Kesk- ja peainertsmomendid
Liitkujundi staatiline moment:
Sx0 = Sx1+Sx2+Sx3 = A1y1 + A2y2 + A3y3 = a*2a*4,67 + a*b*10,5 + (ba)/2*21 = 7*14*4,67
+ 7*9*10,5 + (9*7)/2*21 = 1780,66 (cm 3)
ristlõikepindala A = A1 + A2 + A3 = 98+63+31,5 = 192,5 (cm3)
Pinnakeskme koordinaat yc = Sx/A = 1780,66/192,5 = 9,25 (cm)
Ristlõike keskpeainertsimomendid
Iy = Iy1 + Iy2 + Iy3 = (2a*a3)/12 + (a*b3)/12 + (ab3)/48 = (14*343)/12 + (7*729)/12 +
(7*729)/48 = 400.167 + 425,25 + 106,3125 = 931,73 (cm 4)
Ix = (Ixi + Aiyci2) = =
= (1600,67 + 7*14*7) + (257,25 +220,5) + (85,75 + 31,5*9,33) = 2286,67 + 477,75 +
85,75 + 293, 895 = 3144,065 (cm4)
yc1= a + 1/3*a = 7 + 2,33 = 9,33 (cm)
yc2= a/2 = 7/2 = 3,5 (cm)
yc3= (2*a)/2 = a = 7 (cm)
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