Page 123 - Marks Calculation for Machine Design

P1: Sanjay
January 4, 2005
16:18
Brown.cls
Brown˙C02
U.S. Customary BEAMS SI/Metric 105
Step 2. The couple (C B ) is given by Step 2. The couple (C B ) is given by
C B =−Fb =−(150 lb)(5ft) C B =−Fb =−(700 N)(1.5m)
=−750 ft · lb =−1,050 N · m
Notethattheminussignmeansitisclockwise Notethattheminussignmeansitisclockwise
(cw). (cw).
F
a b
A B

L
FIGURE 2.92 Concentrated force at intermediate point.

Shear Force and Bending Moment Distributions. For the cantilevered beam with a
concentrated force (F) at an intermediate point, shown in Fig. 2.92, which has the balanced
free-body-diagram as shown in Fig. 2.93, the shear force (V ) distribution is shown in
Fig. 2.94.
F
B = 0
x

C = –Fb
B
B y = F
FIGURE 2.93 Free-body-diagram.
Note that the shear force (V ) is zero from the left end of the beam to the location of the
concentrated force (F), at a distance (a). At this point the shear force drops to a constant
negative value (F) and continues at this value to the right end of the beam. The maximum
shear force (V max ) is therefore
V max = F (2.63)
The bending moment (M) is also zero from the left end of the beam to the location of the
concentrated force (F). At this point the bending moment (M) starts to decrease linearly

V

0 x
L
–
–F

FIGURE 2.94 Shear force diagram.