Abstract
The Blenheim Bridge was constructed after the ratification of legislation in New York, which sought to incorporate the Blenheim Bridge Company.
It was constructed under the architectural leadership of Nicholas Powers, who repaired a covered bridge at Schoharie before being asked to build a bridge with a covered design in North Blenheim in 1854. After accepting the contract, the construction of Blenheim Bridge was completed in the year 1855. However, it was destroyed in August 2011 following floods, which were caused by Tropical Storm Irene.
Blenheim Bridge
Located in Blenheim, New York, the Blenheim Bridge was recognized as the longest bridge, made of wood in the United States. The bridge was 228 feet, and was designed and constructed by use of long trusses and an arch, for support. One hundred and one years after the bridge was constructed, the authorities listed Blenheim in the National Register of Historic Places (HAER NY 5).
The seventy one meters long bridge spanned Schoharie Creek in the northern region of th`e New York City. According to historic records, it was the second longest wooden covered bridge in the world, being listed after the famous Bridgeport Covered Bridge.
Besides its length, Blenheim Bridge was one of the oldest wooden bridges in the United States. As mentioned above, Nicholas Powers is highly credited as the chief architect of the bridge. He was welcomed from Vermont to work on the project by an association of businessmen, who were members of the Blenheim Bridge Company.
The bridge remained actively in use until the year 1932, when a steel truss was erected near the bridge to ease traffic. Since that year, the bridge was considered and maintained as a national historic site, and was officially recognized as a National Historic Landmark in the year 1964 (HAER NY 5).
Site History
The history of the Blenheim Bridge dates back in the late 19th century, during the time of Gen. Freegift Patchin. During his time, he constructed a gristmill near the site of the bridge, before establishing the famous hamlet of Patchin Hollow, which is currently known as the North Blenheim. In the year 1875, North Blenheim was given a special description from Hamilton Child (HAER NY 7).
North Blenheim is also known as Patchin Hollow, and it is located on the Western side of Schoharie Creek, near Westkill. Importantly, the site is partitioned by a steep hill, which approaches the creek, leaving a narrow space to allow the passage of a road. Additionally, the site has several social buildings including churches, hotels, schools, stores, wagon shops, blacksmith shops, tailoring shops, saw mills and about fifty households (HAER NY 8).
Furthermore, the site has waster power, which was never improved throughout the history of the site. There is also a steam sash and a factory in the vicinity of the site. Another important fact is that the Blenheim Bridge Company was incorporated in the year 1828 by the New York State legislature, even though no bridge was built for almost thirty years.
In 1850, Major Hezekiah Dickerman from Connecticut visited the place and initiated the construction of a tannery on Schoharie Creek. Moreover, the hemlock back, which was used for tannin was found on the other side of the creek, which prompted Mr. Dickerman to push for the construction of the Bridge in 1854.
It is believed that his influence was quite significance since he had been appointment to the Board of Supervisors and was a shareholder in the construction company, which had been incorporated by the legislature in 1832. For a very long time, the bridge was mainly used for pedestrian traffic of visitors who were willing to enter from the eastern side of the bride, before it was replaced with a concrete and steel bridge (HAER NY 8). The image below shows the site of the bridge:
Construction of the Blenheim Bridge
Nicholas Powers, the man who is credited for the design of the longest wooden bridge in the world went to Schoharie in New York to carry out some repair on a wooden bridge before he was asked to construct a wooden bridge in North Blenheim. He was invited by one of the directors, George Martin.
It is believed that Nicholas was selected to work on the project based on his architectural experience. In addition, the bridge was built “piece by piece back of the current village in North Blenheim” (HAER NY 8). This allowed the masons to work on the stone abutments as the carpenters perfected on wood work. After the two groups had worked on their assignments, the bridge was disassembled and re-erected across the river.
Construction Materials
In terms of the materials, which were used in the construction of the bridge, a total of ninety-four thousand board feet of lumber was used. This was equivalent to one hundred and twenty seven tons. In addition, three thousand six hundred pounds of bolts were used during the construction.
Since it was to be a wooden bridge, joinery was quite significant and this was facilitated by the use of bolts. For effective joinery, one thousand five hundred pounds of washers were also used during the entire construction process. In terms of payment, Nicholas Powers was paid $7.00 a day, totaling to $2000. On the other hand, workmen received $ 1.00 a day. The construction work of the Blenheim Bridge came to completion in the year 1855 at a total cost of $ 6,000 (HAER NY 9).
Repair and maintenance
Since its construction in 1855, the Blenheim Bridge underwent a series of repairs and renovations, which were necessary in making it more functional and safe for usage by pedestrians. For instance, a wooden approach span was constructed in 1869, following the washing away of a channel on the eastern side of the bridge.
Moreover, the management of the bridge experienced another blow when the second approach span collapsed as a result of a threshing machine in 1891 (HAER NY 9). After several deliberations and consultations with the board, the construction of a better iron approach span was approved to solve the problem, which was becoming a thorn in the flesh of leaders.
