Mevcut yüksek katlı betonarme binaların hasar görebilirliğinin kırılganlık eğrileri yardımıyla belirlenmesi
Evaluate damage potential with fragility curves for existing high rise R.C. Building
Yazar: HÜSEYİN KEMAL DAL
Danışman: DOÇ. DR. BEYZA TAŞKIN AKGÜL
İstanbul Teknik Üniversitesi / Fen Bilimleri Enstitüsü / İnşaat Mühendisliği Ana Bilim Dalı / Yapı Mühendisliği Bilim Dalı
Derece: Yüksek Lisans, 2013
Konu: İnşaat Mühendisliği = Civil Engineering

Özet:
Mevcut yapıların depreme karşı performansının belirlenmesi,deprem olmadan önce gerekli önlemlerin alınabilmesi açısından önem arz etmektedir.Bu gereklilik kapsamında 2007 yılında yönetmeliğimize,eleman tasarımı ve mevcut yapıların değerlendirilmesi ile ilgili ilave hükümler koyulmuştur.Performansa bağlı yapı tasarım ilkelerini esas alan yapısal değerlendirme anlayışı,özellikle son zamanlarda deprem bölgelerindeki mevcut binaların deprem olmadan önce performanslarının belirlenmesi ve gerek görülen halde güçlendirmesinin yapılmasıyla ilgili önemli gelişmeler kaydetmiştir. Ülkemizdeki bu gelişim yukarıda bahsi geçen yönetmelik kısmının eklenmesiyle doğru bir çerçeveye oturutulmaya çalışılmıştır.
 "Zaman Tanım Alanında Doğrusal Olmayan Hesap" yöntemi gelişen bilgisayar teknolojisine paralel olarak günümüzde daha çok kullanılmaya başlanmıştır. Beraberinde çok yüksek işlem hacmi getiren bu yöntem için gelişmiş yazılımlar kullanılması gerekir.Bilgisayar teknolojileri bu analizlerin yapılış süresini kısaltsada analiz sonuçlarında çıkan verilerin işlenmesi bile epey vakit almaktadır. Herbir elemanın kritik kesitlerindeki beton ve çeliğinin şekil değiştirmesinin belirlenip yönetmelikte verilen şekildeğiştirme limitleriyle kıyaslanıp önce eleman sonra kat sonrada bütün yapı için hasar limitinin belirlenmesi ve bunun 7 ayrı depremde yapılması bu metodun işlem sıralamasını özetlemektedir.
Bu yöntemi daha uygulanabilir tutmak ve sonuçlarının daha güvenli bir çerçevede yorumlanması adına istatistik biliminden yararlanılabilinir. Benzer taşıyıcı sistem özelliklerine sahip yeter sayıda binaya yine yeter sayıda yapay veya doğal yer sarsıntılarının uygulanıp yapılan çözümler toplanarak bir veri bankası oluşturulup, verilerin dağılımına dikkat edildiğinde Standart Normal Dağılım ile benzerlik gösterdiği görülecektir.Bu sebeble bu verileri genelleştirme imkanı bulunur ve Normal Dağılım sayesinde yapının,ilgili dağılım parametresinde hangi hasar seviyesinde hangi olasılıkla bulunabildiğine  ilişkin yorum yapılabilme imkanı doğar. İlgili hasar seviyelerinin dağılımını gösteren fonksiyonlar literatürde  Kırılganlık veya Hasargörebilirlik Eğrileri şeklinde isimlendirilir.
Elde edilmiş Kırılganlık Eğrilerini referans alarak yapının performansını belirlemek bu çalışmanın temel hedefidir.Bu çerçevede yapı stoğumuzun çoğunluğuna şu an için hitab etmeyen yüksek katlı yapılar incelenmeye çalışılacaktır.
Altı bölümden oluşan yüksek lisans tezinin birinci bölümünde giriş kısmına yer verilmiş ve bu bölümde çalışmanın konusu, amacı ve kapsamı belirtilmiştir.
İkinci bölümde, Kırılganlık Eğrileri hakkında genel bilgiler verilmiştir.
Üçüncü bölümde,İstanbul'da Z3 sınıfı zemin üzerinde bulunan yüksek katlı 4 binanın taşıyıcı sistemi ve kullanılacak deprem kayıtlarının karakteristik özellikleri hakkında bilgiler verilecektir.	
Dördüncü bölümde bu 4 yapının ZTADOH'nın yapılabilmesi için gerekli bilgiler özetlenmeye çalışılımış ve SAP2000 v15.1.0. kullanılarak analiz modelinin nasıl kurulduğu hakkında genel bilgiler verilmiştir.
