CASE STUDY ON TALMADGE MEMORIAL BRIDGE
Chen Sun1
1
Affiliation
Abstract: The aim of case study of Talmadge Memorial Bridge concerns with the analysis of cablestayed bridge at several aspects, such as considerations of aesthetics, loading, strength, serviceability,
construction, temperature, creep, wind, durability, susceptibility to intentional damage and possible
further changes which the Talmadge Memorial Bridge might have to undergo. Aesthetics is very
important part in this bridge design. It takes on the entire design of new crossing, not only express a
slender profile, but also simplify the components. Simplified balance cantilever erection scheme is
designed for this concrete cable-stayed bridge. The vertical load-bearing system, the mechanisms to
maintain lateral stability and the inert resistance to dynamic loads are all considered in the form of design.
It represents the design philosophy of simplicity and constructs the bridge in the safety and most
economic way.
Keywords: Cable-stayed Bridge; Wind; Cantilever Construction
1 Introduction
Talmadge Memorial Bridge is also called Eugene
Talmadge Memorial Bridge that is located in Savannah,
Georgia in United States (USA). It costs 26,000,000
US dollar to build this bridge. The bridge completed in
1990, which is three-span cable, stayed bridge. This
cable-stayed bridge has two planes of total 144 cables
on the bridge that fan out from the tops of the towers.
Due to the old cantilever truss bridge has become a
danger for large shipping entering the port in Savannah,
Georgia. Therefore, this new cable-stayed bridge was
replaced the old cantilever truss bridge. The Talmadge
Memorial Bridge has 186 feet (56.4 metres) of vertical
navigational clearance. Its horizontal clearance is 1,023
feet (312 metres) with both main piers located on the
north and south banks of the Savannah River. The
main span and two side spans of the bridge are 1100
feet (335 meters) and 470 feet (143 meters)
respectively, resulting in a 2,037-foot (621 metres)
cable-stayed unit. The Figure 1 shows a general view
of Talmadge Memorial Bridge over the Savannah
River. The Talmadge Memorial Bridge is a motorway
1
University of Bath, Third Year MEng Civil
Engineering, cs245@bath.ac.uk
bridge with a total length of 1.9miles that is 3.06-kilo
meters. The width of concrete deck is 24.4m (metre)
which carries four lanes of traffic over the Savannah
River with great beauty and style.
Figure 1: General view of Talmadge Memorial Bridge
2 Aesthetics of Bridge
Aesthetics of bridge is the first approach of bridge
design. Beauty should achieve because of good
proportions of the whole bridge and its separate parts.
There are nine areas of aesthetics of bridge, each of
which needs to be consider during bridge design.
2.1 Fulfilment of Purpose--Function
Talmadge Memorial Bridge in order to keep with
philosophy, bridge has the minimum number of
working parts. In Fig 2, it shows a pure, clear form, the
cable-stayed bridge. The cable-stayed form reveals its
load and the way it made and contains nothing
superfluous.
reasonable efficiency. Talmadge Memorial Bridge
chooses an intermediate solution between the extremes
of harp and fan systems, makes it to combine in the
advantages of both systems. The semi-harp system is
not structurally as efficient as the fan system, but there
will not have aesthetics problem. This semi-harp
system in the Talmadge Memorial Bridge avoids ugly
oblique views resulting.
Figure 3: Cable arrangement of Talmadge Memorial
Bridge
2.4 Refining the Form of Design
Figure 2: Cable-stayed Bridge with nothing
superfluous
2.2 Proportion of bridge
The designer of Talmadge Memorial Bridge has
proportion and shape the bridge, so that it is in
harmony with the site. The clear lines of a continuous
concrete deck with the correct balance between the
depth and width provide a wonderful structural form.
The location, size and height of this bridge make it a
highly visible structure. A slender appearance deemed
preferable, especially for the towers that reach 400 feet
(122 metres) above the water. The designer of
Talmadge Memorial Bridge takes on the entire design
of new crossing which also expressed a slender
silhouette. It displays excellent proportion across the
Savannah River.
Refinement of bridge uses to create an aesthetic
bridge. The design philosophy of Talmadge Memorial
Bridge is simplicity. The design of Talmadge Memorial
Bridge make the deck section constant along the total
length of the bridge, and using a simple box section for
the towers, simplified the construction of bridge. The
basic design goal to make the cross-section as simple
as possible that successfully achieved. The deck was
not only easy to construct, it was also one of the
lightest cross sections possible for a cable-stayed
bridge.
