Aktif ve pasif yapı kontrolü

Active and passive structural control systems

Tez No: 66577
Yazar: ÖZGÜL ZOBU
Danışmanlar: DOÇ. DR. A. NECMETTİN GÜNDÜZ
Tez Türü: Yüksek Lisans
Konular: İnşaat Mühendisliği, Civil Engineering
Anahtar Kelimeler: Belirtilmemiş.
Yıl: 1997
Dil: Türkçe
Üniversite: İstanbul Teknik Üniversitesi
Enstitü: Fen Bilimleri Enstitüsü
Ana Bilim Dalı: Yapı Ana Bilim Dalı
Bilim Dalı: Belirtilmemiş.
Sayfa Sayısı: 105

Özet

ÖZET Son yıllarda özellikle Japonya ve Amerika'da geliştirilen ve birçok ülkede uygulanmakta olan yeni sismik kontrol sistemlerinden bahsedilmektedir. Sismik korunma mekanizmaları temelde Aktif Kontrol Sistemleri ve Pasif Kontrol Sistemleri diye iki ana gruba ayrılmaktadır. Pasif sistemler de kendi içinde Pasif Enerji Yutucu Sistemler ve Taban İzolasyonu olmak üzere iki gruba ayrılmaktadır. Pasif Enerji Yutucu Sistemler; yapıya ilave edilen bazı sönümleyici elemanlar ile titreşim sırasında yapıya giren sismik enerjinin bir kısmını absorbe ederek korunma sağlarlar. Taban İzolasyonu olarak bilinen ve yapı ile zemin arasına yerleştirilen özel kauçuktan yapılmış izolatörler ile yapının yataydaki rijitliği azaltılmak suretiyle ve zeminden gelen titreşimlerin yapıyı etkilememesi için yapıyı zeminden ayırma ilkesine dayanan korunma sistemi özellikle yüksek yapılarda; tabanda yukarıya doğru kaldırma (uplift) kuvvetleri meydana geldiği için çok yüksek yapılar için uygun değildir. Aktif Kontrol Sistemleri diye bilinen ve özellikle son yıllarda geliştirilen mekanizmalar ise çok gelişmiş bilgisayarlar ile donatılmış olup; titreşimin etkisini, yapıda karşı bir hareket üreterek sönümlendirmeye çalışan ve çok yüksek binalar için de uygun olan kontrol sistemleridir. Kendi kendini koruyabilen 'Akıllı Binalar' olarak da bilinen bu sistemde sismik harekete karşı koyabilmek için sürekli bir enerji yapıda hazır bulundurulmaktadır. Karma (Hybrid) kontrol sistemleri diye bilinen ve aktif ve pasif kontrol mekanizmalarının birlikte kullanılması ile oluşturulan yeni bir tür korunma sistemi kolay uygulanabilmesi ve ekonomik oluşu nedeni ile dikkatleri çekmektedir. Deprem kuşağında yer alan ülkemizde; sismik zararlardan korunmak için geliştirilmiş ve başarılı bir şekilde birçok ülkede uygulanmakta olan teknolojiler tanıtılmaya çalışılarak,hiç olmazsa belirli bir çevrenin dikkatleri çekilmeye çalışılmıştır. Son olarak da ayaklı (kule) tipteki bir betonarme su deposunun mesnetlere kauçuk izolatörler yerleştirilmek suretiyle pasif kontrol mekanizmasına göre izoleli ve izolesiz durumda sismik davranışı incelenmiştir. Hesaplar SAP90 bilgisayar programı ile yapılarak 1996 Deprem Yönetmeliği'ne uygun tasarım yapılmıştır. Son olarak sözü edilen yapının Time History analizi yapılarak SAP90 programı ile bulunan sonuçlar karşılaştırılmıştır. Time History analizinde 1992 Erzincan Depremi spektrum değerleri kullanılmıştır. İzoleli ve izolesiz durumda yapının taban ve üst katlarında meydana gelen yerdeğiştirmeler ve taban kayma kuvveti hesap edilerek sonuçlar karşılaştırılmıştır. Mesnetlere izolatörler yerleştirilerek yapının yataydaki rijitliğinin azaltılması ile tabanda oluşan kesme kuvvetinde önemli azalma sağlandığı görülmektedir.

