Page 556 - Aircraft Stuctures for Engineering Student

Problems 537

Y

Fy,l I "1

L L L
4 b

Fig. P.12.6

Am. vg = vc = -5PL3/144EI, eB = -ec = PL~~EI
Si =2P/3, S2 = &P/3

FJ,A = P/3: MA = -PL/4
P.12.7 The symmetrical rigid jointed grillage shown in Fig. P. 12.7 is encastrk at 6,
7,8 and 9 and rests on simple supports at 1,2,4 and 5. It is loaded with a vertical point
load P at 3.
Use the stiffness method to find the displacements of the structure and hence calcu-
late the support reactions and the forces in all the members. Plot the bending moment
diagram for 123. All members have the same section properties and GJ = 0.8EI.