Wilhelm Ritter: teacher of Maillart and Ammann

Autor(en): Billington, David P.

Objekttyp: Article

Zeitschrift: Ingénieurs et architectes suisses

Band (Jahr): 113 (1987)

Heft 7

PDF erstellt am: 11.10.2021

Persistenter Link: http://doi.org/10.5169/seals-76366

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http://www.e-periodica.ch CHRISTIAN MENN Ingénieurs el architectes suisses n" 7 26 mars 1987

Tableau 1. — Amplitudes maximales des variations de températures uniformes les ponts selon différentes sources. pour Bibliographie à Taa [°C] [1] J accoud, J.-P. Gradients de tempéra¬ dans les et Ponts en bétons Ponts mixtes Ponts en acier ture ponts. Ingénieurs architectes suisses, Lausanne, vol. 315-322. Grande-Bretagne [8] 51 59 75 108, n°23, 1982, pp. Grande-Bretagne [8] 47 - 66 Italie [9] 50 73 [2] Schuepp, M. Klimatologie der - 1 bis 12. Pologne [9] 59 — 91 Schweiz, Lufttemperatur, Teil Autriche 19] 56 — 84 Schweizerische Meteorologische 1960-1969. Hongrie [91 57 — 85 Anstalt, Zurich, Nos résultats 56 64 84 [3] Emerson, M. Bridge temperatures and movements in the British isles. ments des ouvrages. Elles ont été définies 3. Pour le positionnement des appareils Road research laboratory report LR à partir des températures extrêmes d'appuis, il faut tenir compte des 228, Crowthorne. Berkshire, 1968. de l'air; il s'agit donc également écarts entre la température effective [4] Capps, M. W. R. The thermal beha¬ de valeurs extrêmes le calcul des au cours de l'exécution de l'ouvrage et pour viour of the Beachley viaduct/Wye mouvements des ponts qui ne nécessitent la température moyenne T,„ du lieu. bridge. Road research laboratory pas d'être amplifiées par un La température de l'air, au cours des report LR 234, Crowthorne, Berkshire, 1968. facteur de charge. différentes étapes de l'exécution de 2. Dans la mesure où le format de la l'ouvrage, n'étant a priori pas connue [5] Emerson, M. Bridge temperature esti¬ norme indiquera des valeurs nominales avec précision, on peut s'imaginer que mated from the shade temperature. de charges, à multiplier par un des marges supplémentaires, notamment Transport and road research laboratory LR facteur pour la vérification de la sécurité, pour les dimensions des plaques report 696, Crowthorne, Berkshire, 1976. les valeurs nominales correspondant d'appuis, sont nécessaires pour couvrir aux amplitudes des températures cette incertitude. [6] Emerson, M. Extreme values of uniformes des ponts pourraient être, si le 4. Les variations de la température uni¬ bridge temperatures for design purposes. facteur est égal à 1,4: forme des ouvrages traitées dans cet Transport and road research laboratory report LR 744, — les ponts en béton : article ne sont qu'un aspect des effets pour Crowthorne, Berkshire, 1976. T„ ±20°C; de la température sur les constructions. — pour les ponts mixtes: Le gradient thermique qui se [7] Black, W., Moss, D. S., Emerson, r,„±23°C; développe simultanément dans les M. Bridge temperatures derived from measurement of movement. Transport — les acier: doit être pris en pour ponts en ouvrages également and road research laboratory les T„, ± 30°C. compte, particulièrement pour report LR 748, Crowthorne, Les valeurs nominales ci-dessus vérifications à l'état de service. Des Berkshire, 1976. correspondent fortuitement à des valeurs informations au sujet des gradients de [8] BS 5400. Part 2. 1978. Steel, concrete car le entre les températures dans les ponts et sur moyennes, rapport and composite bridges — Specification amplitudes de températures maximales la manière de les considérer dans for loads. British Standards Institution, et moyennes de l'air est également le dimensionnement sont contenues 1978. de 1,4. Ces valeurs nominales ont une dans la référence [1]. Union internationale des chemins d'occurrence de [9] probabilité 50%; de fer, Sous-commission des ponts. c'est-à-dire que sur une période de Effets des changements de températures. Adresse des auteurs: 2 ans, les températures moyennes Rapport du groupe d'étude Jean-Paul Lebet minimales et maximales des ouvrages 7/J/8. UIC, Utrecht, décembre 1978. Ing. dipl. EPFL/SIA être atteintes. Dans ce peuvent cas, Jean-Claude Badoux, professeur [10] Norme SIA E 160. Actions sur les elles peuvent être considérées comme Ecole polytechnique fédérale structures, projet soumis en consultation. valeur d'accompagnement au sens du de Lausanne Société suisse des ingénieurs et ICOM — Construction métallique 1985. projet SIA 160 mis en consultation des architectes, Zurich, janvier 1015 Lausanne [10].

