2376

deck, with concrete access spans on

The second major point in the design

close supports extended at a distance

of the Normandie Bridge is the combi-

of 116 m from each pylon in the cen-

nation of prestressed concrete and

tral span, as well as the rigid connec-

steel. Composite designs, where con-

tion between deck and pylons, in-

crete and steel are used to their greatest

creases the structure's rigidity. Wind-

efficiency, are strongly endorsed by

induced deflections are drastically re-

the designers of the Normandie Bridge.

duced. Alan Davenport compared the

The Normandie Bridge combines con-

deformability of the Normandie Bridge

crete and steel for the design of the

with the Littlebelt suspension bridge -

deck, prestressed concrete in the access

also efficiently built with a streamlined

spans, on close supports, with an ex-

deck based on the English experience

tension in the main span on both sides.

and a main span of only 600 m - and

Only the central part of the m, in span

concluded that the Normandie Bridge

is an orthotropic steel box girder, much

behaves like a cable-stayed bridge with

lighter (9 t/m, instead of the usual 45

a much shorter main span and is much

t/n) to limit the cable size. The use of

more rigid than a suspension bridge

concrete in the access spans reduces

with a span of 500-600 m.

total costs and increases the bridge's

rigidity, as well as the back staying ef-

ficiency of all rear cables.

This efficient combination of concrete

and steel in cable-stayed decks had

been used before for the design of the

Tampico Bridge in Mexico (360 m,

1988) and of the Ikuchi Bridge in Ja-

pan (490 m, 1991). And prior to that,

much valuable experience had been

gained about using various materials,

such as traditional and lightweight

concrete, in Dutch bridges built by the

cantilever method (Nijmegen bridges,

around 1970). The experience gained

in using different weights for a specific

structural purpose proved to be ex-

tremely useful (the bridges at Ott-

marsheim and Tricastin and the cable-

stayed bridge over the Elorn River).

The Normandie Bridge also uses a

composite design for the upper part of

the pylons, where cables are anchored

Fig. 29

(Fig. 29). It is far more efficient to de-

sign a steel anchorage box to anchor

High Performance Concrete

the cables, since steel plates easily car-

ry tensile stresses from back-stays to

cables suspending the main span. In

The main advantage of high perfor-

addition, it is much easier to fabricate

mance concrete for standard and me-

these steel anchorage boxes - or the

dium span bridges is substantially en-

elements which will constitute them -

hanced durability. But for heavily

in a factory than on site in concrete

loaded elements, such as the pylons of

100 or 200 m above ground. To

cable-stayed bridges with long spans,

achieve the proper geometry, it is nec-

or the concrete deck of the Normandie

essary to precisely adjust the position

Bridge, which has to balance high

of steel elements ants which are later

stresses from wind effects, high perfor-

completed by concrete walls.

mance concrete has great structural

Probably the first application of this

advantages.

technique was in Belgium, for the con-

All concrete on the Normandie Bridge

struction of the Ben Ahin and Wandre

contains silica fume for a characteristic

Bridges, designed by Rene Greisch

strength of 60 MPa. This allowed for a

ond Jean-Marie Cremer. The idea was

reduction in the cross section of the

used again for the Evripos Bridge in

concrete in the pylons and deck and

Greece and for the Chalon-sur-Saone

thus a reduction in weight and founda-

Bridge in France. The problem was

tions.

more complex in the Normandie

Erection of the Access Spans

Bridge, with the transverse inclination

of cables. A design was developed

with Jean-Claude Foucriat, introducing

The erection of access spans on both

horizontal prestressing tendons to press

banks required the contractors to de-

the concrete walls against the steel an-

velop a new technology. Classical

chorage boxes to help the transfer of

erection techniques, with Teflon pads,

vertical forces from steel to concrete.

