How to make a strong bridge by using

How to make a strong bridge by using 15 straws , 35 paddle pop sticks , 3 sheets of cardboard, 50cm of sticky tape, wood glue? my bridge have to be 25cm long and 14cm wide. Thank you for helping

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frollard8 years ago
I'll leave the design of your homework project to you: The key is triangles. Model your bridge after a real bridge, refer to photos from google image search for inspiration if you don't have any local bridges. Use the cardboard for the bridge 'deck', and the popsicle sticks to make triangles.
I've found the key isn't so much in how the deck is supported, but in how the ends are supported. How far are you trying to bridge? What are the ends resting on or supported by? Does the bridge have to rest on the supports or could you have a support below the level of the supports? Could you use the end supports as a rigid base for an 'A' frame (depends on how accurate the distance between end supports are)? Can you modify the popsicle sticks (split or cut them into thinner spars)? What kind of straws-plastic (could become 'rope' in a suspension bridge)? Paper? Broom or hay straws? What kind of cardboard (corrugated? Card stock?) and size (8x11? )? You can fold cardboard for strength, look up box-girder construction. Glue-soaked cardboard can be more rigid when dry. What type of sticky tape? A paper backed tape is different than a plastic type, for adhesion and for tearing strength. Don't forget that small pieces of tape are all you need sometimes-you don't have to use the full width (I made a 6' tower with a single piece of paper and a 1" piece of tape in 7th grade by using the tape carefully and folding paper strips for strength).
Great suggestions! I had a project like this where each building material had a 'cost' associated, and you had to span a 30cm gap and support 2 kilos in the center. Toothpicks were 5-for-1 cent, popsicle sticks were 50 cents, glue (any amount) was 50 cents, etc etc. They wanted to discourage people from using popsicle sticks. I ended up making a delicate triangle 3d structure out of just popsicle sticks, then soaking the whole thing in glue after the initial tack glue had dried. It could support a classmate. :D
Of the types of bridges, I would say that the ones using the compressive strength of your straw triangles or tetrahedrons seem best.

I wonder, though- is there a limit on the amount of glue you can use? If you could braid elastic ropes from threads of dried glue, you might be able to make a tensegrity structure such as these.
Kryptonite8 years ago
Ha, i've got this exact piece of home work, I wanna design my own but I plan to design the whole thing with cylindrical uprights, and triangles for the actual thing. It's pretty easy, send me a picture of your design and I'll see if I can help.