Wilhelm Ritter : Introduction

Teacher of Maillart and Ammann1 This paper seeks to make the contemporary structural engineering profession aware of a 19th century tradition of education which has been almost lost. by David P. Billington2, Princeton (USA) That educational tradition possessed ideas which do not go out of date and This paper was first presented at the Convention of the American Society of Civil which can stimulate a healthy review Engineers in Boston, April 1979, in a session honoring Othmar Ammann ; it was of present research and teaching in later presented in June of 1980 at the Swiss Federal Institute of Technology in structural engineering. Zurich at the request of Professor Christian Menn, who himself stands in the same A good case can be made for the tradition begun by Professors Culmann and Ritter. The paper was first published in judgment that the two greatest bridge the "Journal" of the Structural Division of the American Society of Civil designers of the 20th century were Engineers, Vol. 206, No. ST5, May 1980, pp. 1103-1116 and is reprinted by permission. Robert Maillart (1872-1940) using concrete and Othmar Ammann (1879-1965) using steel. It is a remarkable fact that both had the same Swiss educational 1 Presented at the April 2-6,1979, ASCE Convention and Exposition and Continuing Education and the same professor Program, held in Boston, Mass. background even 2Prof, dept. of Civ. Engrg., Princeton Univ., Princeton, N.J. for bridge design : Wilhelm Ritter (1847- 94 CHRISTIAN MENN Ingénieurs et architectes suisses n" 7 26 mars 1987 1906). It thus seemed of interest to sciences. This clear division originated and Culmann were of most significance explore the career ofthat late 19th century at least in part with the ideas that to the education of Maillart and academic to recapture something of engineering was a new subject, that its content Ammann. his teaching and research, especially that was barely if at all connected to In addition to having the advantage of part which may have influenced his two subjects taught in the universities, and coming later the new school had the even distinguished students. From documentation that its new subjects were closely greater benefit of being a national institute, already published, it can be stated connected to the new prosperity of an the only one of its kind in Switzerland that Ritter had a powerful and lasting emerging industrial economy. The and thus a unifying symbol. Not influence on Maillart's career [l]3. symbols of something new, something only could it attract, thereby, the highest Professor Fritz Stüssi in his book on different, and something useful also quality of faculty into the country but it Ammann also emphasized the significance made the technical school seem to early could serve as a new center of cultural of Ritter and even reproduces 19th century governments symbols of a unity. At the opening ceremonies on some of his early work on suspension national future. October 15,1855, the first president of the bridges [2]. Because it seems correct to Thus, when the new federal government board of regents for the new institute, credit Ritter with direct influence, the in Bern tried to establish two institutions, Senator Johann Konrad Kern (1808-1888) substance of this present paper is to it found two different responses. spoke of how this type ofinstitute needed characterize that influence by briefly There was no major objection to an to bring together harmoniously Switzerland's sketching first the engineering tradition engineering school, but to a new federal different traditions of locality, of within which Ritter studied, second his university there arose strenuous dissent nationality, and of faith ([4], p. 234). own career as a teacher and researcher in from the cantons which already had Recalling clearly all the strife leading to bridge engineering, and finally the ideas universities. The result was that a federal the 1848 Constitution, Kern saw the new central to Ritter's vision ofbridge design. university never appeared but that a school as one where there could peacefully federal technological institute did, in come together Protestants and in 1855 German Founding of Zurich Polytechnikum Zurich, [4[. Roman Catholics, French Swiss and Swiss, those from the There were at least three good reasons canton of The revolutionary fervor that swept why conditions were excellent for the Basel city (density of 830 people per in through Europe in 1848 played a major founding of a new Swiss engineering square kilometer 1850), and those from the Graubunden 12,4 role in Swiss history by providing a school in 1855. First, it came late ; second, (density of people setting in which the Swiss could form a it came as a national enterprise; and per square kilometer). That this ideal centralized government based on a new third, it came after substantial and high- would be made possible through an Constitution. Although there had been a quality planning and debate. engineering school was characteristic of one Swiss Confederation since 1291, it did not Its lateness with respect to the French midcentury view of technology. function as the national state we now and German schools meant that its But perhaps most important of all, to the the school the know until after 1848. A very brief civil founders could benefit from a study of success of new was quality war in late 1847 actually precipitated numerous working examples and could of the debate and planning that led finally the founding of modern Switzerland. choose well-trained people for the first on February 7, 1854 to the federal law Although to this day Switzerland is the faculty. A first proposal drawn in 1851 by establishing the school and then to the most decentralized of the major European French Swiss followed closely French regulations passed by the Federal nations, its impressive economic examples, especially those in the Parisian Assembly on July 31 of the same year. strength owes much to the unity Ecole centrale des arts et manufactures, The two most important figures in the debate and achieved in 1848. but a later proposal guided by the planning were Alfred Escher A major goal of the new government in German Swiss Alfred Escher (1819-1882) from Zurich and Johann Kern from the 1848 had been to establish two federal the same year followed more the German Thurgau. Both were presidents of the Federal 1848 institutions of higher learning in example of Karlsruhe ([4], p. 70). One Assembly after and

