Hooray! We’ve completed our project! Well, we still have some work to do outside, but we’ve presented to a panel of judges, and it all went wonderfully with only a few minor mishaps.
Each one of us was responsible for presenting one slide of the presentation, and we have been preparing what we were going to say today for a little while. We signed up for what we were presenting based on who did the most work outside of class on the project, so those who did the most got to choose what they talked about first. Luckily, we all seemed to know what we were talking about, so nobody got stuck with something they didn’t understand or couldn’t explain.
I was in charge of explaining beam deflection, which wasn’t as tricky as one may think. Using notes from previous points in the semester, as well as my knowledge from working on the project, I was able to put together plenty of information for my slide, and even had time to make a little diagram.
What I said:
“As we learned this semester, beam deflection is measured by the displacement of a beam under the pressure of a load. We tested out and played around with beam deflection concepts earlier in year, measuring how much space a wooden board needed between supports to hold up a student. In doing this, we learned about how certain materials were more stiff than others, as well as how the positioning of the support beams is very important when trying to make it safe for someone to walk across a board. When learning about this, we also investigated and researched Moment of Inertia Principles, which states that a joist is more supportive than a plank. This is supported by the equation I=bh(^3)/12. For instance, a 6×2 joist is almost 14 times stiffer than a 6×2 plank, due to its higher moment of inertia. While the Moment of Inertia (I) isn’t dependent of the materials used, the Modulus of Elasticity is greatly affected, as it measures the stiffness of a product related to its chemical properties. To calculate beam deflection itself, you must use the equation delta max = FL(^3)/48EI . In this equation, elements such as Force (F), Length (L), Elasticity (E), and Inertia (I) are used. Beam deflection incorporates the Moment of Inertia and Modulus of Elasticity, making it partially dependent on the material.
When it came to implementing this concept into our actual courtyard project, we found it necessary while building our three decks. To make sure that our decks were structurally sound, we put in support beams (joists) perpendicular to the deck boards underneath, and these joists were supported by cinder blocks. Without those joists there, any stress that would be put in the middle of the decks would cause for the board to bend, not only immediately but over time as well. If students were constantly sitting on the decks (their intended use) and they didn’t have these beams, the boards would eventually stop supporting the load and potentially break or split. This also meant that we had to choose quality wood to support our deck boards, as elasticity is greatly affected by what materials are used. In this diagram, you can see that the green blocks represent the joists, and the blue ones represent the deck boards. This is a loose model as to how we built our own decks, and gives a general but clear idea as to how the beams are laid out underneath. We have our beams so that the thinner side of the board is what is touching the deck boards, as we know that if the wider side were supporting the boards, the supports would be much more vulnerable to potential bending and breaking.”
Overall, I feel very proud of both myself and of my team as a whole. 6th grader me would have probably laughed at the idea of me being able to be a part of this and building such a great project, and now we’ve gone and done it!