Papers by Mehmet Bakioglu
In this study a new simple approach for seismic vibration control of three dimensional structures... more In this study a new simple approach for seismic vibration control of three dimensional structures is proposed. This simple approach is based on modifying the stiffness and damping parameters of the structure. The additional stiffness and damping parameters are obtained by solving the Riccati equation in closed loop Classical Optimal Control (CLOC) and with the help of the optimal control gain matrix. Since it is not possible to add the exact optimal damping and stiffness parameters to the structure in practice some representative simple methods to obtain the suboptimal passive damping and stiffness parameters from the optimal control gain matrix are proposed [1]. Proposed method is applied to a 3-dimensional tier building structure. For this study, a 3-story steel building designed for the SAC project Los Angeles, California region is considered [2]. The structure is tested under two unidirectional real earthquake excitations. Two active control cases are considered for comparison. In the first case a single active tendon controller is implemented to each story in the north-south direction of the structure. In the second case active tendon controllers are implemented to the structure in both north-south and east-west directions. The results demonstrate that without applying active control forces to the structure, modifying the stiffness and damping parameters can supress the earthquake induced vibrations into the limits desired and the responses are similar to the actively controlled structures under CLOC.
The modeling and numerical solution for berthing a ship to a nonlinear flexible marine structure ... more The modeling and numerical solution for berthing a ship to a nonlinear flexible marine structure equipped with a passive tuned mass damper are studied. For simplicity; rotations and hydrodynamic interaction between the platform and the ship are ignored and constant added mass is assumed. Fenders and piles are represented by nonlinear springs. Internal and external damping forces are assumed as
Journal of Fluid Mechanics, 1984
A linear stability analysis is presented of both hydraulically smooth and transitional flows over... more A linear stability analysis is presented of both hydraulically smooth and transitional flows over an erodible bed. The present theory is developed to account for the formation of ripples. It is essentially an extension of the theory of to include the effect, of viscosity upon the bed wave stability. The theory takes into consideration that the formation of ripples does not depend on flow depths, and that only the bed-load transport is involved in the formation of ripples. The effect of gravity is included in the analysis through the local inclination of the wavy bed surface. The results show that the bed is unstable (i.e. ripples exist) when the grain Reynolds number is less than a certain value. The limiting values of the grain Reynolds number for ripple existence obtained through present analysis are found t o be in good agreement with observations.
Earthquake Engineering & Structural Dynamics, 2001
Considerable e ort has been devoted to develop optimal control methods for reducing structural re... more Considerable e ort has been devoted to develop optimal control methods for reducing structural response under seismic forces. In this study analytical solution of the linear regulator problem applied widely to the control of earthquake-excited structures is obtained by using the su cient conditions of optimality even though almost all of the optimal controls proposed previously for structural control are based on the necessary conditions of optimality. Since the resulting optimal closed-open-loop control cannot be implemented for civil structures exposed to earthquake forces, the solution of the optimal closed-openloop control is carried out approximately based on the prediction of the seismic acceleration values in the near future. Upon obtaining the relation between the exact optimal solution and future values of seismic accelerations, it is shown numerically that the solution of the optimal closed-open-loop control problem can be performed approximately by using only the ÿrst few predicted seismic acceleration values if a given norm criteria is satisÿed. Calculated performance measures indicate that the suggested approximate solution is better than the closed-loop control and as we predict the future values of the excitation more accurately, it will approach the optimal solution.
Computers & Structures, 2002
Exact optimal classical closed-open loop control is not achievable for the buildings under seismi... more Exact optimal classical closed-open loop control is not achievable for the buildings under seismic excitations since it requires the whole knowledge of earthquake in the control interval. In this study, a multipoint instantaneous performance index is proposed for active control of earthquake excited structures. Minimizing the proposed index with the aid of the Lagrange multipliers method results in a simple
This study firstly proposes some representative simple methods to obtain the suboptimal passive d... more This study firstly proposes some representative simple methods to obtain the suboptimal passive damping and stiffness parameters from the optimal control gain matrix since it is not possible to add the exact optimal damping and stiffness parameters to the structure in practice. It is shown numerically that modifying the structural damping and the stiffness in the proposed suboptimal ways may suppress the uncontrolled vibrations while the performance levels depend on the seismic inputs. Since the proposed approach is intrinsically passive and has no adaptive property against changing dynamic effects, this study secondly proposes a new performance index so that the mechanical energy of the structure, control and the seismic energies are considered simultaneously in the minimization procedure. The implementation of the resulting closedloop control algorithm does not require both a priori knowledge of the seismic excitation and the solution of the nonlinear matrix Riccati equation. The performance of the proposed approach is investigated, e.g., structures subjected to three seismic inputs and compared to the performance of the uncontrolled, the classical linear optimal control, and the passive cases. It is shown by the numerical simulation results that the proposed algorithm is capable of suppressing the uncontrolled seismic structural displacements and the absolute accelerations simultaneously and performs almost as well as the classical linear optimal control in reducing the displacements with comparable control effort and performs better than the classical linear optimal control in reducing the absolute accelerations. The results show that while the proposed active approach has similar performance to the classical linear optimal control, the classical linear optimal control increases the absolute accelerations slightly compared to the proposed active approach in regulating displacements, while the proposed active approach regulates and reduces both displacements and absolute accelerations. The proposed approach is promising in protecting both the structural and non-structural members from the seismic forces since a simultaneous reduction both in the displacements and the absolute accelerations is achieved.
