hpc applications in france_toutlemonde

8/12/2019 HPC Applications in France_Toutlemonde

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HPC Applications in France

Dr Franois TOUTLEMONDE

LCPC, Division FDOA (Public Works Researc !ns"i"u"e, #ri$%e &"ruc"ures De'ar"en")

*+ #oulevar$ Leebvre -*-./ Paris Ce$e0 1* France 2rancois3"ou"leon$e4lc'c3r

Course given in Catania, June 22. 2007 Giornata Studio sul tema

Nuove Tecnologie per la realizzazione e la riparazione di strutture di calcestruzzo

Introduction

HPC is generally defined in France as concrete with characteristic cylinder compressivestrength higher than 50 MPa, which is in fact not far from the fibdefinition of water/binder

ratio < 0! However pioneer "se of HPC in France #Malier $%%&' too( place in the middle ofthe )0*s, and was especially applied to bridge str"ct"res, d"e to a favo"rable attit"de ofowners, among which the Highway +dministration, regarding innovation in the field ofconcrete and bridge str"ct"res in general n fact the first HPC applications, especially ino"tstanding pro-ects, which too( place from $%)., did not directly acco"nt for the higherstrength of concrete which was impossible in the technical and administrative frame ofp"blic wor(s before code etension1, b"t "sed 2side* advantages, namely34 fl"idity at the fresh state, which is of special advantage in highly reinforced elements, andmay be related to p"mpability his was of ma-or concern for the 26rande +rche de la78fense*, one ma-or high4rise b"ilding in the b"siness district of Paris, where concrete had tobe p"mped over 900 m incl"ding $00 m rise4 strength at early age, which leads to smaller eec"tion time and th"s important savings

ypical eamples are the :8 sland bridge, where accelerated form removal allowed anadvanced delivery date, and the Pert"iset bridge, the first HPC cable4stayed bridge inFrance, where a strength of ;; MPa at $9 h allowed early tensioning, and where higher earlystrength and red"ced creep and shrin(age were acco"nted for realistically for the first time,4 higher material d"rability, related to red"ced permeability and carbonation, improved frostresistance hese advantages were mainly eploited by owners in the case of cold Champd" Comte viad"ct1 or marine environment Chatea"briand arch bridge on the :ance river1,as well as for specific ind"strial applications3 radioactive waste containers, containmentvessels Civa" n"clear power plant1, etc

+ first "pgrading of the design codes for reinforced and pre4stressed concrete "p to acharacteristic strength of 90 MPa too( place in $%%$ t allowed applying higher compressivestrength, tensile strength and o"ng=s mod"l"s of HPC, which improves the stability ofslender str"ct"res3 tri4dimensional tr"ss str"ct"res as in >ylans46laci?res viad"cts, thindec(s as for the :oi@e bridge, and high4rise piles of long4span cable stayed bridges roisebridge, Aormandie bridge1 n the early %0=s it was also attempted to capitalise theeperience owned especially in bridge applications of HPC More f"ndamental st"dies onmechanical properties of HPC were carried o"t, and a proposal for code etension "p to)0 MPa derived from this wor( #de Barrard et al., $%%9' his etension was formallyapproved in $%%% and leads to the possibility of ta(ing advantage of HPC in even standardstr"ct"res However, since $%%5 and especially within the framewor( of a -oint : 7=national pro-ect= called =DHP=&000=, efforts were done to develop HPC alternative pro-ects toclassical C!0 bridge designs Deside the epected advantages in terms of d"rability, it was

th"s necessary to E"antify the possible materials savings and economical advantages of"sing HPC, on a rational and demonstrative basis n the first part of this paper, ! eamplesof s"ch case st"dies are given, some of which have lead to practical realisation on site

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Application of C80 for standard overpasses near Bourges

Structural applications in standard bridges: context of the competition

Deside HPC applications in o"tstanding bridges, and the increasing possible capacities of"ltra4high performance concrete, which sho"ld be reasonably "sed and eploited in thespecific pro-ects where s"ch epensive materials may be reE"ired, it has contin"o"sly beensearched by the HPC fathers #Malier et al, $%%&' to develop HPC for small and standardstr"ct"res, where benefits of material d"rability and E"ality control especially for pre4castelements1 co"ld be appreciated by the owner, together with material savings and red"cedmaintenance Gith this aim in view, the French Ministry of ransportation enco"raged thedevelopment of a new generation of standard bridges motorway crossings1 made with HPC

Fig"re $3 6eneral view of one HPC innovative overpass on Do"rges Dypass

+ design competition was initiated in $%%5 concerning a f"nctional specification for a & &lanes overpass +mong a large n"mber of very innovative and interesting sol"tions, thewinning design was prod"ced by a -oint vent"re of the 7alla Iera and Do"yg"es contractingcompanies, in partnership with the >pielmann architect office Constr"ction was completed in$%%) for & prototypes on Do"rges Dypass in central France fig $1 + typical file describingthis HPC overpass sol"tion is being prepared after drawing "p technical and economic

concl"sions, so that this str"ct"re can be re4employed easily anywhere on the highwaynetwor(

The structural concept

+ll parts fo"ndations, dec( and s"pports1 are made of HPC with )0 MPa characteristicstrength he frame of the pro-ect consists of a standard overpass type bridge, & & lanemotorway type road crossing, with two &0 to &9 m spans, 50 to $00 gr s(ew, a total dec(width from 5 to $; m with one rib possibly wider with several ribs1, $% $5 pre4stressingtendons, conventional pavements and standard safety barriers Fo"ndations sho"ld be ofconventional type on footings or deep fo"ndations +b"tments and piers had to be anchored

on footings he central pier sho"ld be architect"rally fleible Contin"ity sho"ld be possiblebetween pier and dec(

