Historical Perspective on Prestressed Concrete

David P. Billington, P.E.Gordon Y. S. Wu Professor ofEngineeringDepartment of Civil andEnvironmental EngineeringPrinceton University Princeton, New Jersey

The author, who speaks French and Flemish and spent some of thepost-World War II years in Europe studying engineering, presents anessay on the origins and development of prestressed concrete. Threeengineers are singled out for having had the most profound influenceon the development of prestressed concrete – Eugene Freyssinet,Gustave Magnel, and Ulrich Finsterwalder. Unquestionably, it wasthe painstaking pioneering work of Freyssinet that convinced theengineering world of the viability of prestressed concrete as acompetitive construction material. Throughout Freyssinet’s life, thereis one theme that keeps recurring time and again, namely, “asimplification of forms and an economy of means.” Magnel is notedas a great teacher and for communicating his ideas on prestressing tothe English-speaking world. Finsterwalder pioneered the developmentof the double cantilever method of bridge construction. Severaloutstanding reinforced and prestressed concrete structures in theAmericas and Europe are discussed and illustrated. In retrospect, theauthor regards the principle of prestressing as the single mostimportant new concept in structural engineering during the last halfof the twentieth century.

The idea of prestressing, a prod-uct of the twentieth century, an-nounced the single most signifi-

cant new direction in structuralengineering of any period in history.

It put into the hands of the designeran ability to control structural behav-ior at the same time as it enabled himor her – or forced him or her – to thinkmore deeply about construction.

Moreover, the idea of prestressingopened up new possibilities for form

14 PCI JOURNAL

Historical Perspective onPrestressed Concrete

HISTORICAL-TECHNICAL SERIES

David P. Billington, lecturer-engineer-historian, has been a tenured professor ofcivil engineering at Princeton Universityfor almost his entire professional career.Professor Billington pioneered the conceptof “structural art” by showing that sim-plicity, aesthetics, and economy are pre-sent in all great structures. A prolific au-thor, he has published more than 170papers including ten books. Two of his fa-mous books are The Tower and theBridge: The New Art of Structural Engi-neering and Innovators: The EngineeringPioneers Who Made America Modern. Hismost recent book is The Art of StructuralDesign: A Swiss Legacy. In 1999, Engi-neering News-Record named ProfessorBillington among the top five civil engi-neering educators of the past 125 years. (Author photo courtesy: Princeton Univer-sity, Office of Communications.)

and aesthetics. Ultimately, it is thenew forms that influence the generalculture, and because these forms arevisual we can expect visual artists tobe the first to sense a new direction.

Characteristically, it was theFrenchman, Le Corbusier, the mostartistic of the great twentieth century

NOTE: This article is an updated version of a paperthat was published in the September-October 1976 PCI JOURNAL.

architects, who first announced thenew idea dramatically when, towardsthe end of his highly regarded book,The Radiant City, written in 1933, hereported:1

“I hadn’t seen Freyssinet for years.Then he reappeared and told me allabout the precise and very demandingresearch project in which he had beentotally absorbed in all that time: thediscovery of a new material entirelydifferent from any other already in ex-istence, five or six times more resis-tant than the concretes and steels nowin use.”

Le Corbusier then quotes his friendEugene Freyssinet, speaking of hisdiscovery of prestressed concrete:

“I reached my goal. So now I’mlooking around to see what I can usethis discovery of mine for. And in myopinion, modern society needs hous-ing, parks and highways.”

Le Corbusier responds to this pro-gram by expressing his awe of the en-gineer:

“What admirable powers of divina-tion in this man of science, of preciseand audacious calculations! At a sin-gle glance – in three words – hesummed up the whole program of themodern age. Into that one short sen-tence he has crammed a vast wealth ofpoetry, of lyricism, of solidarity, ofconcern for mankind and the hearts ofmen.”

The beginning of a new way ofbuilding does not usually bring forthsuch a florid outburst. Indeed,Freyssinet’s own descriptions of hisachievement are entirely different,even though it too contains a passionand a vision.2

“I decided to risk all that I had offortune, reputation and strength inmaking the idea of prestressing an in-dustrial reality. Foreseeing a long andhard struggle and a need for financialassistance, I took the precaution oftaking out patents.”

Freyssinet was at the time the co-manager of the large construction firmof Entreprises Limousin. His partner,M. Limousin, considering Freyssinet’sideas unsound, refused to go alongwith him. As Freyssient later de-scribed the controversy:

“Convinced that my attempts wouldsoon ruin me, he considered that hisfriendship made it a duty for him tooppose at all cost what he consideredto be folly. For me, on the contrary,this folly, even if it was to prove dis-astrous, was a mission that I had tofulfill whatever sacrifices might be re-quired.

“At the beginning, these sacrificeswere indeed considerable. I lost thebest of friends, a very good financialsituation, the joys given me by myprofession as an engineer and themany collaborators that I had trainedand loved and worse, who consideredme as a deserter.

“At the age of 50, I was abandoninga life that was already mapped out inorder to throw myself into one thatwas full of uncertainties and perils.”

To get some idea of the type of per-son who would give up security toseek a new way of building, I shallgive a brief sketch of Freyssinet’spre-1933 background, along withsome assessment of his contributionsand a discussion of how prestressingcame to America after World War II

January-February 2004 15

The risk associated with revising an engineeringessay that editors and readers alike still find usefulafter nearly 30 years is that retrospection cansometimes impair the original message. In thiscase, that message focused on three structural en-gineers and on a series of historically significantprojects in prestressed concrete.

Recently, I have returned to the same historical

period leading up to 1976 so that the revisions Iwould make in the present paper had better be leftto a new series of writings, some already pub-lished with others nearing completion. At the endof this almost untouched 1976 paper, I have addeda brief section referring to such new writings andto the valuable discussion made by Paul Abeles tomy 1976 paper.

PREFACE

and flowered in the 1950s.For this last discussion, I shall focus

on the first two major American pre-stressing conferences, one at the Mas-sachusetts Institute of Technology atCambridge in 1951 and the other atthe University of California at Berke-ley in 1957. Much as I would like toexplore in detail the wide develop-ments after 1957, I find these last 45years too broad for me to make coher-ent in a single paper. Instead, I shallend this discourse with several con-temporary examples whose purpose isto show something of the continuingnature of the European influence onAmerican construction.

It is this last idea, often upsetting tothe collective American ego, that con-tains a central cultural meaning of pre-stressing which springs from the factthat the structures of a locale charac-terize the local culture perhaps betterthan any other set of artifacts.

To focus on that fact and to narrowmy scope, I shall consider here onlybridges (with one exception), eventhough we are all aware that prestress-ing has broad application to all kindsof buildings and other structures. Still,the idea of prestressing arose out ofbridge design, and its most impressiveforms, from a purely engineeringviewpoint, appear in bridges.

“The principle of prestressingis the single most important new

concept in structural engineering during the last half

of the twentieth century.”

16 PCI JOURNAL

EUGENE FREYSSINET (1879–1962)

Eugene Freyssinet was born in 1879in the provinces on the Corrèzeplateau east of Bordeau (westernFrance) in a region that he later de-scribed:3

“For many centuries, my ancestorslived clinging to the flanks of the steepgorges through which rush the torrentsof the Corrèze plateau. A land offorests and impenetrable thickets witha harsh climate and a poor soil, it has,throughout the ages, been the refugeof the unsubdued and the rebel.”

