Browsing by Author "Kalkan, İlker"

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Citation - WoS: 23
Effect of the Gfrp Wrapping on the Shear and Bending Behavior of Rc Beams With Gfrp Encasement
(Techno-Press, 2022) ÖzKılıç, Yasin Onuralp; Gemi, Lokman; Madenci, Emrah; Aksoylu, Ceyhun; Kalkan, İlker
The need for establishing the contribution of pultruded FRP encasements and additional FRP wraps around these encasements to the shear strength and load-deflection behavior of reinforced concrete beams is the main motivation of the present study. This paper primarily focuses on the effect of additional wrapping around the composite beam on the flexural and shear behavior of the pultruded GFRP (Glass Fiber Reinforced Polymer) beams infilled with reinforced concrete, taking into account different types of failure according to av/H ratio (arch action, shear-tension, shear-compression and pure bending). For this purpose, nine hybrid beams with variable shear span-to-depth ratio (av/H) were tested. Hybrid beams with 500 mm, 1000 mm, and 1500 mm lengths and cross-sections of 150x100 mm and 100x100 mm were tested under three-point and four-point loading. Based on the testing load-displacement relationship, ductility ratio, energy dissipation capacity of the beams were evaluated with comprehensive macro damage analysis on pultruded GFRP profile and GFRP wrapping. The GFRP wraps were established to have a major contribution to the composite beam ductility (90-125%) and strength (40-75%) in all ranges of beam behavior (shear-dominated or dominated by the coupling of shear and flexure). The composite beams with wraps were showns to reach ductilities and strength values of their counterparts with much greater beam depth.
Citation - WoS: 73
Citation - Scopus: 78
Effects of Waste Powder, Fine and Coarse Marble Aggregates on Concrete Compressive Strength
(MDPI, 2022) Başaran, Boğaçhan; Kalkan, İlker; Aksoylu, Ceyhun; Özkılıç, Yasin Onuralp; Sabri, Mohanad Muayad Sabri
The use of marble wastes in concrete mixtures, causing air and water pollution, has been promoted in the academic and practical spheres of the construction industry. Although the effects of various forms (powder, fine, coarse and mixed) of this waste on the concrete compressive strength has been subject to a decent number of studies in the literature, the difficulties in reaching specific conclusions on the effect of each test parameter constitute a major restraint for the proliferation of the use of marble wastes in the concrete industry. Most of these studies are far from underscoring all of the parameters affecting the concrete compressive strength. Due to the urgent need in the literature for comprehensive studies on concrete mixtures with marble wastes, the results of the axial compression tests on a total of 429 concrete mixtures with marble aggregates were compiled by paying special attention to reporting all test variables (form and content of marble wastes, water-cement ratio, cement content, proportion of coarse and fine aggregates in all aggregates) affecting the concrete strength. In this context, multivariate regression analyses were carried out on the existing test results. These regression analyses yielded to relationships between the change in concrete compressive strength and the test parameters for each and every form of marble waste (powder, fine and coarse aggregate). The study indicated that independent from the form of marble wastes (as powder, fine aggregate or coarse aggregate), aggregate replacements of up to 50% can yield to significant changes in the concrete compressive strength. In addition, the analytical estimates from the developed equations exhibited a high correlation (a least r value of 0.91) with the experimental results from the previous studies, yielding to rather low error values (RMSE value is 5.06 MPa at max). For this reason, the developed equations can consistently predict the changes in concrete compressive strength with varying amounts and forms of the marble aggregates as well as the other test variables.
Citation - WoS: 14
Citation - Scopus: 16
Shear and Bending Performances of Reinforced Concrete Beams With Different Sizes of Circular Openings
(MDPI, 2023) Ozkilic, Yasin Onuralp; Aksoylu, Ceyhun; Hakem, İbrahim Y.; Özdoner, Nebi; Kalkan, İlker; Karalar, Memduh; Stel'makh, Sergey A.
The present study pertains to the effects of transverse opening diameters and shear reinforcement ratios on the shear and flexural behavior of RC beams with two web openings across different spans, i.e., a single opening in each half-span. Within the scope of the study, a total of 12 RC beams with five different opening diameter-to-beam depth ratios (0, 0.20, 0.27, 0.33, 0.40, and 0.47) and two shear reinforcement ratios were tested to failure under four-point bending. The load capacities, ductilities, rigidities and energy dissipation capacities in the elastic and plastic ranges of beam behavior were compared. Furthermore, the load capacities of the beams were compared to the existing analytical shear strength formulations in the literature. The test results indicated that whether an RC beam with openings has adequate or inadequate amounts of shear reinforcement, the frame-type shear failure becomes much more pronounced with increasing opening diameter. The reductions in the load capacity and modulus of toughness with increasing opening diameter are more considerable in the presence of inadequate amounts of shear reinforcement, while the beam ductility is less affected in shear-deficient RC beams with openings as compared to the ones with adequate shear reinforcement.