Beşinci bölümde Prof.Dr.Amr S. ELNASHAI'nin "SEISMIC FRAGILTY ASSESSMENT FOR REINFORCED CONCRETE HIGH-RISE BUILDING"(Mid-America Earthquake Center September 2007 Report 07-14)isimli çalışmasında tanımladığı Kırılganlık Eğrileri baz alınarak yapıların hasargörebilirliği ZTADOH yöntemi sonuçları ışığında belirlenmiştir.
Altıncı bölümde ise çalışmada varılan sonuçlar verilmiştir.

Abstract:
Turkish Republic has geography which is near the active fault line. In the last century, serious earthquake had been happened at this region. These Earthquake magnitudes were higher than 7 and hypocenter depths were bigger than 30 kilometres. For instance, earthquake which was happened in Erzincan where is located eastern part of Turkey in 26 December 1939 had 7.8 Magnitude, in Tokat where is also located eastern part of Turkey at 20 December 1942 magnitude was 7.0, in Samsun where is located northern part of Turkey at 26 November 1943 magnitude was 7.4, in Adapazarı where is located near the Marmara Sea at 22 July 1967 magnitude was 7.2, in Izmit where is located near the Marmara Sea at 17 August 1999 magnitude was 7.4, in Düzce where is located near the Marmara Sea at 12 November 1999 magnitude was 7.2 and in Van where is located eastern part of Turkey at 23 September 2011 magnitude was 7.2. If we consider Izmit Earthquake at 17 August 1999, we understand that this earthquake has one of the biggest devastating impacts.
Impact of Izmit earthquake was felt all around the Marmara Sea and from Ankara to Izmir. Due to Izmit earthquake, 17.480 deaths and 23.781 injured and 505 cripple occurred according to formal report. 285.211 houses and 42.902 workplaces were damaged and 133.683 buildings were collapsed. Approximately 16 million people suffer damaged differently. Direct and indirect losses about economic were 12 - 17 billion dollar according to World Bank data. 
In the light of this fact we can say that North Anatolian Fault Line will continue compressing and storing energy. So the earthquake became a part of life of citizens in Turkey. While all areas of the social life adopt to themselves to life having earthquake, also Structural and Earthquake Engineering had to be developed itself. Performance based structural analysis and evaluating the seismic vulnerability become obligation that is beyond the necessity for Turkey. In this sense, Structural Design Code in Turkey should be improved and enclosed these mentalities.
Determining the seismic performance of existing structures poses importance due to the necessity of taking precautions before such disasters occur. Because of this necessity, the new Structural Design Code which was released in 1999 and revised in 2007 was added new provisions for existing buildings in order to determine their performance criteria and structural member design. The main purpose is designing ductile structural and provides the more energy damping capacity in the structural system. Former experiences shown that most of the buildings collapsed during earthquake had been damaged due to brittle mechanism. Whereas, structural member should be resist against shear mechanism. If we take into account that ratio of energy damping of shear mechanism is lesser than flexural mechanism, the codes must pin down shear mechanism and collapse mode should control by flexural mechanism. 
Another issue is vertical and horizontal irregularities caused by architectural reason. No matter ductile structural design we do, irregularities cause additional inertial effect and they change structural behaviour against earthquake. This behaviour has to take in the computable limit. So that reason Turkish Earthquake Code had been improved and added associated with irregularities effect in 1999.
Due to improvement that is caused additional rules not only affected national structural design but also study of structural assessments approach. This manner of approaching is based on performance design, especially recently, has developed significantly in order to determine the performances of existing buildings even before the earthquake happens and take necessary related precautions. The development of Performance based design has been tried to put on the right track by adding related items to the Structural Design Code. Therefore, researchers are not only consider performance based design but also Earthquake Risk Assessment.
However, Study of Earthquake Risk Assessment gains importance as Performance Based Design. Earthquake Hazard Identification and Structural Vulnerability Evaluation are the main components of earthquake risk assessment. Earthquake Hazard Identification is out of the scope of this study. Structural Vulnerability Evaluation which is the subject of civil engineering and city planning disciplines aims to determine, classify, and assess the fragility of existing building stock and other structures. (Dams, bridges, power plants, etc...). Disaster management purposes a fragility based assessment that considers local structural properties is required. However, local conditions are usually ignored and vulnerability based assessment studies for structures in different countries are adapted to earthquake hazard estimation and disaster mitigation projects in Turkey. Unfortunately, differences in structural characteristics cause significant deviations on damage and loss estimation by influencing the resulting fragility curves. For this reason, we should describe our Fragility Curves according to our building stock and fault behaviour.
