Özel bir sönümleyicinin farklı frekans bantlarında deneysel incelenmesi
Experimental evaluation of a special energy dissipater in various frequency ranges
Yazar: AHMET GÜLLÜ
Danışman: DOÇ. DR. ERCAN YÜKSEL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2012
Konu: İnşaat Mühendisliği = Civil Engineering
Dizin: Enerji tüketimi = Energy consumption

Özet:
Yüksek lisans tezi olarak sunulan bu çalışma, yapılarda sismik etkileri ve dolayısıyla oluşacak hasarları azaltmak için kullanılan pasif sönümleyici sistemlerinden biri olan kurşun ekstrüzyon sönümleyicinin deneysel olarak incelenmesinden oluşmaktadır. İstanbul Teknik Üniversitesi Yapı ve Deprem Mühendisliği Laboratuvarı'nda üretilen sönümleyiciye çift yönlü, değişken yatay yükler uygulayarak kuvvet ? yerdeğiştirme eğrileri çizdirilmiştir. Deneylerden elde edilen veriler yazılan bilgisayar programında giriş bilgisi olarak kullanılmış ve bu sayede sönümleyicinin sönüm katsayısı, sönüm oranı, depolanan ve saklanan rijitliği gibi karakteristik özellikleri ile her bir çevrimde kurşun ekstrüzyon sönümleyici tarafından sönümlenen enerji miktarı hesaplanmıştır.Çalışmanın birinci bölümünde, kurşun ekstrüzyon sönümleyici hakkında kısa bir bilgi ile tez çalışmasının amacı ve kapsamı yer almaktadır. Giriş kısmında kurşun ekstrüzyon sönümleyicinin gelişiminden ve farklı türlerinden bahsedilmiştir. Daha sonra benzer özelliklere sahip pasif sönümleyicilerden viskoelastik sönümleyici ile karşılaştırılma yapılmıştır.İkinci bölümde aktif ve pasif sönümleyiciler hakkında bilgi verildikten sonra kurşun ekstrüzyon sönümleyici hakkında ayrıntılı bilgi verilmiştir. Kurşun ekstrüzyon sönümleyici ve diğer sönümleme sistemleri ile ilgili yapılmış olan literatür araştırması da bu kısımda yer almaktadır.Üçüncü bölümde İstanbul Teknik Üniversitesi Yapı ve Deprem Mühendisliği Laboratuvarında üretilen sönümleyiciden bahsedilmiştir. İlk olarak deneylerin nasıl yapıldığı anlatılmış daha sonra deney sonuçlarını değerlendirmek için yazılan bilgisayar programından bahsedilmiş ve bu programda kullanılan algoritmanın alındığı Constantinou ve Symans'ın ilgili yayını da yine bu kısımda yer almıştır. Bütün bunlardan sonra deney düzeneğinin tasarım sürecinden, yükleme çerçevesinin detaylarından bahsedilmiş ve üretim için gerekli detay çizimlerine yer verilmiştir. Deney düzeneğinin kurulumu, deneyler sırasında karşılaşılan zorluklar ve bunlara karşılık yapılmış olan iyileştirme çalışmalarından da yine bu bölümde bahsedilmiştir. Deneylerden elde edilen veriler yazılan bilgisayar programı ile irdelenmiş ve sönümleyicinin karakteristik özellikleri ortaya konmuşturDördüncü ve sonuncu bölümde ise yapılan bütün deney ve çalışmalardan elde edilen sonuçlar anlatılmıştır.

