Tarihi yapıların deprem performansı ve güçlendirme teknikleri

Abstract

Yurdumuz, birçok medeniyete ev sahipliği yaptığı için zengin bir kültürel mirası vardır. Özellikle Osmanlı İmparatorluğu ve Selçuklular Dönemi'nden birçok cami, türbe, hamam, köprü, su kanalları ve kuyuları bulunmaktadır. Fakat yurdumuzun Kuzey Anadolu Fay Hattı üzerinde bulunması nedeniyle yapılarımız deprem riski ile karşı karşıyadır. İstanbul Büyükşehir Belediyesi ve Vakıflar Genel Müdürlüğü de dahil olmak üzere birçok ulusal kurum, olası bir depremin etkilerini azaltmak için tarihi yapılar üzerinde çalışma yapmaktadır. Tarihi yapıların deprem güvenliği değerlendirmelerini yaparak optimum güçlendirme çalışmalarını uygulamaktadır. Genellikle, tarihi yapılarda mevcut yapısal elemanların performansını incelemek için; yapıda kullanılan malzemeler ve özellikleri, çevre koşulları ve doğal afetler nedeniyle oluşan çatlaklar ve hasarlar belirlenir, yapının tarihçesi ile yapıya daha önceden uygulanan yapısal ve mimari tüm müdahaleler belirlenir. Daha sonra yapı güvenirliğini değerlendirmek için yapısal modelleme çalışmaları yapılır. Oluşturulan model üzerinde gerekli yük analizleri yapılarak yapı performansı irdelenir. Sonuçlara göre en uygun güçlendirme yöntemine karar verilir ve yapıya uygulanır.Bu tez çalışmasının ilk bölümünde, tezin amacı ve konu ile ilgili daha önce yapılan çalışmalar üzerinde durulmuştur.İkinci bölümünde tarihi yapılarımızın geçmişten günümüze korunması ile ilgili alınan tedbirler ve izlenecek yollar özet olarak sunulmuştur.Üçüncü bölümünde yığma yapıların tanımı, yığma yapılarda kullanılan malzemelere ait özellikler, bu yapılarda tercih edilen yapı elemanları, yığma yapıda görülebilecek hasar çeşitleri ve bu hasarların nedenleri, yığma yapılara uygulanabilecek güçlendirme teknikleri, yığma yapılarda performans kavramı, yığma yapıların modelleme teknikleri ve analiz yöntemleri hakkında teorik bilgiler verilmiştir.Dördüncü bölümde İstanbul Tarihi Yarımada'da bulunan Şeyh Süleyman Mescidi örnek yapı olarak ele alınmıştır ve yapı hakkında yapılan çalışmalar sunulmuştur. Yapının bilinen tarihi ve taşıyıcı sistemi hakkında bilgiler verilmiştir. İki bodrum kata sahip olan bu yapıya ait sonlu eleman modeli oluşturulmuştur. Oluşturulan bu modelde, yapının kendi ağırlığı altındaki ve düşey yükler altında ve düşey yükler ve deprem yükleri altında inceleme yapılmıştır. Depremli durumda statik, dinamik, zaman tanım alanındaki yük analizleri yapılarak yapının mevcut durumu incelenmiştir. Çekme ve basınç dayanımları belirlenen yapının zayıf kesitleri görülerek güçlendirme önerisinde bulunulmuştur. Bu önerilen güçlendirmenin yapı performansına etkisi belirtilmiştir.Son bölümde ise elde edilen statik ve dinamik analiz sonuçları irdelenmiş ve genel sonuçlar özetlenmiştir.