Özet (Çeviri)

Idealy, a structure can be designed in a precise manner if ; 1. Exact information is known concerning loads and strengths involved during the life time of this structure, 2. Exact methods of structural analysis are available for use by engineers in the real world, Howewer, uncertainties exist in this informations as well as in the methods of analysis to take care of these uncertainties various factors of safety have been used in the desing of structures. As an alternative approach to the safety problems of structural engineering and a possible way to extend the limiting height of tall buildings. Traditionally, architects and engineers have been interested in constructing structurally sound, functionally efficient, and esthetically elegant high-rise buildings. But super tall buildings under seismic and wind loads, are anticipated to suffer from excessive vibrations under these natural hazards. Vibration in structures can induce added displacement and stress, and may result in significant damage. In addition, it can cause discomfort and psychological effects to inhabitants as well as disturb the functioning of sensitive equipment. Structural vibration, therefore, must be eliminated or at least minimized. Conventional construction techniques can cause very high accelerations in stiff buildings, and large interstory drifts in flexible structures. These two factors make it difficult to ensure the safety of the building components and contents. The horizontal components of the earthquake ground motions are the most damaging to the building. Obviously, for structural safety the buildings should be designed to separate their naturel frequencies from dominant seismic frequencies as well as from possible wind induced vibration frequencies, including frequencies resulting from vortex shedding. The first mode can be regarded as a rigit body mode because its superstructural components are of the second order to the base components. However, owing to its low frequency, the first mode is still dominant in the superstructural deformation so that the superstructural components in the first mode shape can not be neglected. The first base-isolated mode not only controls the superstructural response but also dominates the response of high-frequency attachment. For general soil conditions where the dominant frequencies of the earthquake are in the range between 1 and 10 Hz, base isolation can protect the building by shifting the fundamental frequency of the structure below 1 Hz. XIAseismic protective systems, in general, consist of two categories, namely Passive Control Systems and Active Control Systems. The active control system differs from the passive one in that it requires the supply of external energy to counter the motion of the structure to be protected. An important class of passive aseismic protective systems is the base isolation system, which is able to reduce the horizontal seismic force transmitted to the structure. Base isolation is becoming widely accepted as a design strategy for low-rise buildings, in seismic regions. The idea behinds base isolation is a very simple. This technique involves the separation is of the superstructure using reinforced elastomeric isolators (“seismic shock absorbers”). While base isolation systems are effective for protecting seismic excited buildings this system provides an economic alternative for the seismic design of new structures and the rehabilitation of existing buildings, bridges and equipment. There are some limitations: Passive Systems are limited to low-rise buildings. For tall buildings, uplift forces may be generated in the isolation system leading to an instability failure. The passive protective system alone is not feasible for seismic- excited taller buildings because of the overturning phenomenon. A medium-rise building, even when isolated, could potentially generate overturning moments that would cause uplift off some isolators. Base isolation has not been proposed for taller buildings because of the obvious problems of uplift leading to overturning and the difficulty of achieving a reasonable period shift, for more-flexible, longer-period structures. The passive control technique, using elastomeric and lead-rubber bearings in particular, can be of great promise for reducing seismic forces with almost maintenance-free passive control units. The combination of different types of materials in a compact unit such as a lead-rubber bearing with different sizes of lead inserts makes very useful in choosing the control system. The selection of the lead material may be ascribed to three main factors: 1. In shear, lead yields at a relatively low stress and behaves approximately as an elastic-plastic solid. 2. It is available at high purity and its mechanical properties are predictable. 3. It has good fatigue properties under cyclic loading due to the fact that at room temperature, lead recovers most of its mechanical properties almost immediately. The performance factor depends generally on the details of the bearing. The behaviour of bearings is dependent on many parameters that may affect their over all behaviour and accordingly the response of structures under earthquake excitations, rubber behaves like an incompressible, homogenous, hyperelastic and isotropic solid. Base isolation has not been proposed for taller buildings because of the obvious problems of uplift leading to overturning and the difficulty of achieving a reasonable period shift for more-flexible, longer-period structures. The installation of various types of passive devices including mechanical dampers, is one way to suppress undesirable vibrations. The Tuned Liquid Damper (TLD) is a xnnew type of passive mechanical damper, which relies on the motion of shallow liquid inside a rigid tank for changing the dynamic characteristics of a structure and dissipating its vibration energy. The advantages of TLD are low cost almost zero trigger level easy installation especially in existing structures and bridges and few maintenance requirements. The sloshing frequency of each individual TLD can be easily changed by varying in liquid depth. Recently, the use of MTLDs which consist of a number of small TMDs whose natural frequencies are distributed over a certain range around the fundamental natural frequency of the structure. In these TLDs, water depth has been set to be equal to each other. Recently, the use of multiple TMDs (MTMDs), which consist of a number of small TMDs whose natural frequencies are distributed over a certain range around the fundamental natural frequency of the structure. The idea of the MTMDs is very suitable to the TLD. It can be expected that a multiple TLDs will possess better performance when compared with a conventional TLD where the same liquid depth is employed in all the TLDs. A passive control mechanism operates without using an external energy supply. Therefore, it is inexpensive, but it is only able to control the displacement up to a certain limit. An active control mechanism operates if and only if external energy is continously supplied. Therefore, it is expensive, but it is able to control displacement, velocity or acceleration of the structure or all of these, as desired. Research and development in active control of civil engineering structures has an approximately 25-yr history, starting in the 1970s (e.g. Yao 1972). Optimal control theory is often used to derive control algorithms for active control. Optimal control is a control which minimizes a certain performance index. The effectivenes of the control system is measured by a performance index which consist of: 1. The covariances of the responses, which