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: Structures. column theory, Buckling

  1. Dec 11, 2008 #1
    1. The problem statement, all variables and given/known data

    the question is in the picture.
    the rectangular steel bar shown supports a concentric load of 13000lbf. Both ends are fixed. If te modulus of elasticity is 29x10^6 lbf/in^2, what is the maximum length the rod can be without experiencing buckling failure?

    2. Relevant equations

    3. The attempt at a solution

    what I got was 81.3365. but I am not sure.
    moment of inertia I got .1953125 from the cross section and just used Pcr = (I*E*(pie)^2)/(K*L^2) used .65 for K coz its fixed fixed.

    Attached Files:

    • jj.jpg
      File size:
      33.4 KB
  2. jcsd
  3. Dec 11, 2008 #2


    User Avatar
    Science Advisor
    Homework Helper
    Gold Member

    Your calculation for the moment of inertia is incorrect. I don't know what formula you used, but you should use the Moment of Inertia of a rectangular bar about its weakest axis. Also, your buckling formula is incorrect, the K neeeds to be squared also, and K (ideal case) is 0.5 for a fixed-fixed column.
Share this great discussion with others via Reddit, Google+, Twitter, or Facebook