Simple Truss Design

Project: Design a simple truss to support the highest possible load with a team of 3.

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Duration: The month of April 2021.

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Objective: Design, assemble, and test a simple truss that spanned a 28in distance using acrylic members between 6.5in and 15in long to hold the maximum amount of weight possible at a distance of 13in from one of the ends. Each joint cost 10$, each member was 1$/in, and the truss had to cost less than $275

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Approach: Write a truss analysis program in Matlab to test out various truss designs. Due to the thinness of the acrylic strips, their failure mode in compression was buckling and they could be treated as infinitely strong in tension due to their low buckling strength. Since shorter members were stronger in compression, the idea was to make all the members in compression 6.5 inches while the members in tension could be as long as needed up to 15in.

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Challenges: Coming up with designs that met the cost and member length criteria, and efficiently analyzing different designs.

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Solutions: By sketching designs in SolidWorks it was easy to specify member lengths, check the amount of acrylic used to satisfy cost constraints, and adjust designs by moving joint positions or changing member lengths while keeping other members and joints fixed. The Matlab analysis program helped quickly test different designs.

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Results: The truss had the highest predicted load in the class at 126oz. In practice the truss failed at 98oz, although, due to the progressive buckling nature of the acrylic it was hard to determine exactly when failure occurred.

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Future Improvements: The truss analysis program required an input file that specified all joint locations, which joints where connected, and which joints where supports. This was tedious to create by hand and prone to mistakes. If possible, altering the Matlab script so it could take a SolidWorks sketch as an input would save a lot of time and make the design testing process much more efficient.