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h
e  R  ;
h (4.4)
R 
2
ln
h
R 
2
– for circular cross section with a diameter d
 2 
1 2  d 
e   R  R     . (4.5)
2   2  
 
Clearly, the calculated value for an arbitrary cross-section is
difficult. Therefore, for engineering calculations, you can use the
approximate formula of Davidenkov
J
e  z , (4.6)
R F
where J – axial moment of inertia of the beam cross-section
z
relative to the central axis, which is parallel to the neutral line. If
the curve is flat beams simultaneously undergoes bending and
tensile (compressive) strength of the condition of the normal
stresses will
N M y 
   max    . (4.7)

max
F S r
н
If the material differently resists tension and compression, in
terms of durability dangerous section should be completed for
both the internal and external layers according to the value of
allowable stress   and   .


р с
In most cases small  compared to  . Tangential stresses 
N м
arising from the action of a transverse force Q , usually in the
calculation of the strength are neglected. If necessary, they
approximately calculated by Zhuravs'kyi’s formula as for straight
beams
Q S
  н . (4.8)
b J
z
In calculating the beam projecting large curvature cross-sectional
dimensions of the required beam is selected by trial with the

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