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Recent concrete dams engineering in China
Finite Elements in Analysis and Design 33 (1999) 227}231
Recent concrete dams engineering in China Ray W. Clough* Structures Consultant, P.O. Box 4625, Sunriver, OR 97707, USA
Abstract This is a discussion of personal experiences related to the engineering of concrete dams in China. Included in the discussion are considerations of the behavior of dams during earthquakes. ( 1999 Elsevier Science B.V. All rights reserved. Keywords: Dams; Earthquakes
1. Introduction Dams are a subject of considerable interest to me. Thus, the planning of major dam projects in China has held a great degree of fascination for me. To learn more about what was happening, I took a trip to China and traveled down the Yangtze River to see the site of the greatest dam project ever planned: The Three Gorges Project. The new reservoir will extend from Chungking to Sandouping, where the dam is being built. A river cruise along the full extent of the future reservoir was part of my trip. This discussion is organized as answers to two questions: (1) Why dams? and (2) Why China? It concludes with a brief description of The Three Gorges Project.
2. Why dams? The answer to this question is that dams have been the principal area of my research as well as the subject of most of my consulting experience for the past 25 yr. Even before that * when I was involved mainly in the development of the Finite Element Method as a tool for the analysis of complex structures * concrete dams, especially arch dams, served as the subjects of much of my * Tel.:#1-503-593-5064; fax: #1-541-593-2823. 0168-874X/99/$ - see front matter ( 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 8 7 4 X ( 9 9 ) 0 0 0 4 6 - 3
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R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
analytical work. In fact, I have been interested in the design and analysis of concrete dams for nearly 60 yr, since my early undergraduate years at the University of Washington. Two of my professors at the University of Washington had considerable dam engineering experience, one with the Corps of Engineers and the other with the Bureau of Reclamation, and they often based their class problems on their experiences. So, I was pointed toward dam engineering at an early stage in my career. Moreover, my "rst professional Civil Engineering job was in the hydropower "eld, when I worked for the Bonneville Power Administration during the summer of 1941, between my junior and senior years at the University of Washington. In addition, concrete dams proved to be an excellent subject area for use in developing the "nite element method: both because of the arbitrary geometry of the dam, the foundation, and the reservoir; and also because of interaction e!ects between the materials of these three parts of the system. A numerical approach clearly was needed for such analyses because the geometric and material complexities precluded any direct method of analysis. In my early work with dams, I was concerned only with static loads, but, after a couple of summers spent with the structural dynamics unit at the Boeing Airplane Company, I quickly turned my interest toward the principal dynamics problem of Civil Engineering, earthquake response analysis. So, I began to direct my research and teaching toward the earthquake behavior of structures. My approach to these problems was based mainly on my early experience with Boeing, treating the entire system as an assemblage of elements of appropriate geometries and material properties. In addition, I was in#uenced considerably by one of my colleagues at Berkeley, Professor J.M. Raphael, who had worked for the US Bureau of Reclamation in Denver for several years before joining the Berkeley faculty.
3. Why China? 3.1. My early China experience Very early, my interest in dams put me in touch with an important engineer from China, Professor K.T. Zhang of Tsinghua University in Beijing. We met when we both attended the `International Symposium on Arch Damsa held at Southampton University (UK), in April 1964. I was surprised when Professor Zhang approached me during the conference and said that he was an alumnus of the University of California, Berkeley. He had obtained his M.S. in Structural Engineering with Professor R.E. Davis in 1935, before going on to Harvard University to get his doctorate in Soil Mechanics with Professor Casagrande. Our meeting was the beginning of a long-lasting friendship, which is still continuing. I saw him again during a trip to China in the summer of 1998 to make vibration measurements on Longyangxia Dam on the upper Yellow River. 3.2. Military experience Actually, I had earlier contact with China, in 1945, when I was serving with the US Air Force Aviation Engineers in Okinawa. My older brother was a member of the US State Department stationed in China, and, at that time, he had been assigned to work with General Marshall on the demobilization e!ort. General Marshall thought that the huge amounts of military supplies that
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
229
