• Smart Structures and Systems
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• 제31권3호
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• pp.247-257
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• 2023

In structural health monitoring of large-scale structures, optimal sensor placement plays an important role because of the high cost of sensors and their supporting instruments, as well as the burden of data transmission and storage. In this study, a vibration sensor placement algorithm based on deep reinforcement learning (DRL) is proposed, which can effectively solve non-convex, high-dimensional, and discrete combinatorial sensor placement optimization problems. An objective function is constructed to estimate the quality of a specific vibration sensor placement scheme according to the modal assurance criterion (MAC). Using this objective function, a DRL-based algorithm is presented to determine the optimal vibration sensor placement scheme. Subsequently, we transform the sensor optimal placement process into a Markov decision process and employ a DRL-based optimization algorithm to maximize the objective function for optimal sensor placement. To illustrate the applicability of the proposed method, two examples are presented: a 10-story braced frame and a sea-crossing bridge model. A comparison study is also performed with a genetic algorithm and particle swarm algorithm. The proposed DRL-based algorithm can effectively solve the discrete combinatorial optimization problem for vibration sensor placements and can produce superior performance compared with the other two existing methods.

• Computers and Concrete
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• 제24권3호
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• pp.207-222
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• 2019

This paper has presented an effective and accurate meso-scale finite element model for simulating the fracture process of concrete under compression-shear loading. In the proposed model, concrete is parted into four important phases: aggregates, cement matrix, interfacial transition zone (ITZ), and the initial defects. Aggregate particles were modelled as randomly distributed polygons with a varying size according to the sieve curve developed by Fuller and Thompson. With regard to initial defects, only voids are considered. Cohesive elements with zero thickness are inserted into the initial mesh of cement matrix and along the interface between aggregate and cement matrix to simulate the cracking process of concrete. The constitutive model provided by ABAQUS is modified based on Wang's experiment and used to describe the failure behaviour of cohesive elements. User defined programs for aggregate delivery, cohesive element insertion and modified facture constitutive model are developed based on Python language, and embedded into the commercial FEM package ABAQUS. The effectiveness and accuracy of the proposed model are firstly identified by comparing the numerical results with the experimental ones, and then it is used to investigate the effect of meso-structure on the macro behavior of concrete. The shear strength of concrete under different pressures is also involved in this study, which could provide a reference for the macroscopic simulation of concrete component under shear force.

• Smart Structures and Systems
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• 제10권6호
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• pp.557-572
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• 2012

This paper focuses on the vibration control of long-span reticulated steel structures under multi-dimensional earthquake excitation. The control system and strategy are constructed based on Magneto-Rheological (MR) dampers. The LQR and Hrovat controlling algorithm is adopted to determine optimal MR damping force, while the modified Bingham model (MBM) and inverse neural network (INN) is proposed to solve the real-time controlling current. Three typical long-span reticulated structural systems are detailedly analyzed, including the double-layer cylindrical reticulated shell, single-layer spherical reticulated shell, and cable suspended arch-truss structure. Results show that the proposed control strategy can reduce the displacement and acceleration effectively for three typical structural systems. The displacement control effect under the earthquake excitation with different PGA is similar, while for the cable suspended arch-truss, the acceleration control effect increase distinctly with the earthquake excitation intensity. Moreover, for the cable suspended arch-truss, the strand stress variation can also be effectively reduced by the MR dampers, which is very important for this kind of structure to ensure that the cable would not be destroyed or relaxed.

• 한국지진공학회논문집
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• 제10권6호
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• pp.67-77
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• 2006

우리나라는 일본이나 미국의 서부지역처럼 지진위험도가 매우 높은 지역이 아니다. 그러므로 1988년에 처음으로 내진설계기준이 도입될 때까지 거의 대부분의 구조물들이 지진의 영향을 고려하지 않고 설계되었다. 원자력발전소나 액화천연가스(LNG) 저장 탱크 등의 구조물에 면진 기술이 적용되었지만 우리나라의 기술자들은 면진이나 진동제어에 대해서는 별로 관심이 없었으며 이러한 것은 강진지역에서나 필요한 기술로 생각하였다. 그러나 이러한 기술은 우리나라와 같은 약진지역에서 더 효과적으로 지진과 바람의 영향을 저감시킬 수가 있는 것이다. 다행히 근래에는 극히 소수이기는 하지만 우리나라에서도 면진과 진동제어 기술을 적용하는 교량이나 건물의 수가 점차 늘어나고 있어서 지진이나 바람 등의 영향에 대하여 보다 적극적인 대처를 하기 시작하였다. 그러나 건축 구조물의 면진이나 진동제어에 대하여 설계기준이 제대로 마련되어 있지 않아서 이러한 기술을 적용하는데 실제적으로는 많은 어려움을 겪기도 하는 것이 현실이다. 따라서 우리나라에서도 이러한 기술을 적용할 수 있는 법적 근거를 마련하는 것이 시급한 과제라고 볼 수 있다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2000년도 춘계학술대회논문집
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• pp.239-245
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• 2000

Adaptive bang-bang control algorithm has been proposed by the authors to improve peak response reduction of building structures under unexpected large earthquake. At the previous research, control performance of the proposed algorithm was experimentally confirmed by using a I-DOF test structure. As an extended research, performance tests on a multi-DOF model structure have been conducted to prove the usefulness of the adaptive bang-bang control algorithm using a hydraulic AMD. It is confirmed that the proposed adaptive bang-bang algorithm is applicable to suppress the vibration of multi-DOF structures subject to severe external excitations.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2006년도 춘계학술대회논문집
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• pp.1117-1122
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• 2006

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2008년도 추계학술대회논문집
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• pp.449-449
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• 2008

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1993년도 추계학술대회논문집; 반도아카데미, 26 Nov. 1993
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• pp.5-18
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• 1993

This paper reports the recent trends in active vibration control in Japan, especially, based on papers selected in the Proceedings of First International Conference on Motion and Vibration Control (1st MOVIC) held at Yokohama, Japan on Sept.7-11, 1992. Firstly, it classifiers vibration control methods and vibration controllers, especially active dynamic absorbers which are widely used in mechanical and civil engineering. Secondly, it covers basic problems in the control of vibration of flexible structures such as formulating a reduced-order model required for designing vibration controller, proper arranging of sensors and actuators, and preventing of spillover instability. Finally, the practical use of control theories such as LQ control theory, $H^{\infty}$ control theory, neural network theory, and other topics are discussed..

• Journal of Mechanical Science and Technology
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• 제17권6호
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• pp.805-815
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• 2003

In order to execute efficiently the free vibration analysis of 2-dimensional structures like plate structures, the author developed the finite element-transfer stiffness coefficient method. This method is based on the combination of the modeling techniques in the FEM and the transfer technique of the stiffness coefficient in the transfer stiffness coefficient method. Numerical results of the simply supported and the elastic supported rectangular plates showed that the present method can be successfully applied to the free vibration analysis of plate structures on a personal computer. We confirmed that, in the case of analyzing the free vibration of rectangular plate structures, the present method is superior to the FEM from the viewpoint of computation time and storage.

• Journal of Advanced Marine Engineering and Technology
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• 제35권3호
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• pp.309-316
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• 2011

This paper deals with the experimental study of the vibration suppression of the smart structures. First, a new high-speed active control system is presented using the DSP320C6713 microprocessor. A peripheral system developed is composed of a data acquisition system, A/D and D/A converters, piezoelectric (PZT) actuator/sensors, and drivers using PA 95 for fast data processing. Next, the processing time of the peripheral