Millau Viaduct construction

8/18/2019 Millau Viaduct construction

1/14

CE 3420 Concrete Technology, Jan.-Apr. 2016

ASSIGNENT 2

Submitted by:

!"#hal $a%e#h

CE13&0'3

(ESC$I)TI*N+

For your structure (i.e., the structure selected in Assignment 1), explain the possible

construction methods. If there are many options, choose one and explain why you prefer it.

What are the restrictions imposed by the type of construction method on this structure. an

this structure benefit from the use of an uncon!entional (special) concrete" #xplain the

characteristics and typical properties of the con!entional or special concrete that you suggest.

For your structure and the concrete chosen pre!iously, gi!e the components recommended,

mix design guidelines, formwor$ re%uirements and recommendations for transportation and

placing of concrete. Any other specific problems to be addressed"


2/14

IA !IA(CT

&'# IA* +IA*&

Source: http://www.tourisme-aveyron.com/

&he illau +iaduct is a --/metre long cable stayed bridge in near the city of illau in

southern France. At a height of 02 metres, it is also the tallest bridge in the world.

onstructing a structure of such mythical proportions in such a pristine !alley would

ine!itably place tremendous restrictions and pose great challenges in determining the method

of construction, the choice of materials to use, the design and so on. &his article attempts to

analyse the !arious decisions made by the designers to o!ercome the specific challenges

related to the construction of this bridge.

ET*( */ C*NST$CTI*N

&here are traditionally two methods a!ailable for the construction of cable/stayed bridges 3

&he balanced cantile!er method and the Incremental aunching method.

The alance cant"leer %etho of construction is preferred for bridges ha!ing a few spans

of length ranging from 42 to 042 metres. &he construction commences on both the piers

though the cast in situ method using formwor$s and then, this portion is used as the support

and erection platform for all the subse%uent concrete segments. A tra!elling formwor$ is

usually employed that mo!es along the bridge with the segment being constructed. Finally, both the ends are made to meet in the middle and are 5oined. &hese cast in situ segments are

http://www.tourisme-aveyron.com/http://www.tourisme-aveyron.com/


3/14

generally -mm to 4m in length. uring construction, stability of the end cantile!er is

maintained through use of temporary piers.

Although this is a flexible method widely used in bridge construction with repetiti!e units

increasing the efficiency, it is relati!ely slow. &his limitation has been partially mitigated

through the use of precast segments. Wor$ing at the large heights demanded by the geographyof the !alley in with the !iaduct is located poses significant ris$s to the safety of the wor$ers

and the costs in!ol!ed in lifting materials to heights larger than 022m are tremendous. &he

high altitude winds encountered are further enhanced by the tunnelling effect created by the

presence of mountains. A cantile!ering dec$ would be extremely unstable at such extreme

conditions and so this method was deemed inappropriate.

The long"t"nal lanch"ng %etho is a method made technologically and economically

!iable by de!elopments in launching e%uipment. In this method, the bridge is generally cast in

situ at one end of the abutments in segments. After the construction is completed, the whole

arrangement is pushed forward by the length of one segment with the help of launchinge%uipment and bearings, and the next segment is constructed against the first. A !ertical 5ac$

is used in order to lift the bridge at multiple points simultaneously, and a hori6ontal 5ac$

pushes the structure forward. 7nce the launching is completed, the !ertical 5ac$ relaxes and

the whole structure is laid down on a temporary pad beam. &he procedures of lifting,

launching, descending and withdrawing are performed o!er and o!er again until the bridge

dec$ reaches the other end.

8tep 1 3 IF&I9:; &he entire structure is lifted off the pad beam through the acti!ation of the

lifting oil cylinder.

8tep 0 3 A*9'I9:; &he upper part of the launching system and the structure are mo!edforward with the help of the launching oil cylinder.

8tep - 3 #8#9I9:; &he bridge dec$ structure is released and made to rest on the pad

beam through the relaxation of the lifting oil cylinder.

