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Depreme dayanıklı yapı tasarımında aktif kontrolünün kullanılması

Active control for earthauake resistant structural design

  1. Tez No: 39708
  2. Yazar: ÜNAL ALDEMİR
  3. Danışmanlar: PROF.DR. MEHMET BAKİOĞLU
  4. Tez Türü: Yüksek Lisans
  5. Konular: İnşaat Mühendisliği, Civil Engineering
  6. Anahtar Kelimeler: Belirtilmemiş.
  7. Yıl: 1994
  8. Dil: Türkçe
  9. Üniversite: İstanbul Teknik Üniversitesi
  10. Enstitü: Fen Bilimleri Enstitüsü
  11. Ana Bilim Dalı: Belirtilmemiş.
  12. Bilim Dalı: Belirtilmemiş.
  13. Sayfa Sayısı: 91

Özet

ÖZET Bu çalışmada benzetilmiş deprem ve gerçek deprem kayıtları kullanılarak nonlineer yapıların aktif kontrol altında davranışları incelenmiştir. Kontrol algoritması olarak 1987'de Yang J. tarafından nonlineer yapılar için geliştirilen kapalı- çevrim, açık-çevrim ve kapalı-açık çevrim ani optimal kontrol algoritmalarından ani optimal kapalı-çevrim kontrol algoritması kullanılmıştır. Ani optimal kontrol algoritmalarında, kontrol vektörü u(t) ve yapı mukabele vektörü z(t)'ye göre kuadratik olarak seçilen J performans indeksi her t anında minimize edilmektedir. Nonlineer hareket denklemlerinin çözümünde Wilson-e metodu kullanılmıştır. Aktif kontrolün yapı davranışına etkisini araştırmak için 3 sayısal örnek çözülmüştür. Birinci sayısal örnekte benzetilmiş^ deprem, Kanai-Tajimi güç spektrum fonksiyonu kullanılarak stasyoner olmayan rastgele işlem olarak modellenmiştir. İkinci örnekte 1992 Erzincan depremi, üçüncü örnekte ise Elcentro depremi kullanılmıştır. Birinci ve üçüncü örnekte, tüm yapı mukabelesinin elastik bölgede kaldığı görülmüştür. Fakat ikinci örnekde, aktif kütle sönümleyicisine yakın katların mukabelesi elastik bölgede kalırken, alt katların mukabelesinin elastik bölge dışına çıktığı görülmüştür. Bu neticeyi etkileyen en önemli faktör Q ve R matrislerine atanan değerlerdir. Dolayısıyla Q ve R ağırlık matrislerine atanan değerlere bağlı olarak yapı davranışını elastik bölgede tutmak mümkündür. Fakat bunu garanti altına almak için Q ve R matrislerinin sabit olmayıp, her t anında ölçülüp geri beslenen yapı mukabelesine göre zamanla değişebilen matrisler olmaları gerekmektedir. Bu konuda çalışmalar devam etmektedir. Bu çalışmada ayrıca geniş bir kaynak taraması yapılmıştır. Aktif kontrolün inşaat mühendisliğindeki uygulamaları ile ilgili kaynaklar EK D' de verilmiştir.

Özet (Çeviri)