Seeing himself somewhat in thatlight, Freyssinet went on to conclude

Eugene Freyssinet – Morethan any other person, it

was the relentlesspioneering efforts of this

courageous Frenchengineer-builder who

converted the concept ofprestressing into a

practical reality.

how his heritage influenced buildingand went a long way toward explain-ing his willingness to risk all in orderto work out his own unconventionalideas for prestressing.

“Such conditions of background andlife have formed a tough, violent and

unsociable race, very poor and proud,little inclined to beg assistance andwhich has wrenched, from its arid soil,all that it needed to live. Universal ar-tisans, these men have created forthemselves a civilization the maincharacteristic of which is an extremeconcern for the simplification of formsand economy of means.”

Although his family moved to Parisin the mid-1880s, he never liked thatcity, the “abominable Paris,” as hecalled it. It did not fit at all with the ar-tisan world whose great love was“simplification of forms and economyof means.”

As a student, he was only mediocreand on his first application was re-jected in 1898 by the prestigious EcolePolytechnique. However, he was ac-cepted the following year “with thenot very brilliant position of 161st.”4

Graduating 19th, he succeeded inbeing accepted at the Ecole des Pontset Chaussées where, for the first time,his artisan love of building coincidedwith that of his teachers, those “greatartisans with an enthusiasm for theirwork — Resal, Sejourne, Rabut.” Itwas there, in the lectures of CharlesRabut in 1903-04 that the idea of pre-stressing first came to him:5

“The idea of replacing the elasticforces that are created in the reinforce-ments of concrete by deflection due toloads, by previously imposed and per-manent stresses of sufficient value,came to my mind for the first timeduring a series of lectures given byCharles Rabut at the Ecole des Pontset Chaussées in 1903-04. These lec-

Fig. 1. Le Veurdre Bridge across the Allier River, France (1910-1911). Spans were 222 – 238 – 223 ft (67.5 – 72 – 67.5 m). This bridge incorporated the first use of thrust by jacks at midspan for decentering and also compensating for concrete creep and shrinkage. (Designed and built by Eugene Freyssinet.)

“Freyssinet’s artisan background and love of

buildings influenced him to seekan engineering solution to his

structures through a‘simplification of forms and

economy of means.’”


tures were devoted, on the one hand,to reinforced concrete and, on theother hand, to the systematic study ofspontaneous or provoked deflection instructures.”

This idea never left him and servedas a guide as his early career focusedon the building of bridges in thewilderness of south-central France,where new ideas could flourish solong as they were based on that artisanspirit of simplification of forms andeconomy of means. This was the sameregion in which Gustav Eiffel, 40years before, had worked out newforms and economy in metal bridges.6

Of course, he was also famous for de-signing the Eiffel Tower in Paris.

Two examples of Freyssinet’s earlywork demonstrate both this spirit ofform and the guide of prestressing,namely, the Bernard Arch of 1908 andthe bridge over the Allier River at LeVeurdre (see Fig. 1), designed in 1907and completed in 1912.7

“Towards 1906-07, the idea of ap-plying precompressions was firmenough in my mind to lead me to drawup a project for a 2500-ton capacity tielinking the two abutments of a 50-mspan trial arch.

“This tie and its arch were com-pleted during the summer of 1908 buta study of their deflection and otherobservations taught me the existenceof creep in concrete, a phenomenon

that was then unknown and even ener-getically denied by official science. Inthe case of induced permanent stresses,this was a fearsome unknown. Imme-diately and as carefully and completelyas possible, I began to study this prob-lem but my efforts were rendered vainby my mobilization in August 1914.”

At Le Veurdre, the situation wasmore dramatic and the impact onFreyssinet’s vision was more lasting.He had volunteered to build threebridges over the Allier River for a priceexactly one-third of that which hadbeen bid. As a local engineer of thehighway department, he had suggestedthat the bids be rejected and that he beallowed to act as the builder for thesebridges following his own designs.

As Freyssinet later described the sit-uation:8

“Fifteen days later, an official letterput me in charge of supervising, onbehalf of the Public Authorities, theexecution of these bridges whose de-signer I was, for which I was to be thecontractor and the plans of which hadnever been submitted for anyone’s ap-proval. Mercier [Freyssinet’s superior]then left for Portugal granting me un-limited credit out of his funds butwithout giving me a single man, toolor piece of advice. Never was abuilder given such freedom. I was ab-solute master, receiving orders and ad-vice from no-one.”

This rather terrifying responsibilityhad an even more frightening conclu-sion when several months after thecompletion of the three-span bridge atLe Veurdre, the 238 ft (72 m) spanarches began to deflect downward atan accelerating rate.9

“To halt this, all that was requiredwas to remove these joints [at the archcrown] after having, by using my de-centering jacks in a new application,sufficiently raised the crowns of thearches to do away with the major partof the increases of stress resultingfrom the deformation of the neutralaxis of the arches. There could be noquestion of informing the Head Engi-neer or the Preféts in order to halt traf-fic for they would have panicked andparalyzed me and any day that passedmight bring total collapse for, at thismoment, the strains were increasing ata frightening rate.”

These jacks, the so-called Freyssinet

Fig. 2. Plougastel Bridge across the Elhorn River, France (1930). Three spans of 614 ft (186 m). This bridge had the largest span inreinforced concrete at that time. (Designed and built by Eugene Freyssinet.)

“Had Freyssinet never pursued the idea of

prestressing, he would still havebeen regarded (along with

Robert Maillart) as one of thetwo greatest concrete structuralengineers in the first half of the

twentieth century.”

18 PCI JOURNAL

flat jacks, are still used today in majorstructures such as, for example, in thefoundations of the gigantic prestressedconcrete CN Tower in Toronto,Canada. In the Le Veurdre bridge,Freyssinet placed the jacks in thecrown hinge of the arch and as hewent on to describe the operation:10

“Returning to Moulins in the night, Ijumped onto my bicycle and rode toVeurdre to wake up Biguet and threereliable men. The five of us then re-in-serted the decentering jacks – I had al-ways kept this possibility in reserve –and as soon as there was enough day-light to use the level and staffs; webegan to raise the three arches simul-taneously. It was market day andevery few minutes we had to interruptthe operation to allow a few vehiclesto pass. However, all ended well andonce more aligned, cured of the illness

that had almost killed it, the Veurdrebridge behaved perfectly until its de-struction in the war in 1940.”

Writing in 1949, about the compan-ion bridge at Boutiron, Freyssinetstated that:11

“I have just seen it again and evenafter [my larger and more recent archbridges] I consider it, since the disap-pearance of Le Veurdre, to be thefinest of my bridges.”

In the process of creating thesewilderness works, Freyssinet laid theessential basis for prestressing which,however, had to await almost 20 yearsbefore it became more than just a spe-cial method of arch construction.

