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Homework Help: Braced column under compressive load

  1. May 27, 2012 #1
    Screen Shot 2012-05-27 at 10.21.09 PM.png 1. The problem statement, all variables and given/known data

    2. Relevant equations

    P = EI pi^2 / Leff radius of gyration: SQRT (I/A), slenderness ratio: Leff/r

    3. The attempt at a solution

    So I've found Ixx = 240.81 x 10^6 mm^4, Iyy = 71.9 x 10^6 A = 9600 finding the radiuses of gyration rx = 158.38, ry = 86.54
    effective length of x axis : (one end pinned, i'm assuming the buckling = fixeed and do i use the longer length?) 6*0.7 = 4.2
    efective length of y: 10*1 (both ends pinned)
    I'm not sure about the effective length part, I know I'm meant to find the larger slenderness ratio (which identifies the weaker axis) and then plug that into the P = EI pi^2 / Leff . I don't know how to address a column supported in this way. do I average the lengths or something?
  2. jcsd
  3. May 27, 2012 #2


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    Science Advisor
    Homework Helper
    Gold Member

    You should use k = 1 as the effective length factor in both cases, where L = 10 for major axis and L = 6 for minor axis. This is due to member rotation at the braced support at the buckling mode. See which controls. Also check your buckling formula the L should be squared, Pcr = pi^2 EI/L^2
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