Page 383 - Aircraft Stuctures for Engineering Student

364 Stress analysis of aircraft components

Similarly

(10.3)

The internal shear force S, comprises the resultant Sy!w, of the web shear flows
together with the vertical components of PI and P2. Thus

or

(10.4)

so that
SYl SY2
-
Syvw = s, - PZJ - Pr,2- SZ (10.5)
SZ
Again we note that Sy2 in Eqs (10.4) and (10.5) is negative. Equation (10.5) may be
used to determine the shear flow distribution in the web. For a completely idealized
beam the web shear flow is constant through the depth and is given by Sy,,/h. For
a beam in which the web is fully effective in resisting direct stresses the web shear
flow distribution is found using Eq. (9.75) in which Sy is replaced by SY,+,, and
which, for the beam of Fig. 10.1 , would simplify to
S (
q s- - - 3 [ tDy ds + Blyl) (10.6)
Ixx
or
S
4 s- - - .22 ( [ tDy ds + B2y2) (10.7)
Ixx

Example 10.1
Determine the shear flow distribution in the web of the tapered beam shown in Fig.
10.2, at a section midway along its length. The web of the beam has a thickness of

't

400mm2 t' 1

2 rnm

400 mm2
Section AA

(a)
Fig. 10.2 Tapered beam of Example 10.1.