QUESTION 2 (14 Marks)
PLO
PLO2
CLO
CLO3
(a)
(b)
Marks 11
3
Figure 2 shows the truss consist of square cross-sectional bars made of the same alloy. It is known
that the bar with a 20-mm square cross section was tested to failure and that an ultimate load of
120 kN. If bar AB has a 15-mm square cross section.
(a) Determine the factor of safety (F.S) for bar AB.
(11 Marks)
(b) Determine the dimensions of the cross section of bar AC if it has the same F.S as bar AB.
(3 Marks)
Additional information: F.S = $\frac{\text{ultimate load}}{\text{allowable load}}$ or F.S = $\frac{\text{ultimate stress}}{\text{allowable stress}}$
1.4 m
0.75 m
A
C
0.4 m
↓
B
28 kN
Figure 2: The structure of truss.