Civil Engineering Reference
In-Depth Information
6.9 STEP 7—CHECK MAXIMUM
MIDSPAN DEFLECTION
The service bending moment diagram for the exterior bay is shown next.
2
3.92
Section
M
s1
= 2.1kipft
1
1.74
-0.44
Section
M
s2
= 3.6kipft
2
0
3.4
6.8
10.2
13.6
17
-2.62
1
-4.81
Section
M
s3
= 5kipft
3
3
-6.99
Exterior Bay 1-Foot Slab Strip, ft
Exterior bay 1-foot slab strip:
The maximum allowable deflection is
1
480
1
∆
:=
=
0.425·in
.
lim
Preliminary calculations:
The depth of the neutral axis of the gross
section is
d:
t
slab
==
4·in
.
g
2
The gross moment of inertia is
3
I:
bt
12
⋅
slab
=
=⋅
512 in
4
g
The negative cracking moment is
fI
d
⋅
r
g
M:
=
=⋅
6kip ft
⋅
crNeg
g
The positive cracking moment is
fI
⋅
−
r
g
M:
=
d
6kip ft
=⋅
⋅
crPos
t
slab
g
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