GFRP donatılı betonarme kirişlerin eğilme, kesme ve aderans davranışı
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Dosyalar
Tarih
2023
Yazarlar
Dergi Başlığı
Dergi ISSN
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Yayıncı
Bursa Teknik Üniversitesi, Lisansüstü Eğitim Enstitüsü
Erişim Hakkı
info:eu-repo/semantics/openAccess
Özet
Geleneksel betonarme elemanlarda kullanılan çelik donatı agresif çevresel etkiler nedeniyle korozyona maruz kalır. Donatı korozyonu adı verilen bu olay betonarme elemanın kalıcılığı ve taşıma gücünü azaltır. Öte yandan, betonarme yapılarda çelik donatı manyetik alanlarda tercih edilmez. Bu nedenlerle, son yıllarda özellikle betonarme altyapılarda manyetik alanı etkilemeyen ve korozyona uğramayan FRP (Fiber Reinforced Polymer) donatı çubuğu kullanımı son yıllarda giderek artmaktadır. FRP donatı çubukları çoğunlukla aramit, bazalt, cam ve karbon lif takviyesiyle üretilmekte olup bunlar arasından inşaat sektöründe en çok tercih edileni GFRP (Glass Fiber Reinforced Polymer) donatı çubuğudur. Bu tez çalışmasında, GFRP donatılı betonarme kirişlerin eğilme, kesme ve aderans davranışının araştırılması amaçlanmıştır. Eğilme davranışı yönünden yapılan incelemede; enine ve boyuna GFRP donatılı betonarme kirişlerin geleneksel çelik donatılı kirişlerden farklılıklarının araştırılması amaçlanmıştır. Bu kapsamda, sadece çelik donatılı 25 adet betonarme kiriş ve sadece GFRP donatılı 40 adet betonarme kirişin sonlu eleman modelleri oluşturulmuştur. Bu amaç doğrultusunda, çelik ve GFRP donatılı numuneler maksimum yük kapasitesi, yerdeğiştirme kapasitesi, birim şekil değiştirme enerjisi, çatlak desenleri ve çatlak genişliği üzerinden karşılaştırmalı olarak incelenmiştir. Şekil değiştirme enerjilerinden yola çıkarak ACI440.1R-06' da önerilen minimum donatı oranına bir revizyon önerisi ve GFRP donatılı betonarme kirişlerin tasarımında kullanılacak bir GFRP donatı çubuğu birim şekil değiştirme azaltma faktörü önerisinde bulunulmuştur. Ayrıca, literatürde GFRP donatılı betonarme kirişlerin etkin atalet moment momenti hesabı için önerilen bağıntılardaki düzeltme katsayılar için revizyon önerisinde bulunulmuştur. Kesme davranışı yönünden yapılan incelemede; enine ve boyuna GFRP donatı kullanılarak üretilmiş betonarme kirişlerin yapısal davranışı incelenerek, TS500' den revize edilmiş enine FRP donatılı betonarme kirişlerin kesme tasarımı için bir tahmin modeli önerilmesi amaçlanmıştır. Bu amaç doğrultusunda, enine GFRP donatılı 27 betonarme kirişin sonlu eleman modeli ve enine donatısız 9 betonarme kirişin sonlu eleman modeli oluşturulmuş ve analiz edilmiştir. Bu analizlerden yola çıkarak enine FRP donatılı betonarme kirişlerin tasarımı için TS500' den revize edilmiş bir tahmin modeli önerilmiştir. Önerilen tahmin modeli literatürde bulunan 105 adet deney verisi ve 13 adet tahmin modeli ile karşılaştırmalı olarak incelenmiştir. Önerilen tahmin modelinden elde edilen sonuçların litereatürdeki 13 adet tahmin modeline göre istatistiksel olarak deney verileriyle daha tutarlı olduğu tespit edilmiştir. Ayrıca, değiştirilmiş DPC (Demerit Points Classification) modeline göre önerilen tahmin modeli 13 adet tahmin modeli arasında oldukça iyi performans göstermektedir. FRP donatı çubuklarının yüzey şekli; sargılı, nervürlü, kum kaplanmış, oluklu, örgülü gibi çeşitli şekillerde olabilmektedir. Bu tezde, yüzeyi kum kaplı GFRP (Glass Fiber Reinforced Polymer) donatı çubuğunun kiriş testi yöntemiyle aderans davranışı incelenmiştir. Bu kapsamda; değişken parametre olarak beton dayanımı ve gömülme boyu seçilerek 34 adet kiriş deney numunesi test edilmiştir. Testler sonucunda yüzeyi kum kaplı GFRP donatı çubuklu betonarme deney numunelerinde yük-yerdeğiştirme ilişkileri, donatı çubuğunun betondan sıyrılma durumları incelenerek, aderans gerilmesi iki farklı yaklaşımla belirlenmiştir. İlaveten, numunelerdeki çatlak gelişimi ve diyagonal çatlak açısının karşılaştırmalı olarak incelemesi, göçme modları, deneyden elde edilen aderans gerilmesi-donatı sıyrılması ilişkisinin farklı analitik modellerle karşılaştırmalı incelemesi yapılmıştır. Buradan yola çıkarak, yüzeyi kum kaplı GFRP donatılı betonarme kirişlerde sayısal modellerin oluşturulmasında kullanılmak üzere CMR' yi ve mBPE' nin azalan kısmını dikkate alan aderans gerilmesi-donatı sıyrılması modeli önerilmiştir. Elde edilen deneysel sonuçlara dayanılarak dış yüzeyi kum kaplı GFRP donatılı betonarme elemanın aderans dayanım tahmin modeli önerilmiştir. Ayrıca, kenetlenme boyu için de önerilerde bulunulmuştur.
