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ekbhavesh14 • Dec 23, 2008

# Problem on suspension bridges

hi all..I am a student of 2nd yr.
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.
These point loads would be loaded one at a time with each going through the length of the bridge.

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.
raj87verma88 • Dec 23, 2008
Re: suspension bridges.

I am so sorry, but we are not going to spoon feed you. To search for the formulas and basic theory there are things called 'Textbooks'. If you want to get more detail about your subject then there is a place called 'The Library'.
ekbhavesh14 • Dec 24, 2008
thank you for ur reply sir.
but i did search for it in text books and the net too, and the results i came to know was, that the main suspension cable takes the shape of a parabola once tension starts acting on it.
thus i'll have to derive the eqn of the parabola so formed.
but sir since i have to submit an abstract for my project, i was looking forward for some kind of formulae(if any) so as to put it in there.
more over i am in middle of my exams and i dont wish any of my project or my exams to take a beating due to the other.
please if you can help me..
thank you once again.
gohm • Dec 24, 2008
Try a internet search of "suspension bridge formula" or "suspension bridge tower height formula".

read "A practical treatise on suspension bridges: their design, construction & erection" by D B Steinman

Also, more important you first need to determine the deck load as this is the major load of any suspension cable. Cables need to be a parabolic curve so input your info into that formula will dictate your tower height after load, span distance, cable height to deck, etc. are determined. You should be able to get the rest from there... It's tough balancing exam & projects, been there, but you can do it! don't give up or cut corners.