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6–17.
If the maximum force that any member can support is 8 kN
in tension and 6 kN in compression, determine the
maximum force Pthat can be supported at joint D.
SOLUTION
Method of Joints: In this case, the support reactions are not required for
determining the member forces.
Joint D:
+©F
F
DC
sin 60° -P=0F
DC
=1.1547P1T2+c©F
y
=0;
60°
60°
4m 4m
B
ED
C
A
4m
P
502
SOLUTION
6–18.
Determine the force in each member of the truss and state
if the members are in tension or compression. Set
P1 = 10 kN, P2 = 8 kN.
1 m 1 m2 m
2 m
A
FE
G
BCD
P1P2
6–18. Continued
504
6–19.
Determine the force in each member of the truss and state
if the members are in tension or compression. Set P1 = 8 kN,
P2 = 12 kN.
1 m 1 m2 m
2 m
A
FE
G
BCD
P1P2
6–19. Continued
506
*6–20.
Determine the force in each member of the truss and state
if the members are in tension or compression. Set P1 = 9 kN,
P2 = 15 kN.
3 m
A
BC
D
FE
3 m
4 m
P1
SOLUTION
*6–20. Continued
508
6–21.
Determine the force in each member of the truss and state
if the members are in tension or compression. Set P1 =
30 kN, P2 = 15 kN.
SOLUTION
3 m
A
BC
D
FE
3 m
4 m
P1
5
5
6–22.
3b+Pa2L
3b-(D
D
etermine the force in each member of the double scissors
t
russ in terms of the load P and state if the members are in
t
ension or compression.
BC
L/3
6–23.
Determine the force in each member of the truss in terms
of the load Pand state if the members are in tension or
compression.
SOLUTION
D
E
d
*6–24.
The maximum allowable tensile force in the members of the
truss is and the maximum allowable
compressive force is Determine the
maximum magnitude of the load Pthat can be applied to
the truss.Take d=2m.
1F
c2max =3 kN.
1F
t2max =5 kN,
SOLUTION
AC
D
E
d
d/2
Support reactions:
a
+©ME=0;
Axa3
2db-Pd =0Ax=0.6667P
6–25.
Determine the force in each member of the truss in terms of
the external loading and state if the members are in tension
or compression. Take P = 2 kN.
AB
C
D2 m
2 m
2 m
2 m
PP
30fi
6–26.
The maximum allowable tensile force in the members of the
truss is
(Ft)max =5 kN,
and the maximum allowable
compressive force is
(Fc)max =3 kN.
Determine the
maximum magnitude P of the two loads that can be applied
to the truss.
A
B
C
D2 m
2 m
2 m
2 m
PP
30fi
SOLUTION
6–27.
Determine the force in members DC,HC, and HI of the
truss, and state if the members are in tension or
compression.
SOLUTION
C
G
ED
H
F
I
B
2m 2m 2 m
1.5 m
50 kN
40 kN
40 kN
30 kN
1.5 m
*6–28.
SOLUTION
Determine the force in members ED,EH,and GH of the
truss,and state if the members are in tension or compression.
C
G
ED
H
F
B
2m 2m 2 m
1.5 m
50 kN
40 kN
40 kN
30 kN
1.5 m
6–29.
Determine the force in members HG,HE,and DE of the
truss,and state if the members are in tension or compression.
SOLUTION
A
BC D EF
GHIJ
K
4 ft
3 ft 3 ft3 ft3 ft3 ft
6–30.
Determine the force in members CD,HI,and CJ of the truss,
and state if the members are in tension or compression.
SOLUTION
A
BCDEF
GHIJ
K
4 ft
3 ft 3 ft3 ft3 ft3 ft
6–31.
Determine the force in members CD,CJ, KJ,and DJof the
t
russ which serves to support the deck of a bridge. State if
t
hese members are in tension or compression.
SOLUTION
a
Ans.
a
Ans.
Ans.
Joint D:Ans.F
DJ
=0
F
CJ
=3125 lb =3.12 kip (C)
:
+©F
x
=0;-9375 +11 250 -3
5F
CJ
=0
F
CD
=9375 lb =9.38 kip (C)
+©M
J
=0;-9500(27) +4000(18) +8000(9) +F
CD
(12) =0
F
KJ
=11 250 lb =11.2 kip (T)
+©M
C
=0;-9500(18) +4000(9) +F
KJ
(12) =0
AG
HIJKL
FEDCB
4000 lb
8000 lb 5000 lb
9ft9ft9ft9ft9ft9ft
12 ft
*6–32.
Determine the force in members EI and JI of the truss
w
hich serves to support the deck of a bridge. State if these
m
embers are in tension or compression.
SOLUTION
a
Ans.
Ans.F
EI
=2500 lb =2.50 kip (C)
+c©F
y
=0; 7500 -5000 -F
EI
=0
F
JI
=7500 lb =7.50 kip (T)
+©M
E
=0;
-5000(9) +7500(18) -F
JI
(12) =0
AG
HIJKL
FEDCB
4000 lb
8000 lb 5000 lb
9ft9ft9ft9ft9ft9ft
12 ft
