CIVL 4135
HOMEWORK SET 7 154
CIVL 4135 Flexure
A. Determine whether the reinforcement area meets the ACI requirement for maximum area allowed and then cal-
culate the ultimate moment for the section shown below.
16โ
6โ
16โ
4โ
As=4.0
in2
fโc=4ksi
fy=60ksi
Answer:
Mu= 2950 in--kips
B. a 6โby 12โhole is located in the center of a reinforced concrete cross section to reduce the weight of the beam.
Determine the nominal flexural capacity of the member if the beam is subjected to positive moment.
21โ
24โ
12โ
fcโฒ=3.5 ksi
fy=60 ksi
3--#10 bars
12โ
6โ
6โ
6โ
3โ3โ
Hole
Answer: 4049 in- kips
C. (a) Determine balanced steel As for thr symmetrical cross section shown below to be on the borderline of Ten-
sion and Transition.
(b) What is the maximum area of the steel permitted in the cross section by the ACI code?
(c) Determine the nominal flexural capacity of the member if the beam is subjected to positive moment.
fโc=4.0ksi
fy=60ksi
Answer:
Asb =in
2
As,max =
Mn=?
15โ
5โ
5โ
20โ 27.25โ
5โ
3-#8
