EPIC BRIDGE COLLAPSE (NOT CLICKBAIT!!) *THEY ALL DIED*

I have successfully made it to the last STEAM class of my junior year, and with that comes the first of three last STEAM projects for the year. The last class is called Urban Planning, and we have been focusing on bridges and load for the first unit.  We were assigned the task of working with a partner to design a truss bridge to hold at least 10 pounds of weight. We learned in class that triangles are very strong shapes, so when we were researching to find a bridge shape to inspire our design we decided on the Pennsylvania Petit Truss. We only had 50 popsicle sticks to work with, which was a major limitation. We used all the sticks we were given. By overlapping sticks, and using parts we had broken off in other parts of the bridge, we were able to use everything we were given in a way that made what my partner and I thought was a pretty good looking bridge. We used a combination of our knowledge on vectors, forces, Newton's Law's of Motion, what we learned from visiting the Chicago Riverwalk, and what we learned from a visit with structural engineer Drew Valentine. 

Pennsylvania Petit Truss, Fmiser, 2012

The Pennsylvania Petit Truss Bridge is structured with many trusses. It uses an arch at the top and many small trusses to distribute the weight between all of the bridge. Our bridge measured at about 16 inches long, 2.25 inches wide, and 4.5 inches tall. 

Above you can see our sketch, and final product, with important parts like the top chord and bottom chord, the angles of a truss, and compression and tension labeled. 

Our truss was an equilateral triangle, because each of its sides were one popsicle stick, or 4.5 inches long. Even though we knew this, we used the law of sines and the law of cosines to make sure. When solving for one of the angles, it equaled 60 degrees with both the law of sines and cosines. 

We also learned about the law of conservation of energy in class. This is the law that says energy cannot be created or destroyed, it can only change forms. We used the velocity of our bridge (9.8 due to gravity), the weight of our bridge (2.772 kilograms) and the height of our bridge (0.889 meteres) to calculate the potential and kinetic energy of our bridge. 

We all tried to design our bridges with Sustainable Development Goal 11 in mind. SDG 11 is to make cities and human settlements inclusive, safe, resilient, and sustainable. The bridges in our state of Illinois are some of the most at risk in the nation, so designing good bridges is very pressing here.