A CRITICAL ANALYSIS OF THE DONGHAI BRIDGE, SHANGHAI

Proceedings of Bridge Engineering 2 Conference 2008
23 April 2008, University of Bath, Bath, UK
A CRITICAL ANALYSIS OF THE DONGHAI BRIDGE, SHANGHAI,
CHINA
Ci Song1
1
University of Bath
Abstract: This paper provides a critical analysis of the Donghai Bridge which includes aesthetics, loading,
structure, construction, durability, vandalism, future changes and improvements. It gives the idea how to look a
bridge from an aesthetic view and also how a bridge is actually built. Especially for a crossing-sea project, the
special construction methods are designed due to harsh site conditions and limited construction period.
Keywords: crossing-sea project, cable-stayed bridge, prefabrication
1
Background information
Donghai bridge is located at north of Hangzhou Bay
in East Sea of China. It can also be called as the East Sea
Bridge. By being one of the three collaboration works,
part of Shanghai international shipping center, Donghai
Bridge is the connection in Yangtze Delta vest area (i.e.
Shanghai City, Jiangsu Province and Zhejiang Province).
It services for the overland transport of containers of
Yangshan Deep Water Port of International Shipping
Center and it offers water supply, electricity supply and
communications, etc. The Yangshan Deep Water Port is
China’s first free-trade port upon its completion in 2010.
The Donghai Bridge starts from the Luchao Port in
Shanghai and goes across north area of Hangzhou Bay,
and finally, reaches the small Yangshan Island in Zhejiang
Province. The location of site is shown in Fig 1. Donghai
Bridge is the first truly offshore bridge in china’s bridge
history and it is also the longest cross-sea bridge in the
world. The total cost of project is about 11.8 billion CNY
(1.64 billion USD).
The overall length of Donghai Bridge is 32.5km and
width of the bridge is 31.5m. It is designed to be a
motorway bridge which carries 6 lanes of traffic. This
includes 3.7km onshore section (Luchao Port, Shanghai),
25.3km offshore section (between Luchao Port and Big
Tortoise Island) and 3.5km sea embankment including
another cable stayed bridge – Kezhushan Bridge (between
Big Tortoise Island and Kezhushan Island). The
Kezhushan Bridge is not analyzed in this paper.
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Figure 1: Location of Donghai Bridge
In March 2001, the deep water port project in
Shanghai is formally agreed by the nation. After one year,
in March 2002, the State Council examined and passed
the feasibility research on the first phase of this project.
The construction commenced in June 2002 and continued
for three and half years. In Dec 2005, Donghai Bridge
was completed together with the deep water port (Phase I)
and opened to traffic. Ref. [1] Innovative anti-corrosion
technique is used to prevent the marine corrosion in
Donghai Bridge. So the bridge is designed to stand for
100 years.
2
Aesthetics of the Bridge
The aesthetics of bridges plays a very important role
in the overall success of building a bridge. Fritz
Leonhardt, the most famous bridge engineer of the 20th
century, defined ten aspects of aesthetics of bridges,
which are used to analyze the aesthetic design of Donghai
Bridge.
2.1
Fulfillment of Function
because different thickness of deck is used for the
auxiliary navigation span which is shown in Fig 3. This
can be covered by varying the box girder section
thickness internally, but it is very inefficient and huge
waste of materials.
The structure of Donghai Bridge is very simple and
clearly shown to the public. The main span of the bridge
is a cable-stayed bridge with double pylons. The deck is
held by groups of cables connecting to two pylons. Two
inverse Y- shaped massive pylons give confidence in
stability of the bridge. Cable-stayed bridges are very often
chosen for large span crossing-sea projects due to its
simple construction and clearly fulfillment of functions.
Simplicity leads to the successful design of function of
Donghai Bridge.
2.2
Proportions
Proportions have significant effect on designing
bridges. All balances between masses and voids, depths
and spans need to be achieved. As shown in Fig 2,
Donghai Bridge displays excellent proportions across the
sea. The masses and voids are perfectly balanced. The
height of pylons also matches the maximum span. The
thickness of deck is just correct to the breath of piers.
Everything are balanced and perfectly fit to each other. All
these balances give an impressive aesthetic view of the
bridge.