2.5 Integration into the Environment
The bridge need to integrate a structure into its
environment and landscape, so that it is aesthetically
compatible with its location and route. The Talmadge
Memorial Bridge looks beautiful across the Savannah
River that shows in Fig 4 with large shipping
underneath. A cable-stayed bridge appears attractive
across a wide span of water. It is an ideal for spanning
natural barriers of Wide River.
2.3 Order within the bridge Structure
In some cases, cable-stayed bridges sometimes
provide the ugly oblique view due to the configuration
of the stay cables. In the design of Talmadge Memorial
Bridge, in order to prevent ugly oblique view, they set
the two planes of stay cables in the semi-harp
configuration, which indicate in Fig 3. This bridge
emphasize in the aesthetics of bridge. In the case, this
long cable-stayed bridge will not have problem of ugly
criss-crossing view of cables when the bridge viewed
from oblique angles. The semi-harp arrangement is a
compromise between the fan and harp arrangement
with the stay anchors on the pylon spread out to ease
congestion and the stay angle maximized to give
Figure 4: Talmadge Memorial Bridge across the
Savannah River
2.6 Surface Texture
When integrating the bridge with its surroundings,
the choice of material and the texture of surface play an
important role in the aesthetics of bridge, but
sometimes ignored. A major role is played by the
choice of materials, the texture of the surface,
particular the colour of the surface. Talmadge
Memorial Bridge builds with the concrete, steel and
composite options. It uses a matt finish on this concrete
bridge. The concrete facade has a dull grey colour at
the beginning, but the properties of concrete lead them
to weather badly. The appearance of the concrete will
change after the bridge in service.
Figure 6: Incorporation of nature in Talmadge
Memorial Bridge
2.9 Summary of Aesthetics
2.7 Colour
Colour plays a significant role in the overall
aesthetics effect of bridge. The white cables have used
on Talmadge Memorial Bridge in order to accentuate
certain cables. It can be seen clearly in Fig 5.
Decorative lighting on Talmadge Memorial Bridge can
be a low cost alternative to achieve very desirable
aesthetic effects. Aesthetic lighting also enhance the
beauty and visibility of the bridge at night.
The designer of Talmadge Memorial Bridge
follows the aesthetic rule of bridge, which designs a
beautiful structure. The designer concentrated on
simplifying the components but increased the aesthetic
appeal. It converts the bridge into something of beauty.
The most important aesthetic of Talmadge Memorial
Bridge is to build the structure in a simple way. It
represents the design philosophy of simplicity.
3 General Design of Bridge
In the early stage, the idea of a cable-stayed bridge
was to use cable suspension to replace the piers as
intermediate supports for the girder so that it could
span a longer distance. The Talmadge Memorial
Bridge is a typical long-span cable-stayed bridge that
the basic resistant arrangement of bridges is formed by
three elements: stay cables, deck and towers that show
in the elevation of Fig 7. This cable-stayed bridge has a
continuous concrete deck with two towers erected
above the piers in the middle of the span. This cablestayed bridge displays a clear load-path, which stiffens
the bridge more than the suspension bridge.
Figure 5: White cables and lighting system in
Talmadge Memorial Bridge
2.8 Incorporating of Nature
The beauty of natural is rich source in the
successful structure form of bridges. It is necessary to
incorporate nature into our designs as much as possible.
Two towers of Talmadge Memorial Bridge are set up
on each bank in order to allow for large shipping
entering the port in Savannah. In addition, bridge also
needs to incorporate into the nature. The right hand
side of Talmadge Memorial Bridge shows in the Fig 6
that displays the bridge incorporate with the nature.
Figure 7: Elevation of Talmadge Memorial Bridge
3.1 Deck of Bridge
The deck of Talmadge Memorial Bridge is a
continuous concrete across the three spans of bridge.
Both concrete and steel alternatives with a composite
deck, which developed for the main span design. The
use of mixed concrete and steel designs in cable-stayed
structure can show considerable advantages. The
interest of this composite deck in the main span
construction lies in the appreciable reduction in dead
weight of the structure. As concrete is good in
compression, it is ideal material to resist the high
compressive forces in the deck by the stay cables. This
compression will help the bridge to resist the bending
moment generated by the deck.
The deck cross-section comprises two concrete
edge beams with floor beams supporting a uniform
concrete slab. This beam and slab arrangement
produces the attractive cross section for the deck, but
two planes of stay cables is need for the support. The
typical beam and slab arrangement for this cablestayed bridge shows in the Fig 8. Twin planes of stays
provide some torsional stiffness to the overall
structural behaviour and less stiff deck arrangements.
In order to enhance the ease of construction, the cross
section of the deck is constant along the total length of
Talmadge Memorial Bridge. This kind of bridge
possess both economical and aesthetics characteristics.
