status of segmental bridge construction in europe · 2018. 11. 1. · status of segmental bridge...

Status of Segmental BridgeConstruction in Europe

Peter MattLosinger/VSI

Berne, Switzerland

S egmental bridge construction is amethod in which concrete seg-

ments, either cast in place or precast,are post-tensioned together to form thesuperstructure of a bridge. Segmentalconstruction methods can also be ap-plied to beam or arch bridges in pre-stressed or reinforced concrete.

Although many variations are cur-rently in use, only the three main con-

Note: This paper is based on a presentationgiven at the Segmental Concrete Bridge Confer-ence in Kansas City, Missouri, March 9-10, 1982.The Conference was sponsored by the AssociatedReinforcing Bar Producers — CRSI, FederalHighway Administration, Portland Cement Associ-ation, Post-Tensioning Institute, and PrestressedConcrete Institute.

struction methods will be discussedhere: the span-by-span method (since1960); the free cantilever method (castin place since 1950; precast since1962); and the incremental launchingmethod (since 1962). Cable-stayedbridges will not be discussed here.

This paper is intended to be a de-scription of the actual situation inEurope (see Fig. 1). The survey isbased upon a study of available litera-ture and contacts with several key indi-viduals in the European bridge indus-try. Where objective statistics are un-available, the author's subjective obser-vations and comments are offered.

This review covers the situation in 18

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Fig. 1. Map of Europe showing location of countries whose bridges are included in thesurvey described in article.

Western European (OECD,) countries,where more than 18 different languagesare spoken. Information (gathered in1980) comparing the size of Europe inrelation to the United States is providedin Table 1. It can be noted that Europe,which is densely populated, achieveswith 50 percent more people only 10percent more in gross national productthan the United States. Within Europe,the differences in GNP per capita areenormous, varying from $9244 down to$1901 (in U.S. dollars).

Clearly, Europe is far from being asingle entity. A gap in technology be-tween certain countries parallels theeconomic disparity. Wealthier coun-

tries, due to their higher labor costs,generally prefer labor-saving methodswith high mechanization. Segmentalconstruction was consequently devel-oped in these countries and is appliedto a much lesser extent in the lesswealthy regions of Europe.

Right .now, Europe does not have aunified standard in civil engineering,nor is it likely that such a standard willbe established in the near future. Al-though a "Eurocode" is in the planningstages, the concept faces so many ob-stacles that the prospects for adoptiondo not appear very promising.

The Model Code published jointly bythe CEB and FIP in 1978 certainly rep-

PCI JOURNAL/May-June 1983 105

Table 1. Statistical comparison of Europe and the United States.

Area.(sq km)

Population(millions)

GNP(billion U.S. $)

GNP/Capita(billion U.S. $)

Europe (OECD) 3,594,320 350 2018 5766

United States 9,363,386 228 1832 8035

resents an excellent achievement.However, as indicated by the title, thisis a model rather than a code for regulardesign work. The situation today issuch that each country has its ownstandards.

It is only logical that differences innational character, economy, and stan-dards have led to differences in con-struction practices as well. The largenumber of bridges needed and builtduring a relatively short period follow-ing World War II spurred the develop-ment of the wide variety of constructionmethods known today.

Statistical figures from the FederalRepublic of Germany are indicative ofEuropean construction trends. Between1965 and 1975, the total number ofbridges in Germany increased by 7710,of which 4174 were prestressed con-crete, 3262 were reinforced concrete,77 were steel, and 197 were compositestructures of steel and concrete. Per-haps even more revealing is a compari-son of percentages of the areas ofbridge decks built during this period:

• Prestressed concrete 75.0 percent• Reinforced concrete 14.2 percent• Structural steel ...... 6.7 percent• Composite

steel-concrete ....... 4.1 percent

The above figures, which show theimportance of prestressed concrete inbridge construction, are applicable notonly to West Germany but also to otherEuropean countries.

Although similar statistics from theUnited States were not available, acomparison of the consumed tonnage ofprestressing steel in bridges during thedecade from 1965 to 1975 appears sig-nificant. This comparison is presentedin Table 2. Note that the production ofprestressed concrete bridges in Europewas more than four times the produc-tion in the United States. This is per-haps one of the major reasons whyEurope has been so innovative in thisfield.

WHY SEGMENTALCONSTRUCTION?