had been accumulated to prepare for the invasion of Japan should serve to stock the US Consular o$ces in China, all of which had been taken over by Japan during the war, and he asked my brother to undertake this job. My brother's response was that he did not know anything about military equipment, but that he could recommend someone to help him with the job. So, I became a hero in my Aviation Engineer Battalion on Okinawa when I received orders from General Marshall in China, that were sent by way of General MacArthur in Tokyo, to report to Mr. Ralph Clough of the State Department in Shanghai. Of course, I greatly appreciated this opportunity to work with my brother; and it was an excellent assignment, because we were required to visit the main Consular o$ces all over China, including Canton, Hong Kong, and Shanghai. I could have stayed in China much longer to visit many more Consular o$ces with my brother, but by that time I was eligible to return to the United States for discharge from the Air Force, and that was an appointment that I did not want to miss. 3.3. Continuing China experience My next experience with China was in 1974, when I was selected to be a member of the US Seismology Delegation to China investigating their work in the "eld of Earthquake Prediction. The leader of our delegation was Dr. Frank Press, a seismologist from MIT who subsequently became the President of the U.S. National Academy of Sciences. Except for myself, the members of the delegation were all seismologists, geologists, and geophysicists. I was the only engineer in the group and I had the impression that I had been included to give the delegation some balance in their opinions on the very sensitive subject of earthquake prediction. Following this visit to China, my next trip there was in 1978, when I was a member of the U.S. Earthquake Engineering Delegation, which had been organized to study what China had done in the "eld of Earthquake Engineering since World War II. This delegation was headed by Professor Goerge Housner of CalTech, and included many of my friends from the early years of the Earthquake Engineering Research Institute. This group visited many of the same places that I had seen four years earlier with the Seismology Delegation. But the major emphasis for this new delegation was on engineering works and laboratories. The major change that had taken place in China since my previous trip there was that the Cultural Revolution had ended and the China I saw in 1978 was quite di!erent from the country I had seen in 1974. In 1974, the principal professors and research personnel had been removed from Tsinghua University, as well as most other technical institutions; so the top level people that we were able to meet were all Communist Party appointees and we did not meet the real scienti"c personnel. By 1978, the real administrative and scienti"c personnel of Tsinghua University had returned to their previous posts. Because of this change, when we visited the University on this occasion, my friend K.T. Zhang was waiting for us on the front steps of the Administrative Building and greeted us in his new position as Vice President of the University. I was very happy to see K.T. Zhang again and we quickly renewed our friendship. The "rst thing that he did was to ask me to come back and give a series of lectures on the Finite Element Method and on Earthquake Engineering to the Civil Engineering students at Tsinghua University. The visit in 1978 took place after the `US}China Protocol for Cooperation in Earthquake Studiesa had been signed. Also, a special collaboration had been established between the University of California-Berkeley and Tsinghua University that served as the basis for a continuing
230
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
sequence of research projects involving the two universities. With this protocol in place, it was relatively easy to obtain research funding, and I began a series of projects concerned with the earthquake behavior of concrete dams. In this program, we initially made vibration measurements on dams using rotating mass shaking machines * starting with two arch dams in China, followed by one in California. In each case, the measured responses were correlated with analytical predictions performed by the "nite element method. The excellent agreement we obtained in these cases demonstrated the validity of our analytical procedures. By 1987, I had retired from teaching at Berkeley, and my place in the US}China Cooperation on Concrete Dams was taken by my former student, Dr. Yusof Ghanaat, who had started a company, `Quest Structuresa, to do this type of work. His company received a grant from the National Science Foundation to test another dam in China * the Dongjiang Dam * and I was retained as an advisor on the project. The major di!erence in this new project, which was carried out in 1991, was that the dam vibration was excited by explosives rather than by mechanical shakers. Some of the tests were done using explosives drilled into the foundation rock to a depth of 42 m, while in other cases, the explosives were set-o! in the reservoir water. Again, analytically predicted results were compared with measurements made on the dam, and, in all cases, the agreement was found to be good. A major conclusion of this test was that the results of the explosions detonated in the reservoir were as good as those obtained from explosives drilled into the foundation rock. Based on these results, it was decided that the next test would be done by explosives discharged in the reservoir.
