6–21. The compound beam is subjected to a uniform dead
load of 200 lb>ft and a uniform live load of 150 lb>ft. Determine
(a) the maximum negative moment these loads develop at A,
and (b) the maximum positive shear at D. Assume B is a pin
and C is a roller.
SOLUTION
ABDC
5 ft 5 ft 5 ft
6–23. The beam supports a uniform dead load of 500 lb>ft
and a single live concentrated force of 5 k. Determine
(a) the maximum negative moment at E, and (b) the maximum
positive shear at E. Assume the support at D is a pin, A and C
are rollers, and B is a pin.
SOLUTION
A
9 ft9 ft9 ft9 ft
BCD
E
6–25. Draw the influence lines for (a) the vertical reaction at
A, (b) the shear just to the right of A, and (c) the moment at C.
Assume C is fixed, A is a roller, and B is a pin.
SOLUTION
ABC
8 ft 16 ft 10 ft
6–26. A uniform live load of 0.4 k>ft and a concentrated live
force of 2 k are to be placed on the floor slabs. Determine
(a) the maximum live shear in panel CD, and (b) the maximum
live moment at B.
SOLUTION
DE
CA B
5 ft 5 ft 5 ft5 ft
6–27. Draw the influence line for the moment at E in the
girder. Determine the maximum positive moment in the girder
at E if a single concentrated live force of 1200 lb and a uniform
live load of 200 lb>ft can be placed on the floor beams. Assume
A is a pin and D is a roller.
SOLUTION
CD
E
BA
8 ft 8 ft 4 ft
6–29. Draw the influence lines for (a) the shear in
panel BC of the girder, and (b) the moment at D.
SOLUTION
B
A
CDEF
2 m2 m2 m2 m2 m
6–31. A uniform live load of 200 lb>ft and a single
concentrated live force of 1500 lb are placed on the top beams.
If the beams also support a uniform dead load of 50 lb>ft,
determine (a) the maximum negative shear in panel BC of the
girder and (b) the maximum positive moment in the girder at B.
Assume C is a roller and A is a pin.
SOLUTION
D
C
AB
16 ft 8 ft 8 ft
258
*6–32. Draw the influence lines for (a) the moment at D in
the girder, and (b) the shear in panel BC.
SOLUTION
4 m 4 m 4 m 4 m
E
BC D
A
6–33. A uniform live load of 300 lb>ft and a single
concentrated live force of 2 k are to be placed on the floor
beams. Determine (a) the maximum negative shear in
panel AB, and (b) the maximum negative moment at B.
Assume the supports at A and E are pins and the pipe columns
only exert vertical reactions on the beams.
SOLUTION
CDE
BA
4 ft 4 ft4 ft 4 ft 4 ft
260
6–34. Draw the influence line for the moment at B in the
girder. Determine the maximum positive live moment in the
girder at B if a single concentrated live force of 10 k moves
across the top beams. Assume the supports for these beams can
exert both upward and downward forces on the beams.
SOLUTION
ABE
CD
8 ft 8 ft 8 ft 8 ft 8 ft
(MB) max (+)=10(12) =120 k #ft
Ans.
(MB) max (+)=120 k #ft
Ans.
6–37. A uniform live load of 1.75 kN>m and a single
concentrated live force of 8 kN are placed on the floor beams.
If the beams also support a uniform dead load of 250 N>m,
determine (a) the maximum negative shear in panel BC of the
girder and (b) the maximum positive moment at B.
SOLUTION
C
3 m 1.5 m 1.5 m
A
B
D
6–38. Draw the influence line for the force in (a) member KJ
and (b) member DK.
SOLUTION
A
LK JIH
BCDEF
G
3 m3 m3 m3 m3 m3 m
4
m
6–39. Draw the influence line for the force in (a) member HI,
(b) member FI, and (c) member EF.
SOLUTION
A
LK JIH
BCDEF
G
3 m3 m3 m3 m3 m3 m
4
m
266
*6–40. Draw the influence line for the force in member KJ.
SOLUTION
A
LK JI
H
BCDE FG
8 ft8 ft8 ft8 ft8 ft8 ft
8 ft