Figure 3: Various thickness of deck at auxiliary
navigation spans
2.4
Refinements
There are only two piers at each support across the
width of deck so that no views of opaque barrier will
appear from oblique angles. Not much more refinements
have been done to create the aesthetics of Donghai Bridge.
For the improvement of the refinements to the bridge,
tapering piers can be used rather than a straight one.
2.5
Integration into the Environment
As shown in Fig 2, Donghai Bridge is a cable-stayed
bridge which gives a wonderful pleased view across a
wide span of water. Donghai Bridge has a great success in
integrating its own structure into the surrounding features
and environment.
Figure 2: Proportions of bridge
2.3
Order
Some cable-stayed bridges may have potentially ugly
view from oblique angles due to the crisscrossing of
cables. This problem only happens when two or three
planes of cables were designed to support the structure. In
order to prevent the crisscross cables, Donghai Bridge is
designed to have only one plane of cables. But the
single-plane system reduces the torsional strength of the
structure. So the deck needs to be substantially stiffened
to take the additional torsion and this result very deep
deck which is inefficient. To overcome this problem, an
inverse Y-shaped tower is used instead of just one vertical
pylon. The top of the inverse Y-frame is made vertical and
all cables attached along this part of the pylon with a fan
configuration. The fan configuration of cables gives most
efficient effect to the structure. Therefore, this system
gives maximum benefit for a single plane of cables while
unpleasant oblique views avoided.
For a good ordered bridge, there should be non-stops
or an unbroken line as eyes moving through the entire
length of bridge. The Donghai Bridge fails in this field
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2.6
Surface Texture
Surface texture is very important in bridges, but often
ignored. Ref. [2] Same as all other concrete bridges, the
surface texture of Donghai Bridge is a matt finish. Rough
finishing is very often used in piers, but in this case, most
structural elements are prefabricated and have much finer
finishing than cast in-situ. Therefore, a significant
aesthetic appeal has been added to Donghai Bridge by its
smooth finishing.
2.7
Colour and Character
Black cables have been used in Donghai Bridge to
accentuate the certain cables in day times. Because all
cables of bridge are in black, so they disappear at night.
Only the deck and two pylons are high-lighted with blue
artificial lighting at night. Contributing with two lines of
lamp lighting, the bridge is just like a dragon floating on
the sea when looking from far away.
γ fL = 1.15 (ULS – combination 1)
γ f 3 = 1.10 (ULS – combination 1)
The dead load of deck = Wd. γ fL . γ f 3 =497.4 kN/m
3.2
Figure 4: Night scene of bridge
2.9
Complexity
The main reason for designing a cable-stayed bridge
is because simple construction can be carried out over a
relatively long span. There is not much complexity in the
Donghai Bridge. The most complex section is the main
navigation span which has two inverse Y-shaped pylons
with stays cables attached at top.
The superimposed load is mainly the road fill. The
fill for Donghai Bridge is asphalt. Assume the thickness
of the asphalt is 100mm. The unit weight of asphalt is
2300kg/m³.
The weight of road Wr = 2300×9.81×0.1×30
= 67.7kN/m
γ fL = 1.75 (ULS – combination 1)
γ f 3 = 1.10 (ULS – combination 1)
The superimposed load = Wr. γ fL . γ f 3 =130.3 kN/m
3.3
2.10
Incorporation of Nature
From bird’s eye view, Donghai Bridge is curved in an
S shape. This shape incorporate better into the nature
rather than a straight line shape for a structure built on
water. It is clearly shown in Fig 5. The colour of East Sea
in China appears brown instead of blue. It has much better
effect as dark gray appearance of bridge fitting into
natural colour of deep water.