are related to the safety of the structure, and 2. The covariances of the control forces, which are related to the energy input requirement for the control devices, and thus a measure of economy. If the performance index is given in a quadratic form, which is positive semidefinite with respect to the state of the system and positive definite with respect to the state of the system and positive definite with respect to the control effort the resulting algorithm yields the well-known Lineer Quadratic Regulator (LQR). On the other hand, when an active control system for tall buildings, the required active control forces to be provided by the external energy may be very large. Seismic control means installing functions to reduce seismic vibrations and to respond positively to earthquakes. Generally, active control systems can be classified into open-loop (non feedback) control systems, or closed-loop (feedback) control systems. An optimal closed-loop xiucontrol scheme using a quadratic performance index was employed to reduce the response of structure under base motion generated by a large-scale seismic simulator. The time delay between the observed motion and the implemented control forces, an important factor in control implentation, was integrated in the control algorithm. Effects of time delay in data acquisition and on-line calculation, unsynchronized application of large control forces, interface between controllers and structure, and interface between sensors and structure are very important in control implementation. The Joint Damper systems is one of the various seismic vibrations control methods that Kajima Corporation in Japan has developed by own experiences and unique technologies. The first application of this system in the world is so called KI (Kajima intelligent) Building by us in 1989. The principle of this system is extraordinarily simple: two or more adjacent buildings which vibrate differently during an earthquake are connected by specially designed dampers (Bell Damper, Tsudumi Damper), installation of joint dampers cancels the vibrations of the two buildings out and minimizes vibrations. The Honeycomb Damper system is one of the passive damping systems independently developed by Kajima. The honeycomb damper absorbs seismic energy and reduces vibrational amplitude. The system incorporates steel dampers into the structure of the building as or beams. Its construction is simple, yet it is capable of providing a great damping effect. It can eliminate about 30% of the seismic response. The damper, which is of compact design, can be built in as a part of a wall or beam. HID AM is a contraction for 'High DAMping device'. In the HID AM, passive seismic response control system an oil damper is built into a building's structure. The construction and operating principles are quite simple. The entire device is of cylindirical construction, and oil encased on both sides of the piston. HID AM has an excellent durability and simple maintenance. The only maintenance required is a visual inspection every three years. Braces are arranged in the core wall, and the HID AM is installed between the brace bottom and the beam. Since the device is small and installed in the framework of the building, no special installation space is required. The ultimate active seismic response control system, complete with 'brain' and 'nerv' system has been developed called the Active Variable System 'AVS' which is based on a completely new principle when this AVS system is used in a building, the building makes instantaneous judgements of seismic tremors,and minimizes the tremors by changing its rigidity like a person standing in the moving train, keeping his/her balance by using muscular movements. The AVS system shows excellent efficacy in earthquake response control. It can be installed on each floor, so that the complex tremors of a high rise building can be successfully controlled, this system has been designed as an energy-saving type of system, and can be operated using only a small amount of electric power. Other active control system called the Active Mass Driver 'AMD' system can counteract the shaking and tremors cause by earthquakes and high winds, by driving a weight (added mass) which has been installed in the building. This system is xivcontrolled by a highly-reliable computer system and can counteract complex shaking and tremors. The AMD system works as shown below: 1. Sensors that are installed in several locations, including the ground, in the middle of the building, and the rooftop, detect seismic motions and tremors at the ground and in the building. 2. The control computer analyzes each signal and issues a drive order. 3. The actuator follows the order and drives the added mass. 4. The added mass moves to counteract the seismic motion and tremors. The weight of the added mass is about 1% of the building's weight. By driving this added mass, the shaking and tremors caused by medium-sized and minor earthquakes and by strong winds can be reduced by 1/2 to 1/3. Recently, the concept of hybrid protective systems combining active and passive devices, proposed by Yang for tall buildings against strong earthquakes. One hybrid control system consists of a base isolation system connected to a passive mass damper and the other consists of a base isolation system connected to an active mass damper. A hybrid isolation system design procedure has been developed. DUOX is an active structural response control system based on the principle of pendulum movement. The weight used is of dual system. DUOX demonstrates excellent vibration control through computer-controlled driving of the AMD weight that is mounted on the passive tuned mass damper. Vibrations in all directions can be controlled by two AMDs installed crosswise. The DUOX is like a pendulum which a small person propells well on it. This person skilfully controls the degree of swinging by shifting his weight. Weight of device less than 1% of a building's weight. DUOX operates in the following way: 1. The sensors installed in the basement and on the top floor detect earthquake motion or building vibration and transmit signals. 2. The digital control computer analyzes the signals and activates the drive control. 3. The trigger starts the actuator which drives the weights, thus controlling responses. In the TRIGON system, a weight slides of rollers like a pendulum, actively producing a vibration control force that reduces the building vibration. With the TRIGON device, the pendulum weight with V shaped rail moves on rollers in a pendulum like motion. The weight of the TRIGON is just 1/400 of the building weight. This system can be installed for only about 0.5% of overall construction costs. An innovative vibration -control system is proposed to reduce the dynamic response of tall buildings to wind and seismic loads. This system takes advantage of the so called megasubstructure configuration which is especially popular in tall buildings. The megastructure contains substructures that consist of several floors. Taking advantage of this structural configuration, a new response-control strategy is established as follows: 1. The vibration energy (kinetic energy) of the megastructure due to wind or seismic loads is transferred into substructures. xv2. The transferred energy is dissipated in the substructure. For practical implementations of active/ hybrid control systems in large civil engineering structures, it may not be practical to install sensors to measure the full state vector. On the other hand, an observer may require a significant amount of on line computational efforts, resulting in a system time delay. xvi