Looking at the costs of concretestructures, the following average per-centages stand out:

• Labor ................38 percent• Material ..............46 percent• Equipment ........... 9 percent• Transportation ........ 7 percentLabor and material costs amount to

more than 80 percent of the total cost ofa project. The ratio of labor to material,

Table 2. Comparison of prestressed concrete bridge construction in Europe and theUnited States, based on consumption of prestressing steel.

Total prestressingsteel consumption

Prestressing steelper capita Percent

United States approx. 75,000 t 0.35 kg 100

Europe approx. 500,000 t 1.46 kg 417

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Fig. 2. Beckenried Viaduct, Switzerland.

approximately 45:55, has remainedfairly constant for decades. Between1950 and 1970, however, salaries in-creased approximately 500 percent andsocial welfare costs increased to aneven greater degree; yet material costsfor concrete or reinforcing steel in-creased only about 200 percent.*

A drastic reduction in man-hours overthe years explains why the labor tomaterials cost ratio has remained con-stant. Reasons for the reduction includeincreased mechanization of construc-tion sites, rationalization of single oper-ations, and, last but not least, the de-velopment of efficient segmental con-struction techniques.

A highly repetitive, standardizedconstruction cycle with a minimum ofalterations throughout a particular jobbrings the number of man-hours to a

*Internal documentation, Losinger Ltd., Berne,Switzerland.

minimum, due to the advantages of thelearning curve. It is obvious, therefore,that the segmental construction methodis competitive only if a bridge has acertain minimum length and astraightforward layout. Unusual topog-raphy or other conditions may also leadto the requirement of a segmentalmethod.

One might question the need for sev-eral types of segmental constructionmethods and the reasons why one seg-mental method is not sufficient to coverall needs. It might also be argued thatthese methods have been developed in"old" Europe, therefore reflecting thein-grained customs of different regionsor countries. However, examples showthat, if correctly applied, all the differ-ent construction methods have theirjustification. Furthermore, it should benoted that the development of the vari-ous methods was made possible by theparallel development of the post-ten-sioning technique.


j Fig. 3. Beckenried Viaduct, Switzerland.

SPAN-BY-SPAN METHODThe span-by-span method, which

uses a movable scaffold system, datesback to 1960. In the past 22 years, thisconstruction technique has been usedextensively in Europe, mainly in WestGermany, Austria, and Switzerland. Avariety of launching trusses have beendeveloped, but basically two types canbe distinguished, namely, the under-lying type and the overlying type.

Figs. 2 and 3 show an underlyingtype of truss, which was used for themore than 10,000 ft (3048 m) long Beck-enried Viaduct in Switzerland.' Theviaduct has two parallel superstruc-

*This and subsequentcost indications are takeneither from available literature or the best es-timates of the author.

tures, each 35.4 ft (10.8 m) wide andhaving typical spans of 180 ft (55 m). Ittook two weeks to assemble one span.The total cost per launching truss (totalweight about 750 tons each), includinginitial erection and dismantling, wasabout $1.7 million or $4.55 per sq ft ofbridge deck ($50 per m2).*

Note that the movable scaffold sys-tems were reused for a prestressed seg-mental bridge crossing the Tigris Riverin Iraq.

Fig. 4 shows an overlying type oftruss which was used for the Ahrtal-bridge in West Germany. It was de-signed for a maximum span of 348 ft(106 m). The truss, without formwork,weighed about 2100 tons. The bridge,completed in 1976, has a total length of5000 ft (1500 m) and consists of twoparallel structures with a width of 49.5

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Fig. 4. Ahrtalbridge, Federal Republic of Germany.

ft (15.1 m) each. To the author's knowl-edge, the truss was never reused. Thismeans that the cost, at least $4.5 millionor $9.30 per sq ft ($100 per m 2), had tobe depreciated on this job.

A compromise was found for the con-struction of the more than 6700 ft (2000m) long Gruyere Viaduct in Switzer-land, which was built from 1975 to1979. The typical span is 198 ft (60.5 m)and the superstructure consists of asingle box with a deck slab 78 ft (23.7m) wide (see Figs. 5, 6, and 7).

