Page 488 - Aircraft Stuctures for Engineering Student

11.5 Constraint of open section beams 469

Fig. 11.27 Computation of swept area AR.

and

giving

(1 1.56)

The axial constraint shear flow system, qr, is in equilibrium with the self-
equilibrating direct stress system. Thus, from Eq. (9.22)
d0-r
aqr
-+t-=o
as dz
Hence
---I- - a0r
dqr
dS dZ
Substituting for mr from Eq. (1 1.54) and noting that qr = 0 when s = 0, we have
d3 B
qr = 2AREt 2 ds

or

(1 1.57)

Now

or, from Eq. (1 1.57)