In Turkish Earthquake Code, structural vulnerability is calculated using deterministic method form Section 7 such as the other countries codes. Deterministic method, must be acknowledged, takes long time. It is not rapid methodology in order to specify assessment and determination of disaster of earthquake, especially shortly after the earthquake. It is necessary to give rapid response by Governmental Agency and prompt sources shortly after the earthquake. There are different kinds of methods in the literature based on observation and engineering experimentation in order to use after a short time before earthquake. But they are not component of this study.
The most comprehensive deterministic method is named as "The Nonlinear Time History Analysis" in literature. Firstly, In order to perform this method it requires very high capacity data processing demands. To solve equation of motions, advanced computer system should be used. Equation of motions are obtained associated with system mass that is joining the movement, system rigidity related the elastic-inelastic modulus and moment of inertia (every step of times they will be chanced associated with inertial forces and energy capacity) and structural damping ratio. Lumped Plastic Theory is used in order to make definition of the rigidity of the structural system. Nonlinear parameters are defined using to plastic hinge hypothesis for structural elements.
No matter what we accept which value for damping ratio we always stay away from exact ratio. Because, damping ratio is not only related to material properties but also related to the non-structural elements such as walls, cladding materials, windows etc... For these reasons damping ratio is the most unknown value for the equation of motions. Equations of motions change every step of time and must evaluate each time step separately. However, acceleration records are other part of equation of motion also. Time dependent acceleration values are recorded as secure and reliable. Most of countries have Accelerogram Devices that are spread everywhere and these devices recorded the ground motion parameter in 7 days 24 hours.
Second order nonhomogeneous differential equation should be solved in order to find acting earthquake forces associated with step of time on hyperstatic system. Solving each step is defined to next step as boundary condition. So thanks to earthquake forces, calculated from last step, differential equation becomes homogenous for next step and there is cyclical format about solution of equation. It is already known that structural system shaking by strong ground motion; structural members do not show only linear behaviour. It is expected rigidity matrix that is using in second order differential equation should be chanced according to nonlinear behaviour. This alteration should be reflected at rigidity matrix in direct proportion to decreasing the moment capacity. For obtain to damage capacity of structural, firstly, the critical concrete and steel strains should evaluate for every structural member. Than the strains of members compared to values determined in the related codes. Structural capacity can be obtained after determination of member damage. If we accept the time intervals are very small, it seems inevitably that necessity to use integrated software system. Even though advanced computer technologies reduce the amount of computing significantly, to process outcome data still takes lots of time and effort.
The process which is time consuming as seen is not usable about practically. The most time consuming part is definition of damage on every structural member. Instead of doing this process for each member, Fragility Relation Functions can be used based on Non-Linear Time History analysis. Therefore, Fragility Curves Assessments give a new way for determining structural damage.
The results that is obtained from former design which is based on deterministic method are grouped similar structural system where are located on similar soil group. This streaming makes sense in terms of Statistical Science. This database is verified to be similar to Standard Normal Distribution.
If Structural Damage Levels are associated with the characteristic earthquake data (PGA, PGV, PGD etc.) the damage level probability can be calculated. Also characteristic earthquake data is related to structural parameter (story drift, story shear force, base shear etc...) that is representative structural damage. In order to evaluate to probability of Structural damage level using characteristic data, Logarithmic Inverse Transformation should be done. Distributions of related damage levels and the functions are named as Fragility Curves in the literature. Determining the performance of structures based on obtained Fragility Curves is the main purpose of this study. This study does not consider evaluating the fragility curves. Main purposes of study evaluates damage potential associated with story drift, using previously calculated Fragility Curves from EL NASHAI, for five different structures that stand on same soil type. Within this framework high rise buildings that does not represent building stock in Turkey are analysed. There are four different structures that are placed same soil type, approximately equal height of structure and same seismic region.
This thesis includes five chapters. First chapter explains subject, purpose and scope of the study.
Second Chapter provides general information about Fragility Curves. 
Third Chapter gives information about geometry, height, formwork plan for 4 different high rise buildings that are on Z3 type ground that is identified from Turkish Seismic Code. Also reinforcement bar sizes and numbers are defined for each structural members. Method of filtering of acceleration records that are prepared for Nonlinear Time History Analysis,  specified at this section.
Fourth Chapter comprises the summary data of the required analyses for the four buildings. The general knowledge as analysis geometry, generated the time history case and nonlinear numeric steps, defining the nonlinear material models and section properties using "Section Designer" and Moment-Curvature data application, are given in this section on analysis models that are created with SAP 2000 v15.1.0 
Fifth Chapter displays the damageability of structures as determined based on Prof. Dr. Amr S. EL NASHAI "SEISMIC FRAGILTY ASSESSMENT FOR REINFORCED CONCRETE HIGH-RISE BUILDING"(Mid-America Earthquake Center September 2007 Report 07-14) study that describes Fragility Curves.
Sixth Chapter describes the conclusions of derived from the study.