Superimposed Load
HA Traffic Live Load
Carriageway = 14.25m wide
Deck Span = 160m
Design for a meter width of deck:
Number of notional lanes = 4
Notional land width = 15.75/4 = 3.94m
From Table 13 BS5400:
W = 13.6 kN/m (per notional lane)
Knife Edge Load (KEL) = 120 kN (per notional lane)
For a meter of width of deck:
W = 13.6/3.94 = 3.45 kN/m
KEL = 120/3.94 = 30.46 kN
γ fL = 1.50 (ULS – combination 1)
Design HA Loading for a meter width of deck:
W = 1.50 × 3.45 = 5.175 kN/m
KEL = 1.50 × 30.46 = 45.69 kN
Maximum mid span bending moment with KEL at
mid span = M ult
M ult = (5.175 × 160 2 )/8 + (45.69 × 160)/4
= 18387.6 kNm
γ f 3 = 1.10 for ULS concrete bridge
M ult = 1.10 × 18387.6 = 20226.36 kNm
Figure 5: Bird’s eye view of Donghai Bridge
3
Loading
All loadings in this conference paper are calculated
according to BS5400.
3.1
Dead Load
The cross-section of main navigation section – cable
stayed bridge is composite box section which is too
complicated for consideration. The other type of
cross-section, concrete twin box sections are used to
define the dead load.
Assume the cross-section area of concrete twin box
sections is 16.7m². The unit weight of reinforced concrete
is 2400kg/m³.
The weight of deck Wd = 2400×9.81×16.7=393.2
kN/m
3.4
HB Traffic Live Load
Nominal load per axle = 45 units × 10kN = 450kN
The maximum bending moment will be achieved by
using the shortest HB vehicle. i.e. with 6m spacing.
The maximum moment for a simply supported span
occurs under the inner axle when the vehicle is positioned
such that the mid span bisects the distance between the
centriod of the load and the nearest axle. With a 160m
span and the 6m HB vehicle with equal axle loads, the
inner axle is placed at 1.5m from the mid span. Fig 6
Figure 6: HB loading
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RL = 450(73.7+75.5+81.5+83.8)/160 = 884.5 kN
RR = 4 × 450 – 884.5 = 915.5kN
Moment at X = 884.5 × 81.5 – 450 × 1.8
= 71276.75 kNm
The HB vehicle occupies one lane with HA load in
the adjacent lane. Assume that the HB load is carried by a
notional lane width of deck.
Hence the moment per meter width of deck
= 71276.75/3.94 = 18090.55 kNm
γ fL = 1.30 (ULS – combination 1)
Design HB moment for a meter width of deck:
M ult = 1.30 × 18090.55 = 23517.72 kNm
3.5
Another more important action by wind is uplift of a
vertical downward force. This nominal force is calculated
as Eq. (4) Ref. [2]
Pv
= qA3C L
(4)
The dynamic pressure, q is same as calculated before.
2
The plan area A 3 =11025 m . Because the cross-section
of deck is a twin box-section, the lift coefficient C L =0.75
is
taken.
Calculate Pt from Eq.
(4),
gives
that
Pt =13339kN.
Wind Load
The wind load is analysis by other standards which is
quite different from British Standards. But in this
conference paper, all the loadings are defined according to
BS5400.
The maximum wind gust, v c , which would strike
the bridge is given in equation 1 as
(1)
vc = vK 1 S1 S 2
Assume the mean hourly wind speed is 35m/s and the
Donghai Bridge is 15m above the ground and horizontal
wind loaded length is 340m, so that the gust factor S 2 is
found from table as 1.37 and the funneling factor
which v c =51.3 m/s
The horizontal wind load acting at the centriod of the
part of the bridge under consideration is given by equation
(2) as
(2)
Pt = qA1C D
Temperature Effects
Temperature effects are an important consideration
during bridge design. The simple approach is used here to
consider the temperature fluctuations of Donghai Bridge.
The overall length of Donghai Bridge is 32.5km and
has a mixing of concrete and composite decks. There are
quite lot expansions joints have been put in different
positions of bridge. Assume the maximum distance
between two expansion joints is 140m and the entire
bridge cross section increases in temperature by 25℃.
The distance of bridge will move longitudinally at the
expansion joints is calculated using Eq. (5)
e = ∆Τ.l .α
The coefficient of thermal expansion for steel and
-6
concrete is a= 12 × 10 /℃. The applied length l =100m.
The total extension e = 30mm and 15mm for each
expansion joint to move in longitudinally.
