1. Limited time only! Sign up for a free 30min personal tutor trial with Chegg Tutors
    Dismiss Notice
Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Homework Help: Tough Civil Eng. Problem

  1. Oct 6, 2009 #1
    1. The problem statement, all variables and given/known data

    When building a tall support, often the self weight of the support must be considered. For an optimal support, the volume of material, and hence the cost, will be a minimum. If the maximum allowable stress in concrete is 12 MPa, determine the optimal geometry of the column 100m tall made of concrete to support a mass of 1000 tonnes at its top (like the CN tower).

    2. Relevant equations

    Weight concrete: 24Kn/m^3
    Stiffness: 30000MPa
    Cost: $0.05/kg

    3. The attempt at a solution

    well I guess I can find the total force = 1000(#tonnes) x 9.81.

    Also Stress = Force/Area and from that I can find the radius/diameter of the cylinder.

    But the cylinder is suppose to be sort of "cone" shaped I think for optimal geometry (like the CN Tower)

    Also, would there have to be a function to find the minimum cost and volume of building this structure?

  2. jcsd
  3. Oct 6, 2009 #2
    I can't say much, but as for the minimum cost, you might want to try some linear programming given your constraints
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook