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Trust Design Bridge-Pratt

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This bridge was one of the bridges that we thought as a group that can hold the much weight because of its structures. At first it was really hard to figure out on how to build it but three minds always work better then one so as we figured out the best way to built it we would test it ourselves.

The Pratt truss was first developed in 1844 under patent of Thomas and Caleb Pratt. Since the 1840s through the early twentieth century, the Pratt has diagonals in tension, verticals in compression, except for the hip verticals immediately adjacent to the inclined end posts of the bridge. Pratt trusses were initially built as a combination wood and iron truss, but were soon constructed in iron only. The Pratt type successfully survived the transition to iron constructions well as the second transition to steel usage. The Pratt truss inspired a large number of variations and modified subtypes during the nineteenth and early twentieth centuries

They are a lot of major subtypes of the Pratt design. Like the Double Intersection Pratt Trust. This subtype was patented in 1847 by Squire Whipple and modified in1863 through addition of crossed diagonals by Lehigh Valley Railroad chief Engineer John W. Murphy. Also there's the Pratt Half-Hip subtype was developed during the latter part of the nineteenth century. This bridge is characterized by inclined end posts that do not extend the length of a full panel; this subtype became popular in the United States from the 1890s into the early twentieth century. Then there's the Parker truss was developed by C.H. Parker in a series of patents he filed between 1868 and 1871. Characterized by Pratt design but with an inclined top chord, the Parker truss was popular for longer spans well into the twentieth century. Also there's the Baltimore Truss developed in 1871 by engineers of the Baltimore and Ohio and Pennsylvania railroad, the Baltimore truss subtype was popular into the early twentieth century. The Baltimore truss was characterized by Pratt design featuring additional, auxiliary sub-struts. Then finally there's the Also a variation on the Parker truss design, the Camelback truss was popular for through spans primarily from its inception in the late nineteenth century through the mid-twentieth century.

In all, we experimented with building three bridges to see which one would hold the most weight and one stand there to see if it would break, which it didn't. We were



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