Simple framework, maximum force and stress.

Waelroe
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Homework Statement


A simple framework by two rods linked in A, B and C. Burdened by a force F. The rods is of square cross section 30x30 mm and made by steel 1550-01 -> E = 210 GPa.


[PLAIN]http://img718.imageshack.us/img718/125/ram001.jpg

Determinate maximum force F and the stress in the rods AB and BC.

Homework Equations


I = w*h^2/12

Fb = pi^2*E*I/L^2


The Attempt at a Solution


My guess is that It's enough to calculate the breaking of BC to get the maximum force F.

I = 0,03^4/12 = 6,75*10^-8 m^2

Fb = 22,4 kN

Then I assumed I could use tanX = a/b -> (a=F) -> F = 22,4*tan30 = 12,932 kN.

Could that be the correct answer?


For the stress I guess I should use σ=F/A, just by putting the things I got into that I get 22400/9*10^4 = 24,9 MPa, could that be the stress in BC? But then how do I get the stress in AB?
 
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