Week 9

During last week in lab we got to work on our three-foot bridge design some more.  This was the last week we had to work on our design before the competition.  We built our bridge from scratch again.  Some things we kept in mind while making the bridge was to have a 2”X”3 hole through the middle.  Our first design looked like a square prism with trusses that looked like X’s on the side.  One thing that we did change from last time was the trusses on the inside of the bridge, which would prevent it from twisting.  When we tested the bridge it failed at around 24 pounds.  When we went back to the table we added some minor pieces that we thought would give the bridge more strength.  This ended up doing nothing.  In our final design we put a top truss on the square prism.  This design yielded about 40 pounds.  This was a success in our eyes so this is the design we will submit for the competition. 

            I came into this class with zero knowledge of bridges and came out knowing a ton more.  One thing that I noticed is different about me is that whenever I come across a bridge now I analyze and look at how it is built.  Trusses are one of the most important aspects of bridge design.  We learned how they distribute weight and make bridges that much stronger.  They have been around for about 100 years.  While designing the bridge you really learn how everything affects everything.  The best bridges are not just the ones that can hold the most weight or cost the least, but the ones that have the best cost to weight ratio.  One of the best technical things I learned how to do was figuring out compression and tension by doing physics/calculus.  When building a bridge there are many factors you have to account for including weather and aging.  The list of things that I learned can go on and on but these are just a few.

-John Watson