For this project, the segmental prin-ciple was amplified in that the super-structure was subdivided not only lon-gitudinally, but also transversally. Acomparatively light movable scaffoldsystem with a total weight of about 660tons was used to cast the box onlywithin a 3-week cycle. Note that of thesystem's total tonnage, about 505 tonswere structural steel and the rest werefor formwork, working platforms, roofcover, equipment, and counterweight.The cantilever slabs and their support-ing ribs were constructed by a separatemovable carriage following about 650 ft(200 m) behind. Stages of 32.8 ft (10 m)were completed every third day, so that

the same rate, of progress was achievedfor both the box and the side slabs (Fig.8).

A special feature of the chosen con-cept is the bottom slab of the concretebox girder, made from precast panels.This allowed the elimination of thecostly, heavy, tiltable bottom slabformwork, resulting in a relatively lightlaunching truss.

The total costs of the movable scaf-fold system and the cantilever carriage,both tailor-made for this project,amounted to $1.4 million, or $2.80 persq ft ($30 per m 2). With the exception ofsome mechanical and hydraulic equip-ment, the truss was never used againand was subsequently scrapped.

It is the author's belief that thespan-by-span method is very feasiblefor a span range of 100 to 200 ft (30 to60 m) and a minimum bridge length of3300 and 6600 ft (1000 and 2000 m), re-spectively. Experience has shown that acontractor should try to depreciate suchequipment on his first job, unless hehas guarantees for future applications.

Compared with other segmentalmethods, the following characteristicscan also be noted:


CONSTRUCTION JOINTS

PREFABRICATEDBOTTOMSLAB SLAB *DIMENSIONS AT PIER

a oo .

Fig. 5. Gruyere Viaduct, Switzerland. Longitudinal section (top) and cross section at midspan (bottom).

O

DEAD-END ANCHORAGES TYPE H 5-31 4VSL TENDONS EH 5-31 PER WEB

r J I I H7NDIRECTION OF ^ J 'STRESSING ANCHORAGES TYPE E5-31 ^t]ADVANCE OFCONSTRUCTION F,n dR

Fig. 6. Gruyere Viaduct, Switzerland. Typical layout of post-tensioning tendons.

Fig. 7. Gruyere Viaduct, Switzerland. Launching truss in operation.

launching stage concreting stageFig. 8. Gruyere Viaduct, Switzerland. Formwork carriage.


• The materials (concrete, rein-forcing and prestressing steel) neededcan be minimized because the super-structure is constructed in its final po-sition and very close to the final staticalsystem. This is particularly true whenthe very successful concept of partiallyprestressed concrete is applied, whichunfortunately is still not yet permittedin all European countries.

• Variations in superstructure geom-etry (varying horizontal and verticalcurvatures, etc.) are more easily ac-commodated than with other segmentalmethods.

To combine a launching truss withprecast segments is not yet very com-mon in Europe. The use of unbondedtendons and dry match-cast joints mightchange this. An obvious advantage ofthis procedure would be rapid con-struction.

FREE CANTILEVER METHOD

In this section both the cast-in-placeand precast methods of free cantileverconstruction are considered.

Fig. 9. Orwell Bridge, United Kingdom.'

Cast-in-Place MethodFor spans between 330 and 850 ft

(100 and 260 m) and under difficult to-pographical conditions such as deepvalley or river crossings, the free can-

Fig. 10. Orwell Bridge, United Kingdom.

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tilever cast-in-place method is often theonly feasible solution. Numerous suc-cessful applications can be found in al-most all European countries. With theincreased knowledge of creep behaviorand the elimination of hinges at mid-span, this type of bridge construction isgenerally accepted.

The river spans of the Orwell Bridgein the United Kingdom were builtusing the classical technique (Fig. 9),while the approach spans were con-structed using the span-by-spanmethod. The river crossing has a lengthof 1318 ft (402 m) with spans of 348-632 - 348 ft (106 - 190 - 106 m). Thisportion of the bridge was constructed insegments of maximum length 17 ft (5 m)in a one-week cycle.

The four travellers were of a standarddesign and had already been usedfor the Reichsbridge in Vienna. A pairof travellers of this type costs approxi-mately $275,000. For the OrwellBridge, this amounted to $2.65 per sq ft E

($28.5 per m2). Prospects for reuse ofthe travellers are generally quite good,at least for the upper parts, and espe-cially if a standard design has been ap-plied (Fig. 10).