SUMMARY ACTIVE CONTROL FOR EARTHQUAKE-RESISTANT STRUCTURAL DESIGN In structural engineering,“active structural control”has become an area of research in which the motion of structure is controlled or modified using a control system through some external enrgy supply. Due to following motivating factors, there has been a flurry of research activities in the area of active control of civil engineering structures. 1. In last 20 years, due to trend toward taller, more flexible and longer structures, under large environmental loads such as strong winds and large eartquakes excessive vibrational levels could be reached which result in adversely affecting human comfort and even structural safety. The application of active control is one of the options of protecting such structures agains excessive vibrations. 2. Active or hybrid active-passive systems can be attractive choices for retrofitting or strengthening existing structures against earthquake hazards. Using interior shear walls or base isolation systems are structurally invasive. But, active systems can be more effective and can be incorporated into an existing structure with less interference. 3. In conventional earthquake resistant design, most structures are designed to withstand earthquakes of moderate intensity elastically, and to prevent a collapse during a severe earthquake, thereby preventing loss of human life. However, in many urban areas not only individual buildings, but also entire city functions are becoming intelligence oriented. Therefore, it seems unwise to cling to a design philosophy designated for the severe earthquakes, in which a barely prevented collapse at the structural ultimate limit is recognized as acceptable, providing there is no loss of human life. VIIs such thinking still acceptable? The conventional philosophy, which is several decades old, can result in a decrease in an individual building's function and loss in its financial value, and prevent reuse of the building after severe earthquakes. This should be tolarated in the coming age. A technolog, is required that will not only suppress the vibrations of buildings, but will preserve the information and communication function that sustains a city's life. 4. Civil Engineering structures are not designated to withstand all possible external loads. However, extraordinar excessive loading may occur, resulting in structural failur. So, active control can mean a last resort attempt to save a structure which would not be able to survive. When we consider the high cost of some recent large structures such as deep-water offshore platforms, active control seems to be particularly attractive. 5. Some structures house valuable and sensitive equipment. Their operating safety is of great importance. Thus, to ensure proper operating conditions for such sensitive equipments, active control can be applied at the substructure level. 6. Even though passive control devices such as base isolation systems, tuned mass dampers, viscoelastic dampers installed in some existing structures result in good performance, they have important inherent limitations. For example, a tuned mass damper can only be effective at the vibration mode at which it is tuned. But, an active mass damper can be effective over a much wider frequency range. 7. Since active control elevates structural concepts from a static and passive level to one of dynamicism and adaptabilitiy, it is not only attractive, but potentially revolutionary. Here, we should emphasise that the basic concepts of active control are not new. They have been used as the main tools of electrical and control engineering for many decades. But, even though much of the theoretical basis is in modern control theory, application of contol theories to civil engineering structures is unique in many ways. An active structural control system consists of the following 3 basic parts. vii1. Sensors located about the structure to measure either external excitations, or structural response variables, or both. 2. Devices to process the measured information and to compute necessary control forces needed based on. a given control algorithm. 3. Actuators, usually powered by external energy sources, to produce the required forces. When only the structural response variables are measured, the control configuration is referred to as closed-loop control since the structural response is continually monitored and this information is used to mate continual corrections to the applied control forces. An open-looped control results when the control forces are regulated only by the measured excitations. In case where the information on both the response quantities and excitation are utilized for control design, the term open-closed loop control is used in the literature. In classical optimal control standart quadratic performance index rtf J=\ [ZT(t)QZ(t)+UT(t)RU(t)]dt is used. Jo tf is a duration defined to be longer than that of the earthquake. Q and R are weighting matrices. In classical optimal closed-loop control, Riccati matrix P(t) does not correspond to the optimal closed-loop control for earthquake-excited building structure. Because it is obtained by setting the ground acceleration X0(t) to zero. So, the optimal closed-loop control is achieved by the Ricati matrix only if the earthquake excitation is either zero or a white noise random process. While the classical optimal open-loop control and the optimal closed-open loop control are superior to the Riccati closed-loop control, they are alson not applicable to earthquake-excited structures. Because, in these algorithms unknown vector q(t) should be solved backwards from the terminal time tf, indicating that the entire earthquake accelaration history X0(t) should be known a priori. Although the earthquake acceleration X0(t) is measurable, it is a random process and it is not known a priori. There are other applicable closed-loop control algorithms that are not optimal, such as the methods of pole assignment. The pole assignment method is tedious for complex building structures with many degrees of freedom, and it is not clear where the poles (eigenvalues) of the structures should be assigned. viiiBecause earthquake excitation is a random process, and it is not known a priori. While the earthquake ground motion is not known a priori, the base excitation of the building can be measured“real time”on-line by installing sensors on the basement floor. In other words, at any particular time t, the base excitation record is available up to that time instant t. That type of important information has been used in the development of instantaneous optimal control algorithms. The reason why it is not feasible to apply the classical optimal open-loop or closed-open-loop control algorithm to earthquake-excited structures comes from the definition of the performance index, J. Performance index given in classical control is the integral of quadratic functions over time interval ( 0, tf ), and hence the input excitation in that time interval should be known a priori. So instantaneous optimal control algorithms have been established using_ the time-dependent performance index J(t)=ZT(t)QZ(t)+Ur(t)RU(t). Performance index J(t) is minimized at every time instant t for all 0

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