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CES 3102
HW #4
assigned 10/13/10
due 10/21/10
Influence lines – 2 pages
NAME_______________________________
Draw the influence lines for the reactions (By, Dy), the shear just to the right of B (
R
V
B
), and the
moment at C (M
C
). Next, find the worst case moment at C (pos or neg) due to the three point load
configuration moving over the beam from left to right. Find the value of shear to the right of B as the
loads are configured to find worst case moment at C.
C
B
D
A
7 ft
5 ft
6 ft
20 k
8 k
15 k
8 ft
4 ft
IL By
IL Dy
IL
R
V
B
IL M
C
1
18/11
1
7/11
1
30/11
42/11
7/11
By = 18/11 – x/11
Dy = 7/11 + x/11
= Dy
0 < x < 7
=
By
7 < x < 18
= 6*Dy
0 < x < 12
= 6*Dy – 1(x12)
12 < x < 18
1) 8k @ C
Mc = 8(30/11) + 15(1)(.5454) + 20(42/11) = 46.36 k
R
V
B
= 8(6)(1/11) + 15(10)(1/11) +20(7/11) = 30.73
2) 15K @ C
Mc = 8(2)(.4545) + 15(30/11)  20(3)(.5454) = 15.46 k
R
V
B
= 8(2)(1/11) + 15(6)(1/11) + 20(3)(1/11) = 15.09
3) 20K @ C
Mc = 8(0) + 15(0) + 20(30/11) = 54.55 k
R
V
B
= 8(0) + 15(0) + 20(6)(1/11) = 10.91
Slope = .5454
Slope = .4545
Slope = 1/11
Slope = 1/11
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This note was uploaded on 05/17/2011 for the course CES 3102 taught by Professor Gurley during the Fall '10 term at University of Florida.
 Fall '10
 GURLEY

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