Sönümleyiciler ile bağlı betonarme perde duvarlı yüksek yapılarda eşdeğer sönümleme yöntemlerinin incelenmesi
Evaluation of equivalent damping methods for RC coupled wall high-rise buildings with coupling dampers
Yazar: MUHAMMET EMRE ERDEMLİ
Danışman: YRD. DOÇ. DR. BARIŞ ERKUŞ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Günümüzde, yapıların daha yüksek ve narin yapılması isteği, yapıların yatay kuvvetlere karşı daha hassas hale gelmelerine neden olmaktadır. Bunun sonucu olarak yapılardaki konfor, güvenlik ve afet sonrası kullanım gereksinimlerinin karşılanmasındaki zorluklar yeni taşıyıcı sistem düzenlemelerinin önerilmesi ile giderilmektedir. Bu yeni düzenlemelerden biri olan ve yapıya ek sönümleme özelliği sağlayan sönümleyici cihazların kullanımı gün geçtikçe yaygınlaşmaktadır. Bu bağlamda, sismik risk altındaki bölgelerde inşa edilen yüksek yapılarda yüksek rijitlik ve enerjimi sönümü sağlama özellikleri nedeni ile yaygın olarak kullanılan bağ kirişli perde duvar sistemlerinin performans seviyelerini arttırmak amacı ile sönümleyici cihazların kullanılması güncel araştırma konuları arasındadır. Bu tezin konusu olan sürtünme tipi sönümleyicili çelik bağ kirişleri, perde duvar sistemlerinin performanslarının arttırılmasında kullanılabilecek düzenlemelerden bir tanesidir.
Sönümleyici cihazların tasarımlarının yapılması aşamasında doğrusal olmayan analiz yönteminin kullanılması gerekliliği bu cihazların tasarımı için gerekli sürenin ve iş gücünün artmasına neden olmaktadır. Bu nedenle, sönümleyici cihazların ön tasarımlarının doğrusal analiz metodu ile yapılmasını mümkün kılan eşdeğer sönüm değerinin hesaplanması son derece önemli bir konu haline gelmektedir. Bu çalışmada, eşdeğer sönüm hesap yöntemlerinden modal şekil değiştirme enerjisi yöntemi ve ASCE/FEMA yaklaşımı incelenmiştir. İlk olarak, iki yöntemin doğruluğu incelenmiş daha sonra incelenen yapı için eşdeğer sönümün kullanıldığı doğrusal analiz sonuçları ile doğrusal olmayan çözümleme sonuçları karşılaştırılması yapılmıştır.
Birinci bölümde, ek enerji sönümleyici sistemlerinin ortaya çıkmasındaki temel etkenler, yüksek yapılarda kullanılan ek enerji sönümleyici sistem düzenleri ve bu sistemlerin yapıya kattığı ek sönüm miktarının belirlenmesinde kullanılan yöntemler hakkında genel bilgiler verilmiştir. 
İkinci bölümde, yüksek yapılarda yaygın olarak kullanılan bağ kirişli perde duvar sistemleri ve ek enerji sönümleyici sistemler hakkında bilgiler verilmiştir. 
Üçüncü bölümde, incelenen yapısal sistem özellikleri, analizlerde kullanılan deprem etkileri, doğrusal olmayan analiz modelinin oluşturulması aşamaları ve elde edilen sonuçlar bulunmaktadır.
Dördüncü bölümde, eşdeğer sönüm hesaplama yöntemlerinden modal şekil değiştirme enerjisi yöntemi ve ASCE/FEMA yaklaşımı anlatılmış ve bu yöntemlerin doğruluğu incelenmiştir.
Beşinci bölümde, ASCE/FEMA yaklaşımı ile hesaplanan eşdeğer sönüm değerinin kullanıldığı doğrusal analiz sonuçları ile doğrusal olmayan analiz sonuçları karşılaştırılmıştır.

Abstract:
In recent years, the wish to build higher and more slender designs has caused the buildings to become more susceptible to horizontal forces. As a result of this, the difficulties regarding the fulfilment of comfort, safety and post-disaster usage requirements are addressed with new suggestions for structural system configurations. One of these new configurations is using dampers, they provide supplementary dissipation for the building and are becoming more common every day. In this context, in order to increase the performance levels of coupled shear wall systems, which are widely used for their high stiffness and energy dissipation providing qualities, damping devices are used in the middle of coupling beams as a recent approach. The subject of this thesis, steel link beams with friction dampers, is an example of these configurations. In this configuration, relative displacement occurs on both sides of the coupling beams with lateral load impact and when the yielding displacement of a damper is reached, the damper activates. After activation, the dampers start dissipating energy and this is directly influenced by damper capacity. Compared to supplementary damping systems, this configuration not only affects energy dissipation, but also the coupling ratio of shear walls, which is primarily influential on overall behaviour of the structure. 
The necessity of nonlinear analysis procedures and an advanced dynamics background during the design process of dampers increase the amount of time and workforce required to design them. Thus, calculating an effective damping value which allows a linear analysis method to be applied in the pre-design stage of dampers is a very critical issue in the matter. In this study, the reliabilities of equivalent damping methods are investigated in three steps with the following method:
Firstly, the structural system of a tall building which is built in the Levent region of İstanbul is considered for investigating equivalent damping methods. The building is 163.4m in height, and has a 28x34 m2 base area. The structural system consists of perimeter composite columns, which are attached with reinforced concrete façade beams, and two C shaped core walls which are coupled by steel link beams. The columns are attached to the core walls with 26 mm thick reinforced concrete slabs. Some simplifications are made for the structural system; all stories, composite columns and perimeter beams are assumed identical. For this study, the structural system is modified by placing friction dampers with 1500 kN capacity in the middle of every steel coupling beam. Link beams, which are fuse elements of the structural system, are prone to experience large deflections and dissipate a major part of the earthquake excitation energy. Considering this, placing dampers in the middle of link beams increases the effectiveness of dampers, by providing a larger cyclic curve area and improving the overall performance level of the building.
Secondly, a verification process for two equivalent damping calculation methods, which are the modal strain energy method and the ASCE/FEMA approach, is applied. For this purpose, the equivalent damping values for the first mode of the described building are calculated by using the two methods, and similar results are obtained; %15 supplementary viscous damping for the modal strain energy method, and %13.5 supplementary viscous damping for the ASCE/FEMA approach. As a result of similar damping values, a verification procedure is applied just for the damping value which was obtained from the ASCE/FEMA approach. Two separate analysis models are created for verification; a linear model with equivalent damping and a linear model with nonlinear friction damper element. Time history analysis with seven earthquake records and response spectrum analysis are conducted, and the results are compared. The aim of these comparisons is to show that the damping value which is provided by friction dampers can be represented by the equivalent damping value. Base shear, overturning moment, roof deflection comparisons are presented in this study and marginal differences are observed. As higher modes of tall buildings are more influential in overall behaviour, these differences are attributed to calculating the equivalent damping value only for the first mode of the building. 
Finally, the effect of nonlinear behaviour of structural elements on the equivalent damping value is investigated. For this purpose, a nonlinear model of the considered building is prepared by using PERFORM 3D software. All structural elements are designed taking the nonlinear behaviour of materials and the geometric properties into account. Base shear, overturning moment and deflection values, obtained form time history analysis of the nonlinear model, are compared with the spectrum analysis results of the linear model with equivalent damping, which is also used in the second step. In the equivalent damping calculation process by using the ASCE/FEMA approach, the contribution of nonlinear behaviour of structural elements to the equivalent damping value is neglected, and comparisons are made to evaluate the effect of nonlinear behaviour of structural elements on the equivalent damping value. For the considered building, approximately %50 of dissipated inelastic energy is provided by structural elements and the results are evaluated considering this parameter.
The results and recommendations for future studies can be summarised as follows,
•	In this study, a new approach is used for scaling the earthquake records. This new approach takes into account not only the first mode period of the building; but also the higher mode periods, which affect the scaling value proportional to its modal mass contribution on overall behaviour. The effects of this new approach on the results should be investigated.
•	Equivalent damping calculation methods, the modal strain energy method and the ASCE/FEMA approach yield similar equivalent damping values.
•	Results of the comparison between response spectrum analysis of the linear model with equivalent damping and time history analysis of the linear model with nonlinear friction damper element are as follows,
o	Base shear value of response spectrum analysis is %20 higher than the result of time history analysis.
o	Overturning moment of the structure and roof level deflection value of a column from response spectrum analysis are %10 and %5 higher than the results of time history analysis respectively.
•	In the view of practical engineering, these differences can be regarded as reasonable.
•	The results of time history analysis of the nonlinear model is lower than the demands of response spectrum analysis of the linear model with equivalent damping by a ratio of 0.6 to 0.8.
•	For tall buildings, in the process of equivalent damping calculations, higher modes should be considered in addition to the fundamental modes.
•	In this study, all comparisons are made on the considered building, which has a high performance level. These comparisons should also be made for a building with a standard performance level.
•	In this study, two dampers are placed on every story. For economical concerns, new configurations with less dampers can be investigated. (e.g. Dampers can be used only on levels with the most deformed coupling beams).