Switzerland : remained a federal university in Zurich principle difference was in the organization leading national figures to the and a federal technological institute in of the faculty, which in the French- ends of their lives. Lausanne [3]. It was assumed that education, type system had individual professors It was people of such high national standing like the postal service, the railways, and central administrators, while the as Escher and Kern who debated and the and the customs policy would benefit by German-type had groups of professors in planned new school and who saw a more centralized presence within the departments (Fachschulen) with fewer clearly that it needed to be a great institution, both to reconstructed Confederation. central personnel ([4], pp. 75-76). help unify the country and There were in the Europe of 1848 two Eventually, the Federal Assembly chose to give the new nation international distinct traditions for engineering education. the Karlsruhe system. prestige. They succeeded largely because In the French tradition, founded With the Karlsruhe system chosen, it was of the people they chose, the most important during the Revolution, all education was only natural that the search for the one for civil engineering being standardized and controlled from Paris; founding faculty would turn in that Culmann. indeed, most engineering was taught in direction as well. In 1854, 189 individuals one capital city. The other tradition was were contacted as potential professors; The Culmann Tradition the German, in which educational of these 113 were German, 67 Swiss, institutions had been founded by individual 11 French, three Belgian, two Italian, and Following the designation of Semper as states having diffèrent local characteristics, three English ([4], p. 175). The first group head of the department of Architecture, and in which engineering was also chosen was impressive; at least four of Culmann was Kern's second major taught in many different places without the original 31 professors were men appointment. Born in Bavaria, Culmann there being one dominant school. whose international stature was so high received an engineering diploma from Common to both traditions was the principle that each could have been called the best Karlsruhe in 1841 after which he worked that engineering should have an academic in his field anywhere : architect for the Bavarian state railways until institution completely separated from Gotfried Semper (1803-1879), civil engineer called to Zurich in 1855. In addition to the university, the latter ofwhich taught Carl Culmann (1821-1881), physicist first-hand field experience with railroad the classical studies and the pure Rudolf Clausius (1822-1888), and historian structures built during the early days of Jacob Burckhardt (1818-1897) ([4], the rail boom, Culmann was strongly 3 Les chiffres entre crochets renvoient à la p. 221). Only Burckhardt was Swiss, the motivated to study recently completed bibliographie en fin d'article. other three German and of those Semper structures elsewhere and to systematize 95 CHRISTIAN MENN Ingénieurs et architectes suisses n" 7 26 mars 1987 structural engineering. These goals led standing structural engineering professor the eagle, who draws his circle high over him in two directions that would both over the last quarter of the 19th the heads of his students. What his verbal and strongly influence Ritter. First he made a century. He had one indispensible quality presentation his written publications the 2-year study trip to Britian and the United for the making of a successful follower: lacked, was compensated for by States to learn about bridge building critical reverence of his master. We can personal inspiration with which he enlivened and the and railway construction ; the result was see this in his two brief writings about his lectures warm he in each a widely-read 1851 report [6]. Second, he Culmann. personal interest which took began detailed studies of structural Following Culmann's death in 1881, of his students." analysis; early in his teaching career he Ritter came back to Switzerland from However, mixed the metaphor, Ritter began to systematize these studies and in Riga, where he had been professor, and gives the sense of Culmann better than 1866 published them in his book Graphic he immediately began to think about mere superlatives ever could. For Ritter Statics, probably the single most influential completing Culmann's great project of it was much more important to have book on structural analysis of the writing up the second volume of Graphic discovered the inspiration and personality time [7]. The basic idea behind his work Statics. The more he looked into the of Culmann than the clarity and Because was to demonstrate structural behavior project, the more he became convinced that thoroughness of his work. of through geometric diagrams rather than such an effort could not be done as Ritter's own clear critique ofthat work, through algebraic formulas. "Drawing is Culmann had imagined it. Ritter finally we are much more sympathetic toward the language of the Engineers" he used to decided to write his Applications of his final eulogy to Culmann; it rings it in an say and further [8] : "because the Graphic Statics as five separate volumes much more truly than would geometric way of thinking is a view of the (only four ever appeared) in which he article devoted only to praise: "The gifted thing itself and is therefore the most would think out on his own the organization mastery of his material, the astounding the natural way; while with an analytic and content. Clearly he was continuing ease with which he answered underlying method, as elegant as that may also be, the Culmann tradition but the new most difficult questions, and the the subject hides itselfbehind unfamiliar books were to be his own. There is a radical bases of his character—kindness symbols." difference between taking over and modesty—gained him the undivided sat at In 1875 a revised and expanded version of someone else's partially finished work respect and honor of all who his book appeared and in 1879 it was and simply editing and completing it and his feel." translated into French. By the time ofhis taking someone else's basic ideas and This is not the uncritical adulation of a death in 1881, Culmann's work was using them as the starting point for a loyal assistant, but the human response known and used throughout Europe but fresh approach. As Ritter put it in the of one great man to another. Indeed, it is its value was not uncontested. As his forward to his first new part ([9], p. V): not too far off to state that Ritter, very quoted contrast between geometric and "Evidently Culmann had the idea to keep near the end of his own life, is algebraic methods implies, there was the second volume as close as possible to unconsciously writing his own epitaph and another school of thought, one which the first. The writer [Ritter] had a feeling indeed in a way the epitaph of a 19th century believed more in abstract analyses and of reverence leading him that same way ; engineering education that was, formulas. on the other hand by following even as Ritter was writing his appraisal of In addition to his teaching and writing, Culmann's way the integrity of the treatment Culmann, already on the wane. Culmann was a consultant on practically