Tags: 16 inch span, 300+ pounds, basswood bridge, fernbank bridge
6,510 views in 2012
Fernbank Project: Strongest Bridge Design
I built this bridge for the 2005 Fernbank Science Center bridge design event. This is the strongest bridge I have ever built. The bridge spanned 16 inches, weighed 37 grams, and held 346 pounds. That puts its efficiency over 4200! I had never even come close to getting this amount of strength out of a bridge design before. I was really surprised. One commenter said, “So if this bridge weighed one pound, it could have held up my car.”
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- The award I received
The first time the bridge was tested it did not break. The testing machine was set to only apply 250 pounds. This bridge was too strong for that! Here is the bridge after the second testing:
The secret of a strong bridge design
As you can see, the bridge stayed mostly intact. I talked to a couple engineers at the event and asked them what they thought made my bridge break. One suggested that the bridge failed in torsion, as I did not have any diagonal braces in the bridge. That is definitely a design flaw I will fix if I do this again. I would love to try and break an efficiency of 5000. That would be a strong bridge indeed!
For more information on this competition, see Atlanta Toothpick Bridge Competition. I encourage anyone in the Atlanta area to try and go to this event. Whether you are studying for a criminal justice degree online or MBA operations management degree, take some time off to check this out. It is free and open to all, both young and old. Try your hand at making the strongest bridge. And when you do, send me photos of your bridge 
I am building a double-deck popcicle bridge. Any advise? may u please e-mail me a sketch using 240 popcicles?
I’m making a bridge for engineering class .. It’s meant to be 648mm long.. 100mm tall and 75 mm wide… And a weight of 75 grams… Your design is pretty good.. What sort of joints did you use for it? I’m stuck on deciding what joints to use.. Mine is a Warren truss bridge… My main aim is acheiving a good strength to weight ratio. My bridge weighs 52 grams
what are the blue prints like how many 3×3 pieces of balsa wood and how high?
Thank you
If this design was used with popsicle sticks would it work?
Probably, although you might have make some minor modifications.
What kind of popsicle sticks did you use, just regular, or a certain kind. Also, what kind of glue?
Tessa, I did not use popsicle sticks on this bridge. I used Basswood. I used two types of glue, Weldbond mostly and a little Probond.
okayyyyy so like i have to build a bridge for class out of balsa wood and then we put our bridges on a metal pole and put weights on top. i am afraid that no matter what we do it will be instantly crushed. is this true?
What would be a good design for aluminium
What kind of truus did you use? A howe, pratt, or warren?
This bridge used a hybrid truss design. Mostly it was a Subdivided Warren, but went to the Howe Truss on the ends.
how do you make it with metel in a metel work class ??
im making a balsa wood bridge for class its span is 20cm with 6cm abutments will that bridge work for this? i have tried it in wpbd (west point bridge desine) and it fail it might be cuz the soft ware simulats steel and ashfult not balsa wood.
I’m making a popsicle stick bridge for a competition and I’ve been researching like mad trying to figure out what I want. The bridge can weigh up to 300 grams and spans 28.5 inches. We got popsicle sticks and white elmers glue…
Where are bridges most likely to fail with the elmer’s glue? Would it be at the joints or the sticks themselves?
can you make it by paper???
what do you mean by diagonal braces? and how long did it take u?
i tried to copy your design except with popsicle sticks didnt turn out very well. was kinda crooked and twisted.
hope i can still beat my class in most durable bridge
Good question. Diagonal bracing here refers to any pieces that would have connected the sides of the bridge on a diagonal. So if I had a piece that was glued on the bottom of the left side and sloped up to the top of the right side of the bridge.
I was wondering, how was the bridge loaded?
This bridge was loaded from the top with a metal plate that was attached to a hydraulic loading machine.