An interesting variation of this tech-nique was used for the spectacular Ko-chertalbridge in West Germany, whichwas built between 1977 and 1979. Thestructure has received worldwide at-tention largely because it bridges afairly wide valley at a height of at least600 ft (185 m). Another reason is cer-tainly the applied construction tech-nique. The design of the structure wasthe result of an alternative proposalpresented by a joint venture of twoGerman contractors. The total length is3700 ft (1129 m) with maximum spansof 453 ft (138 m) and a deck width of100 ft (30.5 m) (see Figs. 11 and 12).

The superstructure was built in twostages. Only the box was built in thefirst stage; in the second phase theoblique struts and the cantileveringdeck slabs were installed with a mov-

c^wms

U

it


LJ FORMWORK- UNIT

Fig. 12. Kochertal Bridge, Federal Republic of Germany.

able formwork carriage. Cantilever con-struction at a height of more than 600 ft(180 m) naturally imposes special re-quirements in regard to the equipmentused and the transportation of material.

The optimum solution was found byintroducing an auxiliary overlying steelgirder (Figs. 13 and 14) which served adouble purpose. First, it allowed mate-rial to be transported from the abut-ments to the travellers. Additionally,once an entire cantilever was com-pleted, the underlying travellers (Fig.15) were suspended on the auxiliarygirder and moved to the next pier. Thecontractor obviously found it feasible toinvest more money in equipment inorder to speed up construction and re-duce transportation costs.2

Many other bridges built by thecast-in-place free cantilever method de-serve to be mentioned. The GanterBridge at Simplon Pass in Switzerlandis certainly one of them. The 2225-ft(678 m) long bridge is double-curved inplan, crosses a deep valley with piersup to 400 ft (124.5 m) high, and has amaximum span of 570 ft (174 m)3 (seeFigs. 16 and 17).

A final example is the GatewayBridge, currently under construction in

Brisbane, Australia. Although thebridge is built far from Europe, the de-sign of the river spans is European. Themain span of 852.2 ft (260 m) will seta new world record and will be con-structed by the free cantilever cast-in-place method (Fig. 18). The largesttravellers designed to carry a load ofmore than 400 tons will be used. Thesuperstructure has a 73.5 ft (22.42 m)wide deck slab and consists of a singlecell box with a height of 49.2 ft (15 m)at the piers and 17 ft (5.2 m) at midspan.A cable-stayed bridge was not possiblebecause the bridge shape was dictatedby an upper limitation due to air trafficfrom the nearby Brisbane airport aswell as the shipping clearance?

Precast MethodThe major impetus for precast seg-

mental construction in the westernworld came from France. Table 3,based on 1980 figures, summarizes thebridges described in the technical liter-ature. The authors of this very compre-hensive study made the followingcomment:

"The table shows a great variety ofexecution possibilities both with regard

114

I r

IffEJU

Fig. 13. Kochertal Bridge, Federal Republic of Germany. Construction sequence.


Fig. 14. Kochertal Bridge, Federal Republic of Germany.

Fig. 15. Kochertal Bridge, Federal Republic of Germany.Launching girder and travellers.

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Fig. 17. Ganter Bridge, Switzerland.

Fig. 16. Ganter Bridge, Switzerland.Piers are up to 400 ft (124.5 m) high.

to the erection technique and the typeof joint. With 98 bridges the match-castjoint with epoxy resin joining materialplays a dominant role. The leading po-sition of France is obvious. It was how-ever noted that in the last five years inFrance especially for main spans ofmore than 300 ft (100 m) the cast-in-place free cantilever method has re-es-tablished its dominance. This devel-opment was probably influenced by therelatively short total length of thebridges in question and by the fact thatthe cast-in-place construction has be-come faster. The scarce application ofthe precast segmental technique inGermany can be explained by the to-pographical situation which seldom re-quires very long bridges. On the otherhand, there was so far no DIN-standardallowing this form of construction andthis was probably an even stronger rea-son."

In West Germany, a comprehensive


Table 3: Prestressed concrete bridges with precast segmental superstructures [beyond130 ft (40 m) main span and without reinforcement through the joints].

