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    Metaheuristic algorithms in optimum design of reinforced concrete beam by investigating strength of concrete
    (2020) Ulusoy, Serdar; Kayabekir, Aylin Ece; Bekdaş, Gebrail; Niğdeli, Sinan Melih
    The locations of structural members can be provided according to architectural pro-jects in the design of reinforced concrete (RC) structures. the design of dimensions isthe subject of civil engineering, and these designs are done according to the expe-rience of the designer by considering the regulation suggestions, but these dimen-sions and the required reinforcement plan may not be optimum. For that reason, the dimensions and detailed reinforcement design of RC structures can be found by using optimization methods. To reach optimum results, metaheuristic algorithms can be used. In this study, several metaheuristic algorithms such as harmony search, bat al-gorithm and teaching learning-based optimization are used in the design of several RC beams for cost minimization. the optimum results are presented for different strength of concrete. the results show that using high strength material for high flex-ural moment capacity has lower cost than low stretch concrete since doubly rein-forced design is not an optimum choice. the results prove that a definite metaheuris-tic algorithm cannot be proposed for the best optimum design of an engineering problem. According to the investigation of compressive strength of concrete, it can be said that a low strength material are optimum for low flexural moment, while a high strength material may be the optimum one by the increase of the flexural mo-ment as expected.
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    Novel metaheuristic-based tuning of PID controllers for seismic structures and verification of robustness
    (Elsevier Ltd, 2021) Ulusoy, Serdar; Niğdeli, Sinan Melih; Bekdaş, Gebrail
    In the present study, an active structural control using metaheuristic tuned Proportional-Integral-Derivative (PID) type controllers is presented. The aim of the study is to propose a feasible active control application considering time delay and a feasible control force. In the optimum control methodology, near-fault directivity pulse was considered for ground motion. Three different metaheuristic algorithms are separately employed in the optimum tuning of PID parameters such as proportional gain, integral time and derivative time. The employed algorithms are Flower Pollination Algorithm, Teaching Learning Based Optimization and Jaya algorithm. The maximum control force limit is considered as a design constraint. The methodology contains the time delay consideration and a process to avoid the stability problem on the trial results during the optimization process. The method is explained in three stages as The Pre-Optimization Stage, The Dynamic Analysis Stage and The Optimization Stage. The optimum PID parameters of different algorithms are very different, but the performance of active control is similar since a similar control signal can be generated by different proportion of controller gains such as proportion, integral and derivative processes. As the conclusion of the study, the amount of control force must be chosen carefully since big control forces may resulted with stability problems if the control system has long delay. © 2020
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    Optimum active controlled SDOF structures under pulse-type ground motions via harmony search
    (Springer Science and Business Media Deutschland GmbH, 2021) Ulusoy, Serdar; Niğdeli, Sinan Melih; Bekdaş, Gebrail
    In this study, the active controlled single degree of freedom (SDOF) structures with 0.5, 1.0 and 2.0 s period are investigated under various pulse-type ground motions (1.5, 2.0, and 2.5 s) to optimally tune the parameters of proportional–integral–derivative (PID)-type controllers. The damping ratio value is assumed as 5%. The paper proposes a methodology to determine the proportional gain (Kp), integral gain (Ti), and derivative gain (Td) using Harmony Search algorithm (HS) which is one of the metaheuristic-based methods. The performance index of active controlled structures is the displacement feedback. Also, the control force limit as 50% of the total mass of the structure and the time delay effect 20 ms were considered in term of feasibility and stability of active controlled structures. According to the results, the optimum tuned PID controller parameters has major effects on the structural responses of SDOF structures. © 2021, The Editor(s) (if applicable) and The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd.
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    Performance of optimum tuned PID controller with different feedback strategies on active-controlled structures
    (MDPI-Multidisciplinary Digital Publishing Institute, 2021) Ulusoy, Serdar; Bekdaş, Gebrail; Niğdeli, Sinan Melih; Kim, Sanghun; Geem, Zong Woo
    In this study, multi-story structures with different combinations (on each floor and only the first floor) of active tendon control systems driven by a proportional-integral-derivative (PID) controller were actively controlled. The PID parameters, K-p (proportional gain), T-d (derivative gain), and T-i (integral gain) for each structure, were optimally tuned by using both the harmony search algorithm (HS) and flower pollination algorithm (FPA), which are metaheuristic algorithms. In two different active-controlled structures, which are formed according to the position of the PID, the structural responses under near-fault records defined in FEMA P-695 are examined to determine the appropriate feedback which was applied for displacement, velocity, acceleration, and total acceleration. The performance of the different feedback strategies on these two active-controlled structures is evaluated. As a result, the acceleration feedback is suitable for all combinations of the active control system with a PID controller. The HS algorithm outperforms the optimum results found according to the FPA.
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    The effect of SSI and impulsive motions on optimum active controlled MDOF structure
    (Springer Science and Business Media Deutschland GmbH, 2021) Ulusoy, Serdar; Niğdeli, Sinan Melih; Bekdaş, Gebrail
    In this study, active controlled ten-story structures including soil-structure interaction (SSI) are investigated under different type of ground motions (near-fault and far ground motions) defined in FEMA P-695 to show the effect of earthquake records on SSI. In structures, where active tendons are located on each floor, the proportional-integral-derivative (PID) controllers are used. Optimum tuning of PID control parameters are calculated with the teaching-learning-based algorithm (TLBO) and harmony search algorithms (HSA) which are commonly used metaheuristic algorithms. The properties such as swaying and rocking stiffness and damping of dense and soft soils were added to the foundation of the structures to consider the soil-structure interaction. The changes of structural reactions in two types of earthquake records are examined by decreasing or increasing these properties of soils by 10 and 20%. As a result, reduction and enhancement of properties of soft soil in structural responses are changed significantly, while these values are not changed much for dense soil. © 2021, Springer Nature Switzerland AG.