In order to design a more efficient deck for this
slender bridge, a major advance can be made with the
development of monolithic deck in the Talmadge
Memorial Bridge. This monolithic deck resistances to
the lateral wind load by the deck plate alone which acts
as a horizontal beam between the towers. The damping
effect of this monolithic structure is very high and
vibrations are relatively small. This reason is that
concrete is an excellent material for cable-stayed
structure and its properties in resisting compression
and its mass and damping characteristics in resisting
aerodynamic vibrations.
Figure 8: Beam and slab deck with twin plane of stays
The edge beams of Talmadge Memorial Bridge
provide the anchorage for the stays. They stiffen the
deck longitudinally and support the cross beams
spanning transversely. The stay cables are anchored in
the edge beams where they adjoin the floor beams. The
cable spacing in the Talmadge Memorial Bridge is very
small; the bending moment of the girder between the
cables is also small. The depth of girder section of
Talmadge Memorial Bridge is 1.45m for a 355m main
span.
3.2 Stay Cables of Bridge
In the transverse direction to the longitudinal axis
of Talmadge Memorial Bridge, the stay cables lie in a
twin, symmetrically and vertical plane. Whereas in the
longitudinal direction of this bridge, the arrangement of
stay cables are anchored at each tower in a semi-harp
arrangement with a total of 144 stay cables on the
bridge. That is leading to closely spaced stay cables
that anchored near the top of the towers. As a result of
the closely spaced stay cables concentrated near the top
of the tower, the spacing of stay cables is small and
they are not parallel to each other. The steel cables
situated close to the tower are more steeply inclined
than those in a harp arrangement, which makes it
possible to reduce the stiffness of the horizontal
connection between the towers and the deck. The large
number of stay cables anchored on the tower, which
distribute the forces with greater uniformity through
the deck section and provide the continuous elastic
supports. The closely spaced stay cables lead to the
deck section that can be both lighter and simply in its
construction.
4 Towers of Bridge
The towers in Talmadge Memorial Bridge are the
most visible element in this cable-stayed bridge.
Concrete towers have used in the Talmadge Memorial
Bridge. The cross-section of tower is a simple
rectangular box section. Concrete tower is designed as
this kind of hollow section to save weight and to
reduce the amount of concrete and reforcing bars
required. The tower shape has the biggest influence on
the appearance of a cable-stayed bridge and the final
arrangement of tower is based on aesthetic
considerations. The H towers of Talmadge Memorial
Bridge are the most logical shape structurally for a
two-plane cable-stayed bridge. The tower form of
Talmadge Memorial Bridge is a double cranked shaft.
It allows the cables to be aligned in a vertical plane and
to be attached to the girder, which can pass
continuously through the towers. A horizontal strut is
used between the tower shafts, which show a logical
shape for this two plane cable-stayed bridge.
5 Piers of Bridge
Pier provide the vertical support for span which
transferring the superstructure vertical loads to the
foundations and resisting horizontal forces acting on
the bridge. Selection of the proper pier for Talmadge
Memorial Bridge is based on functional, structural and
geometric requirements of the bridge. Due to Talmadge
Memorial Bridge is built across the Savannah River
and it has a prestress concrete superstructure, therefore
hammerhead piers are the best choice for this bridge.
These piers are aesthetically appealing. They generally
occupy less space, thereby providing much more room
for the large shipping underneath. The following Fig 9
shows the hammerhead pier on the end of the
Talmadge Memorial Bridge.
Figure 9: Hammerhead pier in the end of Talmadge
Memorial Bridge
forces from one end wall to the other. The towers
erection were cast in stages and lifted into position.
The towers require special equipment to erect
components to the height of tower during the
construction process. Reforcing bar cages are lifted
into position by crane during the erection of towers.
Tower cranes connected to the towers as it is erected. It
is good choice for handling for steel forms for the
erection of concrete towers.
Figure 10: Tendon layout at the anchorage area
6 Construction of Bridge
6.2 Construction of Pier Table
The Talmadge Memorial Bridge simplified and
reduced the number of parts that made the bridge easy
to construct. The construction of Talmadge Memorial
Bridge used simplify balanced cantilever erection
scheme and designed the form travellers for this castin-place concrete cable-stayed bridge. This balanced
cantilever erection scheme is very often employed in
cable-stayed bridge construction. During the cast-inplace cantilever construction, the superstructure of
Talmadge Memorial Bridge is erected by the
subsequent casting of deck segments on either side of
the pier. All the elements forming in this cable-stayed
bridge, towers, stay cables and deck participate in the
main resistant scheme that was examined as follow.