As being host to many civilizations in history, Turkey has a rich cultural heritage. Especially from the Ottoman Empire, including mosques, mausoleums, bathhouses, bridges and aqueducts.On the other hand Istanbul is very close to a major earthquake source of Turkey, i.e., the North Anatolian Fault Line. More than a million earthquakes happen in the world each year. Public do not notice most of them because they are very small. However, a quake can be very destructive if it is more powerful. Earthquakes can make buildings fall down and set off landslides. This disaster can also cause many serious diseases such as cholera or dysentry. In addition to this, if an earthquake occurs at the bottom of the sea, it can and create massive waves which are called tsunamis. This huge waves can cause massive devastation.It is not possible to predict certain earthquakes beforehand with the current technology. But, governments and people should take some precautions to prevent loss of lives and destructions of buildings. It is important to construct buildings that are earthquake resistant. Some of the famous building which becomes valuable in terms of culture and history demand longer service life. For the history buildings, reinforcement is required. Reinforcement means to increase one or more than one of the following parameters; tensile capacity, shear capacity, flexural capacity, compressive capacity, member stability, ductility, strenght and stiffness.There are several statements that a major earthquake is likely to strike Istanbul in a short time. Several Turkish national institutions including the Istanbul Metropolitan Municipality and the Directorate General of Foundation are at work to mitigate the effect of a probable earthquake on historical buildings, one of them is related to the seismic evaluation of the historical buildings in the city.In these evaluations, generally a survey of the existing structural elements is carried out and the material used and cracks or damages due to environmental conditions and abuse are determined. All previous documents available related historical building is collected and all previous structural and architectural interventions are determined. Structural safety is evaluated by modeling the building and strengthening interventions are determined, when it is necessary.If a reinforcement is required for historical buildings, should be avoid damage to the original tissue of the structure. Various reinforcement techniques are summarized in this study. This methods can be given; reconstruction, injection, anchored to each other elements of the masonry units, buildup steel elements, bands of FRP, reinforcement of foudation, rubber bands. This methods are extending the life of the structure by increasing the structural performance.At the final state a application drawings are prepared and implementation of the architectural and structural intervention is carried out under proper supervision.In the present study, Sheikh Suleiman Masjid located in Istanbul Historical Peninsula, is investigated by considering gravity loads and seismic loads. Masjid's Byzantine history remains vague. Purely, neither its identity nor its function is known. It was turned into a masjid by Şeyh Süleyman, a sheikh in the reign of Sultan Mehmed II; hence the Turkish name of the building. In Turkish times the building appears too have undergone various renovation, most particularly the doors and windows.This building has two basement floors that first of them is krypta and second of them is cistern. Documents show that humid air-polluted air cycle occurs via cisterns. Thus preventing possible consequences such as disorder, corrosion, to freckling and causing decay. The first basement, krypta is an arcosollium. Arcosolium is an arched recess used as a place of entombment. The external walls of the building continue down to the first basement. They are thickened into the ground. The basements are in the harmony with the structure and soil around its. So, structure and soil interaction is extremely small.The historical structure has an octagonal plan with four arches and four lateral niches of similar sizes. The enterance in a lateral niche where is the opposite to Mihrab. Every niche has a window for the lightining and top of them is cincture. Cinctures distribute loads. So, it supports the structural performance.The building has ribbed roof. There is a stone layer beneath the bricks on top of the roof. Beneath this stone layer it is made by filling amphora. It is still unknown why the filling was made. The main walls of Sheikh Suleiman Masjid are infilled masonry. It is made of stone, brick and external mortar with crushed brick and lime, but internal nucleus made with irregular stones and earthy mortar or even only earth with very little consistence. According to material properties, compressive strenght of the wall is relatively high, but the tensile strenght is very low.The masonry building is modeled by adopting finite element technique where linear and plane elements are used. The homogeneity has been achieved by paying attention to have similar size each element. SAP2000 which is the general purpose programme for structures has been used for this finite element model. Every structural element has modelled with solid elements and every one has shown with different colours. Appearances of the model are given in detail.Proper material properties have been assigned to the model. There is no experimental results concerning the structure characteristics for this masjid. Therefore, mean values are assigned to the model.However, sensitivity of these parameters is studied as well. Stress concentrations in the structural elements obtained from the static, dynamic and time history analysis are compared with the existing crack patterns and damages to comment on the present condition of the building.Various strengthening methods for increasing the structural and seismic performance of the building are discussed in detail.The studying presents a summary of the results of the structural response analyses of the building at the end of thesis, including its response under gravity and seismic loads.