8tep 3 WI&'


4/14

In case of the illau !iaduct, the dec$ was made of steel and not of concrete and this

procedure was suitably adapted to the !ariation. &his method can be used for the construction

of bridges with mild cur!atures of a constant radius and as this structure is cur!ed with a

radius of 02 $m, this method was deemed appropriate. Also, adoption of the incremental

launching method eliminates the need for temporary piers. In bridges li$e these where the!alley in inaccessible, and obstructions to the flow of the ri!er below are undesirable, this is a

huge ad!antage. Also, the bridge is located in an en!ironmentally protected area and minimal

disturbance to the en!ironment is a high priority. As this method needs a much smaller but

more concentrated area for superstructure assembly, the surroundings are not disturbed.

onsidering all these ad!antages, the incremental launching method was decided upon for the

construction of the illau +iaduct.

espite the numerous ad!antages, this method poses many challenges as well. A launch of

this scale had ne!er been attempted before and new e%uipment had to be de!eloped. 8ections

of the dec$ were launched from both ends of the !alley to meet at the middle o!er the ri!er&arn where no supports could be constructed. &he weight of the dec$ caused it to sag with the

worst deflections occurring near the destination pier. An arrangement to lift the structure was

designed to a!oid interaction between the dec$ and the pier. =roblems due to the unanticipated

early deterioration of the &eflon lubrication had to be handled and other system failures

occurred, as it had not been tested before.

Source:http://www.fzt.hawhamburg.de/pers/Scholz/dglr/hh/text_!"!_"!_#_$illau_%iaduct.

pdf

NEE( /*$ AN NC*N!ENTI*NA C*NC$ETE

&he harsh conditions existing at high altitudes and the excessi!e forces on the piers call for

high design strengths. As high strength ine!itably means congested reinforcement where

!ibration would be a problem, self/compactibility was desired. &hese, along with !arious

other factors, led the designers to conclude that 'igh =erformance 8elf ompacting oncrete

would be appropriate for the piers of the structure. ue to the high strengths, the diameter and

bul$iness of the pillars could be reduced. &his led to more slender loo$ing pillars that had

high aesthetic appeal, a factor !ary important in this case considering the natural beauty in

which this structure is located. &he need for !ibration was also eliminated, thus creating a

cleaner wor$ing en!ironment with minimal damage to the surroundings and an enhanced

le!el of safety for the wor$ers. Another ad!antage of self/ compactibility is the reduced time

http://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2010_10_28_Millau_Viaduct.pdfhttp://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2010_10_28_Millau_Viaduct.pdfhttp://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2010_10_28_Millau_Viaduct.pdfhttp://www.fzt.haw-hamburg.de/pers/Scholz/dglr/hh/text_2010_10_28_Millau_Viaduct.pdf


5/14

re%uired for construction. Faster construction implies less time for which capital and

e%uipment is needed and hence, reduced costs.

&he properties of high performance self/compacting concrete can be understood by analysing

the properties of high strength concrete and self/compacting concrete. 'igh mechanical

strengths are displayed by high strength concretes due to an optimi6ed granular s$eleton and ahigher water cement ratio. &he optimi6ed granular s$eleton has a lower pore si6e and

connecti!ity that leads to high durability. 7rdinary self/compacting concretes may ha!e lower

compressi!e strengths but ha!e a !ery high fluidity. &he self/compactibility of any concrete

can be assessed by its three properties 3 passing ability, filling ability and stability against

segregation. 'igh performance self/compacting concretes show a mixture of both the abo!e/

mentioned properties, with high compressi!e strengths and good self/compactibility.

