Civil Engineering Reference
In-Depth Information
Total factored load for negative moments is
kip
ft
w:
=
1.2w
+1.6 w=4.45
⋅
⋅
TFLNeg
D
LNeg
Total service load for positive moments is
kip
ft
w:
=
w+w=3.6
⋅
SPos
D
LPos
Total service load for negative moments is
kip
ft
w:
=
w+w
3.36
⋅
SNeg
D
LNeg
7.5 STEP 3—COMPUTE BENDING
MOMENTS AND SHEAR FORCES
Bending moments and shear forces are determined as indicated in ACI
318-11. The moment coefficients can be used as the beam satisfies the
requirements specified in ACI 318-11. In fact, there are two spans; the ratio
of the longer clear span to the shorter clear span is less than 1.2, the loads
are uniformly distributed, the unfactored live load does not exceed three
times the unfactored dead load, and the members are prismatic. Clear span
values, l
n
, are computed considering a column width of 24 in.:
l
n
:= l
1
- b
col
= 28∙ft
Bending moments
Exterior support
1
24
Moment coefficient
C:
=
mNeg1
M
uNeg1
:= C
mNeg1
·W
TFLNeg
·1
n
2
= 145·ft·kip
Ultimate bending moment
M
s1
:= C
mNeg1
·W
SNeg
·1
n
2
= 145·ft·kip
Service bending moment
Midspan
1
14
Moment coefficient
C:
=
mPos
M
uPos
:= C
mPos
·W
TFLPos
·1
n
2
= 271·ft·kip
Ultimate bending moment
M
s2
:= C
mPos
·W
SPos
·1
n
2
= 202·ft·kip
Service bending moment
Interior support
1
10
Moment coefficient
C:
=
mNeg2
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