Engineering Mechanics

Chapter 14 : Analysis of Perfect Frames (Graphical Method) „„„„„ 303

Example 14.9. Figure 14.23 shows a cantilever truss with two vertical loads of 1 kN each.

Fig. 14.23.
Find the reactions and forces in all the members of the truss.
Solution. First of all, draw the space diagram and name all the members and forces accord-
ing to Bow’s notations as shown in Fig. 14.24 (a).

Fig. 14.24.
Now draw the vector diagram, starting from the free joint (3) as shown in Fig. 14.24 (b).
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 1-2 (AD) 2.3 Tension

2 2-3 (BF) 0.6 Tension

3 3-4 (CF) 1.15 Compression

4 2-4 (EF) 1.15 Tension

5 4-5 (CE) 1.15 Compression

6 2-5 (DE) 2.3 Compression

Reactions

Upper R 1 (ad) = 2.3 kN;

Lower R 5 (cd) = 3.05 kN Ans.