In order to achie!e the desired properties, it is generally necessary to add expensi!e chemical

admixtures and a high cement content. &hus, cost is a disad!antage of '=8. &he addition

of a high %uantity of cement also has undesirable side effects li$e high heat of hydration andhigh autogenous shrin$age. 22 mm. &he superplastici6er demand !aries with the type and concentration of

the mineral admixture employed. oncrete using silica fume has the highest superplastici6er

demand, a property that can be attributed to the fineness of the fume particles. &he adsorption

of superplastici6er on to the surface of fly ash particles is high due to the large surface area of

the particles. &he amount of superplastici6er a!ailable to interact with the cement grains islesser and this leads to a lower fluidity. In case of fly ash, the superplastici6er demand actually

decreases. &his is primarily due to the lubrication pro!ided by the spherical glassy silica fume

particles through a ball bearing effect. In summary, the addition of mineral and chemical

admixtures lead to a concrete that is highly flowable. &he aggregates used in '=8 are

smaller and hence, the mix shows excellent passing ability. 8tability against segregation is

achie!ed through the use of superplastici6er and mineral fines.

C*)$ESSI!E ST$ENGT+

&he compressi!e strength of high strength self/compacting concrete is larger than that ofcon!entional concrete. &his is achie!ed through the use of cementicious mineral admixtures


6/14

that enhance the strength of the concrete through po66olanic reactions and the densification of

the concrete matrix. =o66olanic reactions are reactions between amorphous silica present in

mineral admixtures and the calcium hydroxide produced during the hydration of cement, to

produce strength gi!ing calcium silicate hydrates. alcium hydroxide crystals are wea$ and

they accumulate along the edges of aggregates, creating wea$ spots. In ordinary concretes, thewea$est spot where failure occurs is the interfacial transition 6one between the aggregates and

the cement paste. &he replacement of calcium hydrate with calcium silicate hydrates

strengthens the interfacial transition 6one and the compressi!e strength increases. Another

reason for this increase is the filler effect due to the fine admixture particles that causes a

=#


7/14

compressi!e strengths can be obtained using a 02/percentage replacement by fly ash. &he

incorporation of silica fume increases the strength more than in the case of natural 6eolite, and

this can be attributed to the higher po66olanic acti!ity of the former than the latter. 'owe!er,

it should also be noted that the compressi!e strength does not increase indefinitely for

increases in mineral admixture dosage. It is reported that replacing 42 percent of cement byfly ash will cause a 42 percent decrease in compressi!e strength when compared with the

control mixture.

EECT$ICA $ESISTI!IT+

As it is one of the most important factors contributing to the resistance against corrosion,

electrical resisti!ity is an effecti!e indicator of concrete durability. An electrical resisti!ity of

02/$ilo ohm/cm is the minimum limit for corrosion propagation in a steel rebar and corrosion

will be less in a concrete with !alues abo!e that. In '=8, which incorporates mineraladmixtures, the electrical resisti!ity increases with age. &his is largely because po66olanic

reactions occur at a much slower rate in comparison with normal cement hydration reactions.

Furthermore, higher the replacement le!el of cement with mineral admixtures, higher will be

the recorded electrical resistance. &he 0?/day electrical resistance of mixtures incorporating

silica fume is generally !ery high at about 112 $ilo/ohms, a !alue or 4 times greater than in

the case of fly ash or natural 6eolite. &his obser!ation is primarily due to the higher

po66olanic reacti!ity of silica fume, which results in a denser paste structure. &he paste in a

concrete mix is considered to be more conducti!e than the aggregate phase.

5ATE$ A&S*$)TI*N+

Water absorption is another !ery important property contributing to concrete durability. &his

is because water contains large %uantities of corrosi!e ions that can harm the steel rebars and

the concrete matrix. '=8 generally has !ery low water absorption le!els, primarily due to

its limited pore !olume and pore si6e resulting from the addition of mineral admixtures. Also,

the pore connecti!ity is !ery low and water cannot be transported to the interior. 'ence, a

concrete with limited porosity and water absorption generally has a good durability.

