Introduction to Aircraft Structural Analysis (Elsevier Aerospace Engineering)

144 CHAPTER 5 Energy Methods

Fig.5.21

Statically indeterminate truss of Example 5.9.

in which (^) ADandvCare, respectively, the change in length of the diagonal AD and the vertical
displacement of C due to the actual loads acting on the released truss, whilea 11 ,a 12 , and so on are
flexibilitycoefficients,whichwehavepreviouslydefined.Thecalculationsaresimilartothosecarried
outinExample5.8andareshowninTable5.7.Fromthattable,
(^) AD=
∑n
j= 1
F0,jF1,j(X 1 )Lj
AE

=

−27.1

AE

(i.e.,ADincreasesinlength)

vC=

∑n

j= 1

F0,jF1,j(R 2 )Lj

AE

=

−48.11

AE

(i.e.,Cdisplaceddownwards)

a 11 =

∑n

j= 1

F1,^2 j(X 1 )Lj

AE

=

4.32

AE