The towers of Talmadge Memorial Bridge are built fist
and then erecting the other main elements, such as pier
table, deck and stay cables.
In Talmadge Memorial Bridge, the pier table is the
first section of road deck, which cast in place on the
pier above the Savannah River. The pier table
assembled on the ground and lifted into place by a
large-capacity floating crane that shows in the
following Fig 11. After the lower crossbeam was
completed and while the upper portion of the tower
was under construction, a large barge crane lifted the
pier table to its final position. The large-capacity crane
saved time and made erecting the pier table much
simpler.
6.1 Construction of Bridge Tower
Towers of Talmadge Memorial Bridge were
constructed of concrete and being erected first. Slip
forming was the method that used to simplify
construction of the towers of Talmadge Memorial
Bridge. The lower crossbeam cast on the ground and
lifted to its final elevation by strand jacks attached to
the legs. After the lower crossbeam was complete,
supports constructed on top of it, and formwork
constructed on top of these supports. The upper
crossbeam cast on this formwork. The towers of
Talmadge Memorial Bridge are simple box section.
The cables can be anchored at the front and back wall
of the tower. The tendon layout at the anchorage area
shows in the following Fig 10. Post-tensioning tendons
are used to prestress the walls to transfer the anchoring
Figure 11: Pier table lifted into the tower
6.3 Construction of Bridge Deck and Stay Cables
Talmadge Memorial Bridge used simplify
balanced cantilever erection scheme and designed the
form travellers for this cast-in-place concrete cablestayed bridge. This construction involves cantilevering
the deck out from the towers in a balanced manner and
installing the stay cables as the cantilever extends. The
deck of Talmadge Memorial Bridge is simple beam
and slab arrangement, which has been proved attractive.
The section of deck was preliminary assembled away
from the site due to the specific reasons for its
construction. The section of deck has been started to
cast after the pylon built up. After the tower has been
built up to the first tower stay anchorage points and the
starting deck section at the tower cast. The deck section
was cast at the tower, as shown in Fig 12. The form of
travellers has been installed and the balance cantilever
construction started. When the first deck was
positioned at the tower, the first stays were installed to
support the deck, enabling the form of travellers
released and moved forwards. The form travellers were
set up for the construction of the next section of
cantilevered deck.
ease of construction of this bridge. The general scheme
of construction of Talmadge Memorial Bridge was set
up the towers first, and then the section of deck and
pier table built into the legs that provided the fixed
support. The spans constructed outwards from the
towers towards the centre and back to the approach
ramps. The monolithic girder of Talmadge Memorial
Bridge cast in sections on moveable formwork, while
its counterpart on the other side of cantilever balances
the weight of each new segment.
6.4 Improvement on the construction
Nowadays, there can be a more elegant solution on
the balance cantilever erection of Talmadge Memorial
Bridge according to the recent year’s construction
technology. The traveller’s weight can be reduced by
supporting the front edge on the permanent stay cables,
which help to reduce the enormous hogging moment
during cantilever construction. Huge lever arm can
resist the hogging moment that the bridge structure
gives. It allows reducing the amount of prestress inside
of structure and does not waste prestresss. Therefore, a
back section to balance the cantilever becomes
unnecessary. This kind of construction method is so
widely used recently and so cost-effective in the cablestayed bridge.
7 Bridge Loading
Figure 12: Beam and slab deck cast into the tower
During casting of each deck section, the additional
weight at the end of the cantilever causes hogging
moment in the previously completed deck. The
hogging moment is increased as the construction
equipment and form of traveller are moved forward.
High bending moment is generated over the end of
section. When the next stays are installed, they pull the
deck up and create a sagging moment along the
complete deck. This cycle of hogging and sagging
moments continues as the deck is cantilever out. It is
clearly shown in the Fig 13.
The Talmadge Memorial Bridge is a concrete
cable-stayed bridge and it is a statically indeterminate
structure. In the design of such structure, the most
important loadings we need to consider in a bridge are
dead load, superimposed dead load, live traffic load,
wind load and temperature load. However, creep and
shrinkage load effects is also need to consider in this
bridge, because the creep and shrinkage of the concrete
will change the loads in the deck and stays, and the
deflection of the structures. The dead load,
superimposed dead load and creep and shrinkage
effects are all in the permanent loading condition.
7.1 Permanent Loading Condition
In the long span cable-stayed bridge, such as
Talmadge Memorial Bridge, the permanent load
condition is very important because the live load of this
bridge is relatively very low which will not carry much
bending moment of the bridge. The permanent load
condition includes all structural dead load and
superimposed dead load on the bridge. They are also
including all loads due to permanent imposed
deformations, such as loads imposed due to creep and
shrinkages from the bridge.
