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Volume 15, Number 3 |
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On location in Istanbul for seismic resistance researchby Leonardo Dueñas '01 (MEng) (with John Kelly and Tai-Chieh Wu)
Base isolation (sitting a building upon large flexible rubber bearings) may seem like a strange concept, but it is swiftly gaining recognition as one of the most effective seismic hazard mitigation techniques. As part of the design project that the MEng students in the CEE Dept. develop in their specific areas of interest, a group of us in the 2001 MEng class (Leonardo Dueñas, John Kelly, Tai-chieh Wu, Noelle Bachas) investigated base isolation as a building retrofit option supervised by Prof. Oral Büyüköztürk.
Our project for the High Performance Structures track of the MEng program, "Building Rehabilitation for Improved Seismic Resistance," illustrated the concept of base isolation in Istanbul, Turkey. What was arguably the most severe urban earthquake in modern times devastated Izmit (about 50 miles east of Istanbul) in 1999. Over the past millennium, earthquakes in Turkey have progressively moved from one end of the North Anatolian fault to the other. The past hundred years have seen a gradual westward movement, approaching Istanbul. Recent quakes have killed tens of thousands of people, destroyed industrial areas, and pulverized blocks of concrete apartments.
Our project was based around a case study analyzing Mitchell Hall, a 100-year-old building on the campus of the American Roberts High School. This structure was originally designed by a Boston based engineering firm. Several rehabilitation options such as structural stiffening and damping techniques were first examined and evaluated before base isolation was finally chosen as the most effective alternative.
The fundamental concept in base isolation is to separate the superstructure from its foundations, and thus the ground, through the introduction of a soft layer, much as how the suspension on a car isolates the body from the wheels. This separation of structure and base is achieved by resting the structure upon rubber bearings, friction sliders or many other such devices.
Base isolation is a relatively new technology that has become widely used only in the last 10 years, following a number of severe earthquakes on the US West Coast and in Japan. As yet, it has not been fully introduced into Turkey or Europe as a mitigation technique for either new construction or as a building retrofit strategy.
Why encourage base isolation in Istanbul? Istanbul is famous as the city where East meets West, for its distinguished culture, and for containing some of the most important historic structures in the world. Unique examples of the Roman, Byzantine and Ottoman Empires are interspersed throughout the city, each different but with the common trait of being inimitable and irreplaceable.
As a follow up to the project, we visited Istanbul from May 21 to 25, 2001, to further study the buildings and to promote the concept of base isolation. The members of the Turkey field trip team included Prof. Büyüköztürk and Leonardo Dueñas, John Kelly and Tai-Chieh Wu. The visit involved several presentations to industry (Tekfen Holdings Inc.) and to universities (the Istanbul Technical Univ. and the Gebze Institute of High Technology.)
It was generally agreed that as a retrofit strategy, base isolation was best suited to invaluable historical structures, or to industry along the North Anatolian Fault. Historic buildings in Istanbul appropriate for retrofitting include the Aya Sofia and Blue Mosque, representing spectacular examples of engineering and artistic innovation. Approximately 40% of Turkey's manufacturing takes place along the Izmit Gulf, which coincidentally runs parallel to the active North Anatolian fault. A number of petrochemicals are stored in this area. These two areas were accepted as the most likely targets for this kind of technology to mitigate the environmental and economic impacts of a future earthquake.
As well as exchanging knowledge, participants on this trip enjoyed the opportunity to form friendships and future research partnerships between MIT and Turkish universities. They are aggressively researching the field of earthquake engineering, the use of composite materials for structural improvement, as well as methods of application to the traditional kind of structure found in this part of the world. Equipment such as shaking tables and hydraulic arms which could impart a velocity of up to 500 ft per second were used to test these strategies on a one-to-one scale. It is essential that a mitigation technique not only be effective, but also easy to implement and affordable.
While visiting Istanbul, we had the opportunity to enjoy the Aya Sofia, built in 535 AD; the Blue Mosque; and the old Roman cisterns and aqueducts, which date back to 532 AD. The Grand Bazaar was ideal for picking up a few souvenirs and further experiencing the unique culture of this extraordinary city. Dinner was equally pleasant, whether atop one of the seven hills upon which Istanbul is built, or along the shores of the Bosphorus, eating delicious Turkish cuisine at the edge of Europe, overlooking the lights marking the beginnings of the Asian continent.
Istanbul is an unforgettable city, combining modern day Europe with the mysterious charms of the Middle East. It is truly unique as the location where East meets West, joined by the famous Bosphoros suspension bridge, each combining and complementing the other to form the most memorable experiences.
Finally, we
wish to thank the CEE Dept., Dr. Eric Adams, and Prof. Büyüköztürk as
supervisor of the project and organizer of the trip. This visit has been
the key for opening many more doors in the field of structural motion
control, which is an emerging subject for structural engineering. Base
isolation is just a single piece in a vast puzzle of alternatives to improve
the seismic response of structures. The updated web page of the project
with detailed information can be found at
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"Civil and Environmental Engineering at
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