Science Buddies: "Ask an Expert"

hello all.
I am working on a project where I need to build a model suspension bridge.
the length of the suspension bridge has to be 1000mm (1m), the portion of the deck between the two towers is 700mm (.7m).
the height of the deck from the ground is 200mm (.2m). I wanna know what should be the height of the tower above the deck to keep it most stable.
the bridge would be loaded with point loads varying from 10kgs to 20kgs.
the material to be used is ice-cream sticks(popstickle sticks) only.
I would be highly obliged with a speedy reply, i.e the formula.
thank you.

Hi,

Here are a few resources on suspension bridge design:

http://illumin.usc.edu/article.php?articleID=33&page=1

http://en.wikipedia.org/wiki/Suspension_bridge

http://www.ingentaconnect.com/content/i ... 3/art00003

Here is a google book review on a book on the history and design of bridges which you may find in a library(note a feature to find a library that has it near you - on the right side toward the bottom).

http://books.google.com/books?id=v96pMi ... 314-IA4,M1

Here is a lesson plan on building suspension bridges

http://www2.scholastic.com/browse/lessonplan.jsp?id=664

And here is a review article of several suspension bridges:

http://www.vetmed.wsu.edu/org_nws/NWSci ... awford.PDF

I do not know how to answer your direct question. The major design guidelines I found appear to focus on the ratio of the width of the roadway and the depth of the stiffenening girder substructure to the roadway. The principal issue seems to be preventing undulation instability to crosswinds of the type that caused the Tacoma Narrows bridge to fail soon after construction.

This looks like a really interesting subject to investigate. Have fun with it!

Best Regards,

Barrett Tomlinson