C*$I(E (I//SI*N+&here are !arious mechanisms for the ingress of chlorides in concrete. &hese include

diffusion, capillary suction, migration or a combination of these mechanisms. &he decrease in

the internal relati!e humidity or the self/desiccation of high performance self compacting

concrete affects these transport mechanisms of chloride ingress, and as chloride is a !ery

corrosi!e material, the durability is enhanced. It is also noted that the addition of mineral

admixtures impro!es causes a reduction in the chloride concentration at !arious depths, an

obser!ation that is due to the refined microstructure and pore structure.

Apart from the !arious ad!antages of using '=8, many challenges need to be o!ercome.ue to the strengthening of the interfacial transition 6one and the matrix, the failure becomes


8/14

!ery brittle. &his is an undesirable property as it reduces the time a!ailable for e!acuations.

&he ris$ of spalling is also higher as the structure is so dense that in case of fires, the

expansion of pore water due to !apori6ation cannot be accommodated and the concrete may

explode suddenly. &he shrin$ages are faster and more pronounced and this could lead to

shrin$age crac$ing. &he high density of the matrix pre!ents bleed water from coming up tothe surface to replace e!aporated surface water and this can lead to excessi!e shrin$age

crac$ing if curing is not performed properly.

C*)*NENTS $EC*EN(E(

&he design of '=8 in!ol!es the addition of mineral and chemical admixtures to obtain the

desired properties of high compressi!e strength, durability and self/compactibility. ineral

admixtures that need to be added include supplementary cementicious materials li$e fly ashand silica fume. 8ilica fume is rather expensi!e and fly ash is an excellent alternati!e for

de!eloping countries, especially considering that it is a waste product from thermal power

plants. &he replacement of a part of cement with these mineral admixtures reduces problems

li$e thermal crac$ing and autogenous shrin$age. &o maintain good wor$ability in spite of the

low water cement ratio, superplastici6ers ha!e to be added. In the case of the illau +iaduct,

the superplastici6er used was '


9/14

&he ratio of aggregate components is calculated using the Fun$ and inger theory with the

!alue of the exponent % ta$en as 2.04. An optimum ratio will lead to a particle si6e

distribution that follows the ideal cur!e with low le!els of de!iation. *sing the ratio of

aggregate components determined by the abo!e method, the bul$ density of the compacted

mix can be calculated. 9ext, with the help of the density of the aggregates, the !oid contentcan be calculated.

STE) 2+ )r"%ary pa#te ol%e eter%"nat"on.

As it is needed to fill the !oid !olume between aggregates, the paste !olume in '=8 is

considerably higher than in normal concrete. Also, this large paste !olume ensures the

lubrication of the surface of the aggregates, reducing the friction between them, so that the

re%uired flowability is attained. &he paste !olume for '=8 should generally be in the range

of -2C to 0C by !olume.

=


10/14

Step 3+ (eter%"nat"on o7 the 89 rat"o.

Already established relationships between the water cement ratio and the compressi!e

strength of con!entional concrete can be used in the case of '=8 as well. As the type and

dosage of mineral admixtures are $nown, the water/binder ratio can be computed. &he wEbratio for high performance self/compacting concrete usually ranges from 2.04 to 2.. A water

binder ratio lower than 2.04 can be used when the superplastici6er and paste composition

yields a small enough !alue of plastic !iscosity.

STE) 4+ Calclat"on o7 the %"neral a%":tre, ce%ent an 8ater content.

&he content of each of the mineral admixtures, and of the water can be determined with the

help of the pre!iously determined paste !olume, water/binder ratio, and the cement %uantity

replaced by the mineral admixtures. For the '=8 intended for the construction of the

illau +iaduct, the suggested range for the binder content is in the range of 04 and >04 $g per cubic meter. It must be ensured that the cement content is not lower than that re%uired for

durability and the maximum allowed water content is 022 $g per cubic meter.

Step ;+ Aggregate content eter%"nat"on.

&he aggregate content and the proportion of the indi!idual aggregate components can be

computed based on the ratio of aggregate components and the $nown paste !olume. &he

coarse aggregate content of the mix should be in the range of 0?C to -?C by !olume.

