Page 508 - Aircraft Stuctures for Engineering Student

Problems 489

the applied loads and the appropriate elastic moduli, E for the longitudinal members
and G for the sheet.
Evaluate these expressions in the case where P = 450 000 N; P, = 145 000 N; S =
350N/mm; ae = 275N/mm2; I = 1250mm; b = 250mm; t = 2.5mm and G = 0.38E.
Find the fraction of the total tension at the abutment which is carried by the stringer.
1.25Ps
Ab- Lz-- ;) +-,
Am. '-:b( a,

P.11.7 A symmetrical panel has the form shown in Fig. P. 1 1.7. The longerons are
of constant area, B1 for the edge member and B2 for the central members, and the
sheet is of uniform thickness t. The panel is assembled without stress.
Obtain an expression for the distribution of end load in the central longeron if it is
then raised to a temperature T (constant along its length) above the edge members.
Also give the longitudinal displacement, at one end of the panel, of the central
longeron relative to the edge members.
Assume that end loads are carried only by the longerons, that the sheet carries only
shear, and that transverse members are provided to prevent transverse straining and
to ensure shear effectiveness of the sheet at the ends of the panel.

PI
Am. cosh pz - tanh-sinhp - 1
2
aT 1
Disp. = - tanhp-
P 2
where

Fig. P.11.7

P.11.8 The flat panel shown in Fig. P. 11.8 comprises a sheet of uniform thickness
t, a central stringer of constant area A and edge members of varying area. The panel
is supported on pinned supports and is subjected to externally applied shear flows
SI and S,, together with end loads and P2,0 as shown. The areas of the edge