ÇELİK LİFLİ BETONARME KİRİŞLERİN EĞİLME DAVRANIŞININ MODELLENMESİ

Öz

Bu çalışmada, büyük ölçekli ve çelik lif takviyeli betonarme kirişlerin eğilme davranışının modellenmesi incelenmiştir. Araştırmada, Değiştirilmiş Basınç Alanları Teorisi’ ne (DBAT) dayanan doğrusal olmayan bir sonlu elemanlar yöntemi (DOSE) ile analitik bir yöntem kullanılmıştır. Analiz yöntemlerinde çelik liflerin betonarme çekme dayanımına katkısı farklı yaklaşımlarla modellemiştir. İlk yaklaşımda lifli betonun artık çekme dayanımı çatlak genişliği ile ilişkilendirilmiş ve DBAT tabanlı DOSE yöntemine uyarlanmıştır. Analitik yöntemde ise artık çekme dayanımı çatlak genişliğinden bağımsız olarak kabul edilmiştir. Söz konusu analiz yöntemlerinin performansları literatürden seçilen deneysel bir çalışma üzerinde incelenmiştir. Deneysel çalışmada, değişken oranlarda boyuna donatı ve lif içeriğine sahip dört metre uzunluğundaki beş adet betonarme kirişin dört nokta eğilme testleri gerçekleştirilmiştir. Sonuçlar, DBAT tabanlı DOSE yönteminin, seçilen yükleme ve sınır koşullarında büyük ölçekli betonarme eleman davranışını (yük taşıma kapasitesi, çatlak profilleri ve eğilme rijitliği gibi) başarıyla temsil ettiğini göstermiştir. Diğer yandan, analitik metodun, yük taşıma kapasitesini donatı ve lif oranından bağımsız olarak her zaman daha düşük tespit ettiğini ortaya koymuştur. Bu yöntemdeki hata oranının büyük ölçüde çekme donatısı oranına bağlı olduğu açıkça ortaya konmuştur.

Anahtar Kelimeler

• Çelik Lifli Betonarme
• Çelik Lif Katkısının Analitik Modellenmesi
• Sonlu Elemanlar Analizi
• Çelik Lifli Betonarme Kiriş Eğilme Davranışı.

MODELING THE BENDING BEHAVIOR OF STEEL FIBER-REINFORCED CONCRETE BEAMS

Öz

In this study, modeling of the bending behavior of large-scale steel fiber-reinforced concrete beams (SFRC) was investigated using the Modified Compression Field Theory (MCFT) based non-linear finite element (NLFE) method and an analytical method. The two analysis methods included different modeling approaches for the contribution of steel fibers to the tensile strength of reinforced concrete. In the first approach, the residual tensile strength of fibrous concrete was related to the crack width and adopted into the MCTF-based NLFE method. However, the residual tensile strength was free from the crack width in the second approach, which was employed in the analytical method. The capabilities of the mentioned analysis methods were investigated on an experimental study selected from the literature. The experimental study included the four-point bending tests of five four-meter-long simply supported SFRC beams having various ratios of longitudinal reinforcement and fiber content. Results revealed that the MCTF-based NLFE method performed superior in representing the large-scale member responses (such as load-carrying capacity, crack profiles, and flexural stiffness) for the selected loading and boundary conditions while the simplified analytical tool was found to be always conservative in the determination of strength regardless of conventional reinforcement and fiber ratio. However, the rate of error was apparently proven to be highly dependent on the tensile reinforcement ratio.

Anahtar Kelimeler

• Steel Fiber-Reinforced Concrete (SFRC)
• Analytical Modeling of Steel Fiber Contribution
• Finite Element Analysis
• Bending Behavior of SFRC Beams.

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