Civil Engineering Reference
In-Depth Information
Axial force at O and bending moment introduced at removal of
shores is:
N
M
0
2800 × 10
3
N-m
=
The axial strain at O and the curvature caused by these forces
(Equation (2.32) ) is
ε
O
(
t
0
)
ψ
1
30×10
9
(1.6474 × 2.1367
=
−
1.6788
2
)
(
t
0
)
2.1367
1.6788
1.6788
1.6474
0
2800 × 10
3
×
223
219 m
−1
=
10
−6
bre
and hence the corresponding stress. Superposition of these stresses and
strains and of the values determined in (a) above gives the stress and
strain distributions shown in Fig. 2.9(b).
The values of
ε
O
(
t
0
) and
ψ
(
t
0
) are used to
fi
nd the strain at any
fi
(c) Changes in stress and strain due to creep, shrinkage
and relaxation
Age-adjusted elasticity modulus is
30×10
9
E
c
(
t
,
t
0
)
=
0.75 × 2.5
=
10.435 GPa.
1
+
In the restrained condition, stress in concrete is (Equation (2.45) ):
(
σ
c restrained
)
top
=−
10.435 × 10
9
[2.5(
−
176×10
−6
)
−
350×10
−6
]
=
8.24 MPa
(
σ
c restrained
)
bot
=−
10.435 × 10
9
[2.5(
−
128×10
6
)
−
350×10
−6
]
=
6.99 MPa
To calculate the axial force at O and the bending moment necessary
to prevent creep by Equation (2.42), we must
fi
nd (
ε
O
)
1
and
ψ
1
de
fi
ning
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