If the expansion joints are clogged, some
longitudinal compressive stress is which will be built up
and the stress can be calculated using Eq. (6)
σ = ∆Τ.α.E
Where
q=0.613 vc
(5)
S1 is
v c is calculated by Eq. (1)
1.00 generally. Ref. [2]
3.6
2
(3)
Using the value of v c from Eq. (1) and calculate q,
which is the dynamic wind pressure from Eq. (3), then
m 2 . The solid horizontal projected area
2
A1 =1400 m . C D is the drag coefficient which is read
(6)
Steel will expand more than concrete under same
increased temperature. So use the Young’s Modulus for
steel to calculate the stress. The Young’s Modulus for
steel E = 200,000 N/mm². σ =60N/mm²
q=1.61kN/
from graph by calculated b/d value. Ref. [2] C D =1.2 for
the deck.
Other elements such as parapets and piers must also
be considered according to wind load. The wind load
results for 350m span are shown in Table 1 below:
Table 1: Pt values of different elements of bridge
2
Deck
Piers
Parapets
q(kN/ m )
1.61
1.61
1.61
2
A1 ( m )
1400
6×60
350×0.3
CD
Pt (kN)
1.2
1.2
1.2
2705
696
203
4
Design of Structures
The bridge is designed in S-shape from the plan view
with the minimum radius 2500m. This is not only due to
the aesthetic appeal, but also for the construction
requirements of highway bridge. Firstly, too long straight
section will cause drivers’ visual fatigue and increase the
accidents. Secondly, the central axis of each section
should perpendicular to the direction of rising tide and
falling tide. This method not only reduces water influence
to the bridge, but also helps safe navigation for ships
when passing the Donghai Bridge.
4.1
Main Navigation Section
The width of the beam is 33m and the depth is 4m. It
is a single box with three chambers. The Main span is
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420m. Large span induced huge moment and shear on the
deck. If using concrete box-section, the thickness of
flanges and webs will be much larger than other spans to
take the moment and shear. Therefore, the weight of each
box-section will be extremely massive and cannot be
lifted by crane boat. Even concrete box-section can be
stiffened by adding steel inside the camber, but still not
very efficient and economic. Steel box sections are chosen
to use instead of concrete. The problem of steel box
sections is buckling and this may lead to collapse. In order
to overcome this problem, the top flange is stiffened by
casting a concrete slab on the top. This forms a
concrete-steel composite box section. The top concrete
flange is treated as a continuous slab and webs carry the
shear. The bottom flange is in compression in hogging
regions. Other steel plates are also stiffened by adding
steel profile and bracings inside. As shown in Fig. 7, all
steel plates are surprising thin and lightweight.
Figure 7: Cross-section of composite box girder of main
navigation section
4.2
Offshore Non-navigation Section
The precast continuous beam with the span of 60m or
70m is used for offshore non-navigation section. Instead
of single box section, two identical box sections with one
chamber are selected. The cross-section of box girder is
shown in Fig. 8. All box sections have same thickness
along entire span. Concrete box sections are prefabricated
in segments in island near the site. Each section is
‘mate-cast’, so that the previous segment becomes part of
the formwork for the next one. Ref. [2] Box section
segments are then transferred to the site and all
prestressed by internal prestressing to hold all segments
back in positions. Extra deflectors are also added to the
box section for external prestressing in advance. They are
not used until any deviation occurs during construction or
in future services.
box-sections. The depth of deck is much thicker at
supports than where else. The thickness of deck varies
along the span with the minimum thickness at mid-span
and maximum at supports. Stiffer section attracts bending
moment. So the deck on the support is built thicker to
resist the bending moment. All concrete box-sections are
prestressed by internal prestressing.
4.4
Main Navigation Span – Cable -stayed Bridge
Figure 9: Inverse Y-shaped double pylons with stay
cables in fan configuration
There are several reasons to choose a cable-stayed
bridge rather than suspension bridge crossing a wide span.
Cable-stayed bridges display a more direct load-path from
deck to pylon through the stay cables. Ref. [2] The
construction method of cable-stayed bridges is easy and
each cable is relatively thin and replaceable. The main
element of this bridge is the double pylons with single
plane of cables. Two inverse Y-shaped pylons are selected
with many closely-spaced stays attach to the top vertical
part of pylons as shown in Fig. 9. The height of pylon is
148m. The most efficient configuration – fan system is
used without any ugly oblique views resulting. This form
of structure not only has the aesthetic benefit, but also has
the advantage that torsional stiffness is added to the
bridge by creating a triangular ‘closed’ section. The
height of pylon is 148m. Cable stay is high strength
Pre-fabricated parallel wire strand (PPWS). PPWS is
fabricated by high strength galvanized wire which is
totally paralleled with a section of hexagon or other shape.
