' . ' σ3Μ,
(.12.8,).
ֳ . ϳ ' Τ(. 12.8, ) , . , Τ .
' σ3Μ, F = 0,5σbl (l ') b/6 ( 䳿 F ).
, , 䳺 F, , 䳺 , 䳺 Fs . ,
= Fb/6 + Fsd/2 + Fsc. (4)
, Fs = Fƒ ≈ d/2, (4) :
T = F (b/6 + ƒd) (5)
F σ, (5) : Τ == 0,5σ3Mbl(b/6 + ƒd);
σ3M = 12T/ [bl(b + 6ƒd)]. (6)
' σ3Μ ≤ [σ], σ3Μ (6), [σ]3Μ = (80... 100) .
, .
' . ' , ' ,
, (. 12.9).
, ', , , . . 12.9 T = Fsd = Fƒd = σ3Μb l ƒd,
l , .
' : [σ]3Μ = T/(blƒd) ≤ [σ]3Μ (7)
[σ]3Μ = (70...80) .
' . ' (. 12.6) . . 12.6 ' :
σ3Μ = 4T/(ddl) ≤ [σ]3Μ. (8)
[σ]3Μ = (100...120) .