feet, but it can extend widely from abutment to abutment when rains come. A spring flood of 1869 washed out a channel from the east and caused the necessity to add a wooden approach span. In 1894, an iron approach was built as the wooden one had been destroyed under the weight of passing transport.
As the time is merciless to wooden constructions they need to be constantly maintained. In 1973, some extensive repairs were made to The Blenheim Bridge by Milton Graton. The renovation cost $2,920. Graton noted that the bridge was “was suffering from ‘Covered Bridge Arthritis’ at all bearing areas” (Graton 129) The bridge was resheathed and new thrust blocks of the arch were constructed.
The Blenheim Bridge managed to survive many threats such as fires, strikes of lightning and flash floods. Notwithstanding large expenses, necessary for the Blenheim Bridge maintenance, people and authorities of Schoharie County were very proud and fond of the construction. They observed all its milestone anniversaries and promoted it as a popular tourist destination. The authorities of the county received many propositions to sell the bridge. For example, Franklin B. Resseguie, who wanted to move the bridge to Hiawatha Island, where he was going to open an exhibition. He believed the bridge would become more accessible to visitors. (Cornell). The Schoharie County authorities responded that the bridge was not for sale at any price. (Dayton)
Nicholas Montgomery Powers of Clarendon was a well-known covered bridges builder in Vermont. He was born in 1817 in Pittsford, but studied and lived all his life in Clarendon. He built his first covered bridge at the age of twenty over Furnace Brook at Pittsford Mills. It was a Town lattice truss span. His father had to sign the contract instead of the young engineer because he could not do it himself legally. The project was a success and the bridge functioned for nearly a century until 1931. Powers was engaged in covered bridges building between 1840 and 1880, when that type of bridge construction developed and flourished. Many of his bridges remained in Vermont, but until 1850, he carried out orders from other states. His most prominent bridges were built outside Vermont. Besides the Blenheim Bridge in New York, Powers constructed a huge railroad bridge at Perryville, Maryland in 1866.
Powers possessed unusual mathematical talent to make calculations without noting them down. It might be surprising to learn that he did not have appropriate education, just a strong desire to build very good bridges. His favored truss choice in covered bridges building was the Town lattice. The Blenheim Bridge was a modified Long truss and proved Powers aptitude to experimenting with new designs and models.
Additionally to covered bridges building, Powers owned a large farm and a cheese factory. He tried himself in railroad engineering and other spheres of industrial design, but did not achieve any considerable success. He died in 1897 and was buried in Vermont.
Another person, who can be associated with the Blenheim Bridge building, is Col. Stephen Harriman Long, the long truss designer. He was born in 1784 in New Hampshire and became interested in bridge building and construction since 1827. In that period, he was assigned as a consulting engineer for the Baltimore and Ohio Railroad. Long studied at Dartmouth College and was a teacher at West Point. In 1814, he became an army engineer and since 1816 he investigated numerous sites for canals up the Mississippi River and headed topographic expeditions in the West.
Long was an experienced researcher, and in 1830, he patented wooden truss bridge construction with vertical tension members and diagonal compression members. Then he obtained a patent for variations of this design in 1836 and 1839. That was the first truss type, where exact mathematical calculation of members tension was used for covered bridge construction. Before creation of the long truss engineers used the empirical method, and this type was the first which was scientifically designed. Long used the French scientist Navier speculations and managed to determine the required chord areas in the truss.
The Blenheim Bridge was a unique example of bridge engineering due to its impressive dimensions. It has lasted for more than a century and a half. What stipulated its relative longevity remains a secret. It may be a merit of Power’s talented calculations, or the effectiveness of the Long truss or just the luck and fate.
The bridge transferred the unusual atmosphere of America’s rural past and was closely associated with North Blenheim history. The fact, that Hurricane Irene has destroyed it completely can be considered as a personal loss for all the Schoharie County residents. It might be useless to make its copy by means of modern materials and high-tech technologies. The peculiarity of such relics as the Blenheim Bridge is their shabbiness, spirit and beauty of the past, which is impossible to restore. The best way to prolong the memory of the Blenheim Bridge unique construction is to create a memorable historic space. It might be an open-air pavilion near easterly approach, which would remind the former bridge in shape and proportions, but be less in dimensions.
People, who have some special memories with the bridge might share them at the inside planks and surfaces of the pavilion. As the place has been special for Schoharie County people for such a long period and attracted tourists from different parts of America, some thematic restaurant in Rural American Style might be a sensible idea. It would maintain the nearby territory and the pavilion and might create the atmosphere of casualness so important for meaningful communication. Moreover, no one can guarantee that new hurricanes would be less devastating than the
Another possibility of restoration of the old bridge image is by means of state-of-the-art computer technologies which allow the creation of spaces in 3D format. Some of the bridges anniversaries may be commemorated by a competition of such projects, very popular among the younger generation.
All the remains of the old bridge, found after the hurricane, should be preserved and maintained as long as possible at the favorable conditions for wood safety. Such objects bear unique spirit for people, who love, remember and keep the old bridge in their memories. Such recollections are too valuable to be cherished and preserved. Therefore, it is necessary to make everything possible to disclose the spirit of the past of the Blenheim Bridge .
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