would have been prejudiced; and looks the every important Swiss bridge built during especially so when one at recent Wilhelm Ritter his tenure at Zurich. Moreover, he studied developments... Thus it seemed more stream-flooding in Switzerland and advisable for a fresh and independent Karl Wilhelm Ritter (he dropped his first retaining-wall problems as well as making work to appear." name very early) was born the fourth of a famous study in 1865 ofthe similarities Not only could Culmann's published five children on April 14,1847 in Liestal, a between the stresses in the human approaches be substantially reworked small town just south of Basel, where his methods hip bone and a loaded building crane. but some of his general of father was a teacher in an elementary But the Culmann tradition was more presentation seemed to Ritter to be school for girls [10]. The family came than just geometry over algebra; it had awkward. For example, in his second originally from Altstätten on the Swiss three components which set the tone for edition, Culmann had given both Rhine in the canton of St. Gallen. civil engineering in the Zurich school for geometrical and algebraic methods of solution. Following school in the Liestal locality half a century. These three bases for his Ritter felt this to be redundant and he studied at the Basel trade school be influence were first, his intensive experience the algebraic treatment to out of place (Gewerbeschule, now called Realschule) Statics. Thus in the field from 1841-1855, second, in a work entitled Graphic which in English would today be called a his extensive travels for study of foreign did Ritter at age 35 start out in Zurich in technical, not vocational, high school. In public works, and third, his individual Culmann's own spirit of independent 1865 he entered the Polytechnical School research leading to the development of thinking and critical judgment, ironically in Zurich, graduating first in a class of visual methods for structural analysis. in the form of respectful criticism of 20 civil engineers in 1868. Culmann himself. The Culmann tradition, within which After a year working on a railroad line in Maillart and Ammann studied, required In his second writing of Culmann, a brief Hungary, he was invited by Culmann to more than just a gifted founding 1903 biographical sketch for the German be one of his assistants. After another allowing professor; it demanded a successor to carry biographical dictionary, Ritter near the year he qualified as a Privatdozent forward teaching in the same vein. It is end of his own career reflected on him to run classes both on structural not too much to say that the second Culmann's influence in the following way mechanics to architects and on practical individual is crucial to the establishment ([8], p. 573): "Culmann's method of geometry to students preparing to enter ofa tradition, as opposed to the enshrine- teaching was not easy to follow. Because the school. Also, he began to help ment of a master. Culmann, Maillart of his lively temperament his thoughts students who were having trouble, as and Ammann were fortunate that the often ran ahead of his words. Also his many did, following Culmann's lectures. professor chosen in 1882 to succeed books lacked in many ways the desirable Then, in 1873, Ritter was called to Riga to the founder was Karl Wilhelm Ritler clarity and thoroughness." become a regular professor, a highly unusual (1847-1906). But he followed that rather severe judgment honor for an engineer only 26 years Although not as well known as some of by an image which perhaps because of age. The polytechnical school in Riga his German contemporaries, a good case it follows a negative critique gains in both had been opened only in 1862 and had can be made for calling Ritter the out- credibility and suitability: "He was like quickly become a major institute in 96 CHRISTIAN MENN Ingénieurs et architectes suisses n" 7 26 mars 1987 Russia thanks mainly to its German-language appeared in 1886. One further writing of 1898 the University of Zurich awarded base and to its location so near to great significance also appeared before him an honorary Doctor's degree. Ritter other Western European centers of 1890, a long article which appeared in the was much honored and had great talents, industry and education. Because of first six issues of the new Swiss Building but his susceptibility to deep feelings Culmann's strong international reputation Journal (Schweizerische Bauzeitung SBZ) almost depressions, seem to have been even by 1862, the new school invited one of 1883, on the calculations for stiffened connected with the onset of a nervous of his former assistants Henri Bessard arches and stiffened suspension bridges. agitation that began to make work difficult (1837-1873) to be its first professor ofcivil This article serves to emphasize the wide for him after the turn of the century. engineering. Unfortunately, in the spring compass of Ritter's research and In the spring of 1902, the sickness forced of 1873, Bessard fell from a bridge on a especially his deep inquiry into modern him to give up work and plunged him inspection trip and died. The Riga school bridge forms. into deep melancholy. He went from sent back to Culmann for another assistant This inquiry included a three-month trip Locarno, to Albisbrunn, and to Spiez for and he warmly recommended Ritter. to the United States in 1893 to visit the rest. Finally in the spring and summer of In Riga, Ritter had a fine opportunity to Chicago World's Fair and to study American 1904 he taught again but the effort was develop new teaching ideas, to work on bridges. In 1895, Ritter's book, The too demanding. He went into a sanatorium practical problems arising in the rapidly Bridges ofthe United States, appeared and in Küssnacht until March 1905. He industrializing city of Riga, and to write. his lectures in 1893-1894 were greatly then moved to the Asyl Remismühle He quickly became head of the Civil enlivened as a result of this tour [13]. where he died on October 18, 1906. Engineering Department and editor of Meanwhile, Ritter did a wide variety of Ritter's death concluded a half-century the newly-founded engineering journal, consulting work as well as study the full- tradition ofstructural engineering education Die Rigasche Industriezeitung, in which scale load testing of completed bridges. in Zurich which was to produce over many of his early writings appeared. In 1885 he became a member of the the next half century at least two men Between 1873 and 1882 he matured as a major Zurich city building council. He was by who can be called the two most outstanding European engineering academic and the late 1880s so well known beyond bridge designers of the 20th century; when the call came from Zurich he was Switzerland that in 1889 he received an one in concrete and one in steel. Their ready, not as an assistant is ready to move offer from