Civil Engineering Reference
In-Depth Information
L
l
1
l
2
H
=
H
a
=
H
b
=
kl2/f
2
/
f
P
= 1
kL
V
a
= 1−
k
+
Hc
/
L
V
b
=
k
−
Hc
/
L
B
H
b
C
f
c
H
a
V
b
A
(a)
V
a
+
H
influence line
O
O
l
1
l
2
fL
Figure 2.36
(a, b) Typical influence line of a three-hinged arch.
(b)
through arches with hangers, the segments should coincide with the panel
joints. For solid spandrel arches, 20 segments between the spring lines
should be enough, and the distribution of live and dead loads are best dealt
with as discrete point loads. The fill pressure considers the soil at rest, and
total loads on arch segment are shown in Figure 2.37. More detailed discus-
sions on analysis and construction will be covered in Chapter 9.
2.5.8 Cable-stayed bridge
A cable-stayed bridge is a highly statically indeterminate structure. Cable-
stayed bridge may be analyzed as a planar or space frame with consider-
ation of its linear and nonlinear behavior.
Linear system
—For a linear system, the deflections of the structural sys-
tem under applied loads may be determined by applying the classical theory
(or so-called first-order theory). By assuming Hook's law, linear superposition
is applied to the internal forces, the displacements, and the stresses. However,
for cable-stayed bridges, the linear assumption is on the nonconservative side
for long-span bridges and can be used only for preliminary designs.
G
i
Q
Q
q
q
g
(ξ)
y
Y
ξ
H
H
B
l
B
r
l
/4
l
/4
l
/6
l
/6
ξ
i
x
x
′
l
l
l
(a)
(b)
(c)
Figure 2.37
(a) Arch model and (b, c) critical loads on arch segment.
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