ARCH 252: LONG-SPAN TRUSS INVESTIGATION
1 Jordan Davis & Devannand Persad
Professor Parker
Fall 2012
11/9/12
TABLE OF CONTENTS 3 4 5 6 7 8
Case Study I Bollman Truss Bollman Truss History Process Summary Bibliography
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CASE STUDY I
The Bollman Truss Bridge was built in 1869 and remains one oft he most important historic bridges in the country. The bridge was built on a B&O mainline, but was relocated to an industrial area off of the mainline. This allowed the bridge to survive. The Bollman Truss Bridge remains one of the oldest metal bridges in the country and was designed by a famous bridge engineer, Wendel Bollman. Bollman’s design was the founding metal truss bridge design to be adopted in any eminent number by the railroad industry, and is thus in the development of the metal truss bridge. Today, its the last surviving Bollman Truss example. The bridge has beeen restored twice, once in 1983 and another in 2000.
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BOLLMAN TRUSS The Bollman truss was a rather more intricate design that required a mass amount of materials. This also was the ultimate demise of the design which would happen only a short amount of time after the initial design. The truss is made up of a series of panels that create point loads where they meet the roadbed of the truss. The frame around the truss is then connected from the ends to each point load as shown below. Using these tension members to connect the bottom of the bridge (which is in tension) to the topn of the bridge (which is in compression) would counteract the reaction and thus allow the bridge to stay in equilibrium. This idea onlt lasted for a short while due to the quickly advancing industry at the time. The bridges quickly became more modern and the Bollman truss eventually died out. The Bollman Truss Bridge is the last remaining example of this interestingly intricate design.
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BOLLMAN TRUSS HISTORY In order to look at the history of the Bollman Truss, first we must look at the Bollman Truss Bridge because it is the last remaining example of this truss type. The bollman truss is the truss that allowed our nation’s first railroads to span across rivers and valleys. This is the truss that replaced most of the wooden bridges in the north eastern area of the United States. Do to the steady advancing technology, they were eventually sought to be obsolete. They may still be a few around but only the Bollman Truss Bridge is the most notable of them all. Located in Savage, Maryland, The bridge is an example of America in its youth. The bridge functioned as a gateway for the B&O mainline. Today, it is an historic landmark and also a walking trail for curious travelers.
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PROCESS: The process for building the truss was very simple. First we laser cutted several rectangular pieces (20 pieces) and doubled them up to make 10 columns for the sides of the truss. These pieces also had holes cut into them so that we couls connect the tension members to the base. We cut 20 more pieces of the same shape and doubled them up as well for the bottom and top of the truss. These pieces did not have the tension member holes in them though. Then we cut the four corner rods that run the entire length of the bridge with notches in them so that the columns and joist could fit into the pieces. We connected all of these pieces and then ran yarn from point load to point load until we ended up with the Bollman truss.
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SUMMARY: In conclusion, we discovered some basic designs on how trusses were built during the early years of our country. The reason why we chose this truss type was because we wanted to find a truss that had som significant meaning and historic value. The bollman truss had both and was also aesthetically pleasing to us both. The truss type had a very interesdting way with dealing with tension and compression forces, unlike most of the trusses that we had seen previously. The bollman truss was very unique and had a certain aesthetic about its members that caught my eye. It is also very rare which makes it appealing to me. Overall, The truss taught us how dealing with these forces and also give you an amazing aethetic as well.
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BIBLIOGRAPHY:
Nathan, Holth. Historic Bridges , “Bollman Truss Railroad Bridge.” Last modified 4/17/2007. Accessed November 9, 2012. http://www.historicbridges.org/bridges/browser/?bridgebrowser=maryland/bollman/. J. B. , Calvert. University of Denver, “The Bollman Truss.” Last modified 10/13/2004. Accessed November 13, 2012. http://mysite.du.edu/~jcalvert/tech/bolltrus.htm.
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