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>imple optim"m shapes have been researched he dec( consists of a longit"dinally pre4stressed rib, cast in place on form with prefabricated caissons on both sides forming hollowbloc(s fig &1 hese bloc(s are designed to act as side formwor( for the rib, they consist ofa longit"dinal edge beam, & transverse ribs and a beam with a downstand acting as aformwor( for the rib sides he assembly s"pports a thin slab $; cm1 Jeying providescontin"ity between hollow bloc(s and hollow bloc(s, and between hollow bloc(s and ribshe "se of HPC optimises the cross4section of s"pports and the dec(, by acco"nting for thearchitect"ral views, both for the fineness and the E"ality of finished s"rfaces he concept isinnovative d"e to combined traditional and ind"strial methods3 simple and solid rib cast onsite, prefabricated thin and comple corbels

Fig"re &3 7ec( of HPC overpass >ide pre4cast bloc(s and pre4stressed rib cast in place

Design aspects

Ksing HPC helps to ta(e f"ll advantage of re4bars with 500 MPa yield stress, either in thedec( or s"pports, since the allowable stress is increased "nder damaging crac(ingconditions in relation to concrete strength >teel/concrete mod"lar ratio was ass"med eE"alto % HPC is also attractive for a higher contrib"tion of concrete to resist shear forces andtorsion, which red"ces the transverse dimensions of the central rib Bongit"dinal bending ofthe dec( was comp"ted in crac(ed section in accordance with class of DPLB %$ r"les

etended to )0 MPa concrete, #de Barrard et al., $%%9' Contin"ity of the dec( and theincreased thic(ness of the central pier red"ced applied moments "nder imposed loads in theslenderest part of the span he brac(et on the pier also red"ces the n"mber of pre4stressingcables $% $5 > consisting of .4wire class $)90 MPa very low creep strands1 reE"ired withthe constant height Maim"m stresses are enco"ntered on the central s"pport and in thespan, d"e to good str"ct"ral optimisation low str"ct"ral slenderness of $3;01 ransversebending was st"died by FL modelling, which showed how local forces are transferred intothe prefabricated ribs, the $; cm thic( slab and hollow bloc(s Lffects of vehicle impact onsafety devices and effects of differential shrin(age between the elements longit"dinal (eyand prefabricated elements, central rib and pre4cast elements1 were st"died "sing the samemodel

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able $ Comparative ratios for standard overpass bridges

traditional C;5 sol"tion 7alla Iera / Do"yg"es C)0 sol"tion

>lenderness $/&& $/;0

hic(ness $ m 05! to $ m

LE"ivalent thic(ness 0.5 m 0;. mConcrete vol"me ;%0 m; $)) m;

Passive reinforcement ;% t ;% t

Pre4stressing $& t ) t

7ec( weight %.5 t 5&0 t

Realisation and followings

he specified )0 MPa concrete was obtained "sing the recent HPC mi4design methods #deBarrard, $%%%'3 first comp"ter4aided approach of the mi4proportioning, optimisation of theaggregate grading "sing the :en84BCPC software, st"dy of cement4admit"re compatibility

according to the +F:LM method, ad-"stment of concrete viscosity "sing the BPC4rheometerhe concrete developed for the site has a cement CLM 5&5 content of !50 (g/m; tcontains !0 (g/m;of silica f"me and ;$ of s"perplastici@er, res"lting in easy placement,average &) day strength of more than $00 MPa and perfect s"rface finishes with the "se of"ntreated plywood formwor( + rather low prod"ction rate &0 to &5 m;/h1 has beenconfirmed, as well as the absol"te necessity of thoro"gh immediate c"ring+ll temporary constr"ction has been designed as simple and safe as possible, and can beset "p by any professional bridge contractor, the form on which the central part is po"red islighter than for a conventional overpass bridge, d"e to the smaller cross4section of the dec(he pre4cast hollow bloc(s incorporating the rib side formwor( and the architect"ral concretecantilevers, are designed to be transported by road hey are handled directly with a crane

and installed on the form before ad-"stment Nverall (eying is done in a single operation atthe same time as the rib concrete is cast otal completion time is less than & months for onebridge he contractor estimates the time red"ction to &4; wee(s on site, with methods lesssensitive to bad weather O"antitative ratios are given in able $, for this HPC overpasssol"tion hey are compared with a conventional C;5 sol"tion with two &&5 m spans,emphasising the possible material savings, which are very "sef"l in the case of diffic"ltconditions for fo"ndations, and tend to ta(e a growing importance in the contet of nat"ralreso"rce management in FranceFor f"rther pro-ects, it seems necessary to modify the dec( ends to ens"re pre4stressdiff"sion in an in4sit" cast transverse rib, rather than in the pre4cast slabs Ntherimprovements have been s"ggested3 connection of pre4cast slabs with lateral eternal pre4stressing rather than in4sit" (eying, light thic(ering of the slab for easier re4bars placing

7espite these possibilities of detail improvements, this eperience of standard HPC bridgedevelopment t"rns o"t very fr"itf"l and re4"sable t ill"strates the growing role of the materialengineer in pro-ects, together with the designer, architect and contractor t also emphasisesthe interest of a global economic approach incl"ding material costs directly related tomechanical parameters, placement conditions, aesthetics, maintenance, rational "se ofreso"rces, etc

C80 alternative project for an arch bridge of moderate span

Context and scope of the study

Deside the application of HPC in standard bridges, comparative st"dies were carried o"twithin the frame of DHP=&000 national research coordinated program #o"tlemonde, $%%)'

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gathering owners, designers, contractors and laboratories aiming at the development andapplication of HPC hese st"dies have been foc"sed on =classical= shapes for bridges,where concrete compressive strength is highly appreciated he res"lts are th"s epected tohelp bridge designers in applying HPC in the most favorable conditions