Figure 13: Balance cantilever erection scheme of
Talmadge Memorial Bridge
Simplified and reduced the number of working
parts in Talmadge Memorial Bridge, leading to the
7.1.1 Dead Load
The dead load of Talmadge Memorial Bridge is the
self-weight of structural elements of this concrete
cable-stayed bridge, which remains essentially
unchanged for the life of the bridge. They are including
self-weight of concrete girder and self-weight of
concrete deck slab that are the dead weight of this
bridge.
The deck of Talmadge Memorial Bridge has a
beam and slab arrangement. In the following Table 1, it
displaces the main geometry data for Talmadge
Memorial Bridge.
Table 1: Geometry data of Talmadge Memorial Bridge
Bridge Geometry Data
Total length of bridge
621 m
Spacing of girder
9m
Depth of girder
1.45 m
Thickness of slab
0.28 m
Width of deck
24.4 m
Assume the concrete weight is 24 kN/m³ and
cross-section of girder is 10 m². The depth of deck is
constant along the total length of bridge three spans.
The dead load of structure is calculated as follow:
Weight of girder:
24 × 10 = 240 kN / m
Concrete Slab: (tributary area approach)
24 × [0.28 (621 9 )] × 9 = 1.16 kN m
Total dead weight on the girder:
240 + 1.16 = 242 ⋅ 16 kN m
Total unfactored dead weight on the concrete
girder and bridge deck (per meter length):
242 ⋅ 16 × (24.4 9 ) = 656.5kN / m
7.1.2 Superimposed Dead Load
The superimposed dead load of Talmadge
Memorial Bridge is all materials that go on the top of
the bridge, such as the self-weight of steel stay cables,
concrete barriers, parapets, lighting ducts, future
wearing surface and services. The superimposed dead
load in Talmadge Memorial Bridge is relative high,
because all these above materials will always on the
bridge. They are permanent loads.
7.2 Live Load
Talmadge Memorial Bridge is a 621metres long
span cable-stayed bridge with the total length of
1.9miles that is 3.06-kilo meters. For this long span
cable, live traffic load is small compared with the dead
load. In the design of such Talmadge Memorial Bridge,
we do not need to worry about live traffic loading in
this situation. Assume the dead load and superimposed
dead load will govern the total bending moment at the
ultimate limit state.
7.3 Wind Load
Wind loads are very important in the design of
long-span cable-stayed bridges. Wind can produces
forces in the transverse, longitudinal and vertical
directions of the bridge. Due to the long and light
effects of cable-stayed bridge, they are subject to
vibrations induced by varying wind loads on the bridge
deck. However, we need to pay attention to these wind
effects. By reason of wind effects need to check at
critical stages, not only in the construction stages but
also on the final structure. In the construction stages,
when the deck cantilever out are often more susceptible
to dynamic behaviour than the completed structure.
Talmadge Memorial Bridge is subject to dynamic
forces and movements are not considered in this
bridge. The wind loading of Talmadge Memorial
Bridge can be calculated as follow according to BS
5400. Assume the mean hourly wind speed is 28m/s
and the gust factor is 1.34 for Talmadge Memorial
Bridge. The maximum wind gust will strike the bridge
using the Eq (1) which is 37.52m/s.
Vc = vK 1S1S 2 .
(1)
The horizontal wind load that is acting at the
centroid of the bridge is given by the Eq (2). However,
we need to calculate for both unloaded and loaded
deck. The dynamic pressure head is given by Eq (3)
which is 0.863 kN/m². According to BS 5400,
d = d 2 = 1 + 1.73 = 2.73m
b d 2 = 24.4 / 2.73 = 8.94
and CD =1.2. Therefore, the horizontal wind load for the
unloaded deck is 1755.7 kN; similar for loaded deck is
2364.15 kN. The total design horizontal wind load is
4120 kN. There is another important action by wind is
uplift force on the deck is given by the Eq (4)
Pt = qA 1C D .
(2)
q = 0.613v c 2 .
(3)
Pv = qA 3 C L .
(4)
For this long-span cable-stayed bridge, wind loads
are dominant and can cause collapse this bridge.
Therefore, it is essential to consider the wind effects in
the design of Talmadge Memorial Bridge.