Ref. [4] The wire bundle is wrapped with high strength
polyurethane tape and fixed sockets at both ends of cable.
The standard distance of cables on the pylon is 2m and
8mon the beam. The elevation of main navigation section
– cable-stayed bridge is shown in Fig. 10.
Figure 8: Cross-section of offshore non-navigation
section
4.3
Auxiliary Navigation Section
There are 3 auxiliary navigation bridges with main
span of 120m, 140m, and 160m respectively. Two
identical single box sections with single chamber are also
chosen for these sections. Three auxiliary navigation
sections are actually built as a cantilever bridge with
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Figure 10: Elevation of main cable-stayed bridge
4.5
Expansion Joints and Bearings
Because the deck of cable-stayed bridge mostly made
of steel, so as the temperature increasing, the deck of main
span will expand largely. So expansion joints are put in
the middle of span to allow any horizontal movements up
to 140mm. The normal service life for expansion joints is
longer than 20 years. Ref. [1]
Both steel hinge (rocker) bearings and rubber pot
bearings are used in Donghai Bridge at different positions.
The steel hinge bearing acts as a pin connection and no
horizontal movement is allowed but it can rotate. The
rubber pot bearing is the most popular used one, which is
slightly cheaper than others.
5
5.1
Construction
Complex Construction Conditions
Donghai Bridge is located in site which has
subtropical oceanic monsoon climate. It is on the south
edge of north subtropical zone and east-asia monsoon
region. Mainly wind is North wind and east-south wind
throughout whole year. Strongly influenced by the
monsoon, the site has clearly four seasons; cold in winter
and hot in summer. The annual average temperature is
15.3-16.1°C and annual average rainfall is 1053.9mm.Ref.
[3]
The tidal type of sea area belongs to shallow tide with
irregular and half day characteristics. Two rising tides and
two falling tides happen each day with distinct aspects of
back and forth tide. Ref [1]
Table 2: Characters of tide in east sea of Shanghai
Ref. [3]
Little Yangshan
Luchao Port
Station
Station
(08/1997-12/200
(1978-1994)
1)
Average sea
0.23
0.18
level (m)
Average high
1.86
1.52
tide level (m)
Average low
-1.34
-1.23
tide level (m)
Maximum level
5.14
5.03
difference (m)
Average level
3.20
2.75
difference (m)
Average
5 hours
5 hours
duration of
26minutes
51minutes
rising tide
Average
6 hours
duration of
7 hours
34minutes
falling tide
According to Table 2, the bridge construction is
hugely influenced by typhoon, wave, tide, cold-air and
other bad conditions. According to the capacities of
equipments have been used in reducing effect of wind and
current, the average workable days is less than 180days
per year over three hand half years total construction
period. Therefore, another critical issue need to consider
is the limited construction period. The construction period
of Dong Hai Bridge is only 42 months comparing to the
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large scale of the bridge. Because it serves for the
Yangshan Deep Water Port, so it needs to be completed
together with the first phase of Little Yang-shan Port.
By considering the short construction period and
overall length of Donghai Bridge, travelling formwork
method is used in construction of onshore section. For the
offshore section which is about 98% of the Donghai
Bridge, neither travelling formwork method nor
incremental launching method is applicable due to its
inefficiency and different offshore conditions. So precast
concrete construction is much more preferred with
launching and balanced cantilever construction methods.
At four navigation sections, spans of deck are very large
and launching girder method is uneconomic since
building temporary supports in deep water is very
expansive. So only balanced cantilever method is applied.
When construction goes to the area near the bank of
island where water is very shallow and full of submerged
rocks, the floating cranes cannot reach there, so those
sections are constructed by travelling formwork method
or incremental launching method.
5.2
Soil Conditions and Foundations
There are 12 layers of different soils in the site of
Donghai Bridge. Soils have been defined up to seven
layers from top to bottom as shown in Table 3.
