Scopus İndeksli Yayınlar Koleksiyonu
Permanent URI for this collectionhttps://hdl.handle.net/20.500.12573/395
Browse
4 results
Search Results
Book Part Citation - Scopus: 6Modeling of Suspended Sediment Concentration Carried in Natural Streams Using Fuzzy Genetic Approach(Springer Netherlands, 2014) Kisi, Ozgur; Fedakar, Halil IbrahimThis chapter proposes fuzzy genetic approach so as to predict suspended sediment concentration (SSC) carried in natural rivers for a given stream cross section. Fuzzy genetic models are improved by combining two methods, fuzzy logic and genetic algorithms. The accuracy of fuzzy genetic models was compared with those of the adaptive network-based fuzzy inference system, multilayer perceptrons, and sediment rating curve models. The daily streamflow and suspended sediment data belonging to two stations, Muddy Creek near Vaughn (Station No: 06088300) and Muddy Creek at Vaughn (Station No: 06088500), operated by the US Geological Survey were used as case studies. The root mean square errors and determination coefficient statistics were used for evaluating the accuracy of the models. The comparison results revealed that the fuzzy genetic approach performed better than the other models in the estimation of the SSC. © 2024 Elsevier B.V., All rights reserved.Article Citation - WoS: 7Citation - Scopus: 6Effect of Principal Stress Rotation on Deformation Behavior of Dense Sand-Clay Mixtures(Taylor & Francis Ltd, 2021-07-05) Fedakar, Halil Ibrahim; Rutherford, Cassandra J.; Cetin, BoraThis paper investigated the deformation behaviour of K-consolidated sand-clay mixtures through cyclic triaxial (CT) and hollow cylinder (CHC) tests. The sand-clay mixtures contained 0%, 5%, 10% and 20% clay by weight and were prepared at a relative density of 75%. Clay inclusion caused an increase in the permanent axial strain of mixtures (0.075% to 5% in CT and 0.186% to 5% in CHC), while a relatively insignificant increase in permanent axial strain was observed in the CT specimens containing 5% and 10% clay (0.075% to 1.299%). However, all CHC specimens with clay failed (epsilon(z) >= 5%). It was also observed that shear strain development of sand is significantly influenced by clay inclusion (0.096-2.241%) in CHC tests. Test results clearly show that the effect of a principal stress rotation should be taken into account to better estimate the deformation behaviour of sand-clay mixtures under repetitive traffic loads.Article Citation - WoS: 18Citation - Scopus: 18Deformation Characteristics of Medium-Dense Sand-Clay Mixtures Under a Principal Stress Rotation(Elsevier, 2021-09) Fedakar, Halil Ibrahim; Cetin, Bora; Rutherford, Cassandra J.A moving wheel load induces a principal stress rotation (PSR) in pavement foundation geomaterials including subgrade/subbase soils. Simulating such a stress condition is not possible with stress path tests conducted with conventional cyclic triaxial (CT) equipment. More complex stress paths such as a heart-shaped stress path are required to determine the deformation characteristics of these under a PSR. A heart-shaped stress path can be simulated on a soil specimen in cyclic hollow cylinder (CHC) tests via user-defined waveforms for its stress components (axial stress, and torsional shear stress). In this study, a series of CT and CHC tests were performed to analyze the impact of a PSR on strain behaviors of medium-dense sand-clay mixtures. The specimens contained 0%, 5%, 10%, and 20% clay by weight and were prepared at an initial relative density of 50%. All specimens were anisotropically consolidated under K-0 approximate to 0.5. It was determined that all CT specimens underestimated the strain performances (both axial strain and shear strain) of the sand-clay mixtures. On the other hand, a heartshaped stress path was simulated successfully in CHC tests and thus, all specimens yielded more accurate strain results. At low clay content (<= 10%), the impact of a PSR on strain performances of the sand-clay mixtures was observed to be less (axial strain (epsilon(z)) < 0.12%, and shear strain (gamma(z theta)) 0.8% after number of load cycles (N) = 5000) due to the low stress ratios (CVSR = 0.15 and eta = 1/3). On the other hand, despite the low stress ratios, a PSR caused a rapid increase in axial strain and shear strain (epsilon(z) = 5%, and gamma(z theta) 0.8%) of the specimen containing 20% clay, which resulted in the failure of the specimen at N = 478. Results of this study clearly indicated that the effect of a PSR should be taken into consideration while evaluating the strain characteristics of the sand-clay mixtures that contain clay particularly at high contents (>= 20%) under traffic loads.Article Citation - Scopus: 3Developing Empirical Formulae for Scour Depth in Front of Inclined Bridge Piers(Croatian Association of Civil Engineers, 2023-04) Fedakar, Halil Ibrahim; Dinçer, A. Ersin; Bozkuş, ZaferBecause of the complex flow mechanism around inclined bridge piers, previous studies have proposed different empirical correlations to predict the scouring depth in front of piers, which include regression analysis developed from laboratory measurements. However, because these correlations were developed for particular datasets, a general equation is still required to accurately predict the scour depth in front of inclined bridge piers. The aim of this study is to develop a general equation to predict the local scour depth in front of inclined bridge pier systems using multilayer perceptron (MLP) and radial-basis neural-network (RBNN) techniques. The experimental datasets used in this study were obtained from previous research. The equation for the scour depth of the front pier was developed using five variables. The results of the artificial neural-network (ANN) analyses revealed that the RBNN and MLP models provided more accurate predictions than the previous empirical correlations for the output variables. Accordingly, analytical equations derived from the RBNN and MLP models were proposed to accurately predict the scouring depth in front of inclined bridge piers. Moreover, from the sensitivity analyses results, we determined that the scour depths in front of the front and back piers were primarily influenced by the inclination angle and flow intensity, respectively. © 2023 Elsevier B.V., All rights reserved.