7.4 Temperature Effects
Temperature fluctuation is an important
consideration in the bridge design. There are two
effects in bridge: one is the effective temperature and
another one is temperature difference between the
surfaces of the bridge. The deck of Talmadge Memorial
Bridge allows for the free movement, the changes in
the effective temperature of the deck will cause it to
expand. However, the overall change in effective
temperature will not give rise to any forces in the
structure, but the movement is catered in the bearing
and expansion joint design. The movement of
Talmadge Memorial Bridge can calculate using the
maximum and minimum anticipated bridge deck
temperatures. These values are function of the type of
bridge structure. In order to find the effective
temperature in Talmadge Memorial Bridge, it is
essential to find the maximum and minimum shade air
temperature using the Fig7 and Fig 8 in BS54002:2006. Assume Georgia has the same values with
London. In the Fig7 and Fig 8 of BS 5400, the
maximum and minimum shade air temperatures for
London are 37°C and –20°C respectively. According
to the Table 10 Table 11 of BS 5400, the maximum and
minimum effective temperatures for Talmadge
Memorial Bridge are 36°C and –12°C. The effective
temperature of the bridge will also depend on the depth
of surface on the bridge deck. According to the
structure, group 4 is the right structure for Talmadge
Memorial Bridge. Therefore, the maximum and
minimum effective temperatures are adjusted. The final
maximum and minimum effective temperatures are
37°C and –13°C for Talmadge Memorial Bridge. The
coefficient of thermal expansion for concrete is
0.000012 /°C. The actual movement of bridge can
calculate using the follow Eq (5):
Δ Temperature = (β L ) • (δT ) • (L )
(
)
(5)
= 12 × 10 / °C • (37 + 13) • (621)
−6
= 0.373m ≈ 37mm
In this situation, the bearings need to set on the
each end of Talmadge Memorial Bridge, which will
account for this actual movement of bridge.
Different temperature between various members of
the structure especially that between the top and
bottom surfaces of the deck section. They must
consider in the design of bridge. White cables in the
Talmadge Memorial Bridge will help to maintain the
temperature fluctuation. Orientation of Talmadge
Memorial Bridge toward the sun is another factor to
consider in the design. For example, during the sunrise,
the top surface of the deck will heat up more quickly
than the bottom surface, therefore the compression
stresses is building up at the edge of the deck section
and tensile stresses in the centre. While the temperature
of the top surface will decrease rapidly than the bottom
surface when at the sunset, resulting in the tensile
stresses at the edge of the deck and compression
stresses in the centre. In this situation, the temperature
differences through the deck section cause the
temperature gradient. In addition, it will also cause the
different strains and stresses in the deck section of
Talmadge Memorial Bridge.
The temperature gradient of Talmadge Memorial
Bridge is given in the form of linear temperature
gradients when the bridge is heating and cooling. Form
BS 5400 Fig 9, this is a Group 4 section. The results of
temperature distribution vary with the depth for
Talmadge Memorial Bridge that shows in Table 2.
Temperature differences cause curvature of the deck
and result in internal stresses within the structure.
Table 2: Temperature distribution vary with the depth
Temperature Distribution
h 1 = 150mm
T1 = 16.1°C
h 2 = 250mm
T 2 = 3.60°C
h 3 = 170mm
T3 = 2.26°C
The thermal load of Talmadge Memorial Bridge is
not only effect the load combination of bridge load, but
also control the design of the bridge. There are some
other effects, such as lone term concrete shrinkage and
creep, can be effect the design of Talmadge Memorial
Bridge. These effects take into account explicitly in the
following.
7.5 Shrinkage Effects
The shrinkage characteristics of concrete induce
the internal stress and deformations in bridge
superstructure. Shrinkage effects need to consider in
the design of concrete bridge. This type of effect is
especially critical in the concrete continuous bridge,
such as Talmadge Memorial Bridge. Shrinkage stresses
are low and are considered insignificant in most cases.
For the shrinkage of this bridge, both stresses and
deformations are induced.
Talmadge Memorial Bridge has a beam and slab
deck arrangement. Shrinkage stresses are induced in
both slab and the beam of the Talmadge Memorial
Bridge. Tensile stresses are induced in the concrete slab
and compressive stresses in the top region of the beam.
Creep and shrinkage effects will also affect the
design of expansion joint and bearing in the bridge. We
can work out the shrinkage of the bridge deck using the
following Eq (6). The shrinkage movement of the deck
is 4 mm.
Δ shrinkage = (β ) • (μ ) • (L )
(6)
= 12 × 10 − 6 × 0.5 × 621 .
= 0.00373m ≈ 4mm
7.6 Creep Effects
Creep is a long-term effect and acts in the same
sense with shrinkage effect. The effect is allowed for
by modifying the short-term deflection of the bridge by
a creep reduction factor (1+ØC). Creep is critical
problem in the design of concrete continuous bridge,
such as Talmadge Memorial Bridge. In order to find the
long-term creep effect, it is necessary to work out the
short-term deflection in the midspan of this continuous
bridge. Due to the three spans of this continuous deck
has different length, so they will need to treat
separately and then add all deflections together.
