BRIDGE PROJECT
Solid Mechanics (Engs 33)
Design Lead
SKILLS
SolidWorks FEA & Assembly
Laser Cutter
Design for Assembly
CHALLENGE
Design and test a laser-cut bridge with maximum strength and minimal material with several design constraints.
OVERVIEW
This project for my solid mechanics class (Statics) was not the conventional bridge competition where groups see who can make the strongest bridge. Instead, we were tasked with who could build the most efficient bridge in terms of load per weight. What complicated things even further was that every group was tasked with the challenge of predicting the max deflection and max load the bridge experiences. For this project, I used CAD, FEA and various statics calculations. This project taught me attention to detail must be paramount in order to yield exemplary results.
MY CONTRIBUTIONS
Concept Generation & Analysis
This project began with sketching out bridge designs. From this we took our favorite designs and conducted a FEA on each design to see which preformed the best. We decided upon a double Platt truss as it yielded the best results during FEA testing. We found both the Von Mises stress and the predicted deflection with this FEA. However, we took these results skeptically as FEA does not always give the most accurate results.
Final Design
After finalizing our design, we performed hand calculations for deflection and load to corroborate our findings from the FEA for our bridge. This was done with a very rough approximation for the moment of inertia of the bridge. We calculated the max deflection to be 6 microns which is the thickness of a piece of paper. We quickly realized our approximation was off and multiplied by a factor of 10 and got a close approximation for the deflection that was less than 2 mm off of the predicted deflection.
IMPACT & CONCLUSION
This project's main challenge was the short time frame--we had to design and build an scale model and bridge within 1 week. Also, performing an intricate FEA that included multiple fixtures, and loading points gave us a significant challenge. However our bridge performed second out of all the groups for the weight to load ratio and was extremely successful. It was a great project that presented many challenges and from this I learned a great deal about CAD, FEA, and also the importance of good communication between teams, and attention to detail.
