Page 80 - Marks Calculation for Machine Design

P1: Sanjay
January 4, 2005
Brown˙C02
Brown.cls
62
U.S. Customary 16:18 STRENGTH OF MACHINES SI/Metric
Step 2. From Fig. 2.38 calculate the roller Step 2. From Fig. 2.38 calculate the roller
reaction (B y ) as reaction (B y ) as
wL (750 lb/ft)(6ft) wL (10,000 N/m)(1.8m)
B y = = B y = =
3 3 3 3
4,500 lb 18,000 lb
= = 1,500 lb = = 6,000 N
3 3
w
A B

L
FIGURE 2.39 Concentrated force at midpoint.

Shear Force and Bending Moment Distributions. For the simply-supported beam with a
triangular distributed load (w) acting from left to right across the beam shown in Fig. 2.39,
which has the balanced free-body-diagram shown in Fig. 2.40, the shear force (V ) distri-
bution is shown in Fig. 2.41.
w

A = 0
x

A = wL/6 B = wL/3
y
y
FIGURE 2.40 Free-body-diagram.

V
wL/6
+
0 x
L
–
0.577 L

–wL/3

FIGURE 2.41 Shear force diagram.
The shear force (V ) starts at a positive (wL/6) at the left end of the beam and decreases to
zero at the point (0.577 L), continuing on to a negative (wL/3) at the right end of the beam.