Eminent Structural Engineer: Dr Fritz Leonhardt (1909–1999)
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Eminent Structural Engineer: Dr Fritz Leonhardt (1909–1999) Reiner Saul, Dr, Eng. E. h.; Holger S. Svensson, Eng.; Hans-Peter Andrä, Dr, Eng.; Leonhardt, Andrä und Partner, Beratende Ingenieure VBI, GmbH, Stuttgart, Germany Prologue to the construction – tests on the cable clamps, the friction of the abutments, The most difficult part while writing aerodynamic stability etc. this article was to compile 90 years of an exceptionally creative life into In 1948, Leonhardt designed, again in a concise text. The authors apologise Cologne, a continuous steel box girder the absence of some important names with a main span of 184,5 m and slen- within this text, particularly those who derness ratios of L/56 in the span and played an important role in Dr Leon- L/24 over the piers. Also in 1948, Leon- hardt’s life. hardt designed with Willi Baur his first bridge from prestressed concrete with a span of 30 m, prestressed by concen- Brief CV trated tendons. In 1964, Leonhardt and Baur designed 12.07.1907 Born in Stuttgart a 480 m long bridge with spans of 90 m 1927–1931 Student of Civil Engi- across the Caroni River in Venezuela. neering at the Stuttgart The bridge was built completely be- University (Emil Mörsch, hind the abutment and than launched, Otto Graf) a world novelty for concrete bridges. 1932–1933 Graduate studies at the From this the incremental launching Purdue Universtiy bridges developed, built behind the abutments in length of about 25 m and 1934–1938 Bridge Engineer for Fig. 1: Dr Fritz Leonhardt (1999) Highway Bridges in Stu- then launched. ttgart, Berlin and Co- In the 1980s Leonhardt designed with logne Zellner prestressed concrete bridges Work with Karl Schä- He established – at a time when the for Germany’s new high speed railway chterle and Paul Bonatz word was yet unkown – a management lines, e.g. two bridges across the Main 1936 Marriage with Liselotte buy out which secured the continuity River. Klein of the firm. At this time, Leonhardt and Saul de- 1938 Doctor of Engineering at signed record breaking longspan steel the Stuttgart University Bridges composite bridges: a combined high- 1938–1941 Chief Engineer for the way-railway bridge across the Caroni At the age of 28 years, Leonhardt was suspension bridge Co- River, Venezuela (main span 213,75 m) appointed by the German Highway logne-Rodenkirchen and a railway bridge across the Main Administration as Chief Engineer for 1939 Consulting Engineer River (L = 208 m). Both bridges have the construction of a suspension bridge haunched continuous girders and a bot- 1954 Consulting Firm Leon- across river Rhine at Cologne with a tom slab from concrete over the piers. hardt und Andrä main span of 378 m, Fig. 2. Leonhardt 1958–1974 Professor at the Stuttgart managed to build the bridge within Bridge engineer Fritz Leonhardt is, University, Institute for three years and performed – parallel nevertheless, best known world wide Concrete Structures for his theoretical studies and his de- 1967–1969 President of the Stuttgart signs of cable-stayed bridges. Starting University in 1955 with the design of the North 12.07.1999 Award of the First Fritz Bridge across the Rhine River in Düs- Leonhardt Prize seldorf, Leonhardt and LAP have 30.12.1999 Passed away in Stuttgart worked on more than 140 bridges of this type all over the world, some ex- amples are: The Design Engineer – The Zárate-Brazo Largo Bridges across the Paraná/Argentina, the General world’s fi rst cable-stayed bridge for In 1939 Dr Leonhardt (Fig. 1) estab- Fig. 2: Suspension Bridge across River highway and full railway. lished his design firm, which later be- Rhine at Köln, Germany (1938–1941), – The Pasco-Kennewick Bridge ac- came Leonhardt, Andrä und Partner. mainspan 378 m ross the Columbia River, USA, the 94 Eminent Structural Engineer Structural Engineering International 1/2007 xx252.indd252.indd 9944 55/26/70/26/70 3:17:403:17:40 PPMM Otto, Lingwitz and Argyris, Leonhardt Following the design of the roofs for and his team headed by Jörg Schlaich the Olympics 1972 he established an developed since mid 1968 the structural Investigation Group dedicated to all concept and the detailing of the roofs aspects of lightweight structures in- which were tendered a year later and cluding comparison with and adapta- finished one year ahead of the Olym- tion of natural structures. pics. The Author The Professor, Inventor and Researcher Dr Leonhardt has written numerous papers and was the author and co-au- The Professor thor of 22 books. The most important books were: Leonhardt taught ‘Concrete Struc- Fig. 3: Television towers, from left to right: tures’ at the Stuttgart University from – Spannbeton für die Praxis (Pre- Stuttgart 1956, height 216 m, diameter of 1958 to 1974; his lectures have been stressed Concrete …). Co-authors pulpit 15 m; Hamburg 1967; Frankfurt condensed, with the aid of Eduard – Wolfhardt