Design Process

For the Bridge Designer 2016 portion of the project, we defined the problem of our bridge as “all requirements assigned for the bridge need to be fulfilled while still finding the lowest cost that the bridge can be.”

For the Model Smart 3D portion of the project, we defined our problem as, "how can we make a bridge that can support the most weight and fulfill all requirements keeping its truss figure."

At first, we made a design concept of solely solid bars with similar sizes. We also created a symmetrical concept with only the vertical members being hollow tubes and with different sizes of tubes and bars. Our third design was very similar to our second design, but some of the hollow tubes were diagonal members and this design was not symmetrical.

At first, we created a design concept that combined the Pratt Truss and Howe Truss bridge designs. We also created a design concept that had a triangular shape instead of a rectangular shape while keeping the same truss.

The first concept was not used because while this design was sturdy, it did not fulfill the requirement of fifteen percent hollow tubes. Consequently this design was also the most expensive of the three designs. The second and third concepts were very similar in stability price, with only a one hundred dollar difference between these two designs. However, we decided to go with the second design because it was of a lower cost and it was more aesthetically pleasing, as it was symmetrical.

Our first concept performed decently with all the requirements and held 730 pounds of weight. While our first design did have success, our second design was more creative, held more weight (982 pounds), and still kept all requirements in check. As a result, our second design was chosen as our final concept.

To detail the design, we drew out the design and found how large different solid bars and tubes would have to be to lower the cost even more. We wanted to use the smallest size of the bars and tubes we could, while still fitting the requirements and making sure that tension and compression forces did not get too large. In this design we also specified that the only materials we would be using were carbon steel.

To detail the design, we decided to make our design with the most stable material and thickness to maximize the load our bridge could carry, so we decided to use balsaD3 and 1/2x1/2 sized pieces of wood. We also made sure we fulfilled all requirements of a three foot span, four foot bridge, and 1 foot tall supports in detailing the design. We thought about making the bridge taller, but after adding an extra foot in height onto the bridge, the bridge collapsed. We also tried lowering the height of the bridge by six inches to try to improve its performance, but the results did not improve, so in the end we kept the height at two feet tall.

After creating and going through each solid bar and hollow tube to try to lower the size and cost, we eventually came to our final design of the bridge. We were able to defend this bridge design by showing how it fulfilled all project requirements and had stability under dead and live loads.

In defending our design, we found that this design stayed stable and sturdy even with a large weight of 982 pounds on it. It was creative in its structure and was not a plain Pratt Through Truss.

We tested the bridge by running it in the 2016 Bridge Designer program, and it passed the test in being able to support its own weight and the weight of the truck going across it.

Through testing, we found that the BalsaD3 and 1/2 x 1/2 sizes were the best choices for our bridge, and our bridge was successful in being able to hold almost 1000 pounds, with 982 pounds being the maximum weight it could hold.

After testing the bridge, we saw that the bridge stayed very stable as the truck went across it, and we knew we had gotten it to the lowest price we could in this design. Consequently, this design worked out very well in the end and fulfilled all requirements.

After testing our final design, we were very pleased with how it performed, as it was able to hold a very large maximum weight, while still fulfilling all of the requirements needed.

Our final design worked out very well in the end meeting all requirements of this project. We prepared a small design report on our website to show how our bridge worked, our sketch of the design of the bridge, the price of the bridge, the force component calculations of our bridge, and a video showing the bridge performing well under its own weight and the weight of the truck.

Our final design for the 3D model worked out very well in the end meeting all requirements of this project and in taking an extra step in its creativity. We prepared a small design report on our website that includes a sketch of our designs for the 3D model bridge, the materials and sizes of the members for the bridge, the maximum weight that our bridge was able to hold, and a video showing the bridge performing well and working.