Step 6+ Sperpla#t"c"


11/14

&he abo!e procedure only gi!es a brief explanation of the mix design methodology. A more

detailed account is presented in the paper referred to in the pre!ious page.

/*$5*$? $E@I$EENTS

&he piers of the illau +iaduct are made of concrete and considering the height of the piers,

their tapering cross section and the harsh conditions present, inno!ati!e formwor$ had to be

de!eloped. &he formwor$ would ha!e to be able to resist wind speeds of up to 12 $mph and

should also be able to withstand high speed concreting pressures of 0122 psf. &he !iaduct is to

be constructed in a !alley of pristine beauty and it is imperati!e that the structure does 5ustice

to these surroundings. &he formwor$ needs to be able to pro!ide a smooth surface with no

hori6ontal plywood 5oints and sharp edges and corners. &he formwor$ also has to be able to

ad5ust to the !arying cross section and geometry. In order to achie!e these purposes, the 5ob of

designing the formwor$ was gi!en to =#


12/14

attached to the finished concrete below. ue to the high altitudes, safety was a ma5or concern

and all the le!els were enclosed by a wire mesh with appropriate access points for the

mo!ement of wor$ers. 8labs were cast into the unicellular part of the piers at intermediate

le!els, at a spacing of meters, to facilitate construction and to stiffen the tubular piers. &his

barred the use of self/climbing formwor$ for the interior and a crane/assisted system wasused. &he formwor$ was also designed such that it could adapt to the !arying cross section

along the height by sliding mechanisms.

F7


13/14

For the construction of the illau +iaduct, the concrete for the foundation and the piers was

produced at a plant onsite, to minimi6e transportation costs. Also, %uality control for the

'=8 had to be thorough and an onsite facility was deemed to be appropriate for the

purpose. When mixing the concrete in the truc$, it should not be filled to more than ?2C. It isalso suggested that the truc$ drum must be rotated at small speeds of about 1 to rpm during

transport, and at higher speeds for a few minutes before unloading. &he recommendation for

the diameter of the pump used for placing is or 4 inches and he length should not exceed

-22 meters. &he highest permitted free drop altitude is gi!en as 4 meters and the lateral flow

distance should not exceed 14 meters. It must also be noted that the pumping speed at the

outlet of the pipe must be in the range of 12 to 02 cubic meters per hour.

It is extremely important to ensure that the air is allowed to escape when placing the concrete,

as entrapped air can cause !oids, which wea$en the structure and create irregularities. &he

aesthetics of the structure is !ery !ital and a uniform surface finish must be obtained.Additionally, to ensure that the formwor$ in not damaged due to the pressure exerted by the

high performance self/compacting concrete, the !ertical casting !elocities must ne!er exceed

0 meters per hour. &o ensure good %uality concreting, cold 5oints must be a!oided. 8o, if there

is a delay in placing concrete, the existing fill must be !ibrated before the next layer is poured.

uring is !ery important in '=8 as bleed water does not come to the surface. In order to

a!oid crac$ing, curing must be done effecti!ely for days.

$E/E$ENCES+


14/14

1.http;EEwww.bath.ac.u$EaceEuploadsE8tudent=ro5ectsEBridgeconference022EconferenceEmain

pageE8axtonGillau.pdf

0. http;EEtheconstructor.orgEstructuresEbalanced/cantile!er/method/of/bridge/constructionE>1-E

-. https;EEstructurae.netEstructuresEmillau/!iaduct

. &he 9ew Incremental aunching onstruction &echnology of Hiubao Bridge ong/span

'ybrid Arch/girder 8tructure / .. 8hao

4. http;EEwww.chryso.comEuploadEtGdocumentsEFichierG0E?>12E+iaduct/

illauG:BGB.pdf

>. From ordinary rheology concrete to self compacting concrete; A transition between

frictional and hydrodynamic interactions.

