Yazar "Bozer, Ali" seçeneğine göre listele

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    Effect of modelling parameters on non-linear seismic response of concrete structures
    (Ice Publishing, 2017) Bozer, Ali
    The non-linear numerical analysis of reinforced-concrete structures presents several difficulties due to the complicated behaviour of reinforced concrete under cyclic lateral loading. For practical use, design guidelines provide simplified non-linear models which are implemented in many structural analysis programs. However, restrictions and assumptions on which the models are based may influence the seismic response of existing structures. The primary aim of the work reported in this paper was to identify possible differences in structural response due to selected non-linear modelling parameters. Based on these findings, the aim was then to provide guidance for practical computer models capable of representing a realistic non-linear seismic response. A set of numerical models was constructed and then a force-deformation relationship for each model was compared with experimental results. Sensitivity of response due to changes in each member's modelled plasticity and hysteresis was further investigated on a ten-storey reinforced-concrete building under five different seismic inputs. The analyses confirmed that storey displacements and degree of plastic deformation were influenced by modelling preferences. A fibre model was found to be more reliable in reflecting non-linear behaviour.
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    Effect of Plan Configuration of Reinforced Concrete Shear Walls on the behavior of Flat Slab Buildings
    (Turkish Chamber Civil Engineers, 2020) Bozer, Ali
    In this study, the effect of plan configuration of shear walls on the behavior of flat slab building is investigated. For this purpose two seven-story flat slab buildings are designed. In one of the buildings, plan configuration of shear walls is selected symmetrical, whereas in the other building plan configuration is selected to cause torsional irregularity. Seismic performances of both buildings are then investigated by push-over and time-history analyses. It is observed that plan configuration of structural walls has a significant effect on overall ductility of the flat slab buildings.
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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.
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    Hybrid tracking controller with attached tuned mass damper
    (John Wiley & Sons Ltd, 2013) Bozer, Ali; Altay, Gulay
    The optimization of tuned mass damper (TMD) involves the attachment of a damper to a TMD unit. Although this supplementary damping renders TMD to be operational under broad bandwidth inputs (i.e., wind excitation), it also considerably decreases the efficiency. In this paper, an alternative approach is suggested to eliminate the requirement for supplementary damping, hence to utilize TMD in full efficiency. For this purpose, combined structure/undamped TMD system is equipped with an active controller to track the response of an oscillator with natural frequency set to the operating frequency of the TMD unit. In this case, a proposed controller does not aim returning a system to its zero state; instead, it supports the TMD unit to suppress vibration effectively. This tracking type controller is formulized by both linear quadratic regulator, and H infinity control schemes, and control performances of each system are evaluated through numerical simulations. Copyright (C) 2011 John Wiley & Sons, Ltd.
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    Neural network model for seismic response of braced buildings
    (Ice Publishing, 2017) Doran, Bilge; Shen, Jiehua 'Jay'; Wen, Rou; Akbas, Bulent; Bozer, Ali
    Non-ductile, concentrically braced frames are a common lateral force-resisting system used in low-to-moderate seismic regions in the USA. However, their dynamic responses to earthquake ground motions have not been well examined. Structural engineers usually design them conservatively as brittle structures with a small response-modification factor, while building codes restrict their use to low-rise buildings. In this paper, seismic responses of two typical non-ductile concentrically braced frames, one of three storeys and one of nine storeys, were predicted through a neural network model. Twelve input parameters, covering non-linear features from structural components and the uncertain nature of earthquake ground motions, were used in the modelling. Numerical results extracted from thousands of non-linear time-history analyses under one set of moderate ground motions were used to develop the model. Sensitivity analyses were conducted to evaluate the impacts of input parameters on the peak inter-storey drift ratio, designed as an output parameter in the model. The results are shown to be promising considering the uncertainties in both ground motions and the characteristics of structures.