During the 1920s, Freyssinet de-signed a series of concrete arch struc-tures that made him a world renowneddesigner, not only to engineers, but toarchitects and artists as well. Had henever pursued the idea of prestressing,he would still have been regarded,along with Robert Maillart, as one ofthe two greatest concrete structural en-gineers in the first half of the twenti-eth century.12

The bridge over the Seine River atSaint Pierre du Vauvray, completed in1922, set the world’s span record forconcrete arches at 432 ft (131 m) andfollowed Freyssinet’s method of jack-ing the arch apart at the crown to com-pensate for rib shortening and to liftthe structure off the scaffold.

Then, several years later, he won acompetition for a far larger project,the spanning of the Elhorn River atPlougastel, a project which occupiedhim until 1930. For this structure,Freyssinet designed three hollow-boxarch bridges, each arch 614 ft (186 m)in span (see Fig. 2). Here again, thearches were jacked apart at theircrowns by a controlled prestress.

It was in the course of studies forthis impressive bridge that he took upthe study of creep and shrinkage inconcrete:13

“. . . to know whether one could cre-ate permanent prestresses in concretein spite of its low strains. . .”

Here was a statement of the prob-lem somewhat more general than thespecific question of designing arches.Thus, in 1926, Freyssinet organized aset of experiments and began researchwhich was published posthumously as

“The Relations Between the Strainsand Constitution of Cements and Col-loidal Structured Materials” (1926-1929).14

Freyssinet’s motivation was primar-ily to understand structures made ofconcrete rather than the structure ofconcrete. Indeed, he ends this treatisewith the conclusion that “arches withspans in excess of 1000 meters” canbe built “at a far lower cost than a sus-pension bridge of the same span.”15

His major work did not, however, liein that direction.

By 1928, with the Plougastel Bridgewell under way, Freyssinet had recog-nized the more general significance ofprestressing, patenting his ideas inFrance, Britain, and the UnitedStates.16 For the next four years, hedevoted his full attention to the poten-tials of prestressing.

In November of 1932, Freyssinetsat down and wrote out his progress atthe request of the editor of a newjournal Science et Industrie. In one ofits early issues, dated January 1933,Freyssinet’s article “New Ideas andMethods” appeared.17

Beginning with his ideas on the“thermodynamic theory of binders,”he proceeded to analyze the behaviorof cement, concrete, and reinforcedconcrete, all from the perspective of ascientist. He described tests and theirresults and further explained howstresses over a cross section arise fromshrinkage, from axial compression andfrom bending. Finally, in the fourth ofhis six chapters, he outlined the “con-ditions for the practical use of pre-stressing.”18

1. Using metals with a very highelastic limit.

2. Submitting them to very stronginitial tensions, much greater than70,000 psi (500 MPa).

3. Associating them with concretesof a very low, constant and well-known rate of deformability, whichoffer the additional advantage of veryhigh and regular strengths of resis-tance.

In present-day terms, Freyssinet hadestablished the need for high strengthsteel, for tensioning it to a high initialstress, and for high strength concreteto reduce to a minimum the loss ofinitial prestress.

Fig. 3. First production of prestressedconcrete poles, Montargis, France (1933).(Poles were designed and fabricated byEugene Freyssinet.)


Although many engineers had pro-posed the idea of prestressing even asfar back as 1886, no one had based theidea on a clear understanding of theproperties of the concrete. Thus, allprevious ideas had failed to producewhat is now called prestressed con-crete.19

Freyssinet saw, in general, the widepotential for his idea, which used whathe called “treated” concrete, but inparticular, he had great difficulty inestablishing any commercial value forit. Partly of course, in 1933 Francewas in the midst of the worldwideeconomic depression, but partly too itwas a genuinely radical idea. Seen as ameans for improving arch design, hissystem of crown jacking was acceptedboth in Europe and the United Statesand used as early as 1930 in Oregon;20

but seen as a new material, prestress-ing found little application in its earlyyears.

Freyssinet himself developed a fac-tory at Montargis (south of Paris),France, where he manufactured pre-stressed concrete poles (see Fig. 3) forelectric lines, but he could not makethe business succeed. The factoryclosed not long after his 1933 articleappeared and as Freyssinet later put it“our factory was without customersand was only good for scrap; my wifeand I were ruined.”21

But not for long, because in 1935 hehad the opportunity to prove the mer-

its of prestressing by saving the Mar-time Terminal at Le Havre, parts ofwhich had been settling into the har-bor at the alarming rate of about 1 in.(25.4 mm) per month.

Freyssinet proposed to consolidatethe foundations by prestressing andhis success so convinced the Frenchauthorities that they then supportednumerous large-scale projects between1935 and 1939 where prestressingproved its practical merit. Freyssinet’sretrospective attitude on the MarineTerminal restorations is intriguing:22

“Would I have had the courage totake responsibility had this not consti-tuted for me too, the only chance ofrescuing from oblivion the techniquesthat had cost me my fortune and fiveyears of the hardest work. . . it wasperhaps a chance of saving my confi-dence in myself and in the worth ofmy effort.”

Here, Freyssinet intimates the rolethat chance plays in providing oppor-tunities even though eventual successsurely depended upon those long yearsbetween 1903 and 1933 of direct fieldexperience in structures. ButFreyssinet’s ability to transform hisideas into new structures lay less inchance or even in long experience. Ashe himself said of those experiencedengineers before him who had had thenotion of prestressing:23

“When by chance, they approachedthis domain, the absence of a directing

idea prevented the drawing of conclu-sions that were of any practical conse-quence.”

This directing idea, for Freyssinet,was, in general, that simplification offorms and economy of means so char-acteristic of his artisan heritage; or ashe said once to a group of young engi-neers:24

“I loved this art of building which Iconceived in the same way as my arti-san ancestors, as a means of reducingto the extreme, the human toil neces-sary to attain a useful goal. . . from thebridges of Septfonds and Le Veurdreto those of the Marne and Caracas”(two of his best-known post-WorldWar II bridge projects). Fig. 4 showsthe Luzancy Bridge, one of severalprestressed concrete bridges Freyssinetbuilt across the Marne River.

More specifically, this passion hefelt for prestressing went on to defineprestressed concrete as an entirely newmaterial with the widest possible ap-plication. For Freyssinet, “the fields ofprestressed concrete and reinforcedconcrete have no common frontier.”Either a structure is fully prestressedor it is not to be called prestressedconcrete.

We do not need to accept that rigiddefinition today to recognize how es-sential it apparently was to Freyssinetto have this idea of prestressing as anew material in order to direct his en-ergies into practical applications. It

Fig. 4. Luzancy Bridge across the Marne River, France (1946). This elegant bridge (designed and built by Freyssinet) was the firstmajor bridge in the world built of precast, prestressed segmental construction.

20 PCI JOURNAL

was to be crack free, a structure inwhich the elongation of the highstrength steel was to be independent ofthe strain in the concrete.

One has only to read his writings torealize that Freyssinet was more anadvocate than a teacher, more an origi-nator of ideas than one who explainsthem to others. In his writings, he caneven now communicate clearly to ushis passion but not so well his techni-cal concepts.

It took another sort of person tomake clear the simplicity of prestress-ing and especially to bring it to theUnited States. Without question, themost influential engineer to do thiswas Gustave Magnel.

