Week 4 Blog Update

Last week's lab was spent designing a bridge together with my group. We were able to incorporate key elements in design we discovered on our own and collaborate to create a bridge that only cost $226,559.12. We used simple geometric shapes to design our bridge and slimmed down every connection to cost as little as we could make it. Our goal was to make the lowest cost bridge that could still support the truck so we made everything as slim as possible without breaking. We also tested out different materials and see how they would affect our bridge and costs, but ultimately settled on carbon steel because of the lower cost and impressive strength. We also replaced as many bars on the bridge with hollow tubes to lower the cost dramatically. As for the design of the bridge, we learned from our experiments and experiences that an arch supported by triangles was one of the strongest shapes because of its ability to evenly distribute weight among the entire bridge and conserve money spent on parts. Our next step is to incorporate the lessons we learned through West Point Bridge Designer into our K'nex bridges.

West Point Bridge Designer is a great program to test the strength of bridge. It lets you test out different combinations and look at the data of tension and stress at each point to allow you to really push a bridge to its limits. It follows the AASHTO design specifics so it has a realistic expectation for your bridge. There are a variety of options to manipulate the materials used and the specifications of each material's size and construction to allow a greater variety in bridge design. Some of the limits presented by this program include not being able to design in the third dimension, since you're only allowed to manipulate one side of the bridge and have the other side by the symmetrical to the side you first created. It also does not consider any external forces like wind pushing on the bridge or allow you to stress test for different situations (earthquakes or floods). You're also limited to having a single truck test the bridge so you cannot test the limits of sturdier bridges. The bridge also completely resets itself after each truck pass, thus not allowing you to see the effects of fatigue on the bridge. Our experiences in WPBD revolved around making the cheapest bridge, while in reality it would be a bridge that is both cost effective and long lasting. Safety is the number one concern when it comes to real bridges and the bridges we worked on so far are definitely unsafe for actual use. WPBD is a good program to start on bridge design though because of its accuracy in calculating costs and the stress caused by loads on the bridge. It seems like the perfect program to test a concept bridge out or learn more about bridge design through experimentation.