7.
7 For the simply supported beam subjected to the
loading shown,
(a) Derive equations for the shear force V and the
bending moment M for any location in the beam.
(Place the origin at point A.)
(b) Plot the shear-force and bending-moment
diagrams for the beam using the derived functions.
(c) Report the maximum bending moment and its
location.
Fig. P7.7
Solution
Beam equilibrium:
M A (50 kN)(3 m) (75 kN)(6 m) Dy (10 m) 0
Dy 60 kN
Fy Ay Dy 50 kN 75 kN 0
Ay 65 kN
Section a-a:
For the interval 0 ≤ x < 3 m:
Fy Ay V 65 kN V 0 V 65 kN
M a a Ay x M (65 kN)x M 0 M (65 kN) x
Section b-b:
For the interval 3 m ≤ x < 6 m:
Fy Ay 50 kN V 65 kN 50 kN V 0
V 15 kN
M b b Ay x (50 kN)(x 3 m) M
(65 kN)x (50 kN)(x 3 m) M 0
M (15 kN) x 150 kN-m
Section c-c:
For the interval 6 m ≤ x < 10 m:
Fy Ay 50 kN 75 kN V
65 kN 50 kN 75 kN V 0
V 60 kN
M c c Ay x (50 kN)(x 3 m) (75 kN)(x 6 m) M
(65 kN)x (50 kN)(x 3 m) (75 kN)(x 6 m) M 0
M (60 kN) x 600 kN-m
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(b) Shear-force and bending-moment diagrams (c) Maximum bending moment
and its location
Mmax = 240 kN-m @ x = 6 m
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only
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