After the construction of the iron approach span, the bridge was to serve its purpose without any hitch. However, there was a major repair, which was carried out in 1973 at a total cost of $2,920 (HAER NY 5). This renovation project was led by Milton Graton of Ashland, who was highly reputed for his experience in the construction of covered bridges in New York. According to Milton, the bridge was in urgent need, describing its status as “Covered Bridge Arthritis” at all its bearing points.
Due to the fact that timber was rotting, the bridge had settled at the westerly end and was becoming a security threat to its users. To reinforce the bridge, there was need to place concrete slabs below the lower chords to the first vertical posts. In addition, three feet of the end of the arch were chopped off before they were replaced with new thrust blocks to provide stability to the ailing bridge. Besides these, Milton recommended that the bridge be re-sheathed.
Before it was destroyed by Tropical Storm Irene in 2011, the Blenheim Bridge had experienced a wide range of disasters including lightning, flash floods and being set of fire three times. Despite the fact that repair and maintenance of the bridge always had significant cost implications, most people within its vicinity were extremely fond of it (HAER NY 9).
As a way of nurturing and promoting its history, the people commemorated several anniversaries of the structure and used it to augment the tourism industry of the region. Due to its popularity and history, there have been individuals expressing their willingness to purchase the bridge, the latest being witnessed in 1970 by Franklin Resseguie, who was an attorney in Binghamton.
This decision came about when he was in the process of establishing an exhibit on Hiawatha Island felt that the structure was to be more accessible to most of his visitors. However, his request was not accepted as the Schoharie County Board of Supervisors affirmed that the bridge was not to be sold out at any given price. As mentioned earlier, the bridge was recognized as a National Historic Civil Engineering Landmark in 1974. It was also rehabilitated in the year 1997 (HAER NY 10).
Ownership of the Bridge
For several years, it was noted that a toll keeper lived in a small house that was adjacent to the bridge. The rates of the toll were footmen and teams. After the disbandment of the Blenheim Bridge Company in 1860s, the span was purchased by Mr. Dickerman who later presented it to his daughter, Mrs. Charles Waite. The tolls were collected at the bridge once a year by Waite’s grandson. Similarly, the bridge was purchased by Moses Hubert, who parted with $ 2,000.
However, the bridge was put under the jurisdiction of the State of New York after the charter of Moses expired. In 1930, the County Board of Supervisors was petitioned by residents after it attempted to demolish the bridge and replace it with a better span (HAER NY 9). In 1931, the plea of residents was honored after the board ratified the retention of the structure and transferred its ownership to the County administration and recognized it as a historic relic.
Bridge design
Before it was destroyed late last year, the Blenheim Bridge was an ideal feat for wooden structural engineering in the United States and around the world. Its two hundred feet length put it second on the world list of wooden bridges. It was mainly made of virgin pine, also referred to as the mighty arch of the oak.
Its single center arch was regarded to be its main feature, upon which the bridge rested its weight (Dillon 2). It was a major source of strength for the bridge as it offered full support. The arch stretched in a three-rib section that was attached to the abutments, extending to the ridge pole that was located at the middle of the bridge. This pattern was repeated towards the back to enhance maximum reinforcement.
Trusses were also major features of the bridge. The three trusses were designed to offer support to the bridge. The largest truss was placed at the center of the arch, while the other two were placed twenty seven feet apart.
This design divided the bridge into two major lanes, making it referred to as double-barrel or double-tunnel bridge. The trusses were designed and patented in the year 1830 by Colonel Stephen Long. They mainly took the “X” shape. Long hailed from Hopkinton New Hampshire and was born in 1784 (Dillon 3). He later attended Dartmouth College, before tutoring mathematics in West Point.
The climax of his engineering career was attained after becoming a U.S. army engineer in 1814. During this time, he was involved in numerous surveys that were meant to help the U.S. Army Topographical Engineers. He offered consultancy services during the construction of the Baltimore and Ohio Railroad. He later developed interest in design and construction of bridges (HAER NY 11).
The Long truss was recognized as the first bridge truss to be designed since he had used mathematical formulation during its design, unlike the previous bridge trusses, which had been designed empirically. By using continuous framing over the piers, Long became a forerunner of iron panel-trusses. Blenheim Bridge remained consistent with the patent’s requirements.
However, it was noted that the counterbrace wedges appeared at the bottom instead of being at the top. Nevertheless, many truss bridges were constructed in the 19th century even though most of the trusses appeared to be paired on both sides (Dillon 3). The uniqueness of the Blenheim Bridge was that it was not only built with a single arch, but also followed the traditional technology of construction, which had been used during the construction of bridges until mid 19th century.
The 200’ long span gave the bridge a distinction of being recognized as one of the longest wooden bridges in the world. It is however important to mention that several bridges were in existence at the time when the North Blenheim Bridge was constructed. One of these bridges with a long clear span was the Burr arch-trusses. Additionally, McCall’s Ferry Bridge was recognized as the only covered bridge, which had the longest single span in Pennsylvania.
