West Point Bridge Testing

Project files

West Point Bridge Building Textbook This is the link to the instructions for assembling the bridge.

Bridge Testing This is the link to the instructions for the calculations needed to test the bridge.

These are the gusset plates used in our bridges. In order to successfully print this out we had to change the laser cutter settings. The red lines were set to cut and the yellow lines were set to score. We also changed the material to cardboard. After that, we sent it to the laser cutter and auto-focused it.

What is Kerf? What was its impact?

Kerf is the width of material that is removed in the process of cutting material. For this project, the kerf had little to no impact on this project.

Assembling Pieces

This is the video of the gusset plates being cut. A problem that I encountered was that the original file for the gusset plates was too small for the bridge plan so I had to dilate all the pieces by %10 and printed them again.

This is all of the gusset plates laid out and cut to the correct size. We verified that it was the right size by placing it on the template and seeing if it matches.

After cutting the gusset plates, the different-sized strips had to be cut, folded, and glued to the gusset plates. We started out by gluing one side of the bridge with super glue and then we glued the other side and then the top. after all sides were made we glued them together. This was the final bridge.

What could've been done differently?

One thing that could've been done differently is the little strips that formed triangles along the bridge could've been made more tighter and secure instead of loosely put together

Problems Encountered

A problem that most of the class encountered was that it was difficult to prevent the superglue from sticking to our fingers when we tried to fold and glue the cardboard together.

testing the bridge

This is the design of the bridge testing materials in Corel Draw that my partner and I made. This was made by making a box with the measure measurements given to us and then tracing the parts of the box that need to be scored with red and making the parts that need to be fully cut black.

To make this design we followed these instructions.

After designing and laser cutting the tubes and bars, we were left to assemble. To make the compression tubes, we put a line of super glue on the tab on each tube. Then we took small strips and glued them and wrapped them around the ends of the tubes. Finally, to make the tension strips we took the 3x3cm squares and strips of different widths and glued them on top of each other.

First, we tested tension. We marked a line on the testing machine and clamped the strips to the end of it. Then we put an empty bucket on the other side of the machine and slowly put the sand into it until the strip snapped. We did this 9 different times with 3 different sizes of strips.

To test compression, we did a similar process as we did with tension. We put the tubes at the front of the machines and slowly poured sand in to bucket until the tube crushed. We did this several times with small, large, and medium tubes.

This is the video of us testing the tubes.

This is the table used to record the maximum weight each strip and tube could handle for tension and compression.

These are the two equations that determine and convert the weight of failure. L1 is the length from the bucket to the fulcrum. L2 is the length from the fulcrum to the bar. W is the max weight recorded by each experiment.

Strengths and weaknesses??

What we figured out while testing the different strips for tension is that the wider the strip was the more weight it could handle. For compression, the longer the tubes were the more weight they could handle. This is all seen in our data chart. We also noticed that the farther up the tubes were the more weight they could handle. So when we test our actual bridge the weakest point might be in the middle of the bridge and the strongest might be at the ends of the bridge.

Testing the bridge

Tools used:

Bridge
Two tables
five books
six lego pieces

Process:

We first placed our bridges in between two tables to test our bridges. Then we placed six Lego pieces on the six joints. We then placed 2 books that weighed

1,500 g on top of our bridge. If the bridge held the books then we placed the other set of books on top.

Our bridge was only able to hold the first set of books.

The is the video of me testing my bridge.

When my bridge failed, it failed at the ends of the bridge. The 4mm strips were the first to snap and caused the bridge to fail.

Final Conclusion:

Why is it essential to account for both compression and tension when designing a bridge?

Tension pulls on the bridge and can elongate and stretch it; compression pushes on the bridge and compresses and shortens it. It is crucial to account for tension and compression to design the bridge efficiently and safely.
An Improvement that could be made to the bridge that makes it successfully hold the weight is that the 4mm strips could be thicker to handle the tension better. The strips can also be glued down tighter.

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