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P
F  ;
1
 
 
1

– according to the calculated area determine dimensions of cross
section or select account number from the assortment;
– determine the radius of inertia and rod flexibility according to
tables find  1*;
– compare rates  1 and  1* and if the difference is small, check
the stability condition (5.24) in the case of a significant
difference in values of  1 and  1* perform second
approximation, for which the optimal value of the coefficient
of reduction of the basic allowable stress  2 will be the
arithmetic mean
   *
  1 1 .
2
2
Then repeat all the steps.
To get a satisfactory solution, usually have to perform some
approximations.

Questions for self-assessment

1. What is the phenomenon of instability of compressed
rod?
2. What kind of balance do you know?
3. What is critical power and critical stress?
4. How do you determine the factor of stability of
compressed rod?
5. Which differential equation of bending theory is the
basis for the withdrawal of Euler's formula?
6. What is called flexible rod?
7. What is the radius of inertia of the cross section of the
rod?
8. What kind of Euler’s formula determines the value of
the critical force?
9. How do the stiffness of the cross-section and length of
the rod act at the critical force?

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