For the first of these cases, the opport"nity consisted in the st"dy, at >L:+ FrenchHighways echnical +gency1, of an arch bridge of moderate span, crossing the river Cher atChambonchard central France1 n the initial pro-ect, the top of the arch is &5 m above theorigins he span between them is $$0 m and the total length of the bridge is $)% m t hasbeen decided #B8geron, $%%)' to imagine two alternative sol"tions for this arch, with slightlymodified architect"ral reE"irements he first sol"tion sho"ld "se conventional concrete with!0 MPa design strength, the other one HPC with )0 MPa design strength and containingsilica f"me his latter strength corresponds to the limit of presently official French designr"les #de Barrard et al., $%%9' he choice of HPC containing silica f"me was intended to ta(eadvantage of limited delayed deformations in the designDoth alternative sol"tions had to be optimi@ed in terms of material savings, so that theadvantages and limits of "sing HPC vers"s ordinary concrete can be pointed o"t at the

design stage n fact, HPC had already been "sed even in France in a famo"s arch bridge,mostly for reasons of d"rability and methods effectiveness de Champs, in #Malier, $%%&'1+rch bridges appear as favorable applications of HPC d"e to possibly high compressivestresses in the arch However, the limits of economical application to HPC of =classical=bridge shapes generally optimi@ed for conventional concrete had to be E"estioned in thiscontet #Helland, $%%9'

Fig"re ;3 6eneral shape of the initial bridge pro-ect

Iterative optimization of the proects

he general shape of the pro-ect fig ;1 had to be respected in the alternative sol"tionsh"s the position of arch origins and top, spacing of piles transferring the dec( weight$5.5 m1 and f"nctional reE"irements of the dec( reinforced concrete ribbed slab, $$ mwide, $)% m long1 were (ept he same actions and load combinations were "sed he archhas been chosen as f"nic"lar with respect to permanent loads his choice is classical forlarger span arches, it has been maintained here beca"se of the relatively low traffic loadshe initial parabolic shape of the arch is th"s modified and approimated by . straightsegments1 d"e to material savings in the arch cross section, in the dec( and piles

For architect"ral reasons, the initial pro-ect "sed a bo4girder for the arch, leading to veryred"ced compressive stresses his type of section is well adapted for long span arches, for

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it maimi@es torsion inertia For intermediate spans, an H4shaped section is interesting for itstransverse inertia Here a do"ble 4shaped cross section with transverse bracing at the pilesleads to minim"m material cons"mption, yet satisfying the most critical reE"irements, i.e.notension at serviceability limit state >B>1 with freE"ent load combination, and tensile stresseslimited to ftjact"al tensile strength1 at >B> with infreE"ent load combination t has beenass"med that the arch wo"ld be erected by the cantilever method 6enerally, when (eying, a-ac( is introd"ced to recover compressive stresses he -ac(ing load has been optimi@edabo"t .. of the load reE"ired to cancel the deformation d"e to the dead weight of the architself1 to get minim"m tensile stresses, especially in the anchoring bloc(s he E"estion ofthe dead weight of the arch relatively to s"pported loads piles, dec( and s"perstr"ct"res1has not been f"lly eplored Material savings "sing HPC red"ced dec( thic(ness foreample1 may lead to red"ced compressive stresses in the arch, especially in the case ofmoderate spans, which might not be optim"m, even tho"gh interesting for fo"ndations>implified minim"m sE"are cross4sections have been chosen for piles et piles withred"ced longit"dinal inertia b"t large cross4section might have t"rned o"t better s"ited aposteriori

+ first step of shape optimi@ation and cross4section minimi@ation "sing hypotheses describedhere4above is th"s achieved by comp"ting dead loads, optimi@ing the arch c"rvat"re andchec(ing tensile stresses "nder freE"ent and infreE"ent load combinations at >B> hecritical case is always the >B> infreE"ent combination of actions at long term, incl"dingtemperat"re effects + tensile stress close to ftjis then reached in the lower fiber of the archat the ab"tment Main feat"res of the alternative pro-ects are detailed in #B8geron,o"tlemonde et al., &00$' and s"mmed "p in table &

able &3 Main feat"res of C!0 / C)0 sol"tions >B> stresses long term 4 rare combination1

dec(ma

thic(ness

pilescross4section

$/& arch4shape

webthic(ness

matensile

stress

ma stressin

compressionC!0 09!$ m $$ m $;5 m $& m &0 m 0! m ;$9 MPa $%; MPa

C)0 05 m $$ m $0 m $$ m $) m 0&5 m !%; MPa &;$ MPa

t t"rns o"t that the "sable stress range of C)0 "p to !) MPa instead of &! MPa for C!01 ishardly applied in compression Nn the contrary, the tensile strength is f"lly applied in bothcases available stress limit ftj ; MPa for C!0 vers"s 5$ MPa for C)01 + parallelcomp"tation has been performed for an arch with the same span b"t a red"ced height$5 m1 he cross4section has been minimi@ed as eplained previo"sly he meancompressive stress is higher especially after -ac(ing t t"rns o"t that a ratio of $/5 for theheight / span of the arch can be considered as a practical minim"m for val"able applicationof HPC in terms of high compressive strength