3.4. The next test * Longyangxia dam Our Chinese colleagues selected Longyangxia Dam located on the upper Yellow River, as the next dam to be tested under the US}China Protocol. The reason why we prefer to test dams in China is that they have many new concrete dams and many others still in the design stages, whereas there are very few concrete dams being built in the United States. So, funding for research can be obtained more easily in China by taking it from the construction funding. Moreover, there is little di$culty in getting permission for explosive testing in China, whereas preparation of the Environmental Impact Report required for such testing in the United States would cost many thousands of dollars for each dam, and there is no guarantee that permission could be obtained to carry out the testing. In September 1997, we made a reconnaissance trip in the direction of Longyangxia Dam. The leader of our group was Dr. Yusof Ghanaat of Quest Structures. Our team also included Dr. Robert Hall of the US Waterways Experiment Station in Vicksburg. I was asked to serve as technical advisor. The purpose of our trip was for us to become familiar with the dam and to meet the local engineers who had designed the dam. Those engineers are to conduct the experimental test program, which is to be conducted by setting o! explosions in the reservoir. Our trip went well until we were within 50 miles of the dam. At that point, we learned that we could not go further because heavy rains during the preceding week had caused a #ash #ood that washed out the road leading to the dam. It was expected to take several weeks to get the road open again, so we had to give up the rest of our trip, and instead decided to take a cruise ship down the Yangtze River from Chungking, the upper end of the future reservoir, to the site of the Three Gorges Dam at
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
231
Sandouping, a distance of 370 miles. Accordingly, the test of the Longyangxia Dam was scheduled to be done in the summer of 1998, and the experimental work actually was done at that time. The Three Gorges Dam will be the world's largest concrete dam in terms of the volume of concrete (14.86 million m3) to be poured to create it. Also, it will have the world's largest electricity production capacity at 18,200 MW (compared with 12,600 MW at Itaipu, which presently produces the most power of any dam in the world). In addition, it will improve navigation on the river by allowing 3000 t ships to travel up to Chungking so that the annual river tra$c is expected to increase by a factor of "ve. Although its full generating capacity is needed to pay for the 24.5 billion dollar estimated cost of the project and the increased river tra$c will be very important to the economy of the region, the dam is intended primarily for #ood control. The Yangtze River #oods about once every 10 years. As an example of the devastation those #oods cause, Wuhan * a city of about "ve million people * was under water for three months following a #ood in 1931. The cost of the dam now under construction includes the cost of relocating 2 million people from their locations at the present river level to locations about 550 ft higher and adjacent to the new reservoir, and this task is well under way.
Recent concrete dams engineering in China Ray W. Clough* Structures Consultant, P.O. Box 4625, Sunriver, OR 97707, USA
Abstract This is a discussion of personal experiences related to the engineering of concrete dams in China. Included in the discussion are considerations of the behavior of dams during earthquakes. ( 1999 Elsevier Science B.V. All rights reserved. Keywords: Dams; Earthquakes
1. Introduction Dams are a subject of considerable interest to me. Thus, the planning of major dam projects in China has held a great degree of fascination for me. To learn more about what was happening, I took a trip to China and traveled down the Yangtze River to see the site of the greatest dam project ever planned: The Three Gorges Project. The new reservoir will extend from Chungking to Sandouping, where the dam is being built. A river cruise along the full extent of the future reservoir was part of my trip. This discussion is organized as answers to two questions: (1) Why dams? and (2) Why China? It concludes with a brief description of The Three Gorges Project.
2. Why dams? The answer to this question is that dams have been the principal area of my research as well as the subject of most of my consulting experience for the past 25 yr. Even before that * when I was involved mainly in the development of the Finite Element Method as a tool for the analysis of complex structures * concrete dams, especially arch dams, served as the subjects of much of my * Tel.:#1-503-593-5064; fax: #1-541-593-2823. 0168-874X/99/$ - see front matter ( 1999 Elsevier Science B.V. All rights reserved. PII: S 0 1 6 8 - 8 7 4 X ( 9 9 ) 0 0 0 4 6 - 3
228
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
analytical work. In fact, I have been interested in the design and analysis of concrete dams for nearly 60 yr, since my early undergraduate years at the University of Washington. Two of my professors at the University of Washington had considerable dam engineering experience, one with the Corps of Engineers and the other with the Bureau of Reclamation, and they often based their class problems on their experiences. So, I was pointed toward dam engineering at an early stage in my career. Moreover, my "rst professional Civil Engineering job was in the hydropower "eld, when I worked for the Bonneville Power Administration during the summer of 1941, between my junior and senior years at the University of Washington. In addition, concrete dams proved to be an excellent subject area for use in developing the "nite element method: both because of the arbitrary geometry of the dam, the foundation, and the reservoir; and also because of interaction e!ects between the materials of these three parts of the system. A numerical approach clearly was needed for such analyses because the geometric and material complexities precluded any direct method of analysis. In my early work with dams, I was concerned only with static loads, but, after a couple of summers spent with the structural dynamics unit at the Boeing Airplane Company, I quickly turned my interest toward the principal dynamics problem of Civil Engineering, earthquake response analysis. So, I began to direct my research and teaching toward the earthquake behavior of structures. My approach to these problems was based mainly on my early experience with Boeing, treating the entire system as an assemblage of elements of appropriate geometries and material properties. In addition, I was in#uenced considerably by one of my colleagues at Berkeley, Professor J.M. Raphael, who had worked for the US Bureau of Reclamation in Denver for several years before joining the Berkeley faculty.
3. Why China? 3.1. My early China experience Very early, my interest in dams put me in touch with an important engineer from China, Professor K.T. Zhang of Tsinghua University in Beijing. We met when we both attended the `International Symposium on Arch Damsa held at Southampton University (UK), in April 1964. I was surprised when Professor Zhang approached me during the conference and said that he was an alumnus of the University of California, Berkeley. He had obtained his M.S. in Structural Engineering with Professor R.E. Davis in 1935, before going on to Harvard University to get his doctorate in Soil Mechanics with Professor Casagrande. Our meeting was the beginning of a long-lasting friendship, which is still continuing. I saw him again during a trip to China in the summer of 1998 to make vibration measurements on Longyangxia Dam on the upper Yellow River. 3.2. Military experience Actually, I had earlier contact with China, in 1945, when I was serving with the US Air Force Aviation Engineers in Okinawa. My older brother was a member of the US State Department stationed in China, and, at that time, he had been assigned to work with General Marshall on the demobilization e!ort. General Marshall thought that the huge amounts of military supplies that
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
229
had been accumulated to prepare for the invasion of Japan should serve to stock the US Consular o$ces in China, all of which had been taken over by Japan during the war, and he asked my brother to undertake this job. My brother's response was that he did not know anything about military equipment, but that he could recommend someone to help him with the job. So, I became a hero in my Aviation Engineer Battalion on Okinawa when I received orders from General Marshall in China, that were sent by way of General MacArthur in Tokyo, to report to Mr. Ralph Clough of the State Department in Shanghai. Of course, I greatly appreciated this opportunity to work with my brother; and it was an excellent assignment, because we were required to visit the main Consular o$ces all over China, including Canton, Hong Kong, and Shanghai. I could have stayed in China much longer to visit many more Consular o$ces with my brother, but by that time I was eligible to return to the United States for discharge from the Air Force, and that was an appointment that I did not want to miss. 3.3. Continuing China experience My next experience with China was in 1974, when I was selected to be a member of the US Seismology Delegation to China investigating their work in the "eld of Earthquake Prediction. The leader of our delegation was Dr. Frank Press, a seismologist from MIT who subsequently became the President of the U.S. National Academy of Sciences. Except for myself, the members of the delegation were all seismologists, geologists, and geophysicists. I was the only engineer in the group and I had the impression that I had been included to give the delegation some balance in their opinions on the very sensitive subject of earthquake prediction. Following this visit to China, my next trip there was in 1978, when I was a member of the U.S. Earthquake Engineering Delegation, which had been organized to study what China had done in the "eld of Earthquake Engineering since World War II. This delegation was headed by Professor Goerge Housner of CalTech, and included many of my friends from the early years of the Earthquake Engineering Research Institute. This group visited many of the same places that I had seen four years earlier with the Seismology Delegation. But the major emphasis for this new delegation was on engineering works and laboratories. The major change that had taken place in China since my previous trip there was that the Cultural Revolution had ended and the China I saw in 1978 was quite di!erent from the country I had seen in 1974. In 1974, the principal professors and research personnel had been removed from Tsinghua University, as well as most other technical institutions; so the top level people that we were able to meet were all Communist Party appointees and we did not meet the real scienti"c personnel. By 1978, the real administrative and scienti"c personnel of Tsinghua University had returned to their previous posts. Because of this change, when we visited the University on this occasion, my friend K.T. Zhang was waiting for us on the front steps of the Administrative Building and greeted us in his new position as Vice President of the University. I was very happy to see K.T. Zhang again and we quickly renewed our friendship. The "rst thing that he did was to ask me to come back and give a series of lectures on the Finite Element Method and on Earthquake Engineering to the Civil Engineering students at Tsinghua University. The visit in 1978 took place after the `US}China Protocol for Cooperation in Earthquake Studiesa had been signed. Also, a special collaboration had been established between the University of California-Berkeley and Tsinghua University that served as the basis for a continuing
230
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
sequence of research projects involving the two universities. With this protocol in place, it was relatively easy to obtain research funding, and I began a series of projects concerned with the earthquake behavior of concrete dams. In this program, we initially made vibration measurements on dams using rotating mass shaking machines * starting with two arch dams in China, followed by one in California. In each case, the measured responses were correlated with analytical predictions performed by the "nite element method. The excellent agreement we obtained in these cases demonstrated the validity of our analytical procedures. By 1987, I had retired from teaching at Berkeley, and my place in the US}China Cooperation on Concrete Dams was taken by my former student, Dr. Yusof Ghanaat, who had started a company, `Quest Structuresa, to do this type of work. His company received a grant from the National Science Foundation to test another dam in China * the Dongjiang Dam * and I was retained as an advisor on the project. The major di!erence in this new project, which was carried out in 1991, was that the dam vibration was excited by explosives rather than by mechanical shakers. Some of the tests were done using explosives drilled into the foundation rock to a depth of 42 m, while in other cases, the explosives were set-o! in the reservoir water. Again, analytically predicted results were compared with measurements made on the dam, and, in all cases, the agreement was found to be good. A major conclusion of this test was that the results of the explosions detonated in the reservoir were as good as those obtained from explosives drilled into the foundation rock. Based on these results, it was decided that the next test would be done by explosives discharged in the reservoir.
3.4. The next test * Longyangxia dam Our Chinese colleagues selected Longyangxia Dam located on the upper Yellow River, as the next dam to be tested under the US}China Protocol. The reason why we prefer to test dams in China is that they have many new concrete dams and many others still in the design stages, whereas there are very few concrete dams being built in the United States. So, funding for research can be obtained more easily in China by taking it from the construction funding. Moreover, there is little di$culty in getting permission for explosive testing in China, whereas preparation of the Environmental Impact Report required for such testing in the United States would cost many thousands of dollars for each dam, and there is no guarantee that permission could be obtained to carry out the testing. In September 1997, we made a reconnaissance trip in the direction of Longyangxia Dam. The leader of our group was Dr. Yusof Ghanaat of Quest Structures. Our team also included Dr. Robert Hall of the US Waterways Experiment Station in Vicksburg. I was asked to serve as technical advisor. The purpose of our trip was for us to become familiar with the dam and to meet the local engineers who had designed the dam. Those engineers are to conduct the experimental test program, which is to be conducted by setting o! explosions in the reservoir. Our trip went well until we were within 50 miles of the dam. At that point, we learned that we could not go further because heavy rains during the preceding week had caused a #ash #ood that washed out the road leading to the dam. It was expected to take several weeks to get the road open again, so we had to give up the rest of our trip, and instead decided to take a cruise ship down the Yangtze River from Chungking, the upper end of the future reservoir, to the site of the Three Gorges Dam at
R.W. Clough / Finite Elements in Analysis and Design 33 (1999) 227}231
231
Sandouping, a distance of 370 miles. Accordingly, the test of the Longyangxia Dam was scheduled to be done in the summer of 1998, and the experimental work actually was done at that time. The Three Gorges Dam will be the world's largest concrete dam in terms of the volume of concrete (14.86 million m3) to be poured to create it. Also, it will have the world's largest electricity production capacity at 18,200 MW (compared with 12,600 MW at Itaipu, which presently produces the most power of any dam in the world). In addition, it will improve navigation on the river by allowing 3000 t ships to travel up to Chungking so that the annual river tra$c is expected to increase by a factor of "ve. Although its full generating capacity is needed to pay for the 24.5 billion dollar estimated cost of the project and the increased river tra$c will be very important to the economy of the region, the dam is intended primarily for #ood control. The Yangtze River #oods about once every 10 years. As an example of the devastation those #oods cause, Wuhan * a city of about "ve million people * was under water for three months following a #ood in 1931. The cost of the dam now under construction includes the cost of relocating 2 million people from their locations at the present river level to locations about 550 ft higher and adjacent to the new reservoir, and this task is well under way.