Conference Proceedings of the Society for Experimental Mechanics Series, 2014
In this study a new simple active control algorithm is proposed for controlling the seismic respo... more In this study a new simple active control algorithm is proposed for controlling the seismic responses of elastic 4 three-dimensional structures. This simple proposed control algorithm (PC) is based on minimizing the time dependent 5 performance index, which can be defined as the total energy input of the structure. To investigate the efficiency of this 6 method, a 3-dimensional tier building is considered. This structure is tested under a real earthquake excitation. Emphasis 7 has been placed on comparison of the proposed algorithm with classical linear optimal control. With reference to the results, 8 the proposed simple control algorithm is very effective in suppressing the uncontrolled structural vibrations. The numerical 9 results also demonstrate that with very little control energy consumption, the reduction in the responses is similar in amount 10 to that obtained with classical linear optimal control. The resulting closed-loop control algorithm doesn't require the future 11 knowledge of earthquakes, and it also doesn't require the solution of the nonlinear matrix Riccati equation, which would 12 increase the computer solution time.
International Journal for Numerical Methods in Engineering, 2001
Exact optimal classical closed-open-loop control is not achievable for the buildings under seismi... more Exact optimal classical closed-open-loop control is not achievable for the buildings under seismic excitations since it requires the whole knowledge of earthquake in the control interval. In this study, a new numerical algorithm for the sub-optimal solution of the optimal closed-open-loop control is proposed based on the prediction of near-future earthquake excitation using the Taylor series method and the Kalman ÿltering technique. It is shown numerically that how the solution is related to the predicted earthquake acceleration values. Simulation results show that the proposed numerical algorithm are better than the closed-loop control and the instantaneous optimal control and proposed numerical solution will approach the exact optimal solution if the more distant future values of the earthquake excitation can be predicted more precisely. E ectiveness of the Kalman ÿltering technique is also conÿrmed by comparing the predicted and the observed time history of NS component of the 1940 El Centro earthquake.
Computer-Aided Civil and Infrastructure Engineering, 2012
This study firstly proposes some representative simple methods to obtain the suboptimal passive d... more This study firstly proposes some representative simple methods to obtain the suboptimal passive damping and stiffness parameters from the optimal control gain matrix since it is not possible to add the exact optimal damping and stiffness parameters to the structure in practice. It is shown numerically that modifying the structural damping and the stiffness in the proposed suboptimal ways may suppress the uncontrolled vibrations while the performance levels depend on the seismic inputs. Since the proposed approach is intrinsically passive and has no adaptive property against changing dynamic effects, this study secondly proposes a new performance index so that the mechanical energy of the structure, control and the seismic energies are considered simultaneously in the minimization procedure. The implementation of the resulting closedloop control algorithm does not require both a priori knowledge of the seismic excitation and the solution of the nonlinear matrix Riccati equation. The performance of the proposed approach is investigated, e.g., structures subjected to three seismic inputs and compared to the performance of the uncontrolled, the classical linear optimal control, and the passive cases. It is shown by the numerical simulation results that the proposed algorithm is capable of suppressing the uncontrolled seismic structural displacements and the absolute accelerations simultaneously and performs almost as well as the classical linear optimal control in reducing the displacements with comparable control effort and performs better than the classical linear optimal control in reducing the absolute accelerations. The results show that while the proposed active approach has similar performance to the classical linear optimal control, the classical linear optimal control increases the absolute accelerations slightly compared to the proposed active approach in regulating displacements, while the proposed active approach regulates and reduces both displacements and absolute accelerations. The proposed approach is promising in protecting both the structural and non-structural members from the seismic forces since a simultaneous reduction both in the displacements and the absolute accelerations is achieved.
