Farklı Geleneksel ve Çelik Lifli Beton Katmanlarına Sahip Betonarme Kirişlerin Eğilme Davranışı

Bu çalışmada, farklı geleneksel ve çelik lifli beton katmanlarına sahip betonarme kirişlerin eğilme davranışı incelenmiştir. Boyutları 180×250×3500 mm olan toplamda 10 kiriş, iki grupa bölünerek dört nokta yüklemesi altında eğilme davranışı değerlendirmesi için test edilmiştir. Tüm kirişlerde çekme bölgesinde 416 donatısı kullanılmıştır. Bu araştırmadaki ana değişken kiriş yüksekliğince oluşturulan katmanlardaki beton tipidir. Kirişin yüksekliği her biri 50 mm olan 5 katmana ayrılmıştır. “F” grubunda bulunan geleneksel beton kullanılan kirişlerde, çelik lifli beton katmanları aşağıdan başlayarak geleneksel beton katmanlarının yerlerine yerleştirilmiştir. Örnek olarak, F15P10 kirişinin yüksekliği boyunca aşağıdan 150 mm’si çelik lifli betondan, yukarıda kalan 100 mm’si ise geleneksel betondan imal edilmiştir. “P” grubunda bulunan çelik lifli beton kullanılan kirişlerde ise, geleneksel beton katmanları aşağıdan başlayarak çelik lifli beton katmanlarının yerlerine yerleştirilmiştir. Örnek olarak, P10F15 kirişinin yüksekliği boyunca aşağıdan 100 mm’si geleneksel betondan, yukarıda kalan 150 mm’si ise çelik lifli betondan imal edilmiştir. Kirişlerin yük-sehim eğrileri elde edilmiş ve bu eğriler azami yük, kullanım rijitliği, tepe sonrası rijitlik ve eğilme tokluğu açısından değerlendirilmiştir. Araştırma sonucunda göre, yeterli sünekliğin çekme bölgesinde bulunan çelik lifli beton katmanı ile sağlanabileceği belirlenmiştir. Bu katmanın, çekme bölgesinde olduğu sürece yüksekliğinin ve yerinin davranışı önemli bir şekilde etkilemediği görülmüştür.

Anahtar Kelimeler:

Geleneksel beton, çelik lifli beton, kullanım/tepe-sonrası rijitliği, eğilme tokluğu

Flexural Behavior of Reinforced Concrete Beams with Various Layers of Conventional and Steel Fiber Reinforced Concrete

Flexural behavior of reinforced concrete (RC) beams having various layers of conventional concrete (CC) and steel fiber reinforced concrete (SFRC) were investigated in this study. Two groups of five beams (180×250×3500 mm) were tested under four-point loading to evaluate the flexural behavior. Both of these groups of beams were reinforced with 416 reinforcing bars. The main variable in this research was the concrete type of the layers throughout the height of the specimen. The height of the cross-section of the beams was divided into 5 layers, each having 50 mm thicknesses. In group “F” specimens, SFRC layers were added to the layers of a CC beam, starting from the bottom, as replacements of CC layers, i.e. F15P10 represented that the bottom 150 mm was cast using SFRC whereas the top 100 mm was cast using CC. In group “P” specimens, CC layers were added to the layers of a SFRC beam, starting from the bottom, as replacements of SFRC layers, i.e. P10F15 represented that the bottom 100 mm was cast using CC whereas the top 150 mm was cast using SFRC. Experimental load-deflection curves were evaluated based on ultimate load, service/post-peak stiffnesses, and flexural toughness. It can be concluded that reasonable ductility may be achieved by adding SFRC at the tension side no matter how thick the layer is and where it is located.

Keywords:

Conventional concrete, steel fiber reinforced concrete, service/post-peak stiffness, flexural toughness,

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[1] Balaguru P. N. and Shah S. P., “Fiber-reinforced cement composites”, McGraw-Hill, New York, NY, USA, (1992).
[2] Soroushian P. and Lee C. D., “Constitutive modelling of steel fiber reinforced concrete under direct tension and compression”, Fiber Reinforced Cements and Concretes: Recent Developments: 363-375, (1989).
[3] Henager C. H. and Doherty T. J., “Analysis of reinforced fibrous concrete beams”, Journal of Structural Division, 102-1: 177-188, (1976).
[4] Lok T. S. and Xiao J. R., “Tensile behavior and moment curvature relationship of steel fiber reinforced concrete”, Magazine of Concrete Research, 50-4: 359-368, (1998).
[5] Soranakom C,, Yekani-Fard M., and Mobasher B., “Development of design guidelines for strain-softening fiber reinforced concrete”, International Symposium of Fiber Reinforced Concrete: Design and Application BEFIB 2008: 513-523, (2008).
[6] Ezeldin A. S. and Balaguru P. N., “Normal- and high-strength fiber reinforced concrete under compression”, Journal of Materials in Civil Engineering, 4-4: 415-427, (1992).
[7] Nataraja M. C., Dhang N., and Gupta A. P., “Stress–strain curves for steel-fiber reinforced concrete under compression”, Cement and Concrete Composites, 21-5&6: 383-390, (1999).
[8] Wang C., “Experimental investigation on behavior of steel fiber reinforced concrete”, M. S. Thesis, University of Canterbury, (2006).
[9] Mobasher B., Yao Y., and Soranakom C., “Analytical solutions for flexural design of hybrid steel fiber reinforced concrete beams”, Engineering Structures, 100: 164-177, (2015).
[10] Padmarajaiah S. K. and Ramaswamy A., “Flexural strength predictions of steel fiber reinforced high-strength concrete in fully/partially prestressed beam specimens”, Cement and Concrete Composites, 26: 275-290, (2004).
[11] Swamy R. N. and Al-Ta’an S. A., “Deformation and ultimate strength in flexure of reinforced concrete beams made with steel fiber concrete”, ACI Journal, 78-5: 395-405, (1981).
[12] Van Zijl G. and Mbeweb P. B. K., “Flexural modelling of steel fibre-reinforced concrete beams with and without steel bars”, Engineering Structures, 53: 52-62, (2013).
[13] Soranakom C. and Mobasher B., “Closed-form solutions for flexural response of fibre reinforced concrete beams”, Journal of Engineering Mechanics, 133-8: 933-941, (2007).
[14] Achilleos C., Hadjimitsis D., Neocleous K., Pilakoutas K., Neophytou P. O., and Kallis S., “Proportioning of steel fibre reinforced concrete mixes for pavement construction and their impact on environment and cost”, Sustainability, 3: 965-983, (2011).
[15] Tanoli W. A., Naseer A., and Wahab F., “Effect of steel fibers on compressive and tensile strength of concrete”, International Journal of Advanced Structures and Geotechnical Engineering, 3-04: (2014).
[16] ASTM C39 / C39M-14a, “Standard test method for compressive strength of cylindrical concrete specimens”. ASTM International, West Conshohocken, PA, www.astm.org, (2014).
[17] Baran E. and Arsava T., “Flexural strength design criteria for concrete beams reinforced with high-strength steel strands”, Advances in Structural Engineering, 15: 1781-1792, (2012).