Abstract:
In this M.Sc. thesis, characteristic properties of a lead extrusion damper are investigated in the experimental manner. A prestressed lead extrusion damper produced in Istanbul Technical University Structural and Earthquake Engineering Laboratory (STEELAB) has been tested by using cyclic loading at different frequencies and strokes.An experimental setup is established to fix the designed lead extrusion damper into the proper position and so that to obtain force ? displacement relationships of the device could be possible. The loading frame, which has high lateral stiffness and load carrying capacity, is installed into an existing reaction frame to transfer the resulting forces to the reinforced concrete slab. Additionally adaptor elements and out ? of ? plane stopper systems are used within this experimental study. After having established the loading frame and other elements, experimental study was started.The mathematical method used by Constantinou and Symans (1992) is adopted in this study for determining rigidity and damping characteristics of LED. A computer code has been developped for calculating rigidity and damping properties of the experiments. Once getting test results, the code reads this file as an input file and makes necessary calculations. Owing to this code, evaluation of testing results takes just a few seconds.In the first chapter of the thesis, history of lead extrusion damper and its usage at structures mentioned briefly. Secondly, two types of lead extrusion damper, bulged shaft and constricted tube are explained in detail. It is also described that what are the differences between bulged shaft and constricted tube dampers. Additionally it is discussed that why we select bulged shaft type lead extrusion damper for experiments. Moreover, the damper tests explained briefly.The experimental studies showed that the lead extrusion damper produced in STEELAB has a significant damping ratio at any frequency. As we want to compare the designed lead extrusion damper with other passive damping devices an intensive literature survey has been performed about the viscoelastic dampers which have the similar properties with lead extrusion damper. The literature survey yield that the viscoelastic dampers can reach 25% damping ratio and it can be affected by the environmental conditions while the lead extrusion damper produced and designed in STEELAB reaches about 43% damping ratio. Furthermore viscous liquid of the viscoelastic dampers may loose their viscous properties by the time but lead, the working material of the designed damper, can regain its original properties in a short time after even the temperature is around -5 ºC.In the second chapter, a detailed literature survey is presented covering previous studies on lead extrusion damper and all the other damping devices.At the starting point, it is mentioned that the seismic events like earthquakes, tsunamis or tornados apply significant energy to buildings or other structures and this energy may cause structural damages. It is predicted that these damages occur primiraly at the beam ends and so at the bottom of the columns in the classical structural engineering concept. So that the total collapse of buildings are prevented by these order of damage formation. It may be possible to absorb the seismic energy without having heavy damages by the special damping devices.Using additional damping devices or systems can be desirable for the following reasons,?Additional damping devices/systems may provide additional damping and stiffness to the structure to reduce the response.?Energy dissipation in structures can be confined by usage of the supplemental devices.?Damage to the structure can be limited by the supplemental dampers which are easier to replace than structural components and do not affect the gravity load ? resisting system, [4].Even though estimating the seismic loads is very hard, owing to developments in the computer technologies, dynamic loads affect the structure can be measured before the load effect to the structure and necessary control loads can be calculated at control computer, in the active control systems. These control loads are applied to the structure by the active load mechanisms that placed into structure.On the other hand, passive systems do not require computers and complicated algorithms. Once load affect to the structure, these devices absorb this energy by using different mechanisms. Some passive damping devices are frictional dampers and most of these devices generate rectangular hysteresis loops. Yielding steel dampers use the yield properties of miled steel for damping. When shape memory alloys loaded undergo a reversible phase transformation as they deform and therefore have ability to yield repeatedly without sustaining any permanent deformation. Viscoelastic dampers exhibit combined features of viscous liquid and elastic solid. When they deform, they return to their original shape after each cycle and dissipate a great amount of energy. Some of fluid viscous dampers operate on the principle of fluid flow through orifices, [4].Lead extrusion damper convert the mechanical energy to heat energy by the deformation of lead. It maintains damping even repetitive seismic events because of lead regain its original properties owing to three processes that related which other. They are Recover recrystallization and gain growth.Extrusion prosess come true as forcing a material through an orifice thereby altering its shape. This orifice may be in two different forms. At first, constricted tube type damper, orifice is created by a constriction from the outer cylinder. At second, the bulged shaft damper, one can creat the orifice by a bulgen on the shaft. Producing the bulge shaft damper is easier and cheaper than the producing constricted tube damper. Also the bulged shaft damper has better performance. Therefore bulged shaft type lead extrution damper has been used in this study.In reality, the working with lead is hard. When lead solidified micro voids occur due to trapped air. These voids inhibit fully fill the volume inside of damper. If there are micro voids, damper cannot work at full capacity. Some part of motion is used for compressing the voids and whiles this compressing there is no damp.In the third chapter of the thesis, production phases of the specimens, experimental setup, the details of the experimental studies and the results of the experiments are presented. The experimental studies cover frequencies 0.0167, 0.0200, 0.0222, 0.0250, 0.0333, 0.0500, 0.0667 and 0.1 Hz. The designed damper is tested for the cyclic type loading.