As the semester is winding down you will find the CAD labs filled with MechE’s scrambling to finish their projects. As I mentioned in my previous post, for Mech 12 we had to design a bridge for a given set of parameters and for a specific load case (see above). The bridge had to adhere to specific size dimensions and constraints. It also had to adhere to strict performance standards, i.e. it couldn’t deflect more than 8cm and the worst stress anywhere in the bridge could not exceed 100 MPa. At first I really struggled with this task. I probably made 4-5 completely different designs spending hours making the slightest changes to try and improve their performance. I tried and I tried but couldn’t get any of my bridges below 10cm of deflection. As it turns out, I accidentally added an extra 0 to my distributed load! I was trying to build a bridge that would withstand a load 10 times what it needed to hold! I figured that since my deflection was so close to the allowable limit that I had done my loads correctly. Once a friend found my mistake and I corrected it my bridges performance drastically improved and I was well within the limits of the project. Ultimately I decided on using a K-truss design as it was simple, easy to make changes to, and performed well. Others did completely unique and non-standard designs that ended up working really well too. Anyway, from there I worked to make my bridge lighter. As I mentioned in my other post the team with the lowest combined weight won an extra 2 points on the final exam. I doubt my team will win based on what I’ve heard talking to other groups but I think we did a respectable job all together. Below are some the results I had from the load testing.