The steel rebar used in conventional reinforced concrete members is subject to corrosion due to aggressive environmental influences. This phenomenon, called rebar corrosion, creates a disadvantage because it reduces the durability and bearing capacity of the reinforced concrete element. On the other hand, steel rebar is not preferred in magnetic fields in reinforced concrete structures. For these reasons, use of FRP (Fiber Reinforced Polymer) rebar, which does not affect the magnetic field and does not undergo corrosion, in reinforced concrete constructions has been increasing in recent years. FRP rebars can be produced with aramid, basalt, glass and carbon fiber reinforcement and GFRP (Glass Fiber Reinforced Polymer) rebar is the most preferred FRP rebar in the construction industry. In this thesis, it is aimed to investigate the flexural, shear and bond behavior of reinforced concrete beams with GFRP rebar. In the examination made in terms of flexural behavior; it is aimed to investigate the differences of reinforced concrete beams produced using transverse and longitudinal GFRP rebar from reinforced concrete beams produced using conventional steel rebar. In this context, finite element models of 25 reinforced concrete beams with only steel rebar and 40 reinforced concrete beams with only GFRP rebar were created. For this purpose, the maximum load capacity, displacement capacity, strain energy, crack patterns and crack width parameters of the steel and GFRP reinforced specimens were investigated comparatively. Based on the strain energies, a revision to the minimum reinforcement ratio recommended in ACI440.1R-06 and strain of GFRP rebar reduction factor to be used in the design of reinforced concrete beams with GFRP rebar have been proposed. In addition, a revision proposal has been made for the correction coefficients in the equations proposed for the effective moment of inertia calculation of reinforced concrete beams with GFRP rebar in the literature. In the examination made in terms of shear behaviour; by examining the structural behavior of reinforced concrete beams produced using transverse and longitudinal GFRP rebar, it is aimed to propose a prediction model for the shear design of reinforced concrete beams with transverse FRP rebar revised from TS500. For this purpose, the finite element model of 27 reinforced concrete beams with transverse GFRP rebar and the finite element model of 9 reinforced concrete beams without transverse rebar were designed and analyzed. Based on these analyses, a revised prediction model proposal from TS500 is presented for the design of reinforced concrete beams with transverse FRP rebar. The proposed prediction model has been compared with 105 experimental data and 13 prediction models in the literature. It has been determined that the results obtained from the proposed prediction model are statistically more consistent with the experimental data compared to the 13 prediction models in the literature. Moreover, according to the modified DPC (Demerit Points Classification) model, the proposed prediction model performs quite well among the 13 prediction models. The surface of FRP rebars can be in various shapes such as wrapped, ribbed, sand coated, indented, braided. However, the most preferred of these surfaces is the one coated with sand. In this thesis, the bond behavior of GFRP (Glass Fiber Reinforced Polymer) rebar, whose surface is coated with sand, was investigated by beam test method. In this context; concrete strength and embedment length were selected as variable parameters and 34 beam test specimens were tested. As a result of the tests, the load-displacement relations of the reinforced concrete test specimens with sand-coated GFRP rebars, the slippage conditions of the rebar from the concrete were examined, and the bond stress was determined with two different approaches. In addition, a comparative analysis of crack progress and diagonal crack angle in the specimens, failure modes, the bond-slip relationship obtained from the test were compared with different analytical models. Based on this, a bond-slip model, which takes into account the CMR and the decreasing branch of mBPE, is proposed to be used in the creation of numerical models for reinforced concrete beams with sand-covered GFRP rebar. Based on the experimental results obtained, prediction model suggestion were made for the bond strength of reinforced concrete element with the sand-coated GFRP rebar. In addition, suggestions were made for the development length.