Reinforcement determination and complementary verifications

+n elastic comp"tation of the bending moments is carried o"t for the different combinationsof actions either with >B> or KB> "ltimate limit state1 coefficients For in4plane loads, >B> iscritical for determining the reinforcement and KB> chec(ing does not lead to anys"pplementary re4bar he different loading cases can be drawn on the interaction diagramof the most critical cross4section of the arch, it t"rns o"t that at KB> the cross4sectiondimensions of the C)0 sol"tion wo"ld have been s"fficient even with a concrete having adesign strength of only !0 MPa #B8geron, $%%)' he most critical transverse load is the wind

press"re before (eying, which reE"ires provisional lashing of the beams Ghen the arch is(eyed, both sol"tions are eE"ivalent in terms of resistance he C)0 arch is thinner, itcatches less the wind b"t its stiffness is also lower

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he first modes of instability are identified in a first comp"tation as lateral tipping first ;modes, the first one is the most critical1 and longit"dinal b"c(ling hen an amplit"de ofB/&000 is applied to each mode, B span of the arch1 his displacement is given as aninitial fa"lt for an incremental non4linear comp"tation, "ntil stability is lost + safety factorhardly higher than & is got for the C!0 sol"tion concerning lateral tipping, which is theminim"m generally reE"ired + higher val"e almost ;1 is got for the C)0 pro-ect, which islighter for a higher material stiffness For both cases a very high safety factor abo"t $01 isgot with respect to longit"dinal b"c(ling

7"e to the span and height of the arch, it has been ass"med that it wo"ld be erected by thecantilever method, with provisional cable stabili@ation he E"antity of cables is determinedby the weight of the arch, so that no bending moment is transmitted to the ab"tment thedead weight being eE"ilibrated by the cables1 he weight of the C)0 sol"tion red"ced by&$ 1 leads to a red"ced cable weight 4 $&5 1 However, the provisional lashing forstabili@ation against wind loads before (eying sho"ld not be m"ch altered for the C)0 vers"sthe C!0 sol"tion Desides, piles even if not detailed for architect"ral reE"irements in this

st"dy1 are relatively massive elements and temperat"re elevation problems sho"ld beaddressed for both sol"tions

Bong term deflections and stresses have been comp"ted at different stages before and after-ac(ing, and at long term1 "nder permanent loads "sing detailed code provisions for ta(ingHPC delayed behavior into acco"nt #Be :oy, $%%9' he choice of C)0 containing more than5 of silica f"me with respect to the cement content1 is of prime importance for thisadvantage of dimensional stability of HPC he compressive stresses prod"ced by -ac(ingare maintained all the better than delayed deformations are smaller Lven (eeping in mindthe "ncertainties on standard val"es concerning creep and shrin(age of concrete, it t"rns o"tsee table ;1, that the increment of deflection epected d"ring service life is m"ch red"ced inthe C)0 sol"tion compared to the C!0 one $% cm instead of 59 cm1 his tends to favor an

easier management for the owner in the C)0 sol"tion

able ;3 Bong term deflection and stresses

after (eying and -ac(ing

(ey verticaldisplacement cm1

stress on ab"tments MPa1 stress at the (ey MPa1

lower fiber "pper fiber lower fiber "pper fiber

C!0 $9 !% %; 55 !9

C)0 0) 59 )9 5$ 50

after long term creep and shrin(age

(ey vertical

displacement cm1

stress on ab"tments MPa1 stress at the (ey MPa1

lower fiber "pper fiber lower fiber "pper fiber C!0 4 !0 )& 5) ;9 9!

C)0 4$$ .5 99 !0 90

!ttempts of cost comparison

+ part of initial costs for the owner can be derived from material E"antities of the completedstr"ct"re he total concrete epense is $;%) m;for C)0 instead of $.%$ m;for C!0, ie ared"ction of && For concrete, price incl"des material and casting wor(manship1 n $%%),it was estimated aro"nd $000 F/m;for C!0 $50 Q1 and $900 F/m;for C)0 &!; Q1 hedifference sho"ld not be considered as absol"te t can be attrib"ted in the present French

mar(et contet to longer st"dies and controls concerning HPC for red"ced deliveredE"antities t t"rns o"t see table !1 that the C)0 sol"tion is more epensive especially d"e to

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the costs of the C)0 dec(, where HPC is hardly applied D"t given scattering of the prices,both sol"tions witho"t the dec( can be considered as eE"ivalent in terms of initial costs,besides savings of nat"ral reso"rces and ind"ced savings in maintenance costs betterd"rability of HPC1 +s indicated, the heavier C!0 dec( is not "nfavorable for the C)0 arch

he costs d"e to the method of erection can hardly be completely identified at this step hemost direct conseE"ence of the change of concrete grade is the lighter weight of cables forprovisional stabili@ation 4 $&5 1 he derived savings are estimated to abo"t &00,000 F+dded to material initial costs, and provided the other epenses are "nchanged, this gives alittle advantage to the C)0 sol"tion with C!0 dec(1 or red"ces the difference between bothsol"tions However, it is necessary to recall that consistently with all these estimations, theglobal initial cost of s"ch a bridge is abo"t &5 MF, that is abo"t ! times the material costs thatco"ld be listed here Main initial savings "sing C)0 are th"s d"e to a red"ced concreteepense 4 && 1, red"ced cost of forms, red"ced weight of cables for provisionalstabili@ation O"antity and cost of re4bars are almost "nchanged, as well as for fo"ndations inthis case for an arch, the E"ality of soil is generally good1 :ed"ced erection times may beepected "sing C)0, which may have important economical conseE"ences, d"e to HPC

rapid hardening D"t this has to be planned eplicitly in specifying concrete

able !3 Material initial costs French Francs, val"e $%%) 4 $ FF R 0$5 Q1

C!0 C)0 rel val C)0 vsC!0

E"antity cost FF1 E"antity cost FF1 E"antity cost

Piles

concrete 5.& m; 5.&,000 !&! m; 9.),!00 4 &5% S $)9

passive ribbed re4bars

55 t !%5,000 55 t !%5,000 S 0 S 0

ro"nd re4bars 5; t !.,.00 !&! t ;),$90 4 &0 4 &0 high E"ality forms $,.90 mT !!0,000 $,5$5 mT ;.),.50 4 $;% 4 $;%