would have produced very significant

The steel anchorage tower was divided

horizontal forces due to friction (up to

into 21 elements (the lower one being

5%) and to the slope of the access

divided into two half-elements) to be

ramp (6%). For this reason the initial

lifted by the site crane (capacity: 20 t),

design did not use the incremental

and welded on site. The typical ele-

launching method, although it was of

ment was designed to anchor a pair of

great interest due to the complex cross

cables on each side. The main plates

section shape and to the high rein-

were divided in ties for the transfer of

forcement ratio necessary to resist

forces from the main span to back-

wind forces.

stays in order to lighten the elements,

To be able to use it despite the slope,

reduce in situ welds and facilitate ac-

the contractors invented a so-called

cess from the lateral cells of the pylon

«staircase» method for horizontal span

- with a lift - to the anchorages.

launching. The deck is supported on

each pier by two trapezoidal blocks -

pier

with

the

incrementally

one on each side - which can slide

launched typical spans.

horizontally on the pier. This move-

The steel part of the main span, 624m

ment is permitted by special bearings,

long, has been erected by the cantile-

made of a series of small rollers, on

ver method from the completed access

top of the pier. After the forward

spans with the help of a mobile derrick

movement, the deck is lifted by jacks

to lift the successive segment 19.6 m

commanded from a central computer

long, on

each bank.

and the trapezoidal blocks are pushed

A New Generation of Cables

backwards, ready for a new launching

step. The launching operation proceeds

by successive launching steps: 15 cm

The preliminary design called for

horizontally and then 9 mm vertically

locked coil cables, which were consid-

to correspond to the slope of 6%.

ered very well adapted to such long

Such a procedure was only made pos-

spans, but which arc unfortunately

sible by the use of a series of sensors,

very heavy. Their erection cost thus

to control horizontal and vertical

proved prohibitive.

movements on all supports, and of a

For this reason, the contractors pro-

central microcomputer

which could

posed alternative cables made of indi-

command

horizontal

and

vertical

vidually protected strands of hot-dip

movements. It was of special impor-

galvanised wires which were re-drawn

tance, of course, that vertical move-

to keep all their structural characteris-

ments be the same on all supports at

tics. After coiling and after the corre-

any time.

sponding thermal treatment, the voids

In addition, this new technique reduces

between wires were filled with oil wax

the

necessary

manpower

during

to repel any water. The strand was then

launching, since control is only n nec-

protected by extruded high density

essary at supports, which can be dome

polyethylene at least 1.5 mm thick.

at the central command from, meas-

These strands were placed and ten-

urements obtained by sensors or video

sioned one-by-one. Individual place-

cameras.

ment was extremely economical, but

Erection of the Main Span

tensioning required a new technique,

already developed by the cable sup-

plier for the erection of three bridges:

The 116 m long concrete cantilever

the Arrade and Guadiana Bridges in

which extends the side spa is in the

Portugal, and the Chalon-sur-Saone

main one on each bank, and the 96 m

Bridge in France. The fast strand of

long last side span have been built by

each cable is tensioned to a computed

the balanced cantilever method from

value and equipped with a pressure cell

the pylon with the help of temporary

which gives the tension at any time.

stays. In the last side span, the closure

Each new strand, when installed, is

was

made

6 m

before

r 'aching the

tensioned to have exactly the same ten-

Interconnecting Ropes

Concluding Remarks

sational aspects and some episodes

proved the performed analyses and

during construction indicate the deci-

recommended some additional wind

sive importance of human factors.

tunnel, tests, the results of which were

The Owner gave the design engineers

even more favourable than the first

total responsibility for the design and

evaluations. This confirmation of the

granted them complete freedom to as-

design helped the project very much,

semble the design team. Under these

and from the summer of 1991, all con-

circumstances, improvements could be

tractors worked with enthusiasm and

introduced at each step of the project,

energy to complete the bridge on

with no consideration other than effi-

schedule, within budget and up to the

ciency. This is far superior to design

prescribed standards of quality.

