Civil Engineering Reference
In-Depth Information
7.7.3
Case 3—Interior support
Bending moment due to dead load plus 20% of live load is
w .20w
w
+
D
LNeg
M:
M
⋅
=
197.5ftkip
⋅
⋅
=
3_creep
s3
SNeg
Ratio of modulus of elasticity of bars to modulus of elasticity of concrete is
n
f
= 1.277
Ratio of depth of neutral axis to reinforcement depth, calculated per
Equation (8-12), is
(
)
2
k:
2n
ρ⋅ +ρ ⋅
n
ρ⋅ =
n
0.209
=
3
f3
f
f3f
f3
f
The tensile stress in the FRP is
M
3_creep
f
:
=
12.5ksi
⋅
=
f3_creep
k
3
3
Ad 1
⋅
⋅
−
f3
f3
(
)
“OK” if f
≤
f
f
=
12.8ksi
⋅
f3_creep
f_creep
f_creep
Check_Creep3
:
=
“Not good”otherwise
Check_Creep3 = “OK”
ε
f3_creep
= 0.00219
A
f
d
f1
= 26
·
in
k
creep_R
ε
fu
= 0.00225
Navier's equation is applicable because the maximum concrete stress is
smaller than 0.45
f
′c:
E
c
·ε
c_creep3
= 2577·psi
< 0.45f ′
c
= 2700·psi
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