Arch

concrete 5%5 m; 5%5,000 !&0 m; 9.&,000 4 &%! S $&%

passive ribbed re4bars

!& t ;.),000 !& t ;.),000 S 0 S 0

ro"nd re4bars 9%; t 9&,;.0 9%; t 9&,;.0 S 0 S 0

high E"ality forms &,.50 mT )&5,000 &,900 mT .)0,000 4 55 4 55

Deck

concrete 9&! m; 9&!,000 55! m; ))9,!00 4 $$& S !&$

passive ribbed re4bars 5% t 5;$,000 95 t 5)5,000S $0& S $0&

ro"nd re4bars 55! t !%,)90 55! t !%,)90 S 0 S 0

reg"lar forms $00 mT &5,000 $00 mT &5,000 S 0 S 0

high E"ality forms &&50 mT 9.5,000 &&50 mT 9.5,000 S 0 S 0

concrete c"ring &$0$ mT !&,0&0 &$0$ mT !&,0&0 S 0 S 0

Total 5,361,95 0

5,745,960

S .&

Total (ecept !eck" 3,415,07 0

3,4#$,6#0

S&0

he advantages and limits of HPC for an arch bridge of moderate span can th"s be derivedand s"mmed "p from the case st"died3

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$ 4 f HPC has to be applied, the general shape of the arch sho"ld be s"rbased eno"gh top /span ratio lower than $/51 and the dec( not too m"ch lightened, so that importantcompressive stresses are applied in the arch& 4 For s"ch a moderate span, a do"ble cross section with reg"lar bracing is better s"itedand more economic than a bo4girder or an H4shaped cross section for the arch; 4 C)0 material savings 4 &; in this typical case1 are limited by the tensile strength, whichis reached in the lower fiber of the arch near ab"tments at the serviceability limit statevariable actions "nder infreE"ent combination1 his emphasi@es the reE"irement of avalidated and d"rable high tensile strength for HPC, when the absence of crac(s is reE"iredat the serviceability limit state n the C)0 vs C!0 sol"tion the E"antity of re4bars remainsalmost "nchanged! 4 7elayed strains are m"ch red"ced in the HPC sol"tion, d"e to the choice of silica f"meconcrete he safety factor concerning instability first lateral tipping mode1 is s"bstantiallyincreased5 4 Gith probable economical hypotheses, the optimi@ed C!0 and C)0 pro-ects st"died arero"ghly eE"ivalent in terms of initial costs, yet ind"ced changes in erection methods may bein favor of HPC

C80 alternative project for a box girder prestressed concrete bridge over the river

!eine

+s another type of bridge str"ct"re where concrete compressive strength is fr"itf"lly applied,the case of a pre4stressed bo4girder was st"died "sing the opport"nity of the c"rrentlyst"died viad"ct of Mesnil4le4:oi over the river >eine on +$! motorway western from Parishis st"dy also too( place within DHP=&000 national pro-ect #PiE"et, $%%. $%%)' hereference sit"ation concerns the bridge effectively b"ilt "sing C!0, with a main span of $$0 mfig !1 and classical height / span ratios of abo"t $/&0 "pon pier and $/;. at the (ey fig 51

Fig"re !3 Bongit"dinal profile of Mesnil4le4:oi viad"ct

Fo"r alternative sol"tions were considered, three of which "sing C)0 with silica f"me, whichis the limit of present design r"les, and the last one "sing C$&0 with the same etrapolated1form"lae For the first three sol"tions, the ob-ective was to precisely E"antify at the level ofthe comp"tation for eec"tion1 the possible savings d"e to the s"bstit"tion of C)0 to C!0he optimisation was th"s foc"sed on three points37 :ed"ction of pre4stressing steel E"antity, for the same cross4section and same span as

in the reference C!0 sol"tion, "sing C)07 ncrease in span with an affinity in the longit"dinal profile1, for the same cross4section

and the same pre4stressing tendons as in the reference C!0 sol"tion his strategy was

applied both for C)0 and C$&0 types of concrete, and the possibility of a s"pplementary

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$%$5 cable instead of an empty reservation was "sed in a variant comp"tation toamplify the potential increase

7 :ed"ction of thic(ness and material savings for the transverse profile "sing C)0, for thesame span and pre4stressing as in the C!0 reference sol"tion

"pon pier at the (ey

Fig"re 53 ransverse profile of Mesnil4le4:oi bo girder C!0 alternative1

he optimised alternative sol"tions were determined after verification of the same loadingconfig"rations as for the really b"ilt str"ct"re his helped validating the correctimplementation of HPC code etension form"lae within c"rrent str"ct"ral design codesfreE"ently "sed for this type of segmentally b"ilt concrete bridges he res"lting E"antitiesare detailed on table 5, and the limiting loading case is given with the ratio of the maim"mstress comp"ted over the allowable one, either in tension or in compression

able 53 Main feat"res of C!0 / C)0 / C$&0 sol"tions

co%crete spa% cross &sectio%

pre&stressi%'

hei'ht spa% (pier"

hei'ht spa% (ke)"

c stress ratio

i% co*pressio%

t stress ratio

i% te%sio%

co**e%ts

C!0 $$0m

ref1

ref $&0 tref1

$/$%) $/;.0 ); >B>

infreE"ent

.! >B>

infreE"ent

C)0 ref ref -11%$; t1

$/$%) $/;.0 ;% >B> perm

!. beam

erection

45passreinf

C)0 +12%

$&!m

ref ref $/&&& $/!$! 59

>B> perm

%!

