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Öğe Evaluation of acoustic emission activities in a steel fiber reinforced concrete beam by Ib value analysis [Çelik lifli betonarme kirişte akustik emisyon aktivitelerinin Ib değeri analizi ile değerlendirilmesi](Gazi Universitesi Muhendislik-Mimarlik, 2019) Tayfur S.; Alver N.; Saatcı S.There are numerous nondestructive testing methods that are used to determine damages within structures. Acoustic Emission (AE), being one of these methods makes it possible to obtain significant pieces of information such as origin time, location and type of damage formed in a material during loading by analyzing AE data using various algorithms. Ib value analysis is one of these algorithms which is based on AE signal and this analysis enables to have information on formation of new cracks or propagation of existing cracks by scaling the magnitude of AE activities. In this study, in order to investigate effect of the steel fiber in concrete matrix on Ib value, two reinforced concrete beams were tested under simple bending while one of them was the reference. Afterwards, AE parameters obtained were analyzed, Ib value analyses were applied to amplitude values and these parameters were associated to each other. Furthermore, effect of steel fiber existence on behavior of the beam and distribution of Ib value were examined. © 2019 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Öğe Identifying the effect of CFRP application type on behavior of CFRP-strengthened beams by acoustic emission(DEStech Publications, 2017) Alver N.; Tayfur S.; Tanarslan H.M.Strengthening structures using CFRP (Carbon Fiber Reinforced Polymer) strips is a widely used method because of superior mechanical properties of CFRP. Along with the overall impact of the FRP strengthening, FRP application type is one such important parameter that directly affects the strengthened beam behavior. FRP can be applied in a number of different ways. FRP sheets, either full wraps or strips are the mostly preferred methods for strengthening in recent years. These methods have more or less advantages according to each other. In other words, CFRP application influences the strengthened beam behavior since application type has a direct impact on the failure mechanism. In this study, it was aimed to identify the effect of CFRP application type on behavior of reinforced concrete (RC) beams. For this purpose, CFRP-strengthened RC beams, which were strengthened by different application types such as side-bonded and U-jacketed CFRP sheets, were tested under cyclic loading and monitored by Acoustic Emission (AE) technique. AE data obtained from the tests were processed by parameter and SiGMA analyses. Crack locations, types and orientations were determined and were compared with mechanical results. Thus, failure mechanisms of the specimens were evaluated and effects and discrimination of CFRP application type on the fracture mechanism were revealed.Öğe Imaging of voids in concrete by impact-echo and ultrasonic-echo methods [Betondaki boşlukların darbe-eko ve ultrasonik-eko yöntemleri ile görüntülenmesi](Gazi Universitesi Muhendislik-Mimarlik, 2018) Tayfur S.; Alver N.Impact-echo (IE) and ultrasonic-echo (UE) are widely used elastic wave methods to determine voids in concrete and have successful applications in the field. However, because in most cases it is difficult to interpret the results, researchers have been studying on to develop imaging algorithms. In this study, SIBIE (Stack Imaging of Spectral Amplitudes Based on IE) and SAFT (Synthetic Aperture Focusing Technique) algorithms were used in order to evaluate voids within concrete blocks. For this purpose, concrete blocks containing post-tensioning ducts that include voids were produced and IE and UE tests were carried out to locate the voids. Moreover, apart from the other studies in literature, effect of thickness of the metal ducts on phase change of the ultrasonic signal was determined. As a result of the study, along with successful void visualization, material characterization by means of acoustic impedance characteristics of air and steel was made. © 2018 Gazi Universitesi Muhendislik-Mimarlik. All rights reserved.Öğe Influences of nano-clay amount on flexure behavior of concrete identified by acoustic emission(Pontificia Universidad Catolica de Chile, Escuela de Construccion Civil, 2024) Tayfur S.; Üna H.Y.; Alver N.; Pekbey Y.Nano-modification is an effective method currently used to improve mechanical properties of concrete by adding various nanomaterials. The results obtained from previous studies demonstrate that presence of these particles has positive effects on both mechanical and durability performances of concrete. However, while the existing studies investigate the state of resistance, revealing progressive failure mechanism of nano-particle added concrete under loading is a significant subject. In this regard, Acoustic Emission (AE) method is useful for identification of invisible damage progress by means of basic phenomenon defined as release of energy due to a fracture and propagation of it as elastic waves in a stressed medium. Apart from the existing studies in the literature, this paper is focused on investigation of the influences of nano-clay on mechanical and failure behaviors of concrete by AE. For this purpose, a plain and three different concrete mixtures including 1%, 3% and 5% nano-clay (NC) of cement weight were prepared. 100x100x600 mm beam specimens were produced from these mixtures and were tested under three-point-bending. Furthermore, to reveal invisible failure mechanisms of the specimens, all tests were simultaneously monitored with AE method. The results reveal that presence of nanoclay increases the load capacity and ductility of the concrete specimens which is also confirmed by AE results, as more amount of micro-scale events are obtained. © 2024 Tayfur, S., Yavuz, H., Alver, N., Pekbey, Y. This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivatives 4.0 International License
