A1- Parker

1. Design Goals: In this design my goal was to create a sturdy structure for the lowest possible cost, in order to do this I focused on getting the Compression Force/Strength and Tension Force/Strength ratios as close to 1 as possible. A ratio of one means that the beams used are the smallest and best possible bridge that can be constructed. My bridge has the trusses underneath the bridge deck because it is one of the more common designs that I have seen around. Through the design process I have also found this design to allow for the lowest possible build cost.
2. Two Dimensional Drawing:
   
3.  Truck in the Middle of the Bridge:
   
4.  Load Test Results:
   
5. How the Bridge Changed During Design:
   This bridge has come to shape as a result of many trials and errors to determine the best shape and most cost effective design for a truss bridge. My early designs had the deck on the bottom of the trusses, I found that this was harder to stabilize and led to the need for bigger beams thus increasing the price. I have also changed the method, at first I was using a square with either a single or double diagonal, I have since switched to creating a design that has an extra gusset plate in the middle of the rectangles which allows for 5 shorter beams to form triangles.
6. Bridge Cost:
   The total cost for the bridge shown above is $233,758.78. I feel that I have gotten the cost down to the lowest level that is possible with this design. If I were to change my design, or if more time was allowed I feel that I could lower the bridge cost to the $220,000.00 range.
7. What I Learned:
   From using West Point Bridge Designer, I have learned that changing the size of one member of a bridge can have effects on other areas of the bridge that you were not considering, this played a crucial role in my design. If you look in the chart some of the Strength ratios are low this is due to the fact that lowing the size of that member to increase the ratio had a severe negative impact. I also learned to keep all options open, do not just follow the templates and do not just start making a bridge that costs upward of a million dollars, there is an in between, once you are able to design a structure that works you are able to go in and modify the components to lower the overall cost.