Building a Bridge?

Question

am building a bridge for my class and need some help in the design of the bridge. Here is a list of the items I get:
1.) 100 toothpicks
2.) 200 feet of string
3.) 25 feet of aluminum foil
4.) 10 paper clips
5.) 10 rubber bands
6.) 1 Roll of Scotch Tape
7.) Pair of scissors
8.) 12" ruler
9.) hole punch
10.) 10 pieces of construction paper
11.) 10 note cards

The bridge has to span 5 feet and hold approximately 100 pounds on top of the bridge. I only get 30 minutes to build this bridge in class also. I will have 7 people helping me.

Also, what is the best design in case the weight is hanging from the bottom instead?

Please help.

Answer 1

No glue, so the toothpicks are probably useless.
Roll the construction paper into tubes about 1" in diameter and tape them.
Roll the note cards into tubes to be connectors for the paper tubes, let them expand inside the tubes and tack to one tube with tape.
Fit the tubes together into two identical long tubes over 5 feet long (assuming the paper is big enough)
Pull out a sheet of aluminum foil as long as the tubes and roll both tubes side by side snuggly in the foil, taping it firmly. Repeat.
Shape the tubes into a long arch across the 5 feet against the foundations you better have been given.
Use the string to add guy "wires" to stabilize the structure.
Added complication - mount the paper tubes so the meet in the center, but the ends are spread a few inches, then wrap with foil - if it works, more stable, harder to build.

Answer 2

Ah! My engineering team built a bridge like this in the 6th grade that held 120lbs. As strong as suspension bridges are in real life, there is no way that you would be able to construct one in 30 minutes. The Roman aqueducts are a great example of a quick bridge. The arch is extremely strong if built correctly.
Also, if you aren't up to building arches, keep in mind that the triangle is the strongest shape because the weight that is placed on the point is equally distributed throughout the whole shape. Designing a bridge around triangles would work better then the arch in the weight is hanging from the bottom.

Answer 3

Study some bridge designs - mostly suspension style bridges.

You want to make it to where it can distribute the weight evenly across your structure.