the prestigious Technical general interest in bridges and much of into his master's office, but as Culmann University in Munich, which he declined their later works with special forms can himself was ready in 1855, an independent "out of love for the Polytechnical School be easily traced to the Zurich tradition mind ready to take on major and for his country" ([10], p. 516). The and especially to the ideas of Wilhelm responsibilities but in what was by then a well Federal Council, out of gratitude, granted Ritter. developed school. him a lifetime appointment and the Ritter would later reflect that his first city of Zurich him and his gave family Ideas of Ritter years back in Zurich were the best of his citizenship in that city as a token of their life ([10], p. 513): "The scholarly thanks. These unusual honors for activity were Ritter's ideas, like those of Culmann of colleagues spurred me on to a an professor, and my great engineering they followed from local field experience, extent. Scientific study was seemed the in highly to express nation's pride from international study travel, and from respected here and found its their school and the way quickly new place it now individual research which emphasized into practice, while I was into held in circles. looking European visual methods of analysis. These three questions of structural analysis more and Ritter made a deep personal impression components of a career permitted, in more each year." on his students and associates. He was a more general terms, a type of teaching Culmann's field of teaching had so known his for family man, by students which included first hand experience broadened by 1881 that he was actually his His wife a hospitality. was American, with structures in the natural environment, replaced by two professors : Ritter for Miss Jacoby from Boston, whom he met a wide variety of structural images Graphic Statics and Bridges and Eduard a visit home from in the on Riga summer drawn from the results of building in Gerlich (1836-1904), who had been chief of 1874. They had five children in whose different social settings, and a type of engineer for the construction of the education important early Ritter played an scholarship in which the teacher alone Gotthard line, for the fields of Railroad role, including personally teaching worked out a new approach to older Engineering and Management [11]. his sons how do to engineering drawing. ideas. This new approach needed to be Ritter's work therefore focused more on Graphics even in the home. one that rose directly from design practice developing the applications to Ritter sensitive Personally, possessed but was systematic and general Culmann's graphic statics, feelings. When his friends on studying one of good enough to be of basic value to students structural problems in bridge design, and died from a fall at the Sanetsch Ritter pass, throughout their entire careers. Such was on a wide of practical questions for such mountain range gave up high hiking the continuation of the Culmann tradition which his advice was sought. His first and his him in a state grief kept of sorrow through Ritter and such was the major books were the two of his for weeks end. such times his main parts on At intellectual context within which Maillart The Applications of Graphic Statics, solace was in music. He was a fine pianist and Ammann learned structural Internal Stresses in Beams, in 1888 and and could music play melancholy with engineering between 1890-1894 and Trusses in 1890. The last volumes at crisis. two great feeling moments of 1898-1902, respectively. were Continuous Beams in 1900 and He was also deeply religious, a devoted To look in more detail at that context I Arches in 1906. The last one he was too member of the Methodist church. At the shall take up three of Ritter's writings to sick to complete so his son, engineer same time, he understood and respected give a sense of his approach: the first, Hugo Ritter, completed it for him during the beliefs of others. He was noted for his about the value of first-hand field experience, the last of his life [12]. year fairness and for his unwillingness to the second, about international In addition, Wilhelm Ritler wrote three speak against anyone behind his back. He study, and the third, demonstrating other short books before 1890. One on liked to say that he worked for knowledge Ritter's research insight into structural continuous beams came out in 1871 and and not for money. behavior. was Ritter's work under Culmann. This In 1887 he was made the Director of the On April 9, 1892, there appeared in the work was revised and reprinted in 1883 Polytechnical School, just as had Bauzeitung a short note which argued and translated into French in 1886. A Culmann 15 years before, and he remained in that full-scale load tests on steel bridges second small book appeared in 1879 on this position until 1891. Between 1896 and were not only worthless but possibly tunnel vaulting which was translated into 1898 he was President ofthe Zurich Natural even misleading. A lively debate Italian in 1880. A third book on arches Science Research Organization and in followed, ending on July 9 with a brief 97 CHRISTIAN MENN Ingénieurs et architectes suisses n" 7 26 mars 1987 report [14] of the opinion of Professor vide, as consultant in 1901, a satisfactory withdrawn in favor of some utilitarian Franz Engesser from Karlsruhe who mathematical analysis. Thus he directed principles." "protested against the situation in which and interpreted the full-scale load test He went on to note that American load tests even on little structures of which proved the validity of Maillart's tendencies to avoid complex analyses and to 2 meter span will be widely made, simple calculations. It seems equally true think only of utility rather than beauty because such experiences are not only that no such bridges were built in had worked against the frequent use of useless but also are actually detrimental Germany during this period at least in part arches, a point he illustrated with the since through them time, energy, and because of the unwillingness of persons Eads bridge of 1874 and its three-arch money are squandered and operations like Engesser to abandon their central spans across the Mississippi at St. Louis. are blocked and endangered." reliance on mathematical calculations. Ritter noted that because of its many In the next issue, Ritter wrote a detailed The second aspect of Ritter's ideas, the difficulties, including very high cost, the defense of what had become the common one relating more to widening of the bridge did not encourage Americans to Swiss practice of full-scale load testing engineer's horizons, was illustrated by use such arches. Ritter did, however, [15]. In effect he presented a Swiss position his trip to the United States, as reported show the much less costly and still striking at odds with a German one. In a in his 1895 book