1、Ned H. Burns Symposium on Historic Innovations in Prestressed Concrete Editors Bruce W. Russell Shawn P. Gross American Concrete Institute“ SP-231 Aduuncing corrczte knowlea his conversation about his parents and family history rung true as Bruce thought about his own parents and family. His anecdot
2、es about his childhood linked to Bruce?s own memories about childhood. He waited tables in college to earn spending money as did Bruce. Both their families were rooted in rural Southwestern Arkansas or southeastern Oklahoma. But more than that, the conversation was free flowing, and earnest without
3、pretension. Dr. Burns wanted to know about Bruce?s family, about Candi and about her parents. Do you have children? Where is your wife from? How did you meet? From the very first conversation, it was clear to Bruce that Dr. Bums cared about the person more than anything else. Shawn?s story fittingly
4、 evolves from a conversation that he had with Dr. Bums at the AC1 Convention in San Diego, in the spring of 2000. Eighteen months after completing his doctorate at UT-Austin under Ned?s supervision, Shawn was a young faculty member at Villanova facing all of the standard challenges and pressures tha
5、t young faculty face- developing course notes, laboratory facilities, research programs, and so on. As he always did with former students, Dr. Burns was inquiring as to how things were going. Shawn iV explained that things were going well, and then started to tell Ned about a new project that he was
6、 involved in with one of his courses. Shawn and a colleague had just taken a group of students to Honduras over Spring Break, to work on the construction of a reinforced concrete cross and masonry building structure that the students had been designing in class as their senior design project. The wo
7、rk was being done for Amigos de Jesus-a home for abused and abandoned boys in rural Honduras. As Shawn explained the project, Dr. Burns listened intently, asked questions, and, of course, became genuinely engaged in the conversation. As the conversation ended, Dr. Burns told Shawn that he was proud
8、of his involvement in such a unique project where the students could exercise their technical academic abilities in a way that helps others. He urged Shawn to continue development of the project and even told numerous colleagues and acquaintances about Shawns project. Soon enough, Shawn was being ap
9、proached by others asking for information about the course-all because of the belief that Dr. Burns has in this type of technical service work, and his pride in what his former student was doing. Since that first conversation, Dr. Burns has maintained a strong interest in “The Honduras Project.” Whe
10、n he and Shawn talk about Shawns career at Villanova, it is invariably the first thing that Dr. Burns asks about. Shawn has come to realize that Dr. Bums is still teaching. His interest in the Honduras project is in part Dr. Burns way of characterizing the relative importance of different aspects of
11、 life. He believes in the notion that the most meaningful technical work is that which helps others or meet a societal need. As every former student of Dr. Bums can attest, he encourages all of his students to become engineers who use their technical abilities to “plant trees that they themselves wi
12、ll never sit under.” Somehow we know others experiences are similar to ours. Perhaps it was the day you met Ned Burns, or perhaps it was years later during a conversation or some other encounter when you realized the depth of character and the truly generous nature of Ned Burns. Regardless, Dr. Ned
13、H. Burns has made a lasting impression on many of us, whether colleague, friend, or student. One final word regarding an observation about human nature: there is an expression for it-whether or not a particular person “tends to grow on you.” We are not sure whether the expression is a southern expre
14、ssion or not, but it is meant as an endearing expression of love and friendship that describes a person that becomes more likeable as one spends time around them. Well, we attest to all that Ned Bums is definitely one person that “tends to grow on you.” On behalf of Committee 423, we are pleased to
15、offer this symposium-a celebration of the development of prestressed concrete over the last half-century-as a tribute to a man who played a significant role in that development and, in doing so, has managed to influence so many lives. Bruce K Russell, Chair -Joint ACI/ASCE Committee 423 on Prestress
16、ed Concrete Shawn l? Gross, Secretary -Joint ACIIASCE Committee 423 on Prestressed Concrete November 2005 V vi TABLE OF CONTENTS Preface . iii SP-231-1: Contributions of Gustave Mangel to the Development of Prestressed Concrete I by L.R. Taerwe SP-231-2: Early Applications of Prestressed Concrete in
17、 the United Kingdom 15 by C. Burgoyne SP-231-3: A Historical Review of Prestressed Concrete through Patents 33 by A. Schokker SP-231-4: They Wrote the Book on Prestressed Concrete . 49 by W.N. Marianos, Ir. SP-231-5: Survey of Prestressed/Post-Tensioned Folded Plate Shells for Roof Structures in the
