• Journal of Korean Association for Spatial Structures
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• v.12 no.2
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• pp.65-72
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• 2012

In this stury, control performance of tuned mass damper (TMD) with torsional rigidity for an eccentric structure showing torsional responses is investigated. To this end, an eccentric structure subjected to earthquake excitation is used to evaluate the control performance of torsional TMD by varying installed location and torsional rigidity of TMD, To reduce computational time required for repetitive time history analysis of an example structure having non-proportional damping system due to TMD, an equivalent analytical model is used in this study. Torsional properties of TMD usually neglected in typical TMD are verified to be effective in reduction of torsional responses of the eccentric structure. In the case of eccentric structures, it has been seen that the center of a plane of a structure may not be optimal location of TMD.

• Smart Structures and Systems
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• v.21 no.3
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• pp.287-303
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• 2018

Applications of energy harvesting from mechanical vibrations is becoming popular but the full potential of such applications is yet to be explored. This paper addresses this issue by considering an application of energy harvesting for the dual objective of serving as an indicator of structural health monitoring (SHM) and extent of control. Variation of harvested energy from an undamaged baseline is employed for this purpose and the concept is illustrated by implementing it for active vibrations of a pipe structure. Theoretical and experimental analyses are carried out to determine the energy harvesting potential from undamaged and damaged conditions. The use of energy harvesting as indicator for control is subsequently investigated, considering the effect of the introduction of a tuned mass damper (TMD). It is found that energy harvesting can be used for the detection and monitoring of the location and magnitude of damage occurring within a pipe structure. Additionally, the harvested energy acts as an indicator of the extent of reduction of vibration of pipes when a TMD is attached. This paper extends the range of applications of energy harvesting devices for the monitoring of built infrastructure and illustrates the vast potential of energy harvesters as smart sensors.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.44 no.1
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• pp.40-48
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• 2016

Micro-vibration induced by on-board appendages that have mechanical moving parts has always been treated as an useless objective that has to be isolated, in order to comply with a high-resolution mission requirement of the observation satellite. In this study, we proposed a tuned mass damper energy harvester combined with a conventional passive vibration isolator for exhibiting dual functions of both electrical energy harvesting and micro-vibration isolation. The feasibility of the proposed dual-function complex system has been demonstrated through the comparison with numerical simulations, based on the results of basic characteristic tests, and experiments of the harvested power and micro-vibration.

• Smart Structures and Systems
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• v.13 no.2
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• pp.177-201
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• 2014

With the increased size and flexibility of the tower and blades, structural vibrations are becoming a limiting factor towards the design of even larger and more powerful wind turbines. Research into the use of vibration mitigation devices in the turbine tower has been carried out but the use of dampers in the blades has yet to be investigated in detail. Mitigating vibrations will increase the design life and hence economic viability of the turbine blades and allow for continual operation with decreased downtime. The aim of this paper is to investigate the effectiveness of Semi-Active Tuned Mass Dampers (STMDs) in reducing the edgewise vibrations in the turbine blades. A frequency tracking algorithm based on the Short Time Fourier Transform (STFT) technique is used to tune the damper. A theoretical model has been developed to capture the dynamic behaviour of the blades including the coupling with the tower to accurately model the dynamics of the entire turbine structure. The resulting model consists of time dependent equations of motion and negative damping terms due to the coupling present in the system. The performances of the STMDs based vibration controller have been tested under different loading and operating conditions. Numerical analysis has shown that variation in certain parameters of the system, along with the time varying nature of the system matrices has led to the need for STMDs to allow for real-time tuning to the resonant frequencies of the system.

• Journal of the Society of Naval Architects of Korea
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• v.59 no.3
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• pp.134-140
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• 2022

Ship local structure sometimes experiences severe vibration due to the resonance with an excitation force generated by the propulsion system. In that case, the installation of dynamic vibration absorber such as Tuned Mass Damper (TMD) on the structure can be considered as an effective alternative countermeasure to reduce the troublesome vibration if structural modification or change of excitation frequencies is difficult. Meanwhile, the conventional optimal design method of TMD premises the target structure exposed on an excitation force without the constraint of its magnitude and frequency range. However, the frequencies of major ship excitation forces due to propulsion system are normally bounded and its magnitude is varied according to its operation speed. Hence, the optimal design of TMD to reduce the resonant vibration of ship local structure should be differently approached compared with the conventional ones. For the purpose, this paper proposes an optimal design method of TMD considering maximum frequency and magnitude variation of a target harmonic excitation component. It is done by both lowering the resonant response at the 1st natural frequency and locating the 2nd natural frequency over maximum excitation frequency for the idealized 2 degree of freedom system consisted of the structure and the TMD. For the validation of the proposed method, a numerical design case of TMD for a ship local structure exposed on resonant vibration due to a propeller excitation force is introduced and its performance is compared with the conventionally designed one.

• Advances in concrete construction
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• v.13 no.5
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• pp.385-394
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• 2022

Recently, an increasing number of cutting-edged studies have shown that designing a smart active control for real-time implementation requires piles of hard-work criteria in the design process, including performance controllers to reduce the tracking errors and tolerance to external interference and measure system disturbed perturbations. This article proposes an effective artificial-intelligence method using these rigorous criteria, which can be translated into general control plants for the management of civil engineering installations. To facilitate the calculation, an efficient solution process based on linear matrix (LMI) inequality has been introduced to verify the relevance of the proposed method, and extensive simulators have been carried out for the numerical constructive model in the seismic stimulation of the active rigidity. Additionally, a fuzzy model of the neural network based system (NN) is developed using an interconnected method for LDI (linear differential) representation determined for arbitrary dynamics. This expression is constructed with a nonlinear sector which converts the nonlinear model into a multiple linear deformation of the linear model and a new state sufficient to guarantee the asymptomatic stability of the Lyapunov function of the linear matrix inequality. In the control design, we incorporated H Infinity optimized development algorithm and performance analysis stability. Finally, there is a numerical practical example with simulations to show the results. The implication results in the RMS response with as well as without tuned mass damper (TMD) of the benchmark building under the external excitation, the El-Centro Earthquake, in which it also showed the simulation using evolved bat algorithmic LMI fuzzy controllers in term of RMS in acceleration and displacement of the building.