competitions, now preferred by some

Any decision can be questioned, any

administrations, where projects can be

action criticised. The clear conclusion

selected based not always on structural

is that a complex and ambitious project

; aspects, and where designers can be-

like the Normandie Bridge cannot be

come prisoners of their initial sketches

successfully realised without a strong

and of premature options and deci-

Project Manager - as Bertrand Derou-

sions.

baix has been for this project -to guide

Although there was no public money

it over the years from conception to

in the Normandie Bridge, the French

completion, even

when

questioned

government had to approve the project.

from many sides. Going further than

The Road Director at the time, lean

ever before in any given field calls for

Berthier, decided to invite an as-

courage. The Owner and the local au-

essment of the design by an interna-

thorities remained totally confident in

tional group of experts: Marcel Huet

the design and in the engineers in

(Project Manager of the Tancarville

charge, even in difficult times. This

Bridge), Henri Mathieu,

Charles

was decisive for success; complex

Bngnon, Roger Lacroix, Rene W'alther

structures cannot be built with hesita-

and Jorg Schlaich. This group pro-

tions and doubts!

posed various amendments, some of

References

which were included in the final de-

sign.

Nevertheless, some engineers from one

[1] VIRLOGEUX. M.; FOUCRIAT,

of the erection contractors considered

J.-C; DEROUBAIX, B. Design -of the

the wind forces to have been un-

Normandie Cable-Stayed Bridge near

derestimated and, thus, the safety ques-

Honfleur. Proc. of the Int. Conf. on

tionable. The debate became public,

Cable-Stayed Bridges, Bangkok, pp.

even international.

1111-1122, November, 1987.

The Owner and the Road Direc-

[2] V1RLOGEUX, M. Projet du Pont

tor decided to consult Alan Davenport

de Normandie, Conception generate de

to evaluate the wind tunnel tests and

I'ou-vrage. Proc. of

the

13th IABSE

the estimated wind forces.

He ap-

Congress,

Helsinki,

IABSE,

June,

[9] VIRLOGEUX, M. Le projet du

1988.

Pont de Normandie. ibid.

[3] DEROUBAIX, B.; VIRLOGEUX,

Owner:

M.

Chambre de Commerce et d'lndustrie

Design and Construction of the Nor-

du Havre

mandie Bridge. Proc. of the IABSE

Project Management:

Symposium, St

Petersburg,

Russia,

September 1991.

Mission du Pont de Normandie

[4] VIRLOGEUX, M. Wind Design

and Analysis for the Normandie

Design:

Bridge. In: 'Aerodynamics of Large

SETRA, Sofresid, Quadric, SEEE, So-

Bridges,' A. Larsen, ed. Balkema, Rot-

gelerg, Setec and Europe-Etudes Gecti.

terdam 1992, pp. 183-216.

Normandie

Architect: Charles Lavigne

[5] VIRLOGEUX,

M.

Bridge:

Design

and Construction.

Wind Laboratories:

Proc. of the Inst. of Civil Engs, Struc-

CSTB and ONERA

tures and Buildings, August, 1993, pp.

Contractors (concrete): GIE du Pont

281-302.

Presentation

[6] DEROUBAIX,

B.

du Normandie (Bouygues, Campenon

du projet et developpement de la

Bernard, Dumez, GTM, Quillery,

constructio . In: Le point sur le Projet

Sogea. Spie Batignolles

du Pont de Nor mandie. Annales de

Contractors (steel):

1'ITBTP, Paris, September-October

1993.

Monberg and Thorsen

[7] LEGER, P. Finaiicvment du Pont

de Normandie. ibid.

Sub-contractors:

[8] DAVENPORT, A. Analyse des

Bilfinger -\ Berger, Freyssinet, Munch,

etudes des effets du vent sur le Pont de

Lozai,VSL, SDFM

Normandie. ibid.