18、 United States: 1950 . 1970 . 65 by K.W. Krarner SP-231-6: The Development of Unbonded Post-Tensioning Tendons used in Parking by C. Walker Structures in Deicing Salt Regions . 87 SP-231-7: PC Beams with Unbonded Tendons: Analysis in Cracked, Uncracked and Ultimate State 105 byA.E. Naarnan SP-231-8:
19、 Rational Determination of Friction Losses in Post-Tensioned Construction 129 by P.R. Gupta . SP-231-9: Effects of Friction and Slip-Back on Stresses in Post-Tensioning Tendons 145 by J.F. Stanton . SP-231-10: A Comparison of Methods for Experimentally Determining Prestress Losses in Pretensioned Pr
20、estressed Concrete Girders . 161 by E. Baran, C.K. Shield, and C.E. French SP-231-11: Innovations in Prestressed Concrete Pavement i81 by D.K. Merritt and B.F. McCullough vi i S P-231-12 : Ad van ces i n Post-Te n s i o n ed Pa rki n g Fa c i li t i es Se ism i c De sign 199 by M. Iqbal SP-231-13: O
21、verview of AC1 440.4R-o4 Document on Prestressing Concrete Structures by R. El-Hacha, T.I. Campbell, and C.W. Dolan with FRPTendons 219 SP-231-14: Variable Thickness Barrel Anchor for CFRP Prestressing Rods 237 by A. Al-Mayah, K. Soudki, and A. Plurntree SP-231-15: Behavior of Pretensioned Type II A
22、ASHTO Girders Constructed with Self- by H.R. Hamilton III, T. Labonte, and M.H. Ansley . Consolidating Concrete 253 . SP-231-16: Professor Ned H. Burns, Ph. D.-Scholar, Educator and Engineer 271 by R.W. Furlong, Ph.D., FACI, HonMASCE viii Contributions of Gustave Magnel to the Development of Prestre
23、ssed Concrete by L.R. Taerwe Svnopsis: In the early 1940s Prof. G. Magnel performed extensive research programmes on real scale prestressed concrete beams at Ghent University (Belgium) in orderto elaborate design methodsforthis new material. He also developed his own anchorage system which was used
24、until the mid 60s in Belgium. He gave many lectures in several countries in which he explained in a simple way the principles of prestressed concrete. He was also instrumental in the design of the first prestressed concrete bridge in the USA, the Walnut Lane Bridge in Philadelphia and he was the aut
25、hor of the first English textbook on prestressed concrete. He designed one of the first PC railway bridges in Europe and the first statically indeterminate PC bridge in the world. In the 1950s many engineers from abroad spent some time in Magnels lab in Ghent to perform research and to get acquainte
26、d with practical realizations. Kevwords: history; Magnel; prestressed concrete 1 2 Taerwe Luc R. Taerwe, FACI, graduated as a civil engineer at Ghent University (Ghent, Belgium) where he also obtained his PhD degree (1 985). He is the present director of the Magnel Laboratory for Concrete Research a
27、nd a full professor of concrete structures at Ghent University. He is a member or chairman of several international technical committees (fib, ACI, IABSE, . . .) dealing with concrete or concrete related topics. He is a recipient of the Robert lHermite Award (RILEM) and the IABSE prize. THE “REINFOR
28、CED CONCRETE“ PERIOD Gustave Magnel (Fig. 1) was born in 1889 and graduated as civil engineer at Ghent University in 19 12. From 191 4 until 19 19 he was employed by a London contractor and in 1919 he started his career at Ghent University. Due to his stay in London, he was not only fluent in French
29、 and Dutch (Flemish) but he was also very fluent in English which would turn out to be extremely useful for his later contacts in North-America. In those days, French was the main language used by engineers in Belgium and also a common language in international contacts within Europe. In 1923 he pub
30、lished his first book “Pratique du calcul du bton arm“ on the design of reinforced concrete. In the same year the Belgian Standards Institute published the first design guidelines for reinforced concrete structures, Magnel being the main contributor. One of his first technical papers dealt with the
31、influence of column stiffness on the stresses in continuous reinforced concrete beams. For Magnel it became clear that for the further development of reinforced concrete it was necessary to perform research, in other words, he needed a laboratory. After many political and financial difficulties he s
32、ucceeded in founding the “Laboratory for Reinforced Concrete“ in 1926, which was located in the basement of a former hotel. In this lab, Magnel had at his disposal a 300 kN universal testing machine and a 3000 kN compression testing machine. About the efforts he has to made to realise his laboratory
33、 and keep it operational he wrote the following : “The ultra-rapid evolution of technology, forces univers institutes to adapt themselves continuously to the actual requirements at the risk of failing in their task. This adaptation can not happen on the initiative of the universi 12 m span) and in E
