Scopus İndeksli Yayınlar Koleksiyonu / Scopus Indexed Publications Collection
Permanent URI for this collectionhttps://hdl.handle.net/11147/7148
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Article Citation - WoS: 10Citation - Scopus: 11Numerical Investigation on the Behavior of Reinforced Concrete Slabs Strengthened With Carbon Fiber Textile Reinforcement Under Impact Loads(Elsevier, 2022) Batarlar, Baturay; Saatcı, SelçukIn this study, impact load performance of reinforced concrete members strengthened with carbon fiber textile reinforcement (CFTR) was investigated through numerical simulations. In the first phase of the study, a finite element model was set up to model reinforced concrete slabs of 1500 × 1500 × 200 mm in dimensions, strengthened with CFTR and subjected to multiple impact loads, using software LS-DYNA. This model was validated against experimental data available in the literature and basic modeling parameters, such as material model selection, mesh size, and erosion parameters for better accuracy were determined. In the second phase of the study, a numerical parametric study was conducted using the validated model to reveal the effects of steel and textile reinforcement ratio, slab thickness, striker mass, size, and velocity on the behavior of steel-reinforced concrete slabs strengthened using CFTR. As a result of the study, it was found that CFTR was effective in limiting the peak and residual displacements in reinforced concrete slabs subjected to multiple impacts at the middle. Among 220 mm thick specimens, for the same steel reinforcement ratio, a higher CFTR ratio resulted in lower peak and residual displacement levels after the third impact. On the other hand, when 8 mm diameter steel reinforcement was varied from 100 mm to 200 mm spacing, it was found that steel reinforcement ratio was the dominant factor on the impact behavior over the CFTR ratio. CFTR strengthening was particularly more effective when the members displayed a global response instead of a local one, such as low-velocity high-mass impact loading or in the cases where the striker had a larger diameter. Similarly, thickness was also found to be a major factor on the effectiveness of CFTR. When thickness of the slab was varied from 50 mm to 300 mm, CFTR's effect was found to be more pronounced for thinner slabs in preventing perforation and limiting peak and residual displacements. However, for 200 and 300 mm thick slabs, CFTR did not have a significant effect since local punching behavior was dominant in these slabs and CFTR was not effective in this shear mechanism.Article Citation - WoS: 57Citation - Scopus: 61Viewpoints: Feeding Mechanics, Diet, and Dietary Adaptations in Early Hominins(John Wiley and Sons Inc., 2013) Daegling, David J.; Judex, Stefan; Özçivici, Engin; Ravosa, Matthew J.; Taylor, Andrea B.; Grine, Frederick E.; Teaford, Mark F.; Ungar, Peter S.Inference of feeding adaptation in extinct species is challenging, and reconstructions of the paleobiology of our ancestors have utilized an array of analytical approaches. Comparative anatomy and finite element analysis assist in bracketing the range of capabilities in taxa, while microwear and isotopic analyses give glimpses of individual behavior in the past. These myriad approaches have limitations, but each contributes incrementally toward the recognition of adaptation in the hominin fossil record. Microwear and stable isotope analysis together suggest that australopiths are not united by a single, increasingly specialized dietary adaptation. Their traditional (i.e., morphological) characterization as "nutcrackers" may only apply to a single taxon, Paranthropus robustus. These inferences can be rejected if interpretation of microwear and isotopic data can be shown to be misguided or altogether erroneous. Alternatively, if these sources of inference are valid, it merely indicates that there are phylogenetic and developmental constraints on morphology. Inherently, finite element analysis is limited in its ability to identify adaptation in paleobiological contexts. Its application to the hominin fossil record to date demonstrates only that under similar loading conditions, the form of the stress field in the australopith facial skeleton differs from that in living primates. This observation, by itself, does not reveal feeding adaptation. Ontogenetic studies indicate that functional and evolutionary adaptation need not be conceptually isolated phenomena. Such a perspective helps to inject consideration of mechanobiological principles of bone formation into paleontological inferences. Finite element analysis must employ such principles to become an effective research tool in this context. © 2013 Wiley Periodicals, Inc.