Mevcut bir trafo yapısının deprem performansı ve bu performansın geliştirilmesine yönelik müdahalelerin irdelenmesi
Evaluation of seismic performance and rehabilitation methods for an existing substation structure
Yazar: CANSEV BAYDAR YILMAZ
Danışman: PROF. ALPER İLKİ
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2015
Konu: Mühendislik Bilimleri = Engineering Sciences ; İnşaat Mühendisliği = Civil Engineering

Özet:
Bu tez çalışmasında 1989 yılında projelendirilen, endüstriyel bir tesise ait trafo binasının mevcut durumu ve projeleri incelenmiş, kuvvet ve şekildeğiştirme esaslı değerlendirmesi (duvarlar dikkate alınarak ve duvarlar dikkate alınmadan) yapılarak yapının nasıl bir deprem performansı sergilediği belirlenmiştir. 
Dört bölümden oluşan bu çalışmanın birinci bölümünde, konuya giriş yapılmış ve binaların deprem performansının değerlendirilmesi konusunun ne amaçla ortaya çıktığı açıklanarak deprem performansı değerlendirmesiyle ilgili literatür özetine yer verilmiştir. 
İkinci bölümde, 2007 deprem yönetmeliğinde tanımlanmış olan iki farklı yönteme göre mevcut yapının performans düzeyleri belirlenmiştir. Kullanılan yöntemlerden "eşdeğer deprem yükü yöntemi ile doğrusal elastik değerlendirme yaklaşımı" kuvvet esaslı bir yaklaşımdır. Bu yaklaşımda, dikkate alınan taban kesme kuvvetinin katlara dağıtılması ile yapısal elemanlardaki kesit tesirleri elde edilir. Bu kesit tesirleri ve eleman kapasiteleri dikkate alınarak yapısal elemanların performansları belirlenir. Tez kapsamında kullanılan diğer bir yöntem ise "artımsal eşdeğer deprem yükü yöntemi ile doğrusal elastik olmayan değerlendirme yaklaşımı" dır ve bu yöntem yerdeğiştirme esaslı bir yaklaşımdır. Artımsal eşdeğer deprem yükü yöntemi şekildeğiştirme esaslı bir yöntem olduğu için yapısal elemanların performansları şekildeğiştirme kapasiteleri dikkate alınarak bulunur.
Üçüncü bölümde, yapının mevcut performansının geliştirilmesine yönelik müdahaleler irdelelenmiştir.
Dördüncü bölümde, yapının performans değerlendirmesinde kullanılan methodların  ve yapı performansının geliştirilmesine yönelik müdahalelerin sonuçları karşılaştırılarak değerlendirilmiştir.
Mevcut trafo yapısının malzeme özellikleri, donatı çapı ve yerleşimleri EK A' da verilmiştir. EK B' de ise yapı analizinde kullanılan yüklemeler belirtilmiş, son olarak EK C' de eşdeğer deprem yükü yöntemi ile doğrusal elastik değerlendirme yaklaşımı sonuçları (duvarlı, duvarsız ve kolonları CFRP ile güçlendirilmiş) her bir eleman için detaylı olarak verilmiştir.

Abstract:
In this thesis, earthquake performance of an existing substation structure which was designed in 1989 is investigated through displacement and force-based assessment procedures.
Destructive earthquakes cause loss of life and property aspecially in the high population and industrial zones. Besides these losses, many industrial plants became unserviceable and national economy was damaged. 
Seismic Code of Turkey (2007) is one of the codes which state the design requirements for buildings to be built in disaster areas and also the assessment requirements for existing buildings in disaster areas. As expected, it is not an easy task to give compatible methods applicable for buildings to be designed and for buildings to be assessed. The methods in the Code take into account directly or indirectly non-linear behavior of the structure, when the seismic effects are considered. However, the non-linear behavior of a structure can be considered in various ways, as it is the case in the seismic codes. The adoption of a seismic load reduction factor is one of them. On the other hand the use of the principles of the capacity design is another way of taking into account the non-linear capacity of the structural elements. 