Houmana ammine, ohend haouche, ichel :uerinet, icheline oran!ille , 9icolas

Ehigh/performance/concrete.html

?. echanical and durability properties of self consolidating highperformance concreteincorporating natural 6eolite, silica fumeand y ash / Fereshteh Alsadat 8abet, 9icolas Ali

ibre, ohammad 8he$archi

@.https;EEwww.engineersireland.ieE#ngineersIrelandEmediaE8iteediaEgroupsEi!isionsEci!ilE&

he/Formwor$/to/the/illau/+iaduct.pdf"extJ.pdf

12. http;EEwww.concreteconstruction.netEimagesE+iaducC02deC02illauGtcm4/4@2?.pdf

11. &he mix design for self/compacting high performance concrete containing !arious mineraladmixtures

'a &hanh e, atthias Kller, arsten 8iewert, 'orst/ichael udwig.

10.http;EEwww.5sce.or.5pEcommitteeEconcreteEeEnewsletterEnewsletter21ErecommendationEselfc

ompactE1.pdf L
http://www.bath.ac.uk/ace/uploads/StudentProjects/Bridgeconference2007/conference/mainpage/Saxton_Millau.pdfhttp://www.bath.ac.uk/ace/uploads/StudentProjects/Bridgeconference2007/conference/mainpage/Saxton_Millau.pdfhttp://theconstructor.org/structures/balanced-cantilever-method-of-bridge-construction/6137/http://theconstructor.org/structures/balanced-cantilever-method-of-bridge-construction/6137/https://structurae.net/structures/millau-viaducthttp://www.chryso.com/upload/t_documents/Fichier_L2/48610/Viaduct-Millau_GB_BD.pdfhttp://www.chryso.com/upload/t_documents/Fichier_L2/48610/Viaduct-Millau_GB_BD.pdfhttp://civil-resources.blogspot.in/2010/06/high-performance-concrete.htmlhttps://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/The-Formwork-to-the-Millau-Viaduct.pdf?ext=.pdfhttps://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/The-Formwork-to-the-Millau-Viaduct.pdf?ext=.pdfhttp://www.concreteconstruction.net/images/Viaduc%20de%20Millau_tcm45-590487.pdfhttp://www.jsce.or.jp/committee/concrete/e/newsletter/newsletter01/recommendation/selfcompact/1.pdfhttp://www.jsce.or.jp/committee/concrete/e/newsletter/newsletter01/recommendation/selfcompact/1.pdfhttp://www.bath.ac.uk/ace/uploads/StudentProjects/Bridgeconference2007/conference/mainpage/Saxton_Millau.pdfhttp://www.bath.ac.uk/ace/uploads/StudentProjects/Bridgeconference2007/conference/mainpage/Saxton_Millau.pdfhttp://theconstructor.org/structures/balanced-cantilever-method-of-bridge-construction/6137/http://theconstructor.org/structures/balanced-cantilever-method-of-bridge-construction/6137/https://structurae.net/structures/millau-viaducthttp://www.chryso.com/upload/t_documents/Fichier_L2/48610/Viaduct-Millau_GB_BD.pdfhttp://www.chryso.com/upload/t_documents/Fichier_L2/48610/Viaduct-Millau_GB_BD.pdfhttp://civil-resources.blogspot.in/2010/06/high-performance-concrete.htmlhttps://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/The-Formwork-to-the-Millau-Viaduct.pdf?ext=.pdfhttps://www.engineersireland.ie/EngineersIreland/media/SiteMedia/groups/Divisions/civil/The-Formwork-to-the-Millau-Viaduct.pdf?ext=.pdfhttp://www.concreteconstruction.net/images/Viaduc%20de%20Millau_tcm45-590487.pdfhttp://www.jsce.or.jp/committee/concrete/e/newsletter/newsletter01/recommendation/selfcompact/1.pdfhttp://www.jsce.or.jp/committee/concrete/e/newsletter/newsletter01/recommendation/selfcompact/1.pdf

Millau Viaduct construction

Documents

Transcript of Millau Viaduct construction