In the area of active control of structures, time delay consideration is an important parameter w... more In the area of active control of structures, time delay consideration is an important parameter which must be taken into consideration for realistic numerical models. In this research, the performance of a new active control algorithm for several time delays under two different earthquake excitations was investigated numerically. The proposed performance index does not require a priori knowledge of seismic input and the solution of the nonlinear matrix Riccati equation to apply the control forces . The proposed control introduces the seismic energy term into the performance index so that the mechanical energy of the structure, the control and the seismic energies are considered simultaneously in the minimization procedure, which yields cross terms in the performance index. A two story shear frame was modelled in Matlab-Simulink considering time-delay. A fully active tendon controller system is implemented to the system. 0-50 ms time delay was considered in the dynamic analysis. The change in the time delay steps was 5 ms. The effect of time-delay was investigated under synthetic and Erzincan NS (1995;95 Erzincan station) earthquakes. Kanai-Tajimi power spectral density function was used to generate synthetic earthquake motion. The behavior of the proposed control with time delay considerations is compared with the uncontrolled conventional structure.
Books by Mehmet Bakioglu
In the area of active control of structures, time delay
consideration is an important parameter w... more In the area of active control of structures, time delay
consideration is an important parameter which must be taken
into consideration for realistic numerical models. In this
research, the performance of a new active control algorithm for
several time delays under two different earthquake excitations
was investigated numerically. The proposed performance index
does not require a priori knowledge of seismic input and the
solution of the nonlinear matrix Riccati equation to apply the
control forces [1,2]. The proposed control introduces the
seismic energy term into the performance index so that the
mechanical energy of the structure, the control and the seismic
energies are considered simultaneously in the minimization
procedure, which yields cross terms in the performance index. A
two story shear frame was modelled in Matlab-Simulink
considering time-delay. A fully active tendon controller system
is implemented to the system. 0-50 ms time delay was
considered in the dynamic analysis. The change in the time
delay steps was 5 ms. The effect of time-delay was investigated
under synthetic and Erzincan NS (1995;95 Erzincan station)
earthquakes. Kanai-Tajimi power spectral density function was
used to generate synthetic earthquake motion. The behavior of
the proposed control with time delay considerations is
compared with the uncontrolled conventional structure.
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Papers by Mehmet Bakioglu
Books by Mehmet Bakioglu
consideration is an important parameter which must be taken
into consideration for realistic numerical models. In this
research, the performance of a new active control algorithm for
several time delays under two different earthquake excitations
was investigated numerically. The proposed performance index
does not require a priori knowledge of seismic input and the
solution of the nonlinear matrix Riccati equation to apply the
control forces [1,2]. The proposed control introduces the
seismic energy term into the performance index so that the
mechanical energy of the structure, the control and the seismic
energies are considered simultaneously in the minimization
procedure, which yields cross terms in the performance index. A
two story shear frame was modelled in Matlab-Simulink
considering time-delay. A fully active tendon controller system
is implemented to the system. 0-50 ms time delay was
considered in the dynamic analysis. The change in the time
delay steps was 5 ms. The effect of time-delay was investigated
under synthetic and Erzincan NS (1995;95 Erzincan station)
earthquakes. Kanai-Tajimi power spectral density function was
used to generate synthetic earthquake motion. The behavior of
the proposed control with time delay considerations is
compared with the uncontrolled conventional structure.
consideration is an important parameter which must be taken
into consideration for realistic numerical models. In this
research, the performance of a new active control algorithm for
several time delays under two different earthquake excitations
was investigated numerically. The proposed performance index
does not require a priori knowledge of seismic input and the
solution of the nonlinear matrix Riccati equation to apply the
control forces [1,2]. The proposed control introduces the
seismic energy term into the performance index so that the
mechanical energy of the structure, the control and the seismic
energies are considered simultaneously in the minimization
procedure, which yields cross terms in the performance index. A
two story shear frame was modelled in Matlab-Simulink
considering time-delay. A fully active tendon controller system
is implemented to the system. 0-50 ms time delay was
considered in the dynamic analysis. The change in the time
delay steps was 5 ms. The effect of time-delay was investigated
under synthetic and Erzincan NS (1995;95 Erzincan station)
earthquakes. Kanai-Tajimi power spectral density function was
used to generate synthetic earthquake motion. The behavior of
the proposed control with time delay considerations is
compared with the uncontrolled conventional structure.