GUSTAVE MAGNEL (1889–1955)

After having graduated from theUniversity of Ghent in Belgium, Gus-tave Magnel spent the years of WorldWar I in England where he helpedtrain British engineers the art andpractice in reinforced concrete. Asidefrom establishing his teaching talent,this experience gave him a full com-mand of the English language.25

In 1922, Magnel was appointed alecturer at Ghent to teach reinforced

Gustave Magnel – This multi-talentedBelgian professor combined his design,research, teaching, and writing skills tocommunicate his knowledge ofprestressed concrete to the English-speaking world.

concrete, in 1927 named docent, andin 1937 made professor and director ofthe Laboratory for Reinforced Con-crete.26 Although French was hismother tongue, he switched his teach-ing to Flemish (Dutch) when the Uni-versity at Ghent changed languages inthe late 1920s. He could thus teachfluently in at least three languages. In-deed, some of his students were so en-thralled by his lectures that theywould attend the same lecture whentaught in a different language!

In addition to teaching, Magnel wasa prolific writer, an experienced de-signer, and an able researcher by thetime World War II isolated him inBelgium. During those closeted years,he began to explore Freyssinet’s ideasand to carry out some research on pre-stressed concrete on his own.

Thus, when the war ended andbuilding in Europe began again at anaccelerating pace, Magnel was one ofthe few engineers with long experi-ence in reinforced concrete, who at thesame time had mastered the ideas of

prestressing, and what is even moreimportant, who was ideally suited tocommunicate those ideas to the En-glish-speaking world.

Magnel had already written at leastnine books, some of which had gonethrough three editions when, in 1948,he wrote Le Béton Précontraint ,which was immediately published inEnglish, went through three Britisheditions and was also later publishedin the United States.27

But the single most significant char-acteristic of Magnel was his ability toteach. As one of the few Americanswho followed a complete sequence ofhis courses at Ghent, I can state un-equivocally that he was the bestteacher I ever had. His goals in teach-ing, writing and research were to sim-plify complex problems. As he wrotein his book on prestressed concrete:29

“In the writer’s opinion this prob-lem (of computing the ultimatestrength of prestressed beams) shouldbe solved with the least possible cal-culations, as calculations are based onassumptions which may lead to wrongresults.”

His suspicions of complex calcula-tions were balanced by his confidencein tests and full-scale observations.

“It is therefore proposed to useknown experimental results to producea reasonable formula, avoiding thetemptations to confuse the problemwith pseudo-scientific frills.”

It was this drive for simple, practi-cal formulas and explanations which,

• Magnel’s books and writings(English editions) clearly explainthe idea of prestressing in termsof structural mechanics, whereasFreyssinet in his 1949 articlegives a more descriptive, but lesspractical, discussion.28

• Freyssinet’s writing is more stim-ulating to an experienced engi-neer, Magnel’s more useful toone unacquainted with prestress-ing. Whereas Freyssinet saw pre-stressed concrete as a completelynew material, essentially differ-

ent from reinforced concrete,Magnel emphasized rather thesimplicity of prestressed concretedesign as it related to the, by thenaccepted, ideas about reinforcedconcrete.

• Freyssinet exhorts the designer torethink concrete structures from atotally new perspective whileMagnel demonstrates how proce-dures already known by a prac-ticing engineer in 1948 can beused to design members of pre-stressed concrete.

FREYSSINET AND MAGNEL IN CONTRAST

“The single most significantcharacteristic of Magnel was

his ability to communicate withhis audience, as exemplified by

his teachings and prolific writings – and more importantly

to translate those ideas to theEnglish speaking world.”


combined with his long experience,lent credibility to Magnel’s enthusi-asm for prestressing. Thus, when theopportunity arose in 1948 to explorethe possibility of building a majorpublic structure of prestressed con-crete, it was not surprising that theAmerican engineers in Philadelphiainvolved would turn to the Belgianprofessor, Gustave Magnel, to designtheir bridge.

THE WALNUT LANE BRIDGEIn a speech given at the First United

States Conference on Prestressed Con-crete, Samual S. Baxter, later to be-come president of the American Soci-ety of Civil Engineers, stated that hadthe original arch design for the newWalnut Lane Bridge been bid belowthe engineers’ estimate:30

“It is also quite possible that thisFirst Conference on Prestressed Con-crete might not now be in session . . .”

His claim was probably correct,even though prestressing was alreadybeing tried out elsewhere by 1951 andsome conference would most probablyhave been arranged thereafter. Still,this Philadelphia bridge served tocharacterize the potential for pre-stressed concrete because of its large-scale, 160 ft (48.5 m) main spans, be-cause of its construction economy, andbecause of its acceptance, not only bycity engineers, but also by a powerfulcity Art Jury, two types of people nor-mally associated with traditional (con-servative) attitudes.

As Baxter explained it, the stone-faced arch design of 1974 obtained alow bid of $1,047,790 compared to theengineers’ estimate of $900,000. Bylaw, if the low bid exceeded the esti-mate, it was rejected. Thus, the cityengineers began to search for anothersolution, of which two arose.

The first solution was a plan to re-move the stone facing which in thelow bid amounted to the astoundingsum of $486,490! Here, the Art Juryobjected to the mass of an unfacedarch. The second solution suggesteditself almost by accident.31

“The Bureau of Engineering, Sur-veys and Zoning at that time was con-structing large circular sludge tanks atits new Northeast Treatment Works.

These were being built by the PreloadCorporation of New York (sub-con-tractors for Virginia EngineeringCompany of Newport News, Vir-ginia), using the prestressing tech-nique of winding wires around a thincore. The chance remark of Mr. E. R.Schofield, who was at that time Chiefof the Design Division of the Bureauof Engineering, Surveys and Zoning,to a representative of the Preload Cor-poration, led to a decision to explorethe use of prestressed concrete for thisbridge. Among those with whom Mr.

Schofield talked were Mr. L. Coff,Consulting Engineer of New York,and representatives of the PreloadCorporation. Contacts were also madewith Professor Gustave Magnel inBelgium.”

The city decided to follow Magnel’sideas for a prestressed concrete girderdesign, but they still had to convincethe Art Jury of its viability. Baxterrecords their response, surely one ofthe most historically significant eventsin the relationship between structureand aesthetics.32

Fig. 5. Artist’s painting of the Walnut Lane Bridge, Philadelphia, Pennsylvania, aftercompletion (1951). (Bridge designed by Gustave Magnel.)

Fig. 6. Walnut Lane Bridge as it appeared in 1976.

22 PCI JOURNAL

“The Art Jury, however, on seeingthe preliminary sketches for the newbridge agreed that the comparativelyslim lines of the new bridge would notrequire stone facing.”

Thus, a major structure in one ofPhiladelphia’s most elegant naturalsettings (the beautiful Fairmount Park)became possible because its appear-ance was pleasing enough to permit it

to be economical. The low bid in 1949was $597,600 for the bridge and$100,783 for the approaches; Baxterestimated that this amounted to a “netminimum saving (of) approximately$76,000” over an arch bridge withoutstone facing in 1949.33

Moreover, the Art Jury would prob-ably have required a rubbed finish onthe bare concrete arch, adding at least$40,000 and making the prestressedconcrete solution a minimum of$116,000 less than the arch structure.The saving of over 16 percent clearlymade this large-scale work possibleand influenced the way prestressingentered American practice. Of thethirty papers presented at MIT in Au-gust of 1951, five were by people di-rectly connected to the Walnut LaneBridge.