and in numerous articles 1889 Washington bridge over the Harlem broader sense, he reflected a more in the Bauzeitung. These articles showed river in New York with its two-arch pragmatic and balanced attitude towards Ritter's breadth of view. They ranged spans. Also included was a concise summary understanding structural behavior from sketches of the Chicago Columbian of American suspension bridges against a more theoretical and dogmatic Exposition itself, to reports on Chicago ending with a sketch of Lindenthal's approach which emphasized analysis. It bascule bridges, to a study on engineering proposal for a Hudson river crossing ([13], would be wrong to overgeneralize this education in the United States, and p. 63). This is the last text figure and a distinction ; but in so far as one can finally to a report on bridges over the fittingly prophetic one, since one ofRitter's characterize national attitudes, the Swiss whole country [16]. last students, Othmar Ammann, would tended to be less certain of the emerging The book itself was devoted to wood and go to the United States and begin his mathematical theories in engineering metal bridges; the heading "Eiserne spectacular bridge career by designing and more open to the need for visual Brücken" includes both iron and steel the George Washington bridge that demonstrations of performance. The bridges even though the proper translation would, 36 years later, cross that river. difference between Engesser, a of Eiserne is iron and the word for As every bridge designer knows, however, distinguished German professor, and Ritter on steel is Stahl. overall form means nothing if the this bridge question was primarily a Ritter was surprised that so little on details are not well done. All the pieces difference in attitude and philosophy. bridges was exhibited at the Chicago must fit together and none must be What Ritter presented was the viewpoint World's Fair. As he reported, "with all its structurally weak. To the watch-making Swiss, that public works set in a difficult expanse and plentifulness, the Fair details are an esthetic part of design environment are always built within uncertainty. offered relatively little information on because they require great care. About There was no way in the late 19th bridge structures in the United States" one third of the entire text and illustrations century to predict mathematically the ([13], p. 3). Ritter, knowing the spectacular in Ritter's book were given over to a full response of a public structure ; and in bridge works completed in the United detailed review of joints, connections, spite of many new mathematical theories, States since the Civil War, assumed that eyebars, and rivets. Many of the drawings detailed text books, and immense such world leadership would be proudly are elegant and Ritter criticized others as computer power, the same condition displayed. Instead, the Fair represented not elegant. He proceeded from overall exists in the late 20th century. The much more the American romance with form to detail and emphasized both. validity of any work rests, as Ritter the machine that would so startle Henry The final part of his book consisted of emphasized near the end of his article, Adams (1838-1918) and set off his 12 plates each giving the full details with "the probing expert" who must give contemplation of its potentially destructive and overall form for individual bridges: "a reliable judgment." In short, it always force [17]. three wooden bridges and the rest metal rests finally on the judgment of a person For Ritter, the structures were the main bridges, of which one was a plate-girder and not on the solution to an equation. consideration and to examine them he bridge, one a suspension bridge, one a the and the others truss Thus, for Ritter the first-hand field had to travel throughout country. cantilever, bridges. experience so useful to the engineer was to be The book said little about his travels but Overall Ritter's book was a unique work gained partly through full-scale load did give a clear picture of what interested in the Culmann tradition, and Maillart's tests. Unlike Culmann, he did not have him: the wide variety of overall forms, notes reflected his teacher's international extensive field experience himself; his the broad use of certain non-European study. Almost certainly this American early brilliance led him too soon into a details, and in relatively complete and focus stimulated Ammann as well professor's chair for that. But by way of a elegant plates, a few bridge plans. In and helped him decide to make his career satisfactory replacement he put high short, a broad view of forms, a description in the United States. But Ritter's writings value on the experience he got from of new details, and the relatively were far more significant than the two those load tests. This tradition played a complete technical picture of a few preceding examples might imply. A central role in Maillart's career because it selected bridges. This is just the combination defense of load testing and a report on a allowed him to prove to the profession of insights that most intrigues the study trip are very different from the type not only that his radically slender designs design-oriented student. Such a student of solitary research needed for the were safe, but even more importantly, is genuinely excited to see the wide visual numerous papers and books that Ritter that his radically simple methods of variety of forms that have already been published during his lifetime. One analysis were correct. It is not too much to used to solve what is essentially the same example of such a piece of research state that Ritter's defense of such field set of problems. illustrates the high quality of his mind as experiences, against the German objections, Ritter did not hesitate to introduce well as his taste for simplicity and allowed structures to be built esthetic judgments as, for example, in elegance in calculations. for which complex and so-called more describing the high bridge built in 1888- In 1877 he had first written about rigorous analyses would have obscured 1889 over the Mississipi River at St. Paul stiffened suspension bridges. Then in 1883 the design potentials. ([13], p. 52). "The structure, in spite of its he published a major article expanding Ritter applied this attitude directly to extraordinary size, makes a rather insipid that subject and introducing advanced Maillart's first major design, the Zuoz impression; it leads us to realize that ideas on the analysis for both suspension bridge, for which Ritter could not pro¬ esthetic ideas must have been fully bridges and arch bridges [18]. CHRISTIAN MENN Ingénieurs et architectes suisses n" 7 26 mars 1987 This article probably represents as clear a study of suspension bridge design as any Bibliography [13] W.: Der Brückenbau in den in the 19th century. It did not develop the Ritter, [I] Billington, D. : Robert Maillart's Vereinigten Staaten Amerikas, Albert Josef deflection theory, credited to Bridges : TheAn ofEngineering, Princeton Raustein, Zurich, 1895, 66 pages. Melan and first published 5 years after University Press, Princeton, N. J., [•14] "Über den Wert der Belastungspro¬ Ritter's article [19]. Its historical interest 1979, pp. 7-8, 11-12, 16, 22, 24. ben eiserner Brücken," SBZ, Vol. 20, [2] Stüssi, F. : Othmar H. Ammann : Sein No. 2, p. 12, July 9, 1982. today is not for its presentation of a new Beitrag zur Entwicklung des Brückenbaus, [15] Ritter, W. : "Über den Werl der analysis but rather for its elegant simplicity, Birkhauser Verlag, Basel, 1974, Belastungsproben eiserner Brükken," its design ideas, and its essential pp. 36-38, 85. SBZ, Vol. 20, No. 3, pp. 14-18, July 16, correctness. It is correct in the sense that for [3] Oechsli, W. : History of Switzerland : 1892. 