BRIDGE PROJECT
In my Statics and Mechanics of Materials course sophomore year of college, we were tasked with the responsibility of building a bridge, in assigned teams, that could hold a specified amount of weight and was made with specific materials and dimensions in mind.
OBJECTIVE:
Build a bridge that meets the following guidelines:
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Capable of supporting 175 [lbf]
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The bridge main beams must be 18′′long and constructed of
3/8′′x3/4′′balsa wood -
The truss sections are to be constructed of
3/8′′x3/8′′balsa wood -
The truss sections must be joined by methods of bolting: 8/32 bolts in lengths of 1′′
and 1-1/2′′, 8/32 nuts, and No. 8 washers are provided
RESULT:
Our bridge not only met the provided guidelines, but exceeded them; Our bridge was capable of holding 667 [lbf] before breaking due to shear stress
BRIDGE DESIGN PROCESS
Figure 1
Figure 2
BEGINNING STEPS
To start this project, our group needed to decide on a truss design. We elected to build a Warren truss structure. After deciding this critical piece of information, we drew a global force body diagram (Figure 1). We then used the Method of Sections to calculate the forces in smaller sections of the truss (Figure 2). A MATLAB code that we coded enabled us to find these forces quicker than if we were to do the algebra by hand.
STRESS ANALYSIS
To design and build our bridge, we used a computer software called SolidWorks. In this application, we were able to run simulations on the bridge we built and test the effective weight it could hold. One feature in particular that we used was the stress analysis feature. The compressive and tensile forces can be seen in the image to the right (Figure 3).
Figure 3
BRIDGE MODEL
Another unique feature about SolidWorks is that one can build very realistic models. The images to the left include various points of view of the bridge we created. The truss members are connected by bolts and cost analysis of all the materials used was completed at the end of the project and can be found in the Technical Report above