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    Seismic Performance Evaluation of Reinforced Concrete Moment Frames with Gravity Columns
    (Asce-Amer Soc Civil Engineers, 2020) Akbas, Bulent; Doran, Bilge; Bozer, Ali; Seker, Onur; Faytarouni, Mahmoud; Shen, Jay
    Moment frames with gravity columns in reinforced concrete (RC) buildings have been used extensively for the last decade in the United States. Unlike traditional beam-column-slab structures, they provide some advantages in terms of construction time and architectural and economical aspects in design process. The system consists of gravity-only columns resting directly on slabs and seismic force-resisting moment frames. Reinforced concrete special moment frames in two principal directions are typically placed at the perimeter as a lateral force-resisting system. Even though the design procedure is similar to that used with steel special moment frames, there is generally no column at the corner of the plan in such buildings so as to avoid biaxial bending. This paper investigates the contribution of gravity-only columns to inelastic seismic response of low- and high-rise RC special moment frames. For this purpose, nonlinear dynamic time history analyses are carried out on 5- and 15-story RC buildings designed with current design specifications subjected to design-level earthquake ground motions. Seismic performance evaluation was also carried out through nonlinear dynamic time history analyses. (c) 2020 American Society of Civil Engineers.
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    Seismic performance of shallow depth tuned liquid damper
    (MIM RESEARCH GROUP, 2021) Bozer, Ali
    Tuned Liquid Dampers (TLD) consist of a container that is generally partially filled with water. When the sloshing frequency of the water mass is tuned to the fundamental mode of the primary structure a significant amount of sloshing and wave breaking can be achieved which are the primary sources of energy dissipation. Although TLDs are easy to install, operate and maintain; it is generally challenging to model the nonlinear nature of sloshing water. Equivalent mechanical models provide a simplified solution in which sloshing liquid mass, liquid damping, and sloshing frequency are represented by an equivalent mass, damper, spring system. Equivalent mechanical model derivations are generally based on linear sloshing of water mass, which is possible when the water depth/tank length ratio is high and excitation amplitude is low. In this study, a well-known and widely accepted Housner equivalent mechanical model is used to model water sloshing. The water depth/tank length ratio is kept low to enhance the energy dissipation of TLD. The main objective of this study is to experimentally investigate the effectiveness of TLD and check the accuracy of Housner equivalent mechanical model under seismic excitations and low water depth/tank length ratio. Water depth is optimized by the Artificial Bee Colony algorithm which is a population-based optimization algorithm. Frequency sweep analysis and seismic excitations are employed to investigate TLD performance. It is shown that even TLD behavior is modeled by a simplified linear equivalent mechanical model, it is still effective in reducing structural response under large amplitude seismic excitations and low water level/tank length ratios. This is due to more energy dissipation with an increased amount of sloshing and wave breaking. © 2021 MIM Research Group. All rights reserved.
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    Tasarım Spektral İvme Katsayılarının DBYBHY 2007 ve TBDY 2018 Yönetmeliklerine Göre Karşılaştırması
    (2020) Bozer, Ali
    Yapılara etkiyen deprem yüklerinin hesaplanmasında temel teşkil eden deprem tehlike haritaları, sismik tehlikehesapları ile ilgili yöntemlerindeki, deprem kaynaklarıyla ilgili veri tabanlarındaki ve yer hareketi tahmindenklemleri konularındaki gelişmeler neticesinde 1945 yılından günümüze kadar çeşitli değişikliklereuğramıştır. Bu gelişmelere paralel olarak güncellenen Türkiye Bina Deprem Yönetmeliği uyarınca hesaplanankısa periyot ve 1.0 sn periyot bölgelerindeki spektral değerler bir önceki Deprem Bölgelerinde YapılacakBinalar Hakkında Yönetmeliğe göre değişiklik göstermektedir. Bu çalışmada her iki yönetmeliğe ait hesapadımları ve 81 il merkezinde elde edilen spektral değerler detaylı olarak karşılaştırılmış, hesaplanan verilerTürkiye haritasında işlenerek görsel olarak sunulmuştur. Türkiye Bina Deprem Yönetmeliğine görehesaplanan tasarım spektral değerleri özellikle zayıf zeminlerde, yürürlükte olmayan Deprem BölgelerindeYapılacak Binalar Hakkında Yönetmeliğe göre hesaplanan değerlere kıyasla birçok il merkezimizde artışgöstermiştir.