Table 3: 7 layers of soil from top to bottom Ref. [3]
Compres
Layer
Colour
Soil type
-sibility
1
Grey
Mud
High
Loose
Yellow
2
Sandy silt
Medium Medium
to grey
Muddy silty
3
Grey
High
Loose
clay
4
Grey
Silty clay
High
Loose
Loose to
Medium
5(1)
Grey
Clay
medium
to high
loose
GreyMedium
5(41)
Sandy clay
Medium
green
loose
Medium
Grey-gr
5(42)
Silty clay
Medium dense to
een
dense
Dark
6
green to
Silty clay
Medium Medium
yellow
Medium
7(11)
Yellow
Sandy silt
Medium
dense
Medium
Medium
dense to
7(12)
Yellow
Silty sand
to low
dense
GreyMedium
Silty fine
Medium
yellow
7(2)
dense to
sand
to low
to
dense
yellow
Interbedded
silty clay
Medium
Medium
7(2t)
Grey
loose
and sandy
silt
As shown in Table 3, the soil condition of site is quite
bad, so that pile foundation is chosen for the bridge. Layer
7(12) and Layer 7(2) both have low impressibility and are
formed by good quality dense sands. They are also stably
distributed along the whole site. The depth and thickness
of the soil is also ideal for the pile foundation, so layer 7
is chosen to carry the bearing capacity the pile foundation
5.2.1 GPS systems
Driving piles into the sea bed is very largely
influenced by the currents and waves. It is very difficult
for driving ships to get to the exact positions. There are
not as many monitoring points can be set out as on land.
Therefore, the normal onshore surveying methods are not
very applicable and not accurate enough for the
construction. According to the offshore pile driving
technology, new innovative GPS-RTK technique is used
in this project, known as “The Offshore GPS Pile Driving
Position System”. This system can monitor the position of
ship and accurate any errors from calculations. By the
monitoring of GPS system, the high accuracy is achieved
and the problem is solved.
5.2.2 Pile caps
The outer shell of pile caps are also prefabricated in
island. Each shell is transported to the site and erected to
the pile groups as shown in Fig. 11. Once finished
connecting to piles, the reinforcement is left for the pier,
and the top of pile cap is covered in-situ with concrete.
forward and construction continuous. Main installation
process of cable-stayed bridge is shown in Fig. 12.
Figure 12: Erection process of cable-stayed bridge
Figure 13: Balanced cantilever construction for
cable-stayed bridge
Figure 11: Erection of pile cap
5.3
Main Navigation Section – Cable Stayed Bridge
Tow inverse Y-shaped tower is casted in-situ in the
site. After completed the main tower and auxiliary piers,
one temporary support is installed at each side of tower
along bridge axis to support the first several segments of
precast box sections above. The first five segments are
lifted into position by floating boat crane and erected and
connected on the two temporary supports. Another
segment is lifted into position and first cable is installed
from tower to the deck. After this, the mobile crane is
assembled on the deck and used for further lifting work.
The construction is done by balanced cantilever method.
As the construction reaches the auxiliary pier, the
temporary supports are removed from pylon and side
temporary support is added to the auxiliary pier. One
segment is erected to the top of auxiliary pier first and
then connected to the deck from pylon. Another stay cable
is added to hold the deck. Then the mobile crane moves
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5.3.1 Composite deck
The main navigation span of bridge deck is
constructed using precast concrete topped steel composite
box sections. The profile of box-section is single box with
triple chambers which is shown in Fig 6. The top flange
of box-section is stiffened with prestressed concrete and
bottom flange and web are steel. Each box-section is
prefabricated in large scale prefabricate site on island,
then transported to the construction site and craned and
erected into place. All casting work should be done in
prefabricate site, including assembling and welding steel
box section, casting in-situ concrete top flange to the steel
structure, etc. After all prefabrication steps have been
done, the box-sections are moved to storage to stay for 90
days before using.
Process of balanced cantilever construction for the
deck:
1. Precast box section is transported to site by ship
and lift up into position by crane.
2. Adjust space between last segment. As in position,
start connecting two segments and also fill in an epoxy
resin to the joint to further aid smooth connecting.
