Our first bridge was poorly planned, thus only being a platform with no supports as seen in the photo.
Our bridge did not have any supports. We wanted to build trusses to act as a support to the base. The trusses were made, but we could not properly connect them to the base.
In the end, our bridge didn't even hold the platform, which was 21 pounds.
Above is an edited video of our first attempt of model bridges. This bridge failed epically due to a lack of planning.
The main support of our bridge was our trusses. They support all aspects of the bridge such as the middle, the base, and the ends. The base was already strong, and the trusses added more support. The middle of the bridge wasn't as strong as we would've liked it to be. The trusses allowed the middle to hold as much weight as possible. The ends were also a weaker part of our bridge, but with the support of our trusses that didn't create a problem.
Another strength of our bridge came from layering the the sides of the bridge and attaching the trusses in between the layers.
The accompanying image is a screenshot of the exact moment our bridge broke. As you can see, the trusses stayed strong and didn't break, but the part where the block was being held snapped and the block fell through. In the end, our bridge held a total of 146 pounds.
The video above is the testing of our second bridge.