Method of Erection Type of Joint

Thin Joint Thick Joint

Free Others Oncanti- without scaf- Dry Epoxy Cement Cement Micro

levering scaffolding folding joint resin mortar mortar concrete Total

France 41 9 1 — 44 — 7 — 51

FRG 1 — 3 — 2 — 2 —4

Rest ofEurope 35 3 5 2 31 — 7 3 43Incl. USSR

Countriesoutside 23 — 6 — 21 1 7 29Europe

Total 100 12 15 2 98 1 16 10 127

Fig. 18. Gateway Bridge, Australia, river span 852.2 ft (260 m).

draft of DIN-standard 4227 Part 3E, re-garding the precast segmental method,exists and its final version is expectedin due course. Highlights of the reportinclude the following:

• Microconcrete is mentioned in ad-dition to epoxy resins as a jointing ma-

terial. The maximum thickness is lim-ited to 1/6 in. (4 mm).

• At serviceability limit state in ten-sion zones a minimum compressionstress of 145 psi (1 MPa) must bemaintained, even under additionaltemperature gradient loading.

118

Fig. 19. Chillon Viaduct, Switzerland.

• If a joint is located above a supportor less than half of the beam heightaway, the minimum compression stressmust be increased 217.5 psi (1.5 MPa).

• It must be demonstrated by cal-culation that under a certain load com-bination the developing crack width isnot more than %70 in. (0.15 mm).

• Within the joints, ducts of post-tensioning tendons should be coupled.If this is impossible, other measuresshould be taken to guarantee the seal ofthe duct.

• The insulation of the bridge deckmust be improved locally, above thejoints.

Obviously, these requirements (whenfinally adopted) will be far morestringent than current practice in othercountries, such as France.

Switzerland was among the firstcountries to apply the precast segmen-tal method for construction. The Chil-lon Viaduct, built between 1966 and1969, has a total length of 6900 ft (2100

m) and consists of two parallel super-structures each 42.6 ft (13 m) wide (seeFig. 19). The precast elements weremade in five formwork batteries (usingthe short-line method) and the erectionwas done using an overhead launchingtruss with a total weight of about 230tons and a maximum lifting capacity ofapproximately 80 tons (Fig. 20). Thetotal cost (1982 prices) for the fiveformwork units and the launchinggirder is estimated at $1.7 million, or$5.77 per sq ft ($62 per m2).

This project began during the earlydays of the epoxy jointing technique,and material problems occurred after acertain period. The designer was com-pelled to develop a microconcrete,which was successfully used for theremaining spans.

Although the Chillon Viaduct is es-thetically one of the most pleasingstructures in Switzerland and themethod was later recommended for useon a number of other bridges, it was


Fig. 20. Chillon Viaduct, Switzerland.

Fig. 21. Beckenried Viaduct, Switzerland.

never again successful. The BeckenreidViaduct, which actually should havebeen ideal for precast segmental con-struction, is an example (Fig. 21). Infact, one of the bidders suggested aprecast segmental solution but was un-derbid by the span-by-span proposal.

In recent years, the grouting ofpost-tensioning tendons has become amajor issue in Europe, as its decisiveimportance for the durability of abridge has been rediscovered. It is wellknown that precast segmental con-struction requires special attention withregard to the grouting technique. Someprojects have experienced inter-con-nections in the joints and groups ofducts have had to be simultaneouslygrouted.6

It is obvious that these problemscould be avoided if the ducts were cou-pled in the joints. Proposals and a fewapplications are known, but to the au-

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thor's knowledge they have all beengiven up as unfeasible. It will be inter-esting to see how this problem will besolved in West Germany when re-quirements for a tight duct connectionare adopted.

The Byker Viaduct in Newcastle,Great Britain, is a more recent exampleof the precast segmental method. It is asingle box girder bridge, 2625 ft (800 m)long, with horizontal and verticalcurves and carrying two tracks of aMetro line. The three longest spans of226 ft (69 m) and the two adjacent spanswere built as balanced cantilevers fromthe four main piers. The other ap-proaching spans of 173, 169, and 119 ft(52.8, 51.6, and 36.3 m) were con-structed as continuous cantilevers withtemporary supports.

The 253 segments, each approxi-mately 10 ft (3 m) long, were precast onsite and erected using a simple hoist.The joints consist of epoxy resin com-bined with layers of fiberglass to cor-rect the alignment at the constructionstage.

