a critical analysis of the donghai bridge, shanghai,...

E-mail: [email protected]

A CRITICAL ANALYSIS OF THE DONGHAI BRIDGE, SHANGHAI,

CHINA

Ci Song1

1University 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.

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

Proceedings of Bridge Engineering 2 Conference 2008 23 April 2008, University of Bath, Bath, UK


century, defined ten aspects of aesthetics of bridges,

which are used to analyze the aesthetic design of Donghai

Bridge.

2.1 Fulfillment of Function

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 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

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.

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.

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.


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.

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.

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

fLγ = 1.15 (ULS – combination 1)

3fγ = 1.10 (ULS – combination 1)

The dead load of deck = Wd. fLγ . 3fγ =497.4 kN/m

3.2 Superimposed Load

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


3fγ = 1.10 (ULS – combination 1)

The superimposed load = Wr. fLγ . 3fγ =130.3 kN/m

3.3 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


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 = ultM

ultM = (5.175× 1602

)/8 + (45.69× 160)/4

= 18387.6 kNm

3fγ = 1.10 for ULS concrete bridge

ultM = 1.10× 18387.6 = 20226.36 kNm

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


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


Design HB moment for a meter width of deck:

ultM = 1.30× 18090.55 = 23517.72 kNm

3.5 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, cv , which would strike

the bridge is given in equation 1 as

211c SSvK=v (1)

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 2S is

found from table as 1.37 and the funneling factor 1S is

1.00 generally. Ref. [2] cv is calculated by Eq. (1)

which cv =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

D1t CqA=P (2)

Where q=0.6132

cv (3)

Using the value of cv from Eq. (1) and calculate q,

which is the dynamic wind pressure from Eq. (3), then

q=1.61kN/2m . The solid horizontal projected area

1A =1400

2m . D

C is the drag coefficient which is read

from graph by calculated b/d value. Ref. [2] D

C =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: tP values of different elements of bridge

q(kN/2m ) 1

A (2m ) D

C tP (kN)

Deck 1.61 1400 1.2 2705

Piers 1.61 6×60 1.2 696

Parapets 1.61 350×0.3 1.2 203

Another more important action by wind is uplift of a

vertical downward force. This nominal force is calculated

as Eq. (4) Ref. [2]

L3v CqAP = (4)

The dynamic pressure, q is same as calculated before.

The plan area 3A =110252m . Because the cross-section

of deck is a twin box-section, the lift coefficient LC =0.75

is taken. Calculate tP from Eq. (4), gives that

tP =13339kN.

3.6 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)

.α∆Τ.=e l (5)

The coefficient of thermal expansion for steel and

concrete is a=6-

10×12 /℃. 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)

∆Τ.α.E=σ (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

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


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.

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

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 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 Construction

5.1 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]

Luchao Port

Station

(1978-1994)

Little Yangshan

Station

(08/1997-12/200

1)

Average sea

level (m) 0.23 0.18

Average high

tide level (m) 1.86 1.52

Average low

tide level (m) -1.34 -1.23

Maximum level

difference (m) 5.14 5.03

Average level

difference (m) 3.20 2.75

Average

duration of

rising tide

5 hours

26minutes

5 hours

51minutes

Average

duration of

falling tide

7 hours 6 hours

34minutes

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

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]

Layer Colour Soil type Compres

-sibility

1 Grey Mud High Loose

2 Yellow

to grey Sandy silt Medium Medium

3 Grey Muddy silty

clay High Loose

4 Grey Silty clay High Loose

5(1) Grey Clay Medium

to high

Loose to

medium

loose

5(41) Grey-

green Sandy clay Medium

Medium

loose

5(42) Grey-gr

een Silty clay Medium

Medium

dense to

dense

6

Dark

green to

yellow

Silty clay Medium Medium

7(11) Yellow Sandy silt Medium Medium

dense

7(12) Yellow Silty sand Medium

to low

Medium

dense to

dense

7(2)

Grey-

yellow

to

yellow

Silty fine

sand

Medium

to low

Medium

dense to

dense

7(2t) Grey

Interbedded

silty clay

and sandy

silt

Medium Medium

loose


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.

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

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

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

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 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.

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 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 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.

6.2 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.

7 Protection from vandalism

7.1 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 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

a critical analysis of the donghai bridge, shanghai,...

Documents