Structures. column theory, Buckling

1. Dec 11, 2008

jahoony

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.

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2. Dec 11, 2008

PhanthomJay

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.