Another feature of this bridge wasthe full-scale test to destruction of oneof its 160 ft (48.5 m) long girders. Al-

though, perhaps, unnecessary in prin-ciple, this test did serve dramaticallyto demonstrate, in practice, and infront of at least 500 engineers, thehigh overload capacity of the bridgebuilt along these new lines.34

Fig. 5 is an artist’s picture of theWalnut Lane Bridge taken soon afterits completion in 1951. Fig. 6 is a shotof the same bridge taken in 1976.

Thus, the Walnut Lane Bridge putbefore the American structural engi-neer the image of new possibilities forsafe, economical, and elegant struc-tures. Yet these obvious advantagescame together with a set of questions,even doubts, that all centered on a sus-picion of European ideas that has ex-isted in America at least since the timeof Emerson’s American Scholarspeech of 1837. In Emerson’s terms,the doubts focused on the need tothink deeply about the local Americanenvironment and to create works of

“In the immediate post-WorldWar II years, there was a widely

held view that labor beingcheaper in Europe meant thatmaterial savings dominated

design ideas, whereas materialsbeing cheaper in America,

labor savings were supposed todominate design ideas in the

United States.”

The first major prestressed concrete bridge to be con-structed in the United States was Philadelphia’s WalnutLane Bridge. This bridge, which was conceived and de-signed by Gustave Magnel, was completed in 1950. Itcontains three simply supported girders with a centerclear span of 155 ft (47.3 m) and two end spans of 74 ft(22.6 m) each. The girders are I-shaped, 79 in. (2007mm) deep with a 52 in. (1321 mm) wide top flange.

The flanges in the center span are butted, but in the endspan the beams are placed 8 ft 8 in. (2.64 m) on centersand the slab is cast-in-place. The girders were tensionedby the Magnel-Blaton stressing method, i.e., using twostrands at a time.

The Preload Co. of New York erected this structure.The girders were cast on falsework at the bridge site andmoved horizontally into position on the foundation.

PARTICULARS OF WALNUT LANE BRIDGE


art, political structures and scholarshipthat would be distinct and originalrather than merely copying Europeanculture and taste.

In modern engineering terms, thesedoubts center on the difference be-tween labor and materials. Laborbeing cheaper in Europe means thatmaterial savings dominate designideas, whereas materials being cheaperin America, labor savings are sup-posed to dominate design ideas in theUnited States.

We need to look critically at theseclichés today. They reflect in part aquestionably conservative attitude to-ward design and a justifiably cautiousattitude toward building.

The Walnut Lane Bridge raisedagain this question of labor and mate-rials and it was criticized for being toomuch a European design. Magnel hadmade the design through the PreloadCorporation whose vice president Cur-zon Dobell reported that “it took 152man-hours to assemble and install oneton of prestressing wire” for thebridge.35

Magnel himself was astounded atthe problems associated with gettingAmerican industry to manufacturespecial fittings. He used to lament thatall would have been well, if instead oftwenty end cable fittings, he couldhave ordered one million!

Admiral Jelley, Chief of the Bureauof Yards and Docks, perhaps summa-rized best this viewpoint in his “Clos-ing Summary” to the MIT Conference:

“We have seen American adapta-tions of European practice in bridgeconstruction. The Walnut Lane Bridgein particular was a direct applicationof Dr. Magnel’s system.

“However, the Arroyo Seco pedes-trian bridge (California’s first pre-stressed concrete bridge) had an inter-esting departure from Europeanprecedents – a button type of anchor-age was used. I think that this is sig-nificant because I consider that Euro-pean ideas should not be copiedblindly. Construction conditions inthis country, particularly trade prac-tices, preclude this. American engi-neers must find and develop their ownsolutions.”

This was the situation at the end of1951. The idea of prestressing became

The Fédération Internationale dela Précontrainte (FIP) was officiallyinaugurated at a meeting held at theUniversity Engineering Depart-ment, Cambridge, England, on Au-gust 29, 1952.

This meeting represented the cul-mination of the efforts of severaleminent international engineers andresearch workers who had heldmeetings and discussions over atwo-year period, and in which Eu-gene Freyssinet and Gustave Mag-nel played prominent roles.

Most fittingly, the first presidentof FIP was Freyssinet and the firstdeputy-general vice-president wasMagnel.

During its lifetime, FIP hadMember Groups in 50 countriesand FIP observers in about 25 othernations. In 1974, the president ofFIP was Ben C. Gerwick, Jr. of the

University of California at Berke-ley, and also a consulting engineer.

Two of FIP’s principal activitieshave been to produce technical re-ports and to organize internationalcongresses every four years as wellas special symposia throughout theworld. FIP has held congresses inLondon (1953), Amsterdam (1955),Berlin (1958), Rome and Naples(1962), Paris (1966), Prague(1970), New York (1974), London(1978), Stockholm (1982), NewDelhi (1986), Hamburg (1990),Washington (1994), and Amster-dam (1998).

In 1998, FIP merged with theCEB (Comité Européen du Béton toform fib (Fédération Internationaledu Béton. fib held its first worldcongress in Osaka, Japan, in Octo-ber 2002. Its next congress will beheld in Naples, Italy, in 2006.

FORMATION OF FIP

well accepted in the United States. Itssafety and economy seemed possibleand its visual potential a reality. Nowbegan the long process, even now un-finished, for American engineers tofind and develop their own solutions.

DEVELOPMENTS 1951–1957In his 1951 discussion at MIT, W.

E. Dean noted that in following a pre-stressed concrete design through tocalculations and plans:36

“We encounter a number of factorsthat are puzzling to say the least. Allof these are capable of solution and itis evident that our European counter-parts have solved them to their satis-faction, but whether we can adapt ourpractice and concepts of safety to Eu-ropean thinking remain to be seen.”

This skeptical view, commonamong structural engineers in 1951,had by 1957 changed radically asDean himself expressed in the openingspeech of the World Conference onPrestressed Concrete held in Berkeley,California in 1957:37

“Those who have been associatedwith the prestressed concrete field forthe past several years have reason to

FORMATION OF PCIThe Prestressed Concrete In-

stitute (PCI) was organized at aspecial meeting in Tampa,Florida, June 18, 1954. Twoyears later, the first issue of thePCI JOURNAL was published.

In November of 1959, the PCImoved its headquarters toChicago, Illinois.

Today, the PCI (since renamedPrecast/Prestressed Concrete In-stitute) is a trade/professional or-ganization made up of about2000 producer and supplier com-panies, affiliated state associa-tions, professional engineers andarchitects, and students.

be proud. Their past efforts have beenspectacularly satisfying, present devel-opment is stimulating, the future ap-pears to be not only promising but al-most fantastic in its potential for theuse and maturity of prestressed con-crete design. For in the utilization ofthis economical, versatile and highly

24 PCI JOURNAL

adaptable material we are barely com-ing of age.”

The intervening years brought pre-stressed concrete into the mainstreamof American construction practice; itmoved from the province of the pio-neers such as Freyssinet and Magnelinto the practice of all structural engi-neers not only in North America butthroughout the world.

