Page 372 - Aircraft Stuctures for Engineering Student

Problems 353

Ans. dO/dz = 0.192S/Gta2 (clockwise)
q1 = -OXS/a, q2 = qs = -0.47S/a, q3 = 47 = -0.17S/a

q4 = q6 = 0.13S/a, q5 = 0.18S/a
Parabolic distributions, q positive clockwise.

P.9.17 Figure P.9.17 shows the cross-section of a single cell, thin-walled beam
with a horizontal axis of symmetry. The direct stresses are carried by the booms B1
to B4, while the walls are effective only in carrying shear stresses. Assuming that
the basic theory of bending is applicable, calculate the position of the shear centre
S. The shear modulus G is the same for all walls.
2
Cell area = 135000mm2. Boom areas: B1 = B4 = 450mm , B2 = B3 = 550mm .
2
Wall Length (mm) Thickness (mm)
12, 34 500 0.8
23 580 1 .o
41 200 1.2

Ans. 197.2mm from vertical through booms 2 and 3.

100 mm
- --
-
-----
1.0 mm
100 mm 100 mm
0.8 mm
500 mm
Fig. P.9.17
P.9.18 A thin-walled closed section beam of constant wall thickness t has the
cross-section shown in Fig. P.9.18.

Fig. P.9.18