Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

578 CHAPTER 21 Fuselages

Fig.21.1

(a) Actual fuselage section; (b) idealized fuselage section.

B 11 =B 15 ,B 4 =B 6 =B 12 =B 14 ,andB 5 =B 13 .FromEq.(19.1),

B 1 = 100 +

0.8×149.6

6

(

2 +

σ 2

σ 1

)

+

0.8×149.6

6

(

2 +

σ 16

σ 1

)

thatis,

B 1 = 100 +

0.8×149.6

6

(

2 +

352.0

381.0

)

× 2 =216.6mm^2

Similarly,B 2 =216.6mm^2 ,B 3 =216.6mm^2 ,B 4 =216.7mm^2 .Wenotethatstringers5and13lieon
theneutralaxisofthesectionandarethereforeunstressed;thecalculationofboomareasB 5 andB 13
doesnotthenarise.Forthisparticularsection,Ixy=0,sinceCx(andCy)isanaxisofsymmetry.Further,
My=0sothatEq.(15.18)reducesto

σz=

Mxy

Ixx

inwhich

Ixx= 2 ×216.6×381.0^2 + 4 ×216.6×352.0^2 + 4 ×216.6× 26952

+ 4 ×216.7×145.8^2 =2.52× 108 mm^4

ThesolutioniscompletedinTable21.1.

21.2 Shear...................................................................................................

ForafuselagehavingacrosssectionofthetypeshowninFig.21.1(a),thedeterminationoftheshear
flow distribution in the skin produced by shear is basically the analysis of an idealized single cell