Service date:

January 1995

er the height of the towers for this type

The anchorage caissons are 70 m X 45

of design would have been about 200

m. One anchorage caisson v as con-

m. Besides, a cable-stayed design

structed at sea using a steel box cais-

would have suffered excessive nega-

son prefabricated in a shipyard; the

tive reaction (uplift) at the link shoe of

other was constructed on land.

the side spans. For these reasons and

For the pneumatic caissons, robotic ex-

economic considerations, a suspen-

cavation was employed. A computer-

sion-type bridge was determined to be

controlled caisson shovel was operated

the best choice.

remotely using a video camera. Exca-

vated materials were placed onto an

automatic belt conveyer for removal.

This method ensured worker safety

and construction efficiency under the

high atmospheric pressure (3.5 bar) in

the caisson's chamber. In addition,

special digging machines were used

for the excavation of the hard mud-

stone.

Since an anchorage would be subjected

Fig. 31

to a huge eccentric force due to the ca-

Substructure

ble tension (230 MN) a precise pre-

diction of long-term (100 years') de-

The water depth at the site is approxi-

formation of the mudstone bearing

mately 12 m, and the subsurface

layer was essential) The initial predic-

ground consists of a weak alluvial clay

tion was modified repeatedly using a

layer on top of a mudstone stratum.

measured displacement at each con-

The mudstone bearing layer was found

struction stage, and the values obtained

at levels between -30 and -38 m.

were considered in the design of the

Pneumatic caisson

foundations were

superstructure.

designed and constructed for the two

main towers and the two anchorages.

Item

Content

Type of bridge

3-span, 2 hinged-stiffening truss, doubledeck suspension

girder

Span layout

Stiffening truss: 107.5 + 562.0 + 107.5 m

Cable: 147.5 + 570.0 + 147.0 m

Tower works

Structural type:

Longitudinal direction: flexible hinge at top of tower

Transverse: 3-story frame rigid (1 story above road)

Tower height:

121.866 m (cable theoretical top: 126.0 m)

Height of tower

P36

(Shibaura Main Tower): 2.866 m

foundation:

P37

(Daiba Main Tower): 4.5 m

Centre distance

P36

(Shibaura Main Tower) at foundation:

30.862 m

between towers:

at tower top:

30.084 m

P37

(Daiba Main Tower) at foundation:

30.851 m

at tower top:

30.084 m

Cable works

Cable type:

PWS (parallel wire strand)

Structure

Main span sag: /= 57.6 m; sag ratio: n = 1/9.9

dimensions:

Centre distance between cables: 29.0 m

Cable diameters:

Main span: 762 mm; 127 strands per cable

Side span: 771 mm; 130 strands per cable

Strand:

Diagonal; 69.8 mm 0

Wire:

5.37 mm 0; tensile strength: 160-180 kg/mm2

Hanger rope:

Centre Fit Rope Core (CFRC); 4 ropes/panel point

Stiffening girder works

Structural type:

Main structure: parallel chord Warren truss

Lateral bracing: K-truss

Hanging type:

Anchoring to upper chord

Structure

Main structure height: 8.9 m

dimensions:

Main structure width: width: 29.0 m

Upper floor

Expressway (multi-span continuous steel deck

system:

girder, effective width: 9.25 m) Note: Main span is

of 56 span continuous structure, rigidly connected at

both ends

Lower floor

Port roadway (multi-span continuous steel deck

system:

girder, effective width: 7.5 m, including walkway

1.5-2.5 m wide)

Rail transportation system (multi-span continuous

steel deck girder, RC track gauge: 1.7 m)

The concrete volume of each anchor-

the sand and -27 to 15 °C for the grav-

age, including the top slab of the cais-

el. Finally, preset water pipes further

son, amounted to 60000 m3. In order to

helped to cool the mix after placement.

reduce cracking caused by the heat of

Superstructure

hydration, an ultra-low-heat cement

was used. In addition, liquid nitrogen

was sprayed onto the aggregate, result-

The steel weights for the superstruc-

ing in temperatures of about 3°C for

ture included 14100 t for the towers;