1499-1914, Cambridge, 1922, The articles the scale of the bridge illustrated in his England, [16] following are by Wilhelm p. 402. Ritter: "Skizzen von der Chicagoer paper even today Ritter's method of [4] Oechsli, W.: Geschichte der Gründung Ausstellung," SBZ, Vol. 22, Nos. 11,12, analysis would be a reasonable basis for des Eidg. Polytechnikums mit einer 13, 14, 15, pp. 79-82, 91, 100-101, Übersicht September design; the deflection theory became seiner Entwicklung 1855- 23, 30, October 14, 1893 ; "Die 1905, Frauenfeld, 1905, pp. 35-121. See neue Falten-Zugbrücke in Chicago," important only for longer spans. especially the role of Alfred Escher in SBZ, Vol. 22, No. 12, p. 86, September In the late 20th century it has become bringing the school to Zurich, p. 65. 30,1893. "Das technische Unterrichtswesen common practice to read only the most [5] See Goldschmidt, R.,: Die Stadi der Vereinigten Staaten Amerikas," recent works on any technical subject, Karlsruhe, Karlsruhe, 1915, pp. 300- SBZ, Vol. 24, Nos. 2 and 3, p. 10- 306. Actually Karlsruhe was not designated 11, 21-23, July 14 and 21, 1984. The the earlier ones being taken as outdated, a polytechnical school until report following is a summary of like old But old machinery. like some 1885 ; from its founding in 1825 until Ritter's book but he appears not to have bridges a few early articles on structural the mid 1830s it was in part a secondary written it: "Der Brückenbau in den analysis and design retain their usefulness school. By the late 1830s there Vereinigten Staaten Amerikas," SBZ, was an Engineering Department. Vol. 24, No. 24, 165-170, Dec. 14, when they reflect the mind of a pp. Probably by 1860 Zurich had a more fully 1894. masterful teacher. Such is Cross' 1932 Hardy developed polytechnical school than [17] Adams, H. : The Education of Henry article on moment distribution [20] and Karlsruhe. Adams, Modern Library, New York, [6] C. : Bau der hölzer¬ 1931, such was Ritter's 1883 article on suspension Culmann, "Der (originally published in 1918). Brücken in den Staaten W. : "Statische bridges. nen Vereinigten [18] Ritter, Berechnung von Nordamerika" and "Der Bau der Versteifungsfachwerke der The paper begins with a clear statement der eisernen Brücken in England und Hangebrücken," SBZ, Vol. 1, Nos. 1,2,3,4, of intention. Ritter referred to his 1877 Amerika," Allgemeine Bauzeitung, 5, 6, pp. 6-7, 14, 19-21, 23-25, 31-33, paper, identified its omissions and stated Vienna, Vol. 16 (1851): 69-129 and 36-38," Jan. 6, 13, 20, 27, Feb. 3, 10, Vol. 17 163-222. 1883. that "the following development has the (1952): [7] Culmann, C. : Die Graphische Statik, [19] Steinmann, D. B. : A Practical Treatise goal of making up for the earlier Zurich, 1866. on Suspension Bridges: Their Design, omissions; at the same time the essential [8] Ritter, W. : "Karl Culmann," Allgeme¬ Construction, and Erection, John thing will be to present that earlier work ine Deutsche Biographie, König. Wiley & Sons, Inc., New York, 2nd Akademie der Wissenschaften, 1903, Ed., 1929, p. 246. in as concise a as possible for the way reprinted by Duncker and Humblot, [20] Cross, Hardy: "Analysis of Continu¬ is reader who unfamilar with it." Berlin, 1971, Vol. 47, pp. 571-574. ous Frames by Distributing Fixed- The paper is thus self-contained and written [9] Ritter, W. : Anwendungen der Gra¬ End Moments," Transactions of the for a broad not a narrowly specialized phischen Statik nach Professor Dr. C. ASCE, Vol. 96 (1932) pp. 1-10 with 147 1, Die audience. Culmann, Part im Inneren eines pages of discussion. Balkens wirkenden Kräfte, Zurich, [21] Ammann, O. H.: "Present Status of He next emphasized that since the theory 1888, page V, Vorwort. Design of Suspension Bridges with of elasticity must be used, complicated [10] Thurnheer, G. : "Wilhelm Ritter," Respect to Dynamic Wind Action," formulations result and thus "one is Vierteljahrsschrift der zürcherischen Journal of Boston Society of Civil Naturforschenden Gesellschaft, Zurich, Engineers, Vol. 40, No. 3, July (953, p. 242. compelled to make simplifying assumption." Vol. 1, 1906, p. 510. [22] Ritter, W. and Tetmajer: "Der In fact his whole presentation avoids [II] Meister, E. : "Professor Dr. W. Rit¬ Bericht der Eidgenössischen Experten ter," Memorial in the SBZ, Vol. 48, No. über die Münchensteiner Brük- even calculus and yet it presents a sound 17, pp. 206-208, October 27, 1906. ken-Katastrophe," SBZ, Vol. 18, analysis. [12] Ritter, W. : Anwendungen der Gra¬ No. 18, pp. 114-115, Oct. 31, 1891. This He then gives the theory of the beam- phischen Statik nach Professor Dr. introductory report and a series of later stiffened arch in just the simple, elegant C. Culmann : parts to the main report led to the and practical form that Maillart would Part 1, Die im Inneren eines Balkens Federal Law of Aug. 19,1892 concerning wirkenden Kräfte, Meyer & Zeller, Zurich, the calculations and testing for 40 later to his use years create strikingly 1888, 148 pages. metal bridges and roofs for the Railway, thin deck-stiffened arch bridges. Indeed, Part 2, Das Fachwerk, Meyer & Zeller, see Meister, op. cit, p. CIX. Ritter not only gives a simplified analysis Zurich, 1890, 229 pages. Ritter's co-authored reports of 1901 and Part 3, Der kontinuierliche 1902 the failure a method but he also considers the design Balken, on of concrete Albert Raustein, Zurich, 1900, building in Basel led directly to the "the stiffer the beam and implications: 270 pages. formation of a Commission to prepare the more flexible the arch the greater the Part 4, Der Bogen, Albert Raustein, a Swiss building code for reinforced bending moment in the beam and the Zurich, 1906, 269 pages. concrete. less in the arch." Taking such simple ideas, he next applies them to the suspension bridge where the ratio of the horizontal truss stiffness to stiffness index for modern suspension basis for preliminary design as long as the the cable stiffness determines how much bridges [21]. final design is analyzed by the more exact bending goes into the truss. Ritter