In Europe, the Fédération Interna-tionale de la Précontrainte (FIP) wasinaugurated at Cambridge Universityin August 1952 (see box, p. 23).

In the United States, those six yearssaw the organization of the Pre-stressed Concrete Institute at Tampa,Florida, in June of 1954, the publica-tion of the first specification for pre-tensioned prestressed concrete on Oc-tober 7, 1954, by the PCI and in thesame year the “Criteria for PrestressedConcrete Bridges” by the Bureau ofPublic Roads; and the appearance ofAmerican textbooks on prestressedconcrete structures, the most widelyused being that by T. Y. Lin, writtenlargely during his one-year FulbrightFellowship at Ghent with ProfessorGustave Magnel.

These events were the evidences ofthe rapid growth of prestressed con-crete throughout the United States andthe world; and it was this growth thatthe Berkeley Conference summarized

in the summer of 1957.Five reports on American bridges

appeared and they characterized wellthe developments since 1951:

First was a discussion by Arthur L.Elliott on construction experiencewith prestressed concrete in Californiawhere the state bridge department hadalready contracted for over 60 pro-jects.38 Elliott focused on their prob-lems, especially with inexperiencedcontractors, but clearly showed thathis bridge division had made majorprogress in using the new ideas.

The second report, by E. L. Erick-son, chief, Bridge Division U.S. Bu-reau of Public Roads, described thenewly published “Criteria for Pre-stressed Concrete Bridges,” which hadalready played a central role in en-couraging bridge designers to try pre-stressing and which was beginning toopen up its design for bridges of theinterstate highway system enacted intolaw by the Congress in 1956.39

The third report, by Wayne F.Palmer, described “The 24-Mile LakePontchartrain Prestressed Bridge” re-cently completed near New Orleans.40

This immense project signaled thepracticality of using pretensioned pre-cast elements and proved by competi-tive bidding to be substantiallycheaper than the competitive bid insteel. As Palmer put it:41

• First United States Conferenceon Prestressed Concrete, Mas-sachusetts Institute of Technology,Cambridge, Massachusetts, August14-16, 1951.

• Canadian Conference on Pre-stressed Concrete, Toronto, On-tario, January 28-29, 1954.

• World Conference on Pre-stressed Concrete, University ofCalifornia at Berkeley, California,July 29-August 3, 1957.

• FIP/PCI Congress, New YorkCity, New York, May 26-June 1,1974.

• ACI-CEB-PCI-FIP Symposium,ACI Annual Convention, Philadel-

phia, Pennsylvania, March 31-April1, 1976.

• T.Y. Lin Symposium on Pre-stressed Concrete – Past – Present –Future, University of California atBerkeley, California, June 5, 1976.

• International Symposium onNonlinearity and Continuity in Pre-stressed Concrete, Waterloo, On-tario, Canada, July 4-6, 1983.

• FIP Symposium, Calgary, Al-berta, Canada, August 25-31, 1984.

• FIP Congress, Washington,D.C., May 29-June 2, 1994.

• PCI/FHWA/fib InternationalSymposium on HPC, Orlando,Florida, September 25-27, 2000.

MAJOR INTERNATIONAL PRESTRESSING CONFERENCESIN NORTH AMERICA (1951-2000)

“When bids for both the steel and theconcrete designs were opened, it wasclear that on a project of this kind steelwas no longer a serious competitor.”

The fourth report dealt with thebridges for the Illinois Tollway onwhich the decision had been made tostandardize precast factory-made pre-stressed elements for 224 of the 289bridges.42 Again, comparisons withsteel designs indicated the economy ofprestressed concrete. For the pre-tressed concrete bridges, the unit costswere $13.10 per sq ft whereas for thesteel option it was $16.50 per sq ft, avery substantial difference.

The fifth and final American reporton bridges described a full-scale loadtest of one bridge for the Illinois Toll-way.43

What these reports showed is thatby 1957 there was a major shift infocus, compared to the bridge reportsat the MIT Conference six years ear-lier, i.e., a shift away from individualcustom-made projects like the WalnutLane Bridge and towards mass pro-duced fabrication on immense projectsor, as in the case of California, the useof prestressed concrete by a singlepublic agency. There is no mention ofthe Walnut Lane Bridge in any ofthese articles and very little referenceto European experience. As Deanstated in his opening remarks:44

“It appears that in the field of rela-tively small standardized, mass pro-duced parts, United States construc-tion is presently outstanding. In longspans, continuous structures and themore daring structural applications,foreign technology leads.”

As if to pick up Dean’s challengeabout Europe’s lead in daring struc-tures, T.Y. Lin, the conference chair-man, closed the proceedings by pre-senting a set of drawings by anarchitect for daring structures of pre-stressed concrete. Indeed, Lin’s owncareer since that time substantiatedclearly the positive results of such fu-turistic stimulus.

What I wish to add here is the paral-lel stimulus of looking back at someequally dramatic design ideas whicharose during those early years beforethe Berkeley Conference. Especiallyimportant are the ideas of Ulrich Fin-sterwalder, who during that same pe-


riod in the 1950s embraced prestress-ing and made it a construction tech-nique as well as a design idea.

ULRICH FINSTERWALDER(1897–1988)

Ulrich Finsterwalder, like EugeneFreyssinet, was a builder whose de-signs have frequently been constructedonly because they were bid below othercompeting designs. His major bridgeidea, developed after World War II, isthe double cantilever, built entirelywithout scaffolding (see Fig. 7).

Like Freyssinet and Magnel, Finster-walder came to believe in prestressingafter having a long experience in rein-forced concrete construction and espe-cially, like Freyssinet, in arch and thinshell structures. Finsterwalder learnedmathematics while in a French prisoncamp during World War I.

After the war, he put that knowl-edge to good use in shell theory whichserved as the basis for the many out-standing thin shell concrete structuresdesigned and built by Dyckerhoff and

Widmann A.G., starting in the mid-1920s.

In 1937, he began work developinga prestressing system and designedand built his first bridge.45 Then afterWorld War II, his major prestressingwork began, which he reported on inAmerica in 1952.46

His work since that time was sobroad and varied that it defies simplecharacterization, except to say thatmore than anyone else, perhaps, Fin-sterwalder showed that prestressedconcrete can be a safe, economical,and elegant solution to almost anymajor structural problem that exists inthe modern world.

In a 1970 interview, Finsterwaldermentioned that his favorite bridge wasthe Mangfall Bridge, under design justat the time of the Berkeley Confer-ence. With this bridge, as in other pro-jects, Finsterwalder sought to showthat prestressed concrete could com-pete directly with structural steel, notonly in cost, but also in reducing thestructure’s depth.

In the Mangfall Bridge, built by hiscantilever method but made with opentruss-like walls, his idea was to dupli-cate the girder depth of the steelbridge built in the late 1930s and de-stroyed in World War II. Not only didhe succeed technically, but in design-ing a two-level bridge (see Fig. 8), heprovided the pedestrian with one ofthe most spectacular crossings sincethe Brooklyn Bridge in New York.