3. Add the tendons for prestressing and cast in-situ
10m wide concrete top slab.
4. When strength concrete is over 90%, pull back the
tendons to prestress the segment.
5. Move crane forward
6. Install stays from tower to the segment to pull the
deck up in position.
7. Crane lift next segment on and repeat all the steps
from step 1
The span of offshore non-navigation section is either
60m or 70m. All the segments are prefabricated on the
prefabricate site on island and transport to the wharf each
as a whole section by the way of transverse moving and
longitudinal moving. All the piers and girders are
transported to the site by boats.
The 60m box girders are lift to the position and
erected using crane boat and “Hercules” (2500 tonnes
capacity). The 70m box girders are lift to the position and
erected using crane boat and “Little Swan” (3000 tonnes
capacity), shown in Fig. 16 .
Each box section is first lift to the top of pier and
supported by temporary supports. All connection works
are done in-situ on the temporary supports. After all
segments connected to each other, the deck is converted
into a continuous beam.
Figure 14: Composite box girder lift by mobile crane
As two spans meet about to meet together, the key
segment is prefabricated specially that the steel section is
slightly longer. Because steel deck cannot cast in-situ, so
the closure of the span becomes tricky. One side of key
segment is connected as usual by bolting to the pervious
one. At the other side, use the temporary connection plate
to adjust the position. Once it is in the correct position, a
permanent plate is replaced and closure finished.
5.4
Onshore Section
Section near the Luchao Port selects 50m span
continuous box girder. It is constructed in-situ using
travelling formwork method.
50m span continuous box girder is also selected for
the section near bank of Big Tortoise Island. Because the
crane boat cannot work in shallow water, so that
incremental launching method is used for this section.
5.5
Offshore Non-navigation Section
Figure 16: 70m box girder is lift by “Little Swan”
5.6
Auxiliary Navigation Section
The other three auxiliary navigation channels are
constructed using different methods. The span of
auxiliary navigation section is 120m, 140m and 160m
respectively.
The pier is precast to box section of enforcement
concrete thin wall. The first box girder segment is cast
in-situ on the top of each pier by formwork. All other
segments are also cast in-situ using balanced cantilever
construction which is shown in Fig. 17. The deck is built
outwards in both directions from a pier by mobile
carriages and suspended formwork. The thickness of deck
varies along the span. As the concreting continuous and
the deck tapers, the arrangement of formwork adapted to
get smaller dimensions.
Figure 15: Erection of piers
There are two piers at each support. All the piers for
non-navigation section are precast on island and
transported to site. Each pier is lift to the top of pile cap
and connected to the foundations as shown is Fig. 15.
E-mail: [email protected]
Figure 17: Cast in-situ using balanced cantilever
construction
6
Durability
Donghai Bridge is located at wretch marine
environment. In order to make sure the bridge can stand
for 100 years, a serial of completely, economical and
reasonable anticorrosion system is drafted and applied to
the construction of the bridge. Each element of bridge has
its own strategy and corresponding system due to the
variation of structures, materials and environments.
All the technological requirements are drafted as well.
E.g. raw materials of high performance concrete, ratios of
mixture, production processes, construction methods, etc.
So the site construction can all be guided by these
standards.
6.1
Anticorrosion Strategies for Different Elements:
6.1.1 PHC (Prestressed High Strength Concrete) piles
High performance concrete + steel reinforcement
protection layer + FRP (Fiber Reinforced Plastics)
wrapping reinforcement + filling core reinforcement
method
6.1.2 Steel piles
Sacrificial anodes protection method (replacement
every 35 years) + heavy-duty anticorrosive coating
protection (1000µm, life-time 10 years) + filling core
reinforcement method + predicted steel piles corrosion
amount (7mm). Ref. [3]
Temporary anode pieces are installed during
construction and they are left on it (life-time≥2 years).
6.1.3 Drilling piles
Concrete with mineral admixture + steel protective
canister + steel reinforcement protection layer
6.1.4 Pile caps, piers and girders
High performance concrete + steel reinforcement
protection layer
The surfaces of piers in splash zone are coated by
waterproof painting.