The microconcrete mentioned earlier(trade name "Tixojoint") was later usedagain as a jointing material for otherprecast segmental bridges, includingthe General Belgrano Bridge and Via-ducts Motorway Udine-Carnia-Tarvisioin Italy. It is a pure mineral materialmade of special aluminous cement,quartz sand, water, and additives. It hasthe same physical properties, mechan-ical behavior, and internal stability asthe surrounding concrete and meets therequirements for a jointing material.The joint thickness resulting from theuse of microconcrete is '/12.5 in. (1 to 2mm).

In summary, the precast segmentaltechnique has been successfully ap-plied for many years in some countries,whereas a considerable reluctance canbe noticed in others. It is the author'sbelief that if a bridge has a certain min-imum length, if a high constructionspeed is required, and if in design and

construction the particularities of thetechnique are respected, the precastsegmental method certainly is advan-tageous.

INCREMENTAL LAUNCHINGMETHOD

The incremental launching methoddates back to 1962 when the CaroniBridge was built in Venezuela. Themethod as it is applied today was firstused in 1965 for the Kufstein Inn Bridgein Austria. Since that time, more than200 bridges have been constructedusing this technique. Interestinglyenough, only one bridge of this kindhas been built in the United States.Straight or uniformly curved bridges(vertical and horizontal) with regularspans from 100 to 300 ft (30 to 60 m)and a minimum length of 500 to 650 ft(150 to 200 m) are very well suited tobe pushed out from a stationary pro-duction plant.

The advantages include savings inman-hours and a relatively modest in-vestment in equipment. On the otherhand, material needs (concrete, rein-forcing and prestressing steel) aregreater than if the superstructure werebuilt by the span-by-span method.

A recent example is the SteinaggertalBridge in West Germany, which wascompleted in 1981. It consists of twoparallel superstructures, each 1540 ft(469.5 m) long and 49 ft (15 m) widewith typical spans of 156 ft (47.5 m).The cost for special equipment (e.g.,the launching nose, stationary form-work, etc.) required for such a bridge isapproximately $240,000, or $1.58 per sqft ($17 per m2), a relatively modest sumcompared with other techniques.

For the Steinaggertal Bridge, the lon-gitudinal slope was 5 percent and thefabrication area could only be accom-modated at the upper end (Fig. 22). Aspecial pushing and holdback devicehad to . be developed and it worked as


Fig. 22. Steinaggertal Bridge, Federal Republic of Germany.

intended. The construction speed iscomparable to the span-by-spanmethod. Segments of 50 to 80 ft (15 to25 m) in length can be constructed in aone-week cycle.

The Danube Bridge at Worth demon-strates that spans up to 660 ft (168 m)are possible if temporary • supports areused. The 1325 ft (404 m) long bridgeconsists of two parallel superstructureswhich were both pushed longitudinallyout of the stationary formwork. Thisnecessitated a subsequent transversalpush on one of them, Each superstruc-ture weighed about 16,200 tons.

Experience in Europe has shownthat, under proper circumstances, theincremental launching method is themost economical method for bridgeconstruction.

ARCH BRIDGESThe recent development of arch

bridges is a good example of segmentalconstruction techniques. Arch bridgeshave been built on scaffolding for manyyears. Many of these scaffolding sys-tems were masterpieces, as, for exam--ple, the famous Salginatobel Bridge in

Switzerland, designed by R. Maillart(Fig. 23).

An interesting variation was used forthe Lorraine Bridge in Switzerland(1929; also designed by Maillart) whereprecast concrete blocks were used forthe first time to form the bearing arch.Erection of the blocks began at thecenterline of the bridge and moved to-ward the outer sides of the arch. As aresult, the scaffolding could be muchlighter because the arch itself took mostof the load once a complete row ofblocks was in place.

After World War II, as labor costs be-came a major factor, arch bridges be-came less common. Only in recentyears has a certain revival been noticed,due perhaps to the segmental construc-tion technique, Two examples are pro-vided to demonstrate this,

The Krk I Bridge in Yugoslavia, builtbetween 1976 and 1979, presentlyholds the world record for concretearches, with a 1280-ft (390 m) span. Thethree-cell arch was made primarily ofprecast elements 16.4 ft (5 m) long andjointed together with cast-in-place con-crete joints. The cantileveringtechnique using temporary stays wasapplied to erect the arch (Fig. 24).

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Fig. 23. Salginatobelbridge, Switzerland. Scaffolding.