Citation - WoS: 4
Citation - Scopus: 4
Use of Waste Steel Fibers From Cnc Scraps in Shear-Deficient Reinforced Concrete Beams
(Techno-Press, 2023) Kalkan, İlker; Özkılıç Yasin Onuralp; Aksoylu, Ceyhun; Mydin, Md Azree Othuman; Martins, Carlos Humberto; Hakeem, Ibrahim Y.; Işık, Ercan
The present paper summarizes the results of an experimental program on the influence of using waste lathe scraps in the concrete mixture on the shear behavior of RC beams with different amounts of shear reinforcement. Three different volumetric ratios (1, 2 and %3) for the scraps and three different stirrup spacings (160, 200 and 270 mm) were adopted in the tests. The shear span-to-depth ratios of the beams were 2.67 and the stirrup spacing exceeded the maximum spacing limit in the building codes to unfold the contribution of lathe scraps to the shear resistances of shear-deficient beams, subject to shear-dominated failure (shear-tension). The experiments depicted that the lathe scraps have a pronounced contribution to the shear strength and load-deflection behavior of RC beams with widely-spaced stirrups. Namely, with the addition of 1%, 2% and 3% waste lathe scraps, the load-bearing capacity escalated by 9.1%, 21.8% and 32.8%, respectively, compared to the reference beam. On the other hand, the contribution of the lathe scraps to the load capacity decreases with decreasing stirrup spacing, since the closely-spaced stirrups bear the shear stresses and render the contribution of the scraps to shear resistance insignificant. The load capacity, deformation ductility index (DDI) and modulus of toughness (MOT) values of the beams were shown to increase with the volumetric fraction of scraps if the stirrups are spaced at about two times the beam depth. For the specimens with a stirrup spacing of about the beam depth, the scraps were found to have no considerable contribution to the load capacity and the deformation capacity beyond the ultimate load. In other words, for lathe scrap contents of 1-3%, the DDI values increased by 5-23% and the MOT values by 63.5-165% with respect to the reference beam with a stirrup spacing of 270 mm. The influence of the lathe scraps to the DDI and MOT values were rather limited and even sometimes negative for the stirrup spacing values of 160 and 200 mm.
Uzaması Kısıtlanmış Ctp Donatılı Beton Elemanlarda Rötrenin Kalıcı Donatı Gerilmelerine Etkileri
(2022) Başaran, Boğaçhan; Kalkan, İlker; Aksoylu, Ceyhun
Donatı korozyonu problemine karşı etkin bir çözüm sunan CTP (Cam Takviyeli Polimer) donatılar her ne kadar yüksek çekme dayanımlarına sahip olsalar da bu donatıların sünme dayanımları çekme dayanımlarından oldukça düşüktür. Sünme kopması adı verilen bu davranış şekli, sürekli yükler altındaki yapı elemanlarında CTP donatıların dayanımları sınırlandırılmaktadır. Buna ilaveten, boy değişimi kısıtlanmış yapı elemanlarında beton büzülmesi bu donatılarda ilave nihai gerilmeler ortaya çıkarmaktadır. Dış yük etkilerine ek olarak ortaya çıkan bu ilave gerilmelerin, donatıların sünme dayanımlarında ortaya çıkarabileceği azalmaların mertebesi henüz bilinmemektedir. Yapılması planlanan çalışmada, CTP donatı gerilmelerine etki eden faktörlerin ve bu faktörlerin etki düzeylerinin incelenmesi için 72 adet uzaması kısıtlanmış CTP donatılı beton eleman büzülme deneyine tabi tutulacaktır. Bu kapsamda, çeşitli büzülme oranlarına (%40 ve %80 nem altında) ve basınç dayanım (C30 ve C50) değerlerine sahip beton numuneler içinde farklı elastisite modülü (40, 60 ve 75 GPa) değerleri ve yüzey özellklerine sahip (nervürlü ve sargılı) CTP donatılar farklı oranlarda (%0.14, %0.31 ve %0.56) kullanılacaktır. Çalışma sonucunda, beton büzülmesinden kaynaklı donatılarda oluşacak nihai gerilmeler tespit edilerek, bu gerilmeleri donatı sünme kapasitelerine etki düzeyleri incelenecektir.