Bridge Design Challenge

1)Define Problem:

Your challenge is to design the most economical and efficient bridge possible, given the following criteria: 

Criteria:

• For all bridge members, the ratio of compression force / compression strength (or tension force / tension strength) is less than 25%.

• The structural efficiency (bridge load / bridge weight) is greater than 110%.

• The design efficiency (total cost / structural efficiency) is less than $3,000 / %.

2)Generate Concepts:

Brainstorming:

Select an Approach:

Decision Matrix:

• We used a Google Sheet to make decision matrixes so that everyone in my group (Keroles, Vijay, Kaleb, and Caleb) could decide on which design to choose to fully recreate in real life using the laser cutter. The bottom matrix had each person's rating of each design's best interest and appeal. We chose Kaleb's design because it was simple, strong, met the criteria, and was easy to make with CAD and a laser cutter.

3)Develop a Solution:

Detailed Sketch: 

• While creating a prototype, 1-2 members in our group had to create a detailed sketch by hand on isometric paper about our bridge and the rest of the people in the group would recreate the bridge in the software called, OnShape CAD Software. 

CAD Sketch:

While developing the solution, we ended up having to double the thickness of the truss so that the laser cutter machine could effectively cut through the balsa wood. 

4)Construct & Test Prototype:

Material: Balsa Wood

Using the balsa wood, we put it inside the laser cutter and the laser cutter cut the wood to make the bridge how we desired it, using software from the teacher's laptop.

Test Footage:

• After loading the truss, it was able to hold 820 grams or 0.820 kilograms all spread out on the bridge.

5) Evaluate Solution:

When we tested the bridge, we were able to put on 820 grams or 0.820 kilograms of load on the bridge before it broke. The truss broke on the top right member of the bridge after we placed 820 grams because the member on the top was too thin. Our group believes that if we made the members thicker than what it was, then it will live up to its potential.

This project was a good way to learn how trusses are made and used in the real world. We realized that civil engineers have a lot of work to do when building bridges. Our group worked well together and with a clear goal.  The most challenging part about the project for me was drawing the truss bridge on isometric paper by hand, because I haven't drew isometric in a long time resulting in me forgetting a few things and it took me a long time to remember it and do it correctly.  However, we did a fantastic job, working as a team collaboratively, to get the final load weight of 820 grams or 0.820 kilograms with this truss bridge.