beamerection

C)0 +15%$&)m

ref S$$%$5

FS$01

1/22.8 1/42.5 90 >B> perm

%9 beam

erection

C)0 ref 4$!

lim "

ref 1/25.8 1/46.3 9$ >B> perm

9. >B>

infreE"ent

4$&passreinf

C$&0 +18%$;$m

ref S$$%$5

FS$01

$/&;! $/!;9 ;% >B> perm

$00 >B>

freE"ent

limit 0tension

19


11/18

Ghen the span and cross4section are (ept constant, ie for simple concrete type s"bstit"tion,savings in the reinforcement are significant 5 for passive re4bars, $$ for pre4stressing1,however the capacities of the material are hardly applied Ghen the increase in span issearched, with constant pre4stressing and transverse profile, the limit of tensile strength isenco"ntered d"ring erection steps connection of the last segment of one beam before(eying1 for the C)0 sol"tions and d"ring service life freE"ent load combination for >B>1 forthe C$&0 sol"tion he relative increase in span S $& to S$) 1 may be of interest in case oflocal constraints However the val"able application of concrete high compressive strength islimited Finally, the most promising sol"tion, leading to the thinner aspect ratios, comes fromthe cross4section optimisation fig 91 he limit of the obtained material savings comes fromthe maim"m allowable shear stress, both at >B> and KB>, and from practical dispositionsconcrete cover aro"nd pre4stressing d"cts1 he red"ced web thic(ness is an advantageconcerning thermal effects 6lobally, the capacities of HPC are satisfactorily applied witho"tecessive stress ratio in tension, and the global passive reinforcement ratio is not m"chaltered, which is important regarding the E"ality of concrete placing Finally, the height overspan ratios of $/&9 "pon pier1 and $/!9 at the (ey1 can be (ept in mind to s"m "p theaesthetic and f"nctional capacities of HPC in this type of str"ct"res

"pon the pile at the (ey

Fig"re 93 ransverse profile of Mesnil4le4:oi bo girder C)0 optimised alternative1

High rise piers and p"lons using HPC# experience and trends

+ last typical case st"died in the frame of DHP=&000 pro-ect concerns high rise piers andpylons higher than .0 m, and with a height / diameter ratio higher than $01, where concrete

high strength can be applied d"e to intense and permanent compressive stresses +preliminary design eample is given in table 9 to fi ideas "sing typical pro-ect data For thesame normal load on top and bending moment at the bottom of the pier, the "se of C)0instead of C!0 leads to global savings abo"t 5 of cost red"ction1 mainly d"e to ared"ction of pier thic(ness by a factor & et the reinforcement ratio has to be increasedsignificantly to ens"re this global efficiency

able 93 comparison of simplified design for a pile $50 m high, vertical load $95 MA on top

co%crete l

(+e 500"

thick%ess(*"

-/(.*"

-/("

// per*(Pa"

co%creteol. (*3"

!efor*e!re&bars (t"

cost(k+"

costariatio%

C!0 $ $0 ;;00 ;;% 55 ;!50 &9% 5095

C)0 $ 0) ;;00 ;$) 9; &)0) &$% 5)0. S $5 C)0 &5 0!) ;;00 &)$ %0 $.;$ ;;) !.%5 4 5

11


12/18

6iven recent eamples of s"ch str"ct"res in France Aormandie fig ., d"ring erection1 andLlorn cable stayed bridges, Ierri?res composite bridge and Milla" viad"ct, fig )1 sometrends and recommendations have been drawn hese recommendations #B8geron, d=+loUaet al., &00;' deal with the specificity of concrete reE"irements thermal behavio"r, shrin(age,wor(ability, aspect of facings1, erection methods stabilisation against wind loads, slipping vsclimbing formwor(1, specific design verifications stability, dynamic behavio"r1, and E"alitycontrol d"ring st"dies and eec"tion

Fig"re .3 Aormandie bridge d"ring erection Nverview of the HPC piers and dec(

Fig"re )3 Piers of Milla" viad"ct C90/.51

1/


13/18

n this type of str"ct"res, the potential advantages of HPC are the following37 material savings for the same load to be s"pported, provided the reinforcement ratio or

the stress ratio of the re4bars1 has to be significantly increased,7 preservation of aggregate nat"ral reso"rces,7 red"ction of the cost of fo"ndations,7 higher d"rability, provided restrained shrin(age is controlled, which is of prime

importance for str"ct"res diffic"lt to inspect and repair,7 easier placing when p"mpable or self4levelling HPC is orderedhese advantages have been clearly demonstrated on the basis of recent eamples orcomparative design However they will be f"lly applied on f"t"re sites only if37 a complete set of concrete reE"irements is established and thoro"ghly followed d"ring a

longer1 phase of material st"dies and agreement #de Barrard, $%%9',7 restrained shrin(age in massive parts or between s"ccessive steps1 is controlled7 concrete segregation has been prevented7 stability and wind comp"tations have applied the higher material rigidityF"rthermore in the case of s"ch bridges, the spans are generally large which also favo"rs a

lighter1 HPC dec( in case of a concrete sol"tion

!tructural application of HPC # s"nthesis

Fo"r cases of design and cost comparison of C)0 vs C!0 sol"tion for standard oro"tstanding bridges or bridge str"ct"ral parts have been detailed in the first part of thispaper hese cases correspond to possibly fr"itf"l str"ct"ral applications of HPC in bridgedesign, they were considered as ill"strative and demonstrative for enco"raging "se of HPCin bridge engineering #o"tlemonde et al &00&4b, o"tlemonde et al &00;, Dra@illier ed&005'+ systematic hypothesis of comparison has been the same f"nctional reE"irements he

