Kriyojenik sıcaklık etkisindeki kendiliğinden yerleşen betonlarda kırılma mekaniği performansının belirlenmesi
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Dosyalar
Tarih
2015
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
Düzce Üniversitesi
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Günümüzün en temel ısınma araçlarından biri olan ve ülke olarak diğer ülkelerden ithal ettiğimiz doğalgazın temininde tek bir ülkeye bağımlı olmamak son derece önemlidir. Bu nedenle doğalgazın yüksek hacimlerde depolanması büyük önem arz etmektedir. Doğalgazın depolanması için sıvılaştırılması gerekmekte olup sıvılaşma esnasında doğalgazın hacmi yaklaşık 600 kat küçülmekte ve sıvı haldeki doğalgazın sıcaklığı -162oC olmaktadır. Bu düşük sıcaklıklar kriyojenik sıcaklık olarak adlandırılmaktadır. Beton muhafaza tanklarının doldurma ve boşaltma anındaki termal etkilere ve beklenmedik sızıntı durumlarına karşı dayanıklı olması gerekmektedir. Bu çalışmada, doğalgazın depolandığı beton muhafazalı tankların herhangi bir sızıntı, termal şok vb. durumlarda kriyojenik sıvı ile betonun teması sonucunda ortaya çıkabilecek etkiler ve beton davranışı incelenmiştir. Bu kapsamda beton muhafazalı kriyojenik depolama tankları için kullanımı önerilebilecek yüksek dayanıklı kendiliğinden yerleşen beton tasarımı gerçekleştirilmiştir. Çalışmada kriyojenik etkiyi temsil etmek amacıyla sıvı nitrojen kullanılarak bir ve beş çevrim donma çözülme etkisi sonucunda dayanım özelliklerindeki değişim incelenmiştir. Ayrıca beton içerisindeki nem durumunun etkisini araştırmak üzere numuneler suda ve havada olmak üzere iki farklı kür işlemine tabi tutulmuştur. Enerji yapılarının stratejik önem derecesinin yüksek olması nedeniyle, tasarımları yapılan bu betonların, dayanım parametreleri geleneksel dayanım ölçütlerinin yanı sıra iki parametreli kırılma mekaniği test yöntemi kullanılarak belirlenmiştir. Kırılma mekaniği parametrelerinin belirlenmesi amacıyla üç farklı boyutta, her farklı boyut için üç farklı çentik uzunluğuna sahip kirişler üretilmiştir. Üretilen kirişler üzerinde mekanik testler gerçekleştirilmiştir. Elde edilen veriler geleneksel tasarım metotları ve kırılma mekaniği parametreleri ile ilişkilendirilerek sonuçlara ulaşılmıştır. Sonuç olarak, hava kürü numunelerinin su kürü numunelerine göre kriyojenik çevrime daha dayanıklı olduğu belirlenmiştir. Bir çevrim kriyojenik işlem ardından KIC ve CTODc değerleri artış göstermiştir. Beş çevrim sonucunda ise, bir çevrime kıyasla KIC ve CTODc değerlerinde düşüş görülmüştür. Anahtar sözcükler: Doğalgaz, Kendiliğinden Yerleşen Beton, Kırılma Mekaniği, Kriyojenik sıcaklık
It is important not to be dependent on a single country in the procurement of natural gas that is one of the basic heating sources of today and that we import from other countries. Thus, the storage of natural gas at high volumes is very important. It is required to liquefy the natural gas in order to store it, and the volume of natural gas decreases by about 600 times during liquefaction, and the temperature of natural gas in liquid phase becomes -162oC. These low temperatures are being called cryogenic temperature. The concrete storage tanks are required to be resistant against thermal effects and unexpected leakages during filling and discharge. In this study, the effects possible to arise and the behavior of concrete as the result of contact of cryogenic liquid and concrete in cases of any leakage, thermal shock etc relevant to the concrete encased tanks –where the natural gas is being stored- was examined. Within this scope, high durable self-consolidating concrete design –whose usage may be suggested for concrete encased cryogenic storage tanks- was realized. In the study, the change in the strength properties as the result of one and five cycles freezing and thawing effect was examined by using liquid nitrogen in order to represent cryogenic effect. Moreover, in order to search the effect of humidity within concrete, the samples were subjected to two different curing operations as being in water and in air. Due to high strategic importance of energy structures, the strength parameters of designed concretes were determined by two parameter fracture mechanics test method as well as traditional strength criteria. In order to determine the parameters of fracture mechanics, beams of three different sizes having three different notch lengths for each size were produced. Mechanical tests were performed on the produced beams. The results were obtained by associating the obtained data with the traditional design methods and parameters of fracture mechanics. Consequently, it was determined that samples of air curing were more resistant to cryogenic cycle than the samples of water curing. Following one cycle of cryogenic operation, the KIC and CTODc values had showed an increase. And as the result of five cycles, a decrease was observed in the KIC and CTODc values compared to one cycle.
It is important not to be dependent on a single country in the procurement of natural gas that is one of the basic heating sources of today and that we import from other countries. Thus, the storage of natural gas at high volumes is very important. It is required to liquefy the natural gas in order to store it, and the volume of natural gas decreases by about 600 times during liquefaction, and the temperature of natural gas in liquid phase becomes -162oC. These low temperatures are being called cryogenic temperature. The concrete storage tanks are required to be resistant against thermal effects and unexpected leakages during filling and discharge. In this study, the effects possible to arise and the behavior of concrete as the result of contact of cryogenic liquid and concrete in cases of any leakage, thermal shock etc relevant to the concrete encased tanks –where the natural gas is being stored- was examined. Within this scope, high durable self-consolidating concrete design –whose usage may be suggested for concrete encased cryogenic storage tanks- was realized. In the study, the change in the strength properties as the result of one and five cycles freezing and thawing effect was examined by using liquid nitrogen in order to represent cryogenic effect. Moreover, in order to search the effect of humidity within concrete, the samples were subjected to two different curing operations as being in water and in air. Due to high strategic importance of energy structures, the strength parameters of designed concretes were determined by two parameter fracture mechanics test method as well as traditional strength criteria. In order to determine the parameters of fracture mechanics, beams of three different sizes having three different notch lengths for each size were produced. Mechanical tests were performed on the produced beams. The results were obtained by associating the obtained data with the traditional design methods and parameters of fracture mechanics. Consequently, it was determined that samples of air curing were more resistant to cryogenic cycle than the samples of water curing. Following one cycle of cryogenic operation, the KIC and CTODc values had showed an increase. And as the result of five cycles, a decrease was observed in the KIC and CTODc values compared to one cycle.
Açıklama
YÖK Tez No: 430808
Anahtar Kelimeler
Enerji, Energy, Mühendislik Bilimleri, Engineering Sciences, İnşaat Mühendisliği, Civil Engineering, Beton, Concrete, Doğal gaz, Natural gas, Enerji, Energy, Kriyojenik yöntem, Cryogenic method, Kırılma mekaniği, Fracture mechanics, Yüksek performanslı beton, High performance concrete, Çatlak analizi, Crack analysis, İnşaat mühendisliği, Civil engineering, Cryogenic Temperature, Fracture Mechanics, Natural Gas, Self-Consolidating Concrete