34、eklo (1945-1946 ; 20 m span). In 1947-1948, a new textile factory was built for the UCO company (Union Cotonnire) in Ghent which had, in those days, the largest roof structure worldwide in prestressed concrete, covering a surface of about 35000 m2 and which is still intact (Fig. 6). One hundred prim
35、ary beams with a span of 20.5 m and 600 secondary beams with a span of 13.7 m were necessary. All these beams were precast at the site at a rate of 3 primary beams and 18 secondary beams per week which required a perfectly organised casting yard. Magnel writes about this achievement : “During the la
36、st 3 to 4 months, this project attracts numerous architects, engineers and contractors both from Belgium and fiom abroad. They want to qualify themselves in the field ofprestressed concrete, firstly in our lab and secondly at the building site! In the same period a hangar for planes at Melsbroek, th
37、e former Brussels airport, was erected. The roof was supported by 17 post-tensioned beams having a total depth of 2.9 m and a mass of 300 tons (Fig. 7). Similarly as in the previous project, the beams were cast on the ground and, after post-tensioning, they were lifted into their final position. In
38、1949, the famous Sclayn bridge over the river Meuse was constructed (Fig. 8). This was the first continuous prestressed concrete bridge in the world (Figs. 9 and 10). With two spans of about 63 m each, the bridge was also the longest prestressed bridge in the world. Due to the variable depth of the
39、girder, the external cable profile was almost straight except for the kink at the central support. At that section, the secondary moment due to prestressing was equal to about 68 YO of the local bending moment due to dead weight. THE WALNUT LANE BRIDGE In 1946, Magnel visited for the first time the
40、United States of America as an “advanced fellow“ of the Belgian-American Educational Foundation, founded by Herbert Hoover in 6 Taerwe 1920. The trip was organized by the late Charles C. Zollman, a former student of Professor Magnel at Ghent University. Later he became Magnels unofficial respresenta
41、tive in the United States, responsible for the detailed arrangements of Magnels several trips to this continent. Mr. Zollmans early consulting services for the design and construction of pretensioning plants throughout the United States, his activities in the field of precast concrete as well as his
42、 many contributions to the PCI, have identified him as a pioneer of this industry in North America. During his first visit to the United States, Magnel lectured on prestressed concrete at several places, a subject almost unknown at that time in that country. Magnel had the rare gift to explain compl
43、ex theories and difficult problems in a simple way and thus captivated large audiences. Two significant effects occurred during Magnels first visit to America which had a direct bearing on the development of prestressed concrete in America and which culminated in the realization of Philadelphias Wal
44、nut Lane Bridge, the first prestressed concrete bridge in the USA (Fig. il). The first event was the fact that Magnel was introduced to the Preload Corporation of New York, which eventually became a sub-contractor for the construction of the Walnut Lane Bridge girders. The second event was the fact
45、that Magnel asked Zollman to translate the French manuscript of his book on prestressed concrete into English. After a lot of efforts and difficulties the book was published in London in 1948. The 6000 copies of the first edition were promptly sold out. Eight thousand copies of the second revised an
46、d expanded edition were published in 1950 and a third further edition was published in early 1954. During those early years, Magnels book was the practical tool to which engineering students and practicing engineers referred to for the design and analysis of prestressed concrete structures. The impa
47、ct of this treatise, as weil as many of Magnels other publications, had on the prestressed concrete industry is indeed significant. In the early 1950s, T.Y. Lin spent one year in Magnel Laboratory and after his return to the United States he published his book on “Design of Prestressed Concrete Stru
48、ctures“ (1 955). In the late 1940s Ch. Zollman, who had joined the Preload Corporation in the meantime, could convince the Bureau of Engineering of the City of Philadelphia to realize the superstructure of the Walnut Lane Bridge in prestressed concrete on the basis of a proposal elaborated by Magnel
49、. The Preload Corporation was awarded the sub-contract to fabricate the girders in 1949. In October 1949 a loading test was performed on a 49 m long and 2 m deep test girder, identical to the girders forming the center span of the bridge (Fig. 12). This test demonstration attracted some 300 engineers from seventeen states and five countries who stood in the rain for the entire day to witness the event. The successful testing to destruction at the job site, far away from the comforts of a laboratory, was a significant achievement which instilled public confidence in prest