Ulrich Finsterwalder – Thisimaginative German engineer-constructor has played a verysignificant role in advancing the state-of-the-art of prestressed concrete,especially his development of thedouble cantilever method of erection inbridge construction.

Finsterwalder had the idea of pro-viding a prestressed concrete alterna-tive to every steel bridge design in-cluding those with very long spanswhich had previously been the soleprovince of suspension bridges. Hisstress ribbon bridge, for example, con-ceived at about the same time as theMangfall design, carried prestressedconcrete far beyond its previous lim-its. Later, he made a design for theBosporus Bridge which would havehad a free span of 1500 ft (454 m).47

Fig. 7. Bendorf Bridge over the River Rhine, Germany (1962). (Designed by Ulrich Finsterwalder.)

“Finsterwalder showed thatprestressed concrete can be asafe, economical, and elegantsolution to almost any major

structural problem that exists inthe modern world.”

26 PCI JOURNAL

THE RECENT PASTAppropriately, the first project to be

discussed is the 1972 highway bridgeover the Rio Colorado (see Fig. 9) inCosta Rica designed by T.Y. Lin In-ternational and spanning 479 ft (145m) between supports over a 300 ft (91m) deep valley.48 This new formshows its structural logic clearly in thealmost polygonal lower chord, its deli-cate verticals and its straight light hor-izontal roadway.

The same sense of form appears inthe Chillon Viaduct (see Fig. 10)along the northeast shore of LakeGeneva and designed by ProfessorPiguet of Lausanne, Switzerland.Here, the design was chosen after acompetition in which the criterion ofaesthetics played a major role. Thedouble cantilever method used precastconcrete components post-tensionedtogether. The total final cost of the 11/2

mile (21/2 km) long viaduct was only$14 per sq ft.49

Lastly, and departing slightly fromthe historical focus, is the most recentbridge of Switzerland’s most talentedcontemporary bridge designer, Chris-tian Menn. This magnificent structure,the Ganter Bridge, is on the road goingover the Simplon Pass (see Fig. 11).This structure reflects the continualsearch for form in prestressed concrete.

Fig. 8. Mangfall Bridge at Darching,Germany (1947). (Designed by

Ulrich Finsterwalder.)

In a way, each of these three pro-jects are by mature designers whohave worked with prestressing sinceits early days. Thus, these engineersare very much like the earlier pioneerswhose major contributions came aftera long contemplation of the behaviorof structures.

Whether these designers wouldadmit it or not, the crucial factor wasthe study of history – not a study ofnames and dates, but rather of formsand of full-scale behavior. Ideas instructure come from understandingclearly the works of the recent past;but they also come from abroad aswell as from home.

In understanding more clearly the

works of Freyssinet, Magnel, and Fin-sterwalder, American engineers havebegun adapting prestressed concrete toAmerican conditions. In so doing, de-signers like T. Y. Lin, engineers of thestate of California, and others acrossthe continent have shown how newAmerican forms can become a centralpart of the recent past that engineerseverywhere will need to study.

Freyssinet’s difficult years from1928 to 1935 have led to new formsthat have become symbols of how thestructural environment of the 21st cen-tury can be built, not only to save ma-terials and money but also to add ele-gance and dignity to society equal toany period in our history.


Fig. 9. RioColorado Bridge,Costa Rica (1972).(Designed by T. Y. Lin.)

Fig. 10. Chillon Viaduct, Switzerland (circa 1970). (Designed by Professor Piguet.)

Fig. 11. Ganter Bridge, Switzerland (1980). (Designed by Christian Menn.)

28 PCI JOURNAL

Fig. 13. Felsenau Bridge, Switzerland (1974). (Designed by Christian Menn.)

Fig. 12. Tamins-Reichenau Bridge, Switzerland (1962). (Designed by Christian Menn.)

CONCLUDING REMARKSThis 1976 paper ended with a brief

reference to the Swiss bridge designer,Christian Menn, and to his spectacularGanter Bridge then in design and sincecompleted in 1980. However, withinthat time period of the essay, Mennhad completed already a series ofbridges using prestressed concrete,some of which are now recognized asthe most elegant structures of theirtype, especially the Tamins-Reichenaudeck-stiffened arch of 1962 and theFelsenau segmental cantilever girderof 1974 (see Figs. 12 and 13).50

In both cases, Menn freely used par-tial prestressing as a means for refin-ing his design. This leads me to thevery fine discussion of my 1976 paperby the distinguished Austrian-Britishpioneer of prestressed concrete, PaulAbeles.51 Abeles emphasized the sig-nificance of partial prestressing and ofthe role played by Gustave Magneland Pierre Lardy (1903-1958) inamending Freyssinet’s insistence onthe clear separation of prestressed con-crete from reinforced concrete.

It is now becoming clear that theproper term, structural concrete, willin the future be used to describe a de-sign field that uses both mild steel re-inforcement and prestressing steel invarying combinations.

The idea of structural concrete led


Menn to designs now recognized as ofthe highest quality yet achieved inconcrete. His teacher was Lardy inZurich, and another of Lardy’s stu-dents, Heinz Isler, has created radi-cally new roof forms in thin shell con-crete construction, where the use ofprestressing has been essential (seeFig. 14).

In 1999, I returned to Ghent, whereI had studied under Gustave Magnel48 years earlier. While I was there, Ipresented a paper on Magnel (andAnton Tedesko)52 and four years laterorganized an art museum exhibitionon the works of Isler, Menn, andLardy, along with the works of otherZurich educated engineers includingWilhelm Ritter, Robert Maillart, andOthman Ammann.53

In retrospect, it was Magnel that hadset me on my career and to him I oweits beginning; this inspiration has ledto the discovery of structural engineer-ing as a field that has created some ofthe greatest symbols of the 20th cen-tury and holds even greater potentialfor this new century.

REFERENCES AND NOTES1. Le Corbusier, The Radiant City, Paris,

1933 (English Edition, 1967), p. 340.The author is indebted to MaryMcLeod, a graduate student in archi-tecture, who told him of this quote.

2. Freyssinet, E., “Eugene Freyssinet byHimself,” Travaux, April-May 1966.(Extracts from a lecture given byFreyssinet on May 21, 1954, and pub-lished in Travaux, June 1954), p. 10.

3. Ibid, p. 3.4. Ibid, p. 5.5. Freyssinet, E., “A General Introduc-

tion to the Idea of Prestressing,”Travaux, April-May 1966 (originallywritten in 1949), p. 19.

6. Insolera, I., “I Grandi Viadotti di Eif-fel Nel Massif Central,” Zodiac XIII,1964, pp. 61-111.

7. Freyssinet, op. cit., 1949, p. 19.8. Freyssinet, op. cit., 1954, p. 8.9. Ibid, p. 9.10. Ibid, p. 9.11. Ibid, p. 912. Freyssinet and Maillart were the only

engineers elected in 1937 as honorarycorresponding members of the RoyalInstitute of British Architects alongwith eminent architects including LeCorbusier. See Collins, G., “The Dis-

Fig. 14. Sicli Building, Switzerland (1969). (Designed by Heinz Isler.)

covery of Maillart as Artist,” MaillartPapers , Princeton, 1973, p. 38.Freyssinet was discovered beforeMaillart and written about in the1920s. Le Corbusier used Freyssinet’swork to illustrate his most widely readwork Towards a New Architecture,Paris, 1923, pp. 263-265.