The steel rebar used in conventional reinforced concrete members is subject to corrosion due to aggressive environmental influences. This phenomenon, called rebar corrosion, creates a disadvantage because it reduces the durability and bearing capacity of the reinforced concrete element. On the other hand, steel rebar is not preferred in magnetic fields in reinforced concrete structures. For these reasons, use of FRP (Fiber Reinforced Polymer) rebar, which does not affect the magnetic field and does not undergo corrosion, in reinforced concrete constructions has been increasing in recent years. FRP rebars can be produced with aramid, basalt, glass and carbon fiber reinforcement and GFRP (Glass Fiber Reinforced Polymer) rebar is the most preferred FRP rebar in the construction industry. In this thesis, it is aimed to investigate the flexural, shear and bond behavior of reinforced concrete beams with GFRP rebar. In the examination made in terms of flexural behavior; it is aimed to investigate the differences of reinforced concrete beams produced using transverse and longitudinal GFRP rebar from reinforced concrete beams produced using conventional steel rebar. In this context, finite element models of 25 reinforced concrete beams with only steel rebar and 40 reinforced concrete beams with only GFRP rebar were created. For this purpose, the maximum load capacity, displacement capacity, strain energy, crack patterns and crack width parameters of the steel and GFRP reinforced specimens were investigated comparatively. Based on the strain energies, a revision to the minimum reinforcement ratio recommended in ACI440.1R-06 and strain of GFRP rebar reduction factor to be used in the design of reinforced concrete beams with GFRP rebar have been proposed. In addition, a revision proposal has been made for the correction coefficients in the equations proposed for the effective moment of inertia calculation of reinforced concrete beams with GFRP rebar in the literature. In the examination made in terms of shear behaviour; by examining the structural behavior of reinforced concrete beams produced using transverse and longitudinal GFRP rebar, it is aimed to propose a prediction model for the shear design of reinforced concrete beams with transverse FRP rebar revised from TS500. For this purpose, the finite element model of 27 reinforced concrete beams with transverse GFRP rebar and the finite element model of 9 reinforced concrete beams without transverse rebar were designed and analyzed. Based on these analyses, a revised prediction model proposal from TS500 is presented for the design of reinforced concrete beams with transverse FRP rebar. The proposed prediction model has been compared with 105 experimental data and 13 prediction models in the literature. It has been determined that the results obtained from the proposed prediction model are statistically more consistent with the experimental data compared to the 13 prediction models in the literature. Moreover, according to the modified DPC (Demerit Points Classification) model, the proposed prediction model performs quite well among the 13 prediction models. The surface of FRP rebars can be in various shapes such as wrapped, ribbed, sand coated, indented, braided. However, the most preferred of these surfaces is the one coated with sand. In this thesis, the bond behavior of GFRP (Glass Fiber Reinforced Polymer) rebar, whose surface is coated with sand, was investigated by beam test method. In this context; concrete strength and embedment length were selected as variable parameters and 34 beam test specimens were tested. As a result of the tests, the load-displacement relations of the reinforced concrete test specimens with sand-coated GFRP rebars, the slippage conditions of the rebar from the concrete were examined, and the bond stress was determined with two different approaches. In addition, a comparative analysis of crack progress and diagonal crack angle in the specimens, failure modes, the bond-slip relationship obtained from the test were compared with different analytical models. Based on this, a bond-slip model, which takes into account the CMR and the decreasing branch of mBPE, is proposed to be used in the creation of numerical models for reinforced concrete beams with sand-covered GFRP rebar. Based on the experimental results obtained, prediction model suggestion were made for the bond strength of reinforced concrete element with the sand-coated GFRP rebar. In addition, suggestions were made for the development length.
Açıklama
Anahtar Kelimeler
Deprem Mühendisliği, Earthquake Engineering, Mühendislik Bilimleri, Engineering Sciences, İnşaat Mühendisliği, Civil Engineering, Infrastructure projects, Betonarme yapılar, Reinforced concrete structures, Cam elyaf kompozitler, Glass fiber composites, Kesme donatısı, Shear reinforcement, Lifli kompozitler, Fiber composites, Mühendislik yapıları, Engineering structure, Polimer kompozitler, Polymer composites, Sargı donatısı, Winding reinforcement, Çekme donatısı, Tension reinforcement, Alt yapı projeleri