Benzer Tezler

Tez No
156103
Depreme dayanıklı yapı tasarımında kullanılabilen sismik kontrol yöntemlerinin incelenmesi
The investigation seismic control methods, used on structure design resident to earthquake
ERCAN YOZGAT
Yüksek Lisans
Türkçe
2004
İnşaat Mühendisliği Karadeniz Teknik Üniversitesi
İnşaat Mühendisliği Ana Bilim Dalı
DOÇ.DR. METİN HÜSEM
Tez No
75327
Deprem etkisindeki yapılarda aktif ve pasif kontrol sistemlerinin uygulanması
Başlık çevirisi yok
BARIŞ SARI
Yüksek Lisans
Türkçe
1998
İnşaat Mühendisliği İstanbul Teknik Üniversitesi
İnşaat Mühendisliği Ana Bilim Dalı
DOÇ. DR. A. NECMETTİN GÜNDÜZ
Tez No
126950
Deprem etkisindeki yapıların aktif kütle sönümleyici ve aktif kiriş kontrol sistemleri ile korunması
Active mass damper and active tendon control for earthquake excited structures
MUSTAFA MELİK
Yüksek Lisans
Türkçe
2002
İnşaat Mühendisliği İstanbul Teknik Üniversitesi
İnşaat Mühendisliği Ana Bilim Dalı
DOÇ. DR. A. NECMETTİN GÜNDÜZ
Tez No
507458
Enerji etkinliği açısından bir ilköğretim binasının aktif ve pasif sistem olarak performansının değerlendirilmesi
An evaluation study on performance of a primary school as a active and passive system in terms of energy efficiency
TUĞÇE KÖKSAL
Yüksek Lisans
Türkçe
2018
Mimarlık İstanbul Teknik Üniversitesi
Mimarlık Ana Bilim Dalı
PROF. DR. GÜL KOÇLAR ORAL
Tez No
350587
Bina tasarım parametrelerinin enerji harcamalarına etkilerinin belirlenmesine yönelik bir çalışma
A study on the determination of the effect of building design parameters on energy consumption
ALİ SAVAŞ YASAN
Yüksek Lisans
Türkçe
2011
Mimarlık İstanbul Teknik Üniversitesi
Mimarlık Ana Bilim Dalı
PROF. DR. GÜL KOÇLAR ORAL

Geri Dön