Therefore, the short-term deflection in the main span
and side span of this bridge can calculate using the
following Eqs (7, 8). The L1 and L2 are the span lengths
of main span and side span. W in the Eqs (7, 8) stands
for the dead and superimposed dead load of the bridge.
When work out the final short-term deflection, then use
the Eq (9) to find the long-term creep effect for
Talmadge Memorial Bridge.
δ short − term ( mainspan)
5wL14
=
.
384EI
(7)
5wL 2 4
.
384EI
(8)
δ short − term (sidespan) =
δ long− term = δ short− term ( total) • (1 + φc ) .
(9)
In despite of creep is a long-term effect, but it will
change its profile over its design life. This creep effect
will also affect the final stresses in the deck. In general,
two third parts of concrete bridge affect by the creep
effect in the first few days when the bridge is in service
and the other one-third parts of bridge will affect this
creep effect in the first year of opening.
8 Bearings Design
Bearings are structural devices positioned between
the bridge superstructure and the substructure. They
can transmit loads from superstructure to the
substructure, and accommodate relative movements
between the superstructure and the substructure. By the
reason of creep, shrinkage and temperature effects
which occur on the deck of Talmadge Memorial
Bridge. They are the most common causes of the
translational movements, which can occur in both
transverse and longitudinal directions. In this situation,
it is essential to consider the design of properly
functioning of bearings on this bridge, which
accommodate these movements without imposing
significant secondary stresses on the bridge
superstructure. Bearings should be designed to
accommodate relative movements on Talmadge
Memorial Bridge after their installation. Shrinkage
shortening and temperature movement of bridge deck
should be calculate before choose the proper type of
bearings for Talmadge Memorial Bridge. As before,
these movements have been already calculated. The
Shrinkage shortening of bridge is 4mm and the
temperature movement of bridge deck is 37mm.
Choosing the suitable bearing for Talmadge
Memorial Bridge, not only depend on the functional
requirements of the bridge, but also depend on the
evaluation of bearings. According to the basic
requirement of Talmadge Memorial Bridge, elastomer
pads bearings are chosen for this bridge. They
accommodate both translational and rotational
movements through the deformation of elastomer. Due
to elastomer is flexible in shear but very stiff against
volumetric changes, elastomer restrain expands
laterally under compressive loads. In order to allow for
the thermal and long-term creep and shrinkage of
Talmadge Memorial Bridge, each end of bridge slides
on a bearing at the junction which each end of bridge
are simple prestressed concrete beams on the
hammerhead piers.
9 Susceptibility to Intentional Damage
Aerodynamic stability of cable-stayed bridge is
major concern in the design of this type of bridge. This
is probably because cable-stayed bridge is extremely
slender. Cable-stayed bridge is one typical structure
susceptible to the action of winds problem. Wind
induced vibration is one of the main concerns in the
long span cable-stable bridge. Wind induced instability
and excessive vibration in long span cable-stayed
bridge. There are two issues, which the wind blows to
the long span bridge. One is bridge vibration at very
high frequency that makes the bridge unusable. In this
situation, the bridge will not collapse at wind
condition, but the bridge will sway in the motion of
wind. Another one is bridge vibration at very low
frequency, bridge starts to sway, and then it will
collapse. In order to design the bridge to avoid the
damage from wind, the natural frequency of the bridge
will be in between these two above situation. It is
necessary to check the Talmadge Memorial Bridge for
its dynamic behaviour under the wind loading. The
natural frequencies of this bridge can be calculated in a
simplified way by hand, called Rayleigh-Ritz that uses
in the following Eq (10):
ω n = (β n l )2 • ΕΙ ml 4 .
(10)
In order to ensure Talmadge Memorial Bridge is
constructed in safety, it is necessary to determine
whether the bridge is susceptibility to various
aerodynamic phenomena. The aerodynamic behaviour
of bridge depends mainly on four parameters:
structural form, stiffness, cross section shape and
damping.
Talmadge Memorial Bridge is a typical long span
cable-stayed bridge. For this long cable-stayed bridge,
it is not economical to add more material to increase
the stiffness. However, changing the boundary
condition of this bridge will significantly improve the
stiffness of bridge. Talmadge Memorial Bridge has an
H shaped simple rectangular section that builds up into
frame. The lower part is tapered in order to resist high
wind load, whereas the mid-height crossbar enhances
the tower’s lateral stiffness.
