Engineering Mechanics

Chapter 14 : Analysis of Perfect Frames (Graphical Method) „„„„„ 307

Example 14.13. A frame is supporting two loads of 5 kN each at D and E as shown in
Fig. 14.31.

Fig. 14.31.
Find the forces in the members of the frame and the reactions at A and B.
Solution. First of all, draw the space diagram for the frame and name the members according
to Bow’s notations as shown in Fig. 14.31 (a).

Fig. 14.32.

Now draw the vector diagram for the frame as shown in Fig. 14.32 (b), starting from the joint
E. Measuring the various sides of the vector diagram, the results are tabulated here :

S.No. Member Magnitude of force in kN Nature of force

1 EF 11.2 Compression

2 ED 10.0 Tension

3 DF 5.0 Compression

4 CD 10.6 Tension

5 CF 5.6 Tension

6 FA 16.75 Compression

7 AC 17.5 Compression

8 CB 21.2 Tension

Reactions at A (RA) = 3 - 4 = 29.2 kN Ans.

and reaction at B (RB) = 1 - 4 = 21.2 kN Ans.