Andrä and Willi Baur. 1978 Mönnig, in his famous “Red Books”. – Ingenieurbau – Bauingenieure ge- stalten die Umwelt (Structural En- world’s fi rst cable-stayed bridge gineering – Civil Engineers create with a deck from prestressed precast The Inventor the environment). concrete. Leonhardt was never satisfied with the – Vorlesungen über Massivbau (Lec- “State of the Art”, but always tried to tures on Concrete), Volume 1 to 6. improve proven design and construc- – Bridges – Aesthetics and Design. Television Towers tion procedures. The most important – Türme aller Zeiten – aller Kulturen. In 1953, the South German Broadcast- of these improvements were: Co-author – Erwin Heinle (Towers ing Corporation (SDR) planned to of all times and all cultures). build a 200 m high guyed lattice mast – Aerodynamically stable suspension on a hill, south of Stuttgart. bridges with mono-cable. – Neopotand tefl on sliding bearings The homo politicus Leonhardt developed as an alternative (Wolfhardt Andrä). – a concrete mast with lookout plat- – Parallel wire cables with High AM Dr Leonhardt never joined a political forms, restaurants and broadcasting anchorage (Wolfhardt Andrä). party but he was always interested in facilities at its top; and he convinced – Perfobond strips (Wolfhardt Andrä politics and criticised developments the Lord Mayor of Stuttgart and the + Hans-Peter Andrä). which he judged to be wrong. Director of the SDR to build this al- – Leoba prestressing system and in- He was for instance against the rear- ternative. Construction started in June cremental launching of prestressed mament of Germany because he had 1954 and opening took place in Feb- concrete bridges (Willi Baur). ruary 1956. This tower Fig. 3 marked experienced the horrors of World a break-through in the design of tele- War II and felt that money might be vision towers – not only in Germany, The Researcher better spent than by weapons. where every major city asked for its The research work of Dr Leonhardt He critizised his own profession, archi- own, tower, but also around the world. was basically related – but not limited tects and investors for their careless – to concrete structures. Some exam- treatment of nature; in 1975 he gave ples are: Cable-Net Roofs a lecture on “Bauen als Umweltzer- störung” (Building as destruction of – “Stuttgarter Schubversuche” (Stut- In 1967 Behnisch and Partner won the the environment) which justified his tgart Shear Tests) together with design competition for the Olympics point of view. 1972 in Munich. The indoor pool, the René Walther which resulted in gymnasium, the stadium and the con- codes on the dimensioning for shear Last but not least, he was very ac- nections between them were covered and torsion. tive in civil engineering societies like by extremely complex tentlike roofs, – Distribution of cracks in concrete IABSE which he supported in 1976 by Fig. 4. Together with experts like Frei under tension with Horst Falkner, a proclamation “Werden Sie Mitglied which was the basis for jointless der Internationalen Vereinigung für structures. Brückenbau und Hochbau” (Become – Stud Shear strips as reinforcement a member of the IABSE). against punching, with Hans-Peter Andrä, which allowed to omit the ceiling joists. Dr Leonhardt – Private After the collapse of the Tacoma Nar- Although he never joined a sports club rows Bridge Leonhardt started ex- Dr Leonhardt was very sportive, fol- perimental and analytical research on lowing the wisdom: “Mens sana in cor- wind induced vibrations of suspen- pore sano” (A sound mind in a sound sion bridges which he presented at the body). In 1929 he crossed the Alps by Fig. 4: Tentlike roofs for the Olympic IABSE Conference in Rio de Janeiro hiking. This activity was so important Games in Munich (1968–1971) in 1964. to him that he later wrote the article Structural Engineering International 1/2007 Eminent Structural Engineer 95 xx252.indd252.indd 9955 55/26/70/26/70 3:17:453:17:45 PPMM “Vom Wert des Wanderns und der for outstanding achievements in struc- heilsamen Wirkung der Natur” (On tural engineering. the value of hiking and the salutary ef- The first FLP was awarded on 12th fects of nature). July, 1999 to Dr Michel Virlogeux Whenever he visited a site if his sched- amidst 500 jubilee-guests from all over ule permitted, he always travelled a the world, Fig. 5. step further. His first and longest travel was in 1957 – a three month 15000 km trip from Buenos Aires to Lima, Peru. Epilogue Dr Leonhardt was also an avid music Fig. 5: Award of the First Fritz Leonhardt The authors joined Leonhardt, Andrä lover. Guided by his wife he attended Prize to Dr Michel Virlogeux und Partner between 1968 and 1977 classical concerts regularly. and have worked with Dr Leonhardt for three decades. All who were lucky Honours and Distinctions Siemens-Ring; Honorary Medal to spend such a great part of their pro- Emil Mörsch; Grashof Memorial fessional life with him are grateful for The eminent work of Prof.