1 Department of Civil and Environment Engineering CGN 4980/CGN 6939 FE/Graduate Seminar Review Examples Fall 2005
Dec 17, 2015
1
Department of Civil and Environment Engineering
CGN 4980/CGN 6939
FE/Graduate Seminar Review Examples
Fall 2005
2
Determine the force in each member of the truss and state if the members are in tension or compression.
Solution:
12
The rod has a weight W and rests against the floor and wal for which the coefficients of static friction are A and B, respectively. Determine the smallest value of for which the rod will not move.
Given:
Find:
Solution:
15
FA
NA
NBW
L sin
FA
FB
slipping must occur at A & B
A
BA
BA
AB
BAA
BBB
AAA
μ2
μμ1tan
μμ1
WμN
μμ1
WN
ngsubstituti and
NμF
NμF
16
The three bars have a weight of WA = 20 lb, WB = 40 lb and WC = 60 lb, respectively. If the coefficients of static friction at the surfaces are as shown, determine the smallest horizontal force P needed to move block A.
Given:
Find:
Solution:
18
NAD
FAD
WABAB
FBC
NCB=WCC+Tsin+Tsin
NCB
FCB
T
WCC
If blocks A & B move first
lb 81.82N and lb 46.36T
017
15TN.5
017
15TNμ
017
15TF
:0F
06017
8TN
:0F
CB
CB
CBCB
CB
x
CB
y
19
NAD
FAD
WABAB
FBC
NCB=WCC+Tsin+Tsin
NCB
FCB
T
WCC
If blocks A & B move first
lb 69.27P
.2N.5NP
0NμNμP
:0F
lb 141.82N
060NN
060NN
:0F
ADCB
ADADCBCB
x
AD
CBAD
CBAD
y
20
FAB
T
T
If blocks A move first
017
15T.3N
017
15TNμ
:0F
000117
8TN
:0F
AB
ABAB
x
AB
y
NAB
NAD
NAD
FAD
WAA
FAB
NAB
WCBCB
0NμNμ-P
:0F
020N-N
:0F
ADADABAB
x
ABAD
y
lb 63.52P
lb 139.05N
lb 119.05N
lb 40.48T
AD
AB
Therefore block A moves first
21
Given: rod,
Find: x
Solution:
Determine the distance x to the center of mass of the homogeneous rod bent into the shape shown. If the rod has a mass per unit length of 0.5 kg/m, determine the reactions at the fixed support O.
22
1.44mL
2
3
x4
91
27
8
1
0
x4
91L
dxdx
dy1dLL
gintegratin
x2
3
dx
dy
xy
xx'
dxdx
dy1dydxdL
1
0
1
0
2
2
1
2
13
222
dx
33
Each of the three members of the frame has a mass per unit length of 6 kg/m Locate the position (x, y) of the center of gravity. Neglect the size of the pins at the joints and the thickness of the members. Also, locate the reactions at the pin A and roller E.
Solution:
35
Segment L(m) x'(m) y'(m) x'L(m2) x'L(m2)1 8 4 13 32 1042 7.211 2 10 14.42 72.113 13 0 6.5 0 84.5
28.211 46.42 260.61
mL
Lyy
mL
Lxx
24.9211.28
61.260'
65.1211.28
42.46'
1
2
3
36
0=A
0=F
1319.N=A
0=WE+A
0=F
342.=E
0=W(8)E
0=M
N 1660.5=1)(6)28.211(9.8=W
x
x
y
yy
y
y
y
A
∑
∑
∑1
2
3
37
Determine the moment of inertia Iy for the slender rod. The rod’s density and cross-sectional area A are constant. Express the results in terms of the rod’s total mass m.