The bridge was built in 1815 by Theodore Burr and its clear span was 360’. Although this magnificent bridge was destroyed by ice, three years after its completion, other covered bridges with arch-spans were later constructed. It is therefore believed that Nicholas Powers based his design at North Blenheim on these early bridges (HAER NY 11). The image below shows Blenheim Bridge:
Description
The total length of the Blenheim Bridge was 232’-0” with a clear span of 210’. In terms of height, the bridge was 24’ high from the deck to its roof. In addition, it had a width of 26’-3” with every roadway measuring 10’-2” between the trusses, which lied on the sides of the arch.
Based on the measurements, which were taken in 1936 by the Historic American Building Survey, the framing timber that was used was from local white pine while the shear blocks, splices and prestressing wedges were mainly from the local white oak (HAER NY 6). On the other hand, the bolts and the tie roads were wrought iron while the washers were mainly made of cast iron.
As designed by Colonel Stephen Long in 1830, the truss had four upper parallel lines of planks together with wooden fish splices. These splices were bolted at each panel point and mid panel-point. On the other hand, the lower chord was made of four parallel lines of planks, which had fish splices in the same manner as those for the upper chord.
There were also posts of paired timber measuring approximately 7×7”, forming a total of twenty two panels, which were spaced at 10’-0” on the center. The main purpose of these chords was to permit the connection between the upper and the lower chords. Additionally, the bridge had braces of paired timber, measuring approximately 5×8 and unpaired counter braces, which were approximated to be 4.5×8”, existing between the posts (HAER NY 6).
With regard to the measurements of the posts, it is worth noting that the dimensions of braces and posts decreased in size, starting from the end of the trusses towards the center of the designed span. This was strategically designed in order to take into consideration the force exerted by different forces. As a result, this neutralized individual stresses, thus contributing to the formation of an effective and stable structure.
In connecting the posts, they were passed through the lower chord after which they were set into notches. After this arrangement, they were fastened using bolts of approximately 0.75” in diameter. Additionally, the counter diagonals were notched into the lower and upper plys of the arch.
In order to realize stronger joints, there were wooden wedges placed in the joints between the posts and the bottom side of the counterbraces (HAER NY 6). The main function of the wedges as prescribed by Stephen Long was to prestress the truss during construction.
It is worth noting that the massive arch was designed to appear in the same plane with the counterbraces of the truss, which was located at the center of the bridge. It was mainly made of three plys of wood, which measured 9.5×10.5” and were separated by use of spacer blocks. Moreover, the timbers attached on each ply were spliced together, while the three plys were fastened at the bridge braces and the support posts.
On the hand, the arch of the bridge sprung from skewbacks placed at angles on the abutments. Of importance is the fact that these skewbacks were made of stone before they were replaced with concrete. These allowed it to rise 30’ to the ridge, spanning 210’ (HAER NY 6). During a major repair that was done by Milton Graton in 1973, he revealed that the arch was made of different types of wood. Graton said that the designer had used spruce arch timber and the white oak in order to promote effective reinforcement to the structure.
Another important feature of the North Blenheim Bridge, which requires description, is the floor. The floor of the bridge was covered with wooden floor beams, measuring 4.5Ă—10. These beams firmly rested on the lower chord of the bridge, forming part of the floor system (HAER NY 6).
The main reason why Nicholas Powers included the beams in his design was to support the wooden plank deck. Furthermore, the design allowed the lower lateral bracing to be jointed between the lower chords. Additionally, tie rods were added at the end of each panel point to allow complete reinforcement. The image below shows a complete view of the bridge:
Retrieved from: https://en.wikipedia.org/wiki/File:Old_Blenheim_Bridge_Alternate_11Mar2008.jpg
If it were built today
There is no doubt that if the North Blenheim Bridge was to be constructed in the year 2012, it would present a different structure all together. This is mainly due to a wide range of factors including but not limited to change in technology and availability of several building materials (Tang 46). For instance, while the Blenheim Bridge was mainly constructed using wood, modern bridges are steel-made, due to the existing high demand and usage of steel around the globe.
Since the introduction of steel as a core construction material, there has been significance transition in bridge technology. For instance, current bridges are constructed using steel plates as girders, steel bars for concrete reinforcement, steel cold for cables and steel wires prestressing (Tang 57). In addition, due to the introduction of new technology, construction has become expensive.
Conclusion
From the above descriptive analysis of the Blenheim Bridge, it is evident that its history remains magnificent in wood technology. The architectural design of Nicholas Powers remains outstanding even in the 21st century. Despite the fact that the bridge was destroyed in August 2011, it influenced many structural engineers in exploring wood technology. This will equally inspire generations especially in the same field.
Works Cited
Dillon, James 1983, Old Blenheim Bridge. Web.
HAER NY 2006, Historic American Buildings Survey/Historic American Engineering Record. Web.
Tang, Man-Chung 2008, Evolution of Bridge Technology. Web.