in Mr wests class I am building a bridge made out of straws. I only have twenty straws and I have to build it strong enough to carry a 500 grams weight of metal. It can only be a beam bridge so it can't be connected in any kind of way to the supports that hold it up. Beam bridges only support them selves nothing supports them. So if the bridge gets to heavy it will bend and snap in half or fall off of the supports.
The design to the bridge is critical and so far me and my partners bridge holds 100 grams. That is good since it is maybe a quarter done