following general concl"sions can be dawn from these cases$ 4 he aspect ratio of the C)0 str"ct"res is always thinner, and the optimised shapes lead toglobal concrete vol"me savings from abo"t $5 to 50 & 4 he optimised C)0 alternative has th"s generally an initial material cost somewhat lowerthan the reference C!0 sol"tion between 0 and $0 savings1 Possible ind"ced savings arediffic"lt to E"antify in a general frame; 4 + mandatory condition of worthy application of C)0 consists in dealing with highcompressive stress levels3 for an arch, it has to be s"rbased eno"ghV for a bo4girder, thespan has to be long eno"ghV for a pier or an arch, the s"pported load has to be high eno"gh! 4 Nn the contrary, if classical shapes are not modified, tensile or shear maim"m allowablestresses t"rn o"t to be the limiting factors for the C)0 sol"tion, and prevent a so"ndapplication of C$00 or C$&0

5 4 n all st"died cases, the "se of silica f"me concrete leads to a significant red"ction ofdelayed strains and load redistrib"tion9 4 7"ring erection or "nder wind loads, the stability th"s the safety1 of HPC sol"tions isgenerally increased. 4 Finally, for the comparison of initial costs, the correct acco"nting of methods since thebeginning of the pro-ect is of prime importance to ta(e all the benefits of an HPC sol"tion

hese concl"sions established within the contet of $%%%4etended French design codes#o"tlemonde et al &00&4a' still stand valid when comparing technical advantages of HPC /reg"lar concrete alternative sol"tions However, some other aspects also infl"ence theval"able application of HPC, mainly the economic aspects of E"ality control and the technical

level of the staff in charge of mi4proportioning and miing, and the technical level of thepro-ect chec(er his has tended for recent times to favo"r applications in pre4cast prod"cts,high4rise b"ildings and large bridges

1.


14/18

Present trends of HPC application in France

7"ring the last five years, ma-or evol"tions also too( place in France concerning concrete,having an infl"ence on HPC applications

$ +pproval of LA &09 standard for concrete specificationhis highlighted the E"estion of concrete d"rability vs epos"re classes Combined withcover specification in LA $%%&, which led to important calibration wor(s at the national level#o"tlemonde Coin, &005', this concern of d"rability highlights the important potential ofHPC #Daroghel4Do"ny &00!' his potential has also been emphasi@ed and rationallydemonstrated with the promotion of scientifically4based d"rability indees #Daroghel4Do"ny etal &00!, Daroghel4Do"ny &00.' +pplication of s"ch concepts especially in cases where thebridge contractor also is f"rther operator has demonstrated interest of HPC for ens"ring lowmaintenance costs, as in Iasco de 6ama bridge in Port"gal, Confederation bridge inCanada, Milla" bridge in France or :ion4+ntirion bridge in 6reece fig %1 However forsmaller wor(s and ecept direct technical advantages for the str"ct"re 4 eg dec( of

Dea"caire4arascon cable4stayed bridge, high4rise piers of "lle bridge fig $01 4 the recentconcern of 7LF ris( may have ind"ced a rather caref"l attit"de regarding possible"ncontrolled hydration heat W for which HPC may not be advantageo"s

Fig"re % 3 :ion4+ntirion bridge >ee #C"ssigh et al &00.' for details of concrete specification

Fig"re $0 3 "lle viad"ct High4rise piers made of C.0 ens"ring strength and intrinsic free@e4thaw resistance

15


15/18

& 7evelopment of fl"id concrete specification and control>elf4compacting concrete represents an important brea(4thro"gh which significantly modifiescosts of concrete mi4design and placement Moreover, it has conseE"ences of increasingimportance in terms of noise dist"rbance, either in a pre4cast concrete plant or in "rban-obsites Provisional r"les for >CC acceptance were ta(en early #C"ssigh et al &000' n thepresent state of practice concerning admit"res and mi4design, >CC rob"stness withrespect to -obsite and environmental variations, reE"ired also for architect"ral p"rposes#o"tlemonde ed &00!', is ens"red by "sing relatively high4strength self4compactingconcrete X C!5/551 mportant scientific advances have been gained concerning rationalmi4design of s"ch concrete #de Barrard $%%%', prevision of concrete p"mpability #Japlan&00$', possible red"ction of miing times #Chopin &00;', and modelling of fresh concreteflow hese advances limit drawbac(s of first HPC eperience in terms of stic(y hard to placeconcrete with ris( of cement4admit"re incompatibility However, they are mainly "sed in thecontet of a globally controlled concrete s"pply process, which is mainly the case for pre4castconcrete or large sites with own concrete plant For the ready4mi concrete ind"stry,additional costs of HPC still seem to remain diffic"ltly accepted

; Consolidation of (nowledge on HPC within the frame of L"rocodes provisionsmportant research efforts #o"tlemonde et al &00&4b, o"tlemonde et al &00;4b' weredevoted d"ring the late nineties to ens"ring the validity of design code provisions whenapplied to HPC and also IHPC C)0/%5 and "p1, so that both the still presently valid Frenchdesign code and the c"rrently enforced L"rocode & co"ld be safely and val"ably "sed, giventhe French eperience of HPC str"ct"res Ma-or contrib"tions concerned tensile strength ofHPC #o"tlemonde et al &00!4b', shear strength of beams and specific design of @ones"nder concentrated loadings, creep val"es, etc #o"tlemonde et al &00;4a, o"tlemonde etal &00!4a' he technical benefits of HPC lower creep, for eample, has been proven asval"ably applied in an etension of the techniE"e of prebended beams #o"tlemonde >taE"et &009' Gidespread "se of the L"rocodes incl"ding ed"cation of designers still

remains in France an ongoing important wor( to be carried o"t, which for the moment mayprevent from developing innovative sol"tions f"lly eploiting the offered design possibilities

