User:Erhoads1/sandbox
Introduction[edit]
Wooden covered bridges were once a large part of our nation's culture and infrastructure. They used cheap and accessible materials, as well as furniture joints to connect the beams. These joints were used because the people knew how to make them, and make them well.
Structural Description[edit]
Bartram's Covered Bridge is located in Newtown Square, PA. [1]The bridge was built in 1860 by Ferdinand Wood, but was named after Mordecai Bartram.[1] It is 80 feet long, and 13 feet wide.[1] It was created to be as "Hi and Wide as a Load of Hay"[1] to fit the agricultural needs of the area at the time. It uses a Burr Truss design.
Economic impact[edit]
This bridge is extremely economical because the cost was shared over two townships, and the material was cheap, and construction was quick. The choice of wood is very wise given the time and the cost of the material. The region has abundant trees, including many hardwoods such as beech trees which further lowered costs, since the materials were local. The bridge was constructed in 1860 when most structures were made from either wood or stone. Wood is by far the cheaper of the materials, and when joined correctly, it can hold tensile forces. Since wood can support tension and bending loads, the bridge could be built at the level of the banks, instead of building a stone arch beneath the deck of the bridge. Additionally, it is much faster to construct a wooden structure than a stone one. Overall, the bridge cost just $1,133 and to date, has only been repaired a few times. The economic impact was not just immediate; currently, the bridge is a historic landmark and helps fund the Historical Society of Newtown Square.
Efficiency[edit]
Bartram’s bridge is an efficient solution to the many streams that cross the region. It was created “Hi and Wide as a Load of Hay”[1] to service the needs at the time which were mainly agricultural. Its size allowed it to continue to be used until 1941, when it was closed to the public. The choice of the extremely efficient Burr Truss allowed the bridge to have outstanding stiffness and stability with both live and dead loads. The bridge had to hold its own gravity load, the live loads of the horses and the carriages, and any wind loads. The gravity load is easily supported by the arch alone, and the combination of the arch and truss give exceptional stiffness for the live loads. Combination of the truss and arch also allows more of the members to remain in compression which uses the joints to their full effectiveness.
Elegance[edit]
The bridge is also an elegant solution. By combining the two forms of arch and truss, the resulting structure is much stronger than either form alone. An arch is relatively weak with live loads, and the truss holds most of the live loads the bridge faced. The structure is mostly indicative of the load path when on the inside, and the interior is clear and flat. A unique feature of the bridge is its windows. They are an opening of the covering in the middle of the bridge, each with its own small roof. The windows only appear to exist in order to promote air flow, not to give a view of the beautiful creek that flows beneath it. Additionally, on the entrances of the bridge, the slats are slanted to line up with the roof instead of with the ground. This is both aesthetically pleasing and helps direct the water from the interior of the bridge.
Analysis as Structural Art[edit]
A structure can be structural art if it meets certain criteria: social, scientific and symbolic importance. Unfortunately, the Bartram’s bridge never became more than a bridge. Despite having the words “Lincoln, Save Union and Congress” printed on the side, there is no record of it having any impact over more than local trade. However, this statement alone could show that it was also a sign post, or a well visited area. It symbolized the hope for a better world in the future, and the will to move to get it. There was very little information on the bridge to be found in the respect of its symbolic power. It did not use new construction techniques, nor a new truss design. It lacks any unique social impact, scientific novelities or symbolic meaning that would make this structure, structural art.