6.1.5 Stay Cables
All the cables are made by galvanized steel wires
which are coated by a layer of zinc to prevent corrosion.
Hot extrusion HDPE (High Density Polyethylene) cable
jacket is wrapped to each cable and sealed to prevent
storm water logging.
6.1.6 Bearings
Triple anti-corrosion methods are used on bearing:
weathering steel (including 09CuPCrNiA, 15CrCuMn and
ZG20Mn) + metal coating + heavy-duty anticorrosive
painting. Ref. [3]
6.1.7 Expansion joints and handrails
Expansion joints and handrails are protected by hot
dip galvanizing anticorrosive method.
7
7.1
Exposed Testing Station:
The reason for setting the exposed testing station is to
monitor the actual effects of anticorrosive systems in
Donghai Bridge. It also provides important basis and
testing results for future maintenances of bridge. On the
other hand, the exposed testing station collects data of
offshore anticorrosive technique used in Donghai Bridge
and accumulates experiences for the future applications
with improvements. The exposed testing station is built at
north-west of Big Tortoise Island.
E-mail: [email protected]
Anti-collision system
In order to protect the bridge from vandalism by
boats and ships, both of VTS (Vessel Traffic
Administrative System) and safety protection system are
applied.
Some independent anti-collision piers are arranged at
both sides of main navigation channel around tower bases.
The light collision can be absorbed and resisted directly
by the anti-collision piers. But for the heavy collisions,
anti-collision piers are not strong enough, so that the pier
foundation together with other anti-collision facilities will
restrict the impact.
According to the navigation standard, boats shapes,
collision forces and anti-collision facilities, for the
auxiliary navigation channel, a special orange colour
protective box is adopted. The pile cap of each pier is
wrapped by the orange protective box. There are lots little
holes on the protective box which can absorb and reduce
the impact. This system is very economic because no
extra protective piers are required.
Figure 18: Orange protective box
7.2
Anti-collision Parapets
Donghai Bridge services for the ports. High standard
requirements for safety are very important and must be
achieved. Special researches have been done to the
anti-collision system of parapets. The anti-collision
parapets are designed for standard containers which have
a weight up to 55 tones. Designed maximum colliding
speed is 60km/h and colliding angle is 15 degree. After
several tests and comparisons, the steel-concrete
composite material is selected for parapets.
8
6.2
Protection from vandalism
Future Changes and Improvements:
There are 4 navigation channels in Donghai Bridge.
One is located in the main navigation section. It is for
5000DWT vessel and the clearance is 300x40m. It is a
single channel with double directions. One is for
1000DWT vessel and the clearance is 100x25m (double
channels single direction)；And Two are for 500DWT
vessel, the clearance is 56x17.5m (double channels single
direction), located near the Luchao harbor and little
Wugui Island. Ref [1]
Considering the overall length of Donghai Bridge is
32.5km, 4 navigation channels may not enough for the
future. One of the solutions is that one more cable-stayed
bridge is added to the route of bridge on the Luchao Port
side. But this will make the structure very complex
because another cable-stayed bridge, Kezhushan Bridge,
which is connect to the Donghai Bridge already. The
maximum span of Kezhushan Bridge is 332m and it
connects the end of Donghai Bridge to the Yangshan Deep
Water Port. In fact, Kezhushan Bridge does not have any
navigation requirements, so it is quite a waste to having a
long span cable-stayed bridge there.
9
Summery
For a bridge have overall length 32.5km, the Donghai
Bridge is excellently designed and dramatically
constructed in three and half years. It also gives
impressive aesthetic feeling while the philosophy of
simplicity applies.
References
[1] http://dorim.mokpo.ac.kr/~kwerc/data_file/Symposiu
m/session2/Zeng-Huan%20Zhang.pdf
[2] Ibell, T., c. 1997. Bridge Engineering 1 lecture notes,
University of Bath
[3] Deep Water Port and Donghai Bridge Project
http://co.163.com/neteaseivp/forum/dirSearch.jsp
[4] http://en.spccc.com/website/searchProductSingle.acti
on?proId=8080808016c1e8130116c1f670ed0002
[5] Lin, Yuanpei. Shanghai Lupu Bridge and Donghai
Bridge
E-mail: [email protected]