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    Determination of displacements on built-up steel beams during experiments by image processing
    (Elsevier Sci Ltd, 2021) Ozsariyildiz, Saban S.; Dugenci, Oguz; Sulev, Ertan
    In this study, an image processing technique is developed for measuring the displacements during flexural loading experiments of structural beams as an alternative to measurements by traditional gauging devices. In this context, four-point bending tests were carried out on three built-up (welded) steel beams, one of them without stiffening plates and the others with stiffening plates. In the experiments, while the load-deflection values in each loading step were taken using load cells and LVDTs, a video recording of the experiments was simultaneously taken. The load-deflection curves were comparatively constructed using both the values measured with LDVTs and the data obtained by image processing. In order to match the data obtained using the point flow method of image processing technique to the gauged measurements, the scale coefficients in pixel / mm unit were calculated. The mean absolute error (MAE) and root mean square error RMSE error values were computed to determine the efficacy of the scale coefficients. The MAE and RMSE values for the beam without the stiffening plates turned out to be 3.42 and 4.52, while they were 1.29 and 1.82 for the beams with the stiffening plates. According to these results, the higher the lateral torsional buckling, the more difficult it is to determine the verification coefficient. The accuracy of the image processing method developed herein for determination of in-plane displacements can be further improved easily for experiments involving out-of-plane displacements due to local buckling also if the recordings of more cameras from different angles are included in the analyses. (c) 2021 Elsevier Ltd. All rights reserved.
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    Finding optimal parameters of tuned mass dampers
    (Wiley, 2015) Ozsariyildiz, Saban S.; Bozer, Ali
    In this paper, optimum design of tuned mass damper for seismically excited structures is discussed. In the design process, a benchmark multi-degree of freedom system is considered, and the performance measure of the optimization criterion is selected as the H-2 and H norms of the transfer function of the combined tuned mass damper and building system. Differential evolution algorithm is then utilized to minimize these objective functions. The objective function choice on performance and the effectiveness of differential evolution optimization algorithm in comparison with other algorithms in the literature are investigated through numerical simulations. Copyright (c) 2014 John Wiley & Sons, Ltd.
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    Free parameter search of multiple tuned mass dampers by using artificial bee colony algorithm
    (John Wiley & Sons Ltd, 2018) Bozer, Ali; Ozsariyildiz, Saban S.
    In optimization of multiple tuned mass dampers (MTMDs), certain restrictions or preconditions such as uniform distribution of stiffness, mass, or frequency spacing had been applied for simplification, but in turn, solution of individual stiffness and damping parameters are not the true optima. The main purpose of this paper is to obtain the true optima of individual stiffness and damping parameters of MTMD system. In the proposed method, parameters of TMD units are treated as free search optimization variables, and an efficient optimization algorithm, namely, artificial bee colony algorithm has been utilized in obtaining optimum parameters of MTMDs. Performance proposed method with respect to uncontrolled structure is verified through numerical analyses and compared with other reported methods. Comparisons show a superior performance of proposed approach. The basic properties of optimum design, the effectiveness, and robustness with respect to number of dampers are also discussed.