13. Freyssinet, op. cit., 1954, p. 10.14. Freyssinet, E., “The Relations Be-

tween the Strains and Constitution ofCements and Colloidal Structured Ma-terial,” Travaux, April-May 1966, p.570 (originally written between 1926-1929).

15. Ibid, p. 9.16. Billig, Kurt, Prestressed Concrete,

London, 1952, pp. 28 and 43.17. Freyssinet, E., “New Ideas and Meth-

ods,” Science et Industrie, January1933, published also in English inTravaux, April-May 1966, pp. 607-622.

18. Ibid, p. 617.19. Apparently the only exception was R.

E. Dill who in 1925 did recognize theimportance of prestress losses due tocreep and shrinkage of the concrete.See Billig, op. cit., pp. 32-34. P. H.Jackson had, among his numerouspatents, one that in retrospect can becalled prestressing, but as far as isknown had no influence on others andwas never used practically.

20. McCullough, C. B., and Thayer, E. S.,Elastic Arch Bridges, New York City,NY, 1931, pp. 325-358.

21. Freyssinet, op. cit., 1954, p. 12.22. Ibid, p. 13.23. Freyssinet, op. cit., 1949, p. 25.

24. Freyssinet, op. cit., 1954, p. 18.25. Evans, R. H., “Speech,” In Memoriam

Gustave Magnel, October 1956, p. 51.26. Anseele, E., “Speech,” Ibid, p. 31.27. Magnel, Gustave, Prestressed Con-

crete, Third Edition, London, 1954.28. Freyssinet, Eugene, “A General Intro-

duction to the Idea of Prestressing,”Travaux, April-May 1966, pp. 19-49,originally published in 1949.

29. Magnel, op. cit., p. 84.30. Baxter S. S., and Barofsky, M., “Con-

struction of the Walnut Lane Bridge,”Proceedings, First United States Con-ference on Prestressed Concrete, Mas-sachusetts Institute of Technology,Cambridge, MA, August 1951, p. 47.

31. Ibid, pp. 47-48. According to M. For-merod, then chief engineer forPreload, it was one of his engineers,Charles Zollman, later one of the orga-nizers of the Berkeley Conference,who suggested Gustave Magnel. Zoll-man had been a student of Magnel’s atGhent and had helped him with theEnglish language version of his book.

32. Ibid, p. 48.33. Ibid, p. 48. The low bid in 1947 for the

arch without stone facing was$561,300, which when corrected fromthe rise in costs according to the Engi-neering News-Record cost indexwould have risen to $673,560 in 1949.

34. Anderson, A. R., “Field Testing of Pre-stressed Concrete Structures,” Pro-ceedings, First United States Confer-ence on Prestressed Concrete,Massachusetts Institute of Technology,Cambridge, MA, August 1951, pp.215-217. The test was described by G.

30 PCI JOURNAL

Magnel in “Prototype PrestressedBeam Justifies Walnut Lane Bridge,”ACI Journal, Proceedings V. 47, De-cember 1950, pp. 301-316; and by M.Fornerod in the Bulletin of the IABSE,Zurich, 1950; it also appears in detail inMagnel’s book, op. cit., pp. 188-200.

35. Dobell, C., “Prestressed ConcreteTanks,” Proceedings, First UnitedStates Conference on Prestressed Con-crete, Massachusetts Institute of Tech-nology Cambridge, MA, August 1951,p. 9.

36. Dean, W. E., “General Design andEconomic Considerations in the Plan-ning of Prestressed Concrete Struc-tures – Discussion,” Proceedings, FirstUnited States Conference on Pre-stressed Concrete, Massachusetts Insti-tute of Technology, Cambridge, MA,August 1951, p. 184.

37. Dean, W. E., “Prestressed Concrete –A Youth Comes of Age,” Proceedings,World Conference on Prestressed Con-crete, University of California, Berke-ley, CA, July 29-August 3, 1957, p.A1-3.

38. Elliot, A. L., “Construction Experiencewith Prestressed Concrete in Califor-nia,” Proceedings, World Conferenceon Prestressed Concrete, University ofCalifornia, Berkeley, CA, July 29-August 3, 1957, p. A8-1.

39. Erickson, E. L., “The Bureau of PublicRoads, Criteria for Prestressed Con-crete Bridges,” Proceedings, WorldConference on Prestressed Concrete,University of California, Berkeley,CA, July 29-August 3, 1957, p. A9-1.

40. Palmer, Wayne F., “The 24-Mile LakePontchartrain Prestressed Bridge,”Proceedings, World Conference onPrestressed Concrete, University ofCalifornia, Berkeley, CA, July 29-Au-gust 3, 1957, p. A10-1.

41. Ibid, p. A10-2.42. Bender, M. E., “Prestressed Concrete

Bridges for the Illinois Toll Highway,”Proceedings, World Conference onPrestressed Concrete, University ofCalifornia, Berkeley, CA, July 29-August 3, 1957, p. A11-1.

43. Janney, J., and Eney, W. J., “Full ScaleTest of Bridges on Northern IllinoisToll Highways,” Proceedings, WorldConference on Prestressed Concrete,University of California, Berkeley, CA,July 29-August 3, 1957, p. A12-1.

44. Dean, W. E., op. cit., p. A1-1.45. Finsterwalder, U., “Eisenbetontrager

met selbsttatiger Vorspannung,” DerBauingenieur, Heft 35/36, 1938.

46. Finsterwalder, U., “Free-Span Pre-stressed Concrete Bridge,” ACI Jour-nal, Proceedings V. 49, No. 3, Novem-ber 1952, pp. 225-232.

47. Finsterwalder, U., “Prestressed Con-crete Bridge Construction,” ACI Jour-nal , Proceedings V. 62, No. 9,September 1965, pp. 1037-1046.

48. Lin, T. Y., and Kulka, Felix, “Con-struction of Rio Colorado Bridge,”PCI JOURNAL, V. 18, No. 6, Novem-ber-December 1973, pp. 92-101.

49. Menn, C., “New Bridges,” MaillartPapers, Princeton, NJ, 1973, p. 115.

50. “Swiss Bridges Design Spans Timeand Distance,” Civil Engineering,November 1981, pp. 42-46.

51. Abeles, Paul W., Comments on “His-torical Perspective on Prestressed Con-crete” and Closure by David P.Billington, PCI JOURNAL, V. 22, No.3, May-June 1977, pp. 109-116.

52. “Transferring Technology from Eu-rope to America: Cases in Concrete –Thin Shells and Prestressing, Sartoni-ana, V. 13, 2000, pp. 47-72. “The In-troduction of Prestressed Concrete intothe United States: Magnel and theWalnut Lane Bridge and Beyond,”Japanese Concrete Journal, V. 40,2001 (January 2002), pp. 82-90 (withRyan Woodward).

53. Billington, David P., The Art of Struc-tural Design: A Swiss Legacy, YaleUniversity Press (Hardback), Prince-ton University Art Museum (Paper-back), Princeton, NJ, 2003.

Documents

Historical Perspective on Prestressed Concrete