Civil Engineering Project

The version 1 of our balsa wood bridge was designed using a vertically mirrored design. My partner, Gabe, and I built each side with six exterior pieces and five interior connecting beams. As shown above, the interior pieces connect in the center of the side and are glued to the 9'' piece that stretches across the entire side. At each vertex we attached gusset plates, circular pieces of balsa wood that distributed the stress from the joint onto a larger area.

After completing both sides of the bridge, we connected them using horizontal and diagonal members. The diagonal members were essential in preventing the bridge from collapsing horizontally; a triangle is much harder to shift than a rectangle, which readily deforms into a parallelogram. These can be seen in the second picture below. Directly below shows the completed version 1 of our bridge. The bridge sat on four feet which are not particularly easy to see in the picture below. The weight was hung from a hook that sat on four horizontal members in the middle of the bridge. To reduce weight, we trimmed our gusset plates so that they did not extend passed the exterior lines of our bridge.

Here is a video of how our version one performed. As you can see, the bridge broke. However, this was part of the learning experience. Our bridge was very sturdy; it did not move side to side at all. The issue was with the distribution of the weight that was being applied. The single member that held the hook received too much direct pressure and broke under the stress.