Browsing by Author "Yaşayanlar, Süleyman"

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Citation - WoS: 2
Citation - Scopus: 1
Çelik Fiber Katkısının Farklı Boyuna Donatı Oranına Sahip Betonarme Döşemelerin Zımbalama Davranışı Üzerinde Etkileri
(Gazi Üniversitesi, 2019) Saatçi, Selçuk; Yaşayanlar, Süleyman; Yaşayanlar, Yonca; Batarlar, Baturay
In this study, reinforced concrete slabs in two groups, having 0.004 (D1 series) and 0.002 (D2 series) longitudinal reinforcement ratios in two orthogonal directions, were cast with concrete mixes containing 0%, 0.5%, 1% and 1.5% steel fiber ratios in volume. Slabs were 2150x2150x150 mm in dimensions. Eight slabs were tested in total under static loads. For slabs without steel fibers, the slab with higher reinforcement ratio showed punching failure before the yielding of longitudinal bars, whereas the slab with lower reinforcement ratio displayed a significantly higher ductility before final punching failure. Addition of steel fibers increased the punching load capacity up to two times. However, although addition of steel fibers also increased the maximum displacements in D1 series slabs, it did not make any significant effect on the maximum displacements of D2 series slabs. Maximum displacements were still controlled by the yielding of longitudinal reinforcement. Increasing the steel fiber ratio increased both the punching capacity and the maximum displacements in D1 series slabs, but it did not make a significant difference in behavior of D2 series beyond 1% fiber ratio. An analytical study of the test specimens were also performed using Critical Shear Crack Theory and based on comparisons of experimental and analytical results some improvements in the model were proposed. © 2019 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.
Continuum Damage Mechanics Based Modelling of Laminated Fiber Reinforced Composites
(01. Izmir Institute of Technology, 2023-06) Yaşayanlar, Süleyman; Özdemir, İzzet
Multiscale modeling, which merges the worlds of macro- and micromechanics, is establishing itself as a viable alternative to experimental procedures in the characterization of the mechanical behavior of complex materials. Advanced composite materials are a perfect field for the application of such modeling concepts. This thesis focuses on failure mechanics of fiber reinforced composites and addresses the modeling of failure processes at both micro- and macro-scales. First, a novel damage-plasticity model is developed and implemented within finite element software Abaqus as a user defined element. It is verified that the model gives mesh objective results, and the model is calibrated with experimental stress-strain curves from the literature. Representative volume elements (RVEs) based micro-mechanical models are constructed where damage-plasticity model and cohesive surfaces are employed to capture failure in matrix and matrix-fiber interface, respectively. A sufficiently large number of RVE analysis results are used to generate discrete failure envelopes. These failure envelopes are compared with continuous ones resulting from Puck's criteria. Furthermore, the influence of microstructural imperfections is investigated systematically, and an extended version of Puck's criteria is assessed from a micro-mechanical perspective as well. In the last part of the thesis, a macroscopic model is proposed which combines Puck's criteria with localizing implicit gradient damage model. It is shown that the model provides consistent results such that the failure angle obtained at material point and the orientation of the emerging macroscopic damage band match provided that sufficiently small internal length scale parameter is used.
Impact Resistance of Steel Fiber Reinforced Concrete Slabs
(Izmir Institute of Technology, 2015-07) Yaşayanlar, Süleyman; Saatcı, Selçuk
As rare as it may seem, impact loads can act on a structure in its lifespan. For structures such as nuclear energy facilities, industrial facilities, and military buildings design for impact loads may be required. Steel fibers are increasingly used in the design and construction of such reinforced concrete structures. However, studies on the effect of steel fibers on the impact resistance of reinforced concrete structures are rare in the literature. This study investigates the global behavior of reinforced concrete slabs with different ratios of steel fibers under static and impact loading. 10 steel fiber reinforced concrete slabs with dimensions of 2150x2150x150 mm were tested with varying steel fiber volume ratios of 0.5 %, 1.0 % and 1.5 %. Specimens were manufactured as twins, as one to be tested under static loading and one to be tested under impact loading. Static tests were carried out by applying a static load at the midpoint with a hydraulic jack, whereas impact tests were applied through free falling drop-weights. Observed behavior and collected data were compared with companion studies of Batarlar (2013) and Arsan (2014), as they have used the same test setup with different parameters. As a result, it was seen that even steel a fiber addition of 0.5 % in volume was sufficient to provide a ductile behavior both under static and impact loading. Steel fibers significantly enhanced the impact behavior by increasing the strength and resiliency of the specimens.