Bridges Built to Last

I chose to do this project because I have a strong passion and curiosity for civil engineering. My interest started in mechanical engineering, until I attended a seminar at UNBC where I was able to talk to engineers in many fields. I learnt that Civil Engineering was one of the most versatile branches of engineering. For this project I was interested in how each of these bridges have a different structure and purpose, and I was curious to know how much weight each bridge could support and see how much of a difference there was in their breaking point.

I predicted that the Truss Bridge will be able to hold the most weight based off the structural design, and that the Beam Bridge will hold the least amount of weight. I predicted that the Truss Bridge would hold 7.5 pounds, the Arch Bridge would hold 4 pounds, and the Beam Bridge would hold 2.5 pounds.

The general public can benefit from well structured bridges to transport them over areas that are not accessible any other way, for example over waterways, highways, and gulley's. This would make the world a better place by increasing the accessibility to places the public otherwise would not have been be able to visit and explore.

I used the Britannica Encyclopedia to research different bridge types to get a better understanding as to what types of bridges would work best for my project. After reading about multiple bridge types I found that there were three styles (truss, Arch, and Beam) that would be the best choice for the testing of my project.

I used Fusion 360 software to design three styles of bridges, and then I used a Bambu 3D printer to print five models of each bridge design, using PETG filament. I kept one model of each design for display and the other four were used for weight testing. During testing I placed each bridge in a gap between two sawhorses and attached a testing rig to the bridges and hung two five gallon buckets from them. For the next step I added sand and weights to the buckets until the bridges failed. After the failure I used a scale to weigh the buckets and then recorded the data, averaging the weight of all four fail points.

I controlled the variables by 3D Printing multiple bridges of each type (Truss, Arch and Beam) and having the same footprint for each bridge type that was tested (EG: Dimensions, Design and materials)

When designing my bridges I left a small hole in the center of each bridge (prototype) so that I could attach the testing rig. The testing rig was used to hold the buckets in the middle of each bridge type and filled with sand and weights until each bridge broke. After each bridge broke I weighed the buckets and recorded the data (as shown in the graph above)

During testing I learned that bridges can hold a lot of weight, even when built on a smaller scale. I also learned that having proper reinforcement and supports are important because it can affect the amount of weight that can be held by the bridge, especially when conducting the weight test on the beam bridge I designed. I found that the beam bridge was the weakest because it was lacking the proper reinforcements needed between beams. After the testing was completed I realized that I could have designed and 3D printed my bridges with additional supports or support styles to see how that would affect the strength of each bridge.

In conclusion, I was right about which bridges would be the weakest and the strongest, but I was incorrect about the weight that each of them would be able to withstand. I could have built these bridges with additional supports to increase the weight that each bridge could hold. I also learned that having additional supports and reinforcements in the beam bridge would improve the structural integrity as the test I preformed was a catastrophic failure due to the major bend at the center of the deck. I would like to further explore how changing the internal supports will affect the structure and load capacity of each bridge.

Moving forward I would like to expand on this project by increasing my knowledge and understanding of bridges and how they are designed. I would like to add more supports, and even make more than one design of a specific bridge, for example, designing two different styles of a Truss Bridge with different support styles to better understand how one design can be more superior than the other.

I would like to thank my mom and dad for guiding me through this project. My dad played a major role by welding together my testing rig, as well as letting me use his 3D Printer and software to design my bridges. My parents support and encouragement helped me get through some tough parts of this project.

Reasearch -

Author - Hubert Shirley-Smith, David P. Billington, Philip N. Billington

Title - "arch bridge"

URL - www.britannica.com/technology/arch-bridge

Author - Britannica Editors (most recently revised and updated by Melissa Petruzzello)

Title - "Truss Bridge Engineering"

URL - www.britannica.com/technology/truss-bridge

Author - Britannica Editors (most recently revised and updated by Melissa Petruzzello)

Title "Beam Bridge Also known as: girder bridge"

URL - www.britannica.com/technology/beam-bridge

Images -

Author - Matthew Brown, Gene Johnson

URL - https://fortune.com/2023/06/25/freight-train-montana-bridge-collapse-yellowstone-river-asphalt-sulfur/

Author - Matthew Brown, Gene Johnson

Author – Unknown

URL - https://www.mainspring.co.uk/industry-news/dresden-tram-bridge-collapses/

Date – September 13th, 2024

Author – Sarah Cassi

URL - https://www.lehighvalleylive.com/northampton-county/2021/04/effort-to-save-historic-saucon-valley-bridge-doomed-after-part-of-it-collapses-into-creek.html

Date - Apr. 05, 2021

Other images provided by myself