Fig. 24. Krk Bridge, Yugoslavia.

PCI JOURNAUMay-June 1983 123

Fig. 25. Neckarburgbridge, Federal Republic of Germany. Launching of superstructure.

Another example was the construc-tion of the Neckarburgbridge in Ger-many. This structure was completed in1978. Here, the 506-ft (154.4 m) archspan was made by the cantilever cast-in-place method using temporary stays.The superstructure was built using theincremental launching method thussuccessfully combining two segmentaltechniques in one bridge (Fig. 25).

EUROPEAN BIDDINGPRACTICES

There is no uniform bidding systemin Europe. However, those countrieswhich have been most innovative inbridge design and construction tend tohave more liberal bidding systems.Procedures vary considerably evenwithin countries, but they have onecommon denominator, namely, consul-tants and contractors can present alter-native designs.

For the Beckenried Viaduct, the

owner basically outlined the scope ofwork to be done in the bidding phase,giving the data needed (i.e., geologicalreport, road geometry, constructiontime, etc.) for preparing a comprehen-sive proposal. During a prequalificationphase, the owner selected six differentjoint venture groups of contractors andindependent consultants.The biddershad eight months to prepare their owndesigns and price them accordingly.

Bidders were free to choose thespans, structural system, materials, andconstruction technique. The location ofthe abutment was fixed at one end, butflexibility was provided in regard tohow and where to end the bridge.

The owner expected from each of thesix groups a technically sound and es-thetically pleasing project at minimumcost with minimum risk during con-struction in addition to a subsequentlylow maintenance cost. Each joint ven-ture had to price its proposal on thebasis of a bill of quantity established

124

according to the specific solution. Tocover at least a part of the bidder'scosts, the owner paid $90,000 to eachjoint venture group. In addition, a totalof $200,000 was distributed among thegroups, ranging from $135,000 given tothe winning team to $115,000 to thesixth-ranked team.

The proposals were then evaluatedby a jury consisting of experts from ad-ministration, universities, and consult-ing firms, and the results were pub-lished. As in most cases, the low bidderwas selected for the job. However,there were other bids where the bestsolution was adopted but priced higherfor technical and esthetic reasons.

Such a flexible bidding system has agreat benefit in that it brings forwardnew ideas to ultimately advance thebridge industry. However, it is only jus-tified for bridge projects of a fairly largesize.

CONCLUDING REMARKSIn general, segmental construction is

very popular in Europe. Its develop-ment has certainly helped to keepbridge costs on a reasonable level de-spite overall inflation. Due to thevarying parameters in bridge design(span, length, geometry, constructiontime, and other factors), each specificmethod can be justified, as long as it isapplied judiciously.

REFERENCES1. Banziger, D. J., "The Beckenried Via-

duct," published by D. J. Banziger,Zurich, 1981.

2. Baumann, H., "The Kocher-Valley BridgeGeislingen, Design and Execution," Pre-sentation Day of Concrete 1979, GermanConcrete Association (B.V.), 1979.

3. Menn, C., Rigendinger, H., and Maag,W., "The Bridge Over the Ganter Valleyfor the New Simplon Road in Switzer-land," published by L'Industria Italianadel Cemento, 1982.

4. Matt, P., Roelli, P., Vaucher, A., andVoumard, J. M., "The Gateway-Bridge inBrisbane, Australia," published by SIA(Swiss Engineers and Architects), 1983.

5. Guckenberger, K., Daschner, F., andKupfer, H., "Prestressed Concrete Seg-mental Girders in Bridge Construction,"German Committee of Reinforced Con-crete, Brochure 311, published byWilhelm Ernst & Sohn, 1980.

6. Delmas, C., Brabant, P., and Chretien, C.,"The Grouting of Prestressing Tendons ofthe Saint-Cloud Viaduct," Travaux (Con-struction-Magazine), December 1975, pp.40-47.

7. Duvoy, C. E., and Colobraro, R. V., "TheChaco-Corrientes Bridge Across the RioParana River in Argentine," Travaux,August-September 1975, pp. 47-54.

8. Fritschi, R., "Incremental LaunchingMethod With Transversal Launching,Construction of the Donau BridgeWorth," Presentation Day of Concrete1979, German Concrete Association(B.V.).

PCt JOURNAUMay-June 1983 125

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