Ritter's article is liberally illustrated with procedure he has already given. At the developed these stiffnesses by calculating diagrams, some drawing on graphic statics, end he gives a review of practical separately the vertical deflections and his equations are always simple. problems, such as construction sequence and of the cable and of the stiffening truss Where they involve more than a few trusses of variable section, and how they under unit loadings, setting the deflections terms, he puts non-dimensional terms in relate to the design. equal because the suspenders tables for easier use. In summary Ritter was doing research tie the two parts together, and thus Near the end he gives a fully worked-out but writing the results for the designer determining the load carried by the truss and example for an actual 57 meter span not for other researchers. He was seeking that carried by the cable. This is just the suspension footbridge in Switzerland. to clarify the behavior of structures type of simple idea that Ammann would Following that comes a section on rather than to develop methods of analysis. use about 60 years later to develop his approximations that provide a reasonable Finally he used examples of actual 99 CHRISTIAN MENN Ingenieurs et architectes suisses n" 7 26 mars 1987 structures with which to illustrate formulations to specific applications. He Acknowledgments numerically his ideas and he considered thus stood at conjunctions and let the construction questions along with those students pass on. He did not become in The research leading to this paper is of analysis. any way either a competitor to them by supported by grants from the National for the One further characteristic of Ritter's was having a design office or a master ofthem Endowment Humanities (RO- 27518-78-24) and the National Science his and for by a modesty concern clarifying having design ideology. Foundation (SOC77-06609-A01) for the and simplifying. In a footnote Ritter He was the essential link between the writing of a biography of Robert Maillart. observed that Professor A. Ritter (no awkward and sometime unclear theories This present paper is taken from the relationship) in a recent book has given of Culmann and the elegant clarity of the completed manuscript for the first volume of that biography. The writer is grateful to essentially the same suspension bridge late works of Maillart and Ammann. He the staff of the librairies at Princeton theory but that it was not clearly enough was an interpreter of technical events : to University and the Federal Technical presented to be easily useful. his students through his lectures, to the Institute in Zurich as well as to Hans Hauri An old metaphor strikes one as useful in profession through his writings, and to and Tom Peters ofthat Institute. For the overall biographical study of Maillart the describing Ritter's influence. In his the public officials his detailed through writer is deeply indebted to the collaboration approach to his students' education, he consultant studies that led to Swiss codes with his daughter, Marie-Claire stands very much as a bridge does in its for both metal structures and works of Blumer-Maillart and with her husband environment. As an educator, carrying reinforced concrete [22]. Edouard Blumer. students for only small fractions of their Ritter's name has nearly been lost and his lives, he was yet an essential link between style of teaching and research has been their past inborn talents and their out of fashion for years, but he touched with field experience, wide knowledge of relatively long future careers. As a teacher, students, of whom Maillart and international structures, and solitary he communicated the recent tradition of Ammann were only the most spectacular individual writing that interprets new his country and of his profession through examples. ideas for the profession in a practical and the specific objects about which he It is thus that the occasion of honoring clear manner. The Culmann-Ritter tradition lectured. Finally, as a writer, he took great designers like Maillart and cannot be duplicated but it can scientific formulations and shaped them Ammann has led for once to the question stimulate education for the future. with as little complexity as possible into of how education influences practice. simple clear ideas so that his students With these two it seems clear that would see better the design potentials. Wilhelm Ritter played a significant role. Adresse de l'auteur: He was not a designer, although he More generally what the example of David P. Billington. F. ASCE taught from designs; he was not a public Ritter may stand for is a rethinking of Professor Department of civil Engineering, official, although he taught public works ; education in structural engineering Princeton University he was not a natural scientist, although which considers the need for teaching Princeton. New Jersey (USA) he worked with science to reduce general and research that includes close contact

dans le l'environnement marin, les chocs probables Comportement temps de bateaux, le comportement des et aptitude au service fondations et du tablier à long terme. L'ingénieur attribue souvent le fluage au béton et la relaxation à l'acier (de précontrainte). Or, fluage et relaxation sont des phénomènes liés de sorte qu'il y a également relaxation le béton et fluage par Renaud Favre, Lausanne pour pour l'acier. Rappelons que la fonction relaxation r représente l'évolution de la contrainte intervenant dans un projet sont à revoir. dans le temps sous déformation unitaire 1. Introduction Si on prend à titre d'exemple le nouveau constante e0 1 (fig. 1) : pont qui va relier La Rochelle à l'île de Ré L'étude et la vérification de l'aptitude au Aa, \ a(t,t0) en France, au service ne sera 1 + service sont devenues primordiales dans l'aptitude r(t,t0) très modestement influencée les la conception des structures. Comme le que par charges concentrées du trafic prescrites La solution de l'équation dite béton subit des déformations à long intégrale par les normes, mais beaucoup plus de Volterra terme par suite de son retrait et de son par fluage, son comportement dans le temps doit être connu, ou du moins estimé, et introduit dans les raisonnements qui permettent de réaliser un bon projet d'ouvrages en béton armé ou précontraint. REPONSE

1 i » Il est évident que la prise en compte du SOLLICITATION comportement dans le temps du béton se heurte à bien des réticences de la de part <-)A(Tr l'ingénieur de la pratique. Il se voit confronté avec suffisamment de problèmes dans l'accomplissement de son dur mais passionnant métier pour ne pas être très enclin à de nouvelles démarches. Il lui sera néanmoins utile de réfléchir à la pondération de ses efforts. Souvent, il y a en effet lieu de réduire la minutie de certaines vérifications au profit d'autres. Fig. I. — Relaxation. Souvent, les critères à la base des choix 100