Fig"re $$ :oof of Milla" viad"ct toll gate, made of KHPF:C

! 7evelopment and application of KHPF:CFinally, after $%%9 pioneer applications in >herbroo(e footbridge and beams for coolingtowers of L7F power plants, "ltra4high performance fibre reinforced concrete entered thetime of a new ind"strial development with the reali@ation of the first KHPF:C road bridge inDo"rg l?s Ialence &00$1, and the p"blishing of design and control recommendations#:esplendino et al &00&' nd"strial competition has got significant with this (ind of materialsas a sign of capability of concrete mi4design and placement control and aptit"de to

innovation Lven tho"gh cons"mption of KHPF:C is still very limited, it gains growinginterest d"e to epected d"rability, lightness, low reso"rce cons"mption, architect"ral

1*


16/18

possibilities #Do"teille :esplendino &005' 7esign and reali@ation eperience, for eamplewith erection of the roof of Milla" viad"ct toll gate fig $$1, is collected within the Frenchmirror gro"p of fib )9 tas( gro"p, also ta(ing advantage of research pro-ects res"lts onpossible KHPF:C applications #o"tlemonde et al &005' Ghile KHPF:C raise the limits ofconcrete strength application, they help drawing "pwards the technical interest for concreteperformance tailoring, and sho"ld gain an increasing n"mber of prototype applications Giththis approach, rationally4based choice of concrete strength higher than C!0, andspecification of related other properties, is getting wider and wider acceptance

+ltogether, these present feat"res and evol"tions may tend to favo"r HPC application, b"tnot mainly for its strength properties, even given the trend to save nat"ral reso"rces Foreconomic reasons which still remain a strong press"re on constr"ction ind"stry especially forho"sing, the ready4mi concrete ind"stry is not very prone to s"pply with HPC anywhere inFrance, even tho"gh it has proven to be feasible, and an important proportion of ready4miplants have standard proposal of C90 grade Considering the present sit"ation of HPCapplication, it is to be stated that more than 90 of concrete "sed in pre4cast ind"stry hasstrength higher than C90 Moreover, HPC sol"tions are generally considered W at least in

alternative pro-ects 4 for large bridges, and freE"ently chosen Lven tho"gh it represents avery specific aspect of the mar(et, HPC is also mainly "sed for high4rise b"ildings especiallyin Ba 78fense b"siness district of Paris F"rther evol"tions may be drawn by a renewedinterest for steel4concrete composite constr"ction Nnce connection and restrained shrin(ageiss"es can be rationally solved, which is now the case, HPC associated with steel hasimportant economical and technical advantages of lightness, rigidity and stability, which mayfavo"r f"rther application of pioneer sol"tions li(e the :oi@e bridge #Ca"sse Montens $%%&'or overpass P>$; concept #Chevallier Petit-ean &00$', possibly "sing KHPF:C#o"tlemonde et al &005' Finally in o"r opinion, HPC growing application co"ld be the res"ltof a growing concern of d"rability and s"stainability of constr"ctions, provided the level ofaesthetic and architect"ral performance of HPC pro-ects is maintained, and provided the costof E"ality control which is necessary for ens"ring HPC satisfactory s"pply, is considered as

an investment balanced by savings in placement, constr"ction methods and maintenancecostsY which may still reE"ire some open4minded people within the systems

$eferences

Daroghel4Do"ny I et al &00!1 2o%ceptio% !es bto%s por %e !re !e ie !o%%e!es ora'es,+F6C, 7oc"ments scientifiE"es et techniE"es, Paris, &59 p

Daroghel4Do"ny &00!1 Bes sp8cificit8s des b8tons Z ha"tes performancesCaract8ristiE"es microstr"ct"rales et propri8t8s relatives Z la d"rabilit8 8val"8es enconditions de laboratoire o" en conditions nat"relles, t!es et recherches !es P2, N+!!,BCPC, Paris, )0 p

Daroghel4Do"ny I &00.1 Drabilit) %!icators relea%t tools for a% i*proe!assess*e%t of 82 !rabilit), 5[ conf nt CNA>LC= 0., o"rs, France, !49 -"in &00.,\Concrete "nder severe conditions Lnvironment and loading], o"tlemonde et al ed, vol $,pp 9.4)!

Do"teille >, :esplendino &0051 7erniers d8veloppements dans l*"tilisation des b8tonsfibr8s "ltra4performants en France Proc. 2:$005, A+2, Paris, 19 p.

Dra@illier 7 et al.$%%91 nnovative design of small highway bridges in HPC Proc. 4th%t./)*p. o% the tili;atio% of


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Ca"sse 6, Montens > $%%&1 he :oi@e Dridge, LC= 0., o"rs, France,!49 -"in &00., \Concrete "nder severe conditions Lnvironment and loading], o"tlemonde etal ed, vol $, pp );%4)50

Helland > $%%91 Ktili@ation of HPC Proc. 4th %t. /)*p. o% the tili;atio% of L:+, Dagne"

B8geron F, o"tlemonde F, Do"chon L, Bef?vre ^, Codis 6 &00$1 +pplication of High

Performance Concrete in an arch of moderate span Comparative st"dy ;rd

nt Conf onarch bridgesA82L:+, 7oc"ments scientifiE"es et techniE"es, Dagne", &00&,$5& p

>taE"et >, o"tlemonde F &0091 %%oatio% por les ora'es ferroiaires e% +ra%ce %e potre *ite prflchie e% ?Tcience BtdPaper ref $)54;

1-


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o"tlemonde F, B8geron F, Dra@illier 7 &00&4a1 8atio%al strctral !esi'% si%'

hpc applications in france_toutlemonde

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