The flow of wind over the slender deck of the
cable-stayed bridge induces vertical bending and
torsional oscillation of deck section. Small change in
deck section will significantly affect the aerodynamic
behaviour. The monolithic deck is designed for
Talmadge Memorial Bridge. It resists to wind load by
the deck plate alone which acts as a horizontal beam
between the towers. This deck section is economical,
posses high stiffness and exhibit relatively small
deflection. The damping effect of this monolithic
structure is very high and vibration is relatively small.
In the Fig 14, indicates the lateral stability of this
cable-stayed bridge.
Talmadge Memorial Bridge, it is essential to consider
any cracks forming in the concrete next to the tendons.
The potential width and depths of possible cracks need
to be estimated during the design. The risk of cracking
perpendicular to prestress tendons can be apply some
of prestress to the concrete in advance of any shrinkage
or thermal strains occurring. In addition, for this kind
of long-span cable-stayed bridge, it can make optional
use of concrete’s high- performance attributes.
11 Possible Future Changes of Talmadge Memorial
Bridge
Figure 14: Lateral stability of cable-stayed bridge
Long span cable-stayed bridges pass judgment on
the most dramatic, capturing the public’s awareness
with highly visible and innovative structures. The
Talmadge Memorial Bridge was famous for the design
philosophy of simplicity. They make the cross-section
of deck constant as the bridge length. Due to the
compression stress in the deck increases proportionally
to the span length, the maximum span length of a
uniform girder is limited by its allowable stress. If we
use a girder variable with the cross section in
Talmadge Memorial Bridge, so the bridge can span
much longer than before.
The deck was not only easy to construct, it was
also one of the lightest cross sections possible for a
cable-stayed bridge. This lightness deck section of the
Talmadge Memorial Bridge will reduce the damping of
the bridge; the wind effects will drive the design of the
Talmadge Memorial Bridge entirely. However, this
cable-stayed bridge resist the lateral wind load by the
deck plane alone which acts as a horizontal beam
between the towers. In this case, the roadway of this
bridge must make heavier to provide the damping of
the structure. This is because the mass of the deck has
been contributes to the structure’s stability, since this
makes the deck less responsive to the disturbing forces.
As we know, concrete has high mass and damping
characteristics, and it will provide a high level of
internal damping in the system. Talmadge Memorial
Bridge is typical concrete cable-stayed bridge, which
has high level of internal damping. It will reduce its
susceptibility to vibration significantly.
Another important phenomenon that must be
consider in the design of Talmadge Memorial Bridge
that is the effect of stay cables oscillation during the
cable-stayed bridge construction. Talmadge Memorial
Bridge uses a balance cantilever erection for the
construction of concrete deck. During the balance
cantilever erection of this slender concrete deck, it will
likely prone to wind induced movement. This effect
will in turn excite the stay cables producing violent
oscillations. It is necessary to restrain the vibration of
cable stays in the design of Talmadge Memorial
Bridge. The vibration can be reduced by a simply
method, that is incorporated in most stay systems and
does not alter the appearance of the bridge, is with
damping devices installed between the anchorage and
the stay cables. Damping devices act to reduce any
local bending moment in the end of stay cables and
damp out any vibration in Talmadge Memorial Bridge.
The heavier weight and higher damping of concrete
deck and cable stays make the Talmadge Memorial
Bridge less susceptible to vibrations and dynamic
effects.
The design of Talmadge Memorial Bridge keeps
the philosophy of simplicity, but builds a beautiful
cable-stayed bridge across the Savannah River. It
simplifies the components in the bridge, but maximizes
the values of the bridge. It achieves not only simplicity,
but also build in the most safety and most economic
way.
10 Durability of Bridge
References:
Concrete structures, which have been exposed to
aggressive environments, suffer from durability
problems, such as Talmadge Memorial Bridge built
across the Savannah River. Long-term durability of
bridge becomes a major concern in the design of this
concrete bridge. As we know, cracks in concrete
structure are an inevitable occurrence. In Talmadge
Memorial Bridge, concrete has been microscopically
cracked by hydration shrinkage. In the design of
[1] R. Walther, B. Houriet, W. Isler, P. Moia, J.F.
Klein, 1988, Cable stayed bridges, Telford.
[2] Matthew Wells, introduction by Hugh Pearman,
2002, 30 Bridges, New York: Watson-Guptill.
[3] Nigel R. Hewson, 2003, Prestressed concrete
bridges: design and construction, London:
Thomas Telford.
[4] Wai-Fah Chen and Lian Duan, 1999, Bridge
Engineering Handbook, CRC Press, LLC
12 Conclusion