We decided to base our bridge on a truss bidge because it is one of the strongest bridges there is. As you can see in the photo we made triangles for the sides to support the weights and made a strong top to the bridge that we would use to hold together the two sides. We connected the sides to the top and hung the weight from the top which would transfer the pressure onto the sides. With this transferring of pressure to the sides we reinforced them, so they wouldn't break.
The Truss Concept
Here is an up close photo of the truss design of the bridge. We made sure to reinforce the triangles as much as we could with the popsicle sticks that we had remaining after building the rest of the bridge. Then, based off our research we learned that crosses are one of the strongest ways to reinforce a structure. So, we added the crosses to the bridge to hold all the pressure on the sides.
The Breaking Point
This photo shows one of the major weaknesses that were in our bridge. Throughout the bridge we had parts that weren't straight and well glued. In the picture it shows the first place that the bridge broke. Here the two parts weren't straight, so they couldn't be connected properly. This caused the weight not to get distributed correctly and put all the stress on the poorly connected parts. When this area started to crack we knew that was the weakest link.
On bridge number one we learned that for a strong bridge to be created there has to be a high attention to detail, so that the parts can get properly connected. We also figured out that if we wanted to make a bridge with multiple parts; we needed to make sure we constantly checked if they were going to fit together before we put glue on it.
Our final bridge was a three layer bridge that had square popsicle stick stacks in different parts of the bridge to hold some of the forces that the weights were putting on it. Since we pursued a beam design this time we didn't have to make any sides and we could focus our efforts on making one strong platform. This platform would span twenty-two inches and hold the weight in the middle where there was a stack of popsicle sticks to hold it.
Here is an up close photo of the platforms that would hold the weight. The platforms had ten sticks on the bottom and had crosses on top of them to hold them together. We stacked three platforms on top of each other to make the strongest connections we could. Our hopes of this were to make a stronger place for the block on the bridge to rest.
To connect all the different parts of the new bridge we formed the crosses we had in the first bridge since they survived in the last bridge. When this bridge broke the crosses still survived and we were very happy with how much better this bridge worked than the last one that we made.
How it Broke
In the end, the bridge still did not succeed up to our expectations due to the weaker connections on the bridge. As you can see in the photo we tried to renforce the connections as much as we could, so that the bridge would stay intact. The video below shows the bridge breaking through the connections. Then, the bridge split and almost none of the popcicle sticks broke which shows that we should have renforced the parts where the glue gave out.