The use of the seismic load reduction factor is easy to apply and probably for this reason it is adopted widely by the large number of seismic codes. In a common application of the seismic force reduction factor it is applied to all elements of the structures disregarding the ductility degree of the individual elements. This type of the application of the seismic force reduction factor can be found in the Turkish Seismic Code for buildings to be designed as well. This application can be found in the equivalent static load method, the multi mode method and the time domain analysis method stated by the Code. However, the Code requires that the nonlinear behavior of the existing structures should be considered by a parameter which may be regarded as a load reduction factor which depends on the type of the elements as well as on the type and degree of the internal force. In fact this is much more realistic approach that the application of the global force reduction factor to all structural elements, provided that the information level of the element of the structure is high. In the Code there is an alternative method as well, where the nonlinear behavior of the structures is taken into account by using the plastic hinge hypothesis under the assumption that enough information exists for the structural elements for defining the characteristics of the hinge. In this case single or multi mode pushover analysis is applied for evaluating the lateral load capacity of the structure beyond the elastic range.
Structural engineering experts and other authorities concur on the opinion that the seismic performance assessment of constructed facilities is an important subject. The aim of the performance based evaluation is generally to predict the damage (inelastic deformations) of the structure under expected earthquakes and to determine whether the structural system has enough ductility to support those inelastic deformations and whether those inelastic deformations are acceptable by the owner of the building. For the performance based evaluation, various approaches are developed which can be considered in two groups. First one is the linear methods. Engineers are familiar to the linear methods and they use them in everyday engineering design practice. Second one is the nonlinear methods which are more realistic than the linear ones to simulate the behavior of structures under earthquake. Non-linear methods can be also categorized as Nonlinear Static Procedure and Nonlinear Dynamic Procedure based on the time dependence of the procedure.
Nonlinear Static Procedure (NSP) so called pushover analysis has a widespread use in practice. The main effort of the performance evaluation in NSP is to obtain the seismic capacity curve and the target displacement of the structural system under considered earthquake. The capacity curve of a structural system is obtained from a nonlinear model which includes force-deformation relations of the cross-sections, i.e., bending moment-rotation relations. Pushover analysis is applied by adopting a lateral load pattern compatible to the first mode shape. The capacity curve of the system represents a non-linear relationship between the lateral load and the top displacement and shows the weak and the strong points of the system. The displacement demand of the SDOF system is determined by using the effective period, the relevant spectrum and the displacement modification factors. The seismic deformation demands of the structural components are determined due to the performance point of the structure. Deformation demands are checked as if they can be compensated by the existing capacity of the section.
At the first section of the thesis, the topic is introduced and a summary of literature is presented. 
In the second section, seismic performance levels of the examined substation structure are determined according to two different methods which are available in "Specification for Buildings to be Built in Earthquake Regions" put into force in 2007. Equivalent seismic load method with linear elastic evaluation approach is a force-based approach. This force-based method takes into account the ductile behavior of the structure indirectly through the seismic load reduction factors and capacity design principles. In accordance with this approach, base shear force is distributed to each storey considering mass participating ratios and internal forces are obtained. Structural performance is determined with these internal forces and member capacities. Incremental equivalent seismic load method is a non-linear seismic assessment procedure. As a matter of fact, this method which takes into account inelastic behaviour can be used in direct determination of internal force and deformation demand of the structure under the earthquake.
At the third section several rehabilitation methods are studied for improving earthquake performance of existing structure.
In the fourth section these methods are examined and evaluated in a comperative manner. Moreover, in this section all consequences of analysis are explained for all evaluation approaches. 
In conclusion, material properties, reinforcement size and reinforcement layout of the examined substation structure is included in Appendix-A. Besides, loads which are assigned to the structure for SAP2000 analysis is presented in Appendix-B. Finally, in Appendix-C, all member end forces and damage failures of the members for equivalent seismic load method are submitted.