HISTORY OF PRESTRESSING
Conception of reinforced concrete structures marked absolutely new construction direction. Due to the development of prestressing technology, designers got the possibility to control the behavior of the structure, to carry out less expensive and more optimal projects with more flexible design and aesthetic qualities of the structure. Today prestressed concrete can be used in almost every field of construction.
Conception of prestressed concrete structures in its modern meaning appeared due to the French engineer Eugène Freyssinet. The idea of prestressed concrete structures was around for a long time, but it was Eugène Freyssinet who finally formed it and put it into practice. Graduated from French Ecole Polytechnique and National School of Roads and Bridges, Freyssinet studied properties and characteristics of concrete structures through his entire career.
His many years’ experience and researches led him to the patent for the technology of building structures using prestressed concrete. He received this patent in 1928 for High Strength Steel Strands stressed in the concrete beam.
First the prestressing steel was used in the concrete member to resist to the tensile force, thus significantly reducing the necessary quantity of steel passive reinforcement. Soon after receiving the patent, Freyssinet opened its first plant for fabrication of prestressed structures in France. It was a great success from a technical point of view, and a great failure from the commercial one, because the start of production coincided with economic recession, and in 1933 he had to shut down the plant. But already in 1935 Freyssinet was able to prove all the advantages of prestressing in practice. Due to this technology he was able to save the marine terminal in Havre (France), the part of which was sinking at the rate of 25,4mm per month. Freyssinet proposed to reinforce the foundation with prestressing. His unmatched success contributed to the development and widespread application of technology.
In the United States it was Gustave Magnel, Belgian engineer and professor, who stood at the origins of prestressing in the USA. Working in his laboratory in Belgium during World War II, Magnel conducted numerous researches and tests of prestressed concrete, among which were the full-scale study of prestressed concrete girders and more detailed study of concrete and reinforcement creep.
Gustav Magnel mainly studied the creep of high strength wires and creep and shrinkage of normal reinforced concrete. Based on his researches it was concluded that high strength prestressing wires creep much less than low-strength mild reinforcing steel used in ordinary reinforced concrete.
By the end of World War II Magnel became one of several engineers who had knowledge in the field of design and construction of prestressed structures. Due to this fact in 1948 Magnel had an opportunity to put his vast theoretical knowledge into practice, when American engineers from Philadelphia asked him to design the first serious construction project with prestressed concrete in the USA, the Walnut Lane Bridge. For this project it was essential to choose the most economic technology, but at the same time save the esthetic part of the project. Thus, the prestressing technology was chosen. From this moment the history of prestressing development in the USA began.
Viktor Mikhailov, Soviet scientist, specialist of civil structures, made a great contribution in the development of prestressing in Russia. That is why we can call him the founding father of prestressed concrete application in the USSR. At that time prestressing was widely used, mainly for the civil and industrial construction projects. The USSR produced about 30 million m3 of prestressed concrete structures per year, and it was much bigger than other countries could manufacture. Prestressed concrete was usually produced by pretensioning (tensioning of reinforced strands to the supports). Such production could be done in any region of the country. Such waste geography became possible due to introduction of electrothermal prestressing.
Prestressing technology has been also widely used in construction of various projects in Saint Petersburg. Among them we can emphasize Sports Center “Yubileyniy”, built in 1967. For its time this project was considered as experimental one due to the application of stay cable system for the construction of technical ceiling of the main arena. The ceiling is supported by steel prestressing tendons stressed between central drum and external reinforced concrete ring laying on high bearing pylons. Such structure has a form of “bicycle wheel” and doesn’t have any intermediate supports.
Prestressing technology was also used for construction of Alexander Nevsky bridge. Steel strands with diameter of 70mm were used to connect the separate bridge segments (according to information from SP SBI «Mostotrest»). In bridge structures they are passed through designed temporary openings.
Prestressing system was also largerly used in construction of containments for Russian Nuclear Power Plants. Balakovskaya, Kalininskaya, Rostovskaya Nuclear Power Plants were built using prestressing technology.
Unfortunately after collapse of the Soviet Union the amount of prestressed structures produced decreased in 10 times. However recently more and more construction market players tend to install prestressing systems in their projects. Particularly, prestressing technology is used for the floors of residential, office and commercial buildings, because of large column and transverse walls spacing . In whole, since the patent receipt in 1928, the system was constantly developed and modified, progressing in many different aspects, starting from the improvement of corrosion protection and finishing with the impact on the environment. But its main advantages, such as materials saving, less loading on the foundation, relative lightness of the structure, flexible design and esthetic appearance are still more than important, and frequently become the key factor when choosing the technology.