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    Computer-Aided Mold Design Algorithm for Precast Concrete Elements
    (Amer Concrete Inst, 2014) Aktas, Gultekin; Tanrikulu, Ahmed Kamil; Baran, Tarik
    This paper aims to determine a computer-aided mold design algorithm for precast concrete products to be produced by external vibrators. For this purpose, the behaviors of two different precast concrete molds were investigated experimentally and analytically. Experiments were performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on the mold while it is empty and full of fresh concrete. Test results indicate that the difference between displacement amplitudes of empty and full molds is considerably high. Three-dimensional analytical modeling of molds used in experiments was prepared by finite element method using software. Modeling of the full mold was made to solve the problem of dynamic interaction of fresh concrete mold. In light of experimental, numerical, and literature studies, a mold design algorithm was established for precast concrete elements. Using this algorithm, a computer-aided mold design was carried out theoretically for a sample mold system.
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    Displacement prediction of precast concrete under vibration using artificial neural networks
    (Techno-Press, 2020) Aktas, Gultekin; Ozerdem, Mehmet Sirac
    This paper intends to progress models to accurately estimate the behavior of fresh concrete under vibration using artificial neural networks (ANNs). To this end, behavior of a full scale precast concrete mold was investigated numerically. Experimental study was carried out under vibration with the use of a computer-based data acquisition system. In this study measurements were taken at three points using two vibrators. Transducers were used to measure time-dependent lateral displacements at these points on mold while both mold is empty and full of fresh concrete. Modeling of empty and full mold was made using ANNs. Benefiting ANNs used in this study for modeling fresh concrete, mold design can be performed. For the modeling of ANNs: Experimental data were divided randomly into two parts such as training set and testing set. Training set was used for ANN's learning stage. And the remaining part was used for testing the ANNs. Finally, ANN modeling was compared with measured data. The comparisons show that the experimental data and ANN results are compatible.
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    EXPERIMENTAL CONFIRMATION FOR THE VALIDITY OF RITZ METHOD IN STRUCTURAL DYNAMIC ANALYSIS
    (Polish Soc Theoretical & Applied Mechanics, 2014) Aktas, Gultekin; Karasin, Abdulhalim
    The issue of Ritz vectors and their advantages is well-known in the field of structural engineering. This study deals with Ritz analysis and its experimental support. To that end, two different precast concrete molds were handled. Experiments were performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure displacement histories on the mold. Three dimensional finite element (3D FEM) simulation modeling of the concrete mold was carried out to obtain deflection histories on the mold. The computed displacement histories were compared with the experimental testing results. The comparisons show that the experimental and numerical results are compatible.
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    A finite grid solution for circular plates on elastic foundations
    (Korean Society Of Civil Engineers-Ksce, 2015) Karasin, Halim; Gulkan, Polat; Aktas, Gultekin
    The transmission of vertical or horizontal structural forces to the supporting soil is a challenge to analyze for structures on elastic foundation which represent a complex medium. The two-parameter elastic foundation model that provides a mechanical interaction between the individual spring elements shows a more realistic behavior of the soil reaction than does the single parameter Winkler model. Since the structural behavior of a beam resembles that of a strip in a plate, in this study, the exact stiffness and mass matrices of the beam element on two-parameter elastic foundation is extended to plates. The framework method that replaces a continuous surface by an idealized discrete system can represent a two-dimensional plate. In the light of this situation, circular plates are modeled as an assemblage of individual beam elements interconnected at their neighboring joints in radial and tangential direction. So, a useful tool called finite grid solution as a numerical method developed in this study lead to solve circular plates resting on two parameter elastic foundation problems. Examples for bending of ring, circular and annual plates on elastic foundation are solved to compare with known analytical solutions and other numerical solutions. The comparisons show that the literature and the computed results are compatible.
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    Investigation of fresh concrete behavior under vibration using mass-spring model
    (Techno-Press, 2016) Aktas, Gultekin
    This paper deals with the behavior of fresh concrete that is under vibration using mass-spring model (MSM). To this end, behaviors of two different full scale precast concrete molds were investigated experimentally and theoretically. Experiments were performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on mold while mold is empty and full of fresh concrete. Analytical modeling of molds used in experiments were prepared by three dimensional finite element method (3D FEM) using software. Modeling of full mold, using MSM, was made to solve the problem of dynamic interaction between fresh concrete and mold. Numerical displacement histories obtained from time history analysis were compared with experimental results. The comparisons show that the measured and computed results are compatible.
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    Prediction of behavior of fresh concrete exposed to vibration using artificial neural networks and regression model
    (Techno-Press, 2016) Aktas, Gultekin; Ozerdem, Mehmet Sirac
    This paper aims to develop models to accurately predict the behavior of fresh concrete exposed to vibration using artificial neural networks (ANNs) model and regression model (RM). For this purpose, behavior of a full scale precast concrete mold was investigated experimentally and numerically. Experiment was performed under vibration with the use of a computer-based data acquisition system. Transducers were used to measure time-dependent lateral displacements at some points on mold while both mold is empty and full of fresh concrete. Modeling of empty and full mold was made using both ANNs and RM. For the modeling of ANNs: Experimental data were divided randomly into two parts. One of them was used for training of the ANNs and the remaining part was used for testing the ANNs. For the modeling of RM: Sinusoidal regression model equation was determined and the predicted data was compared with measured data. Finally, both models were compared with each other. The comparisons of both models show that the measured and testing results are compatible. Regression analysis is a traditional method that can be used for modeling with simple methods. However, this study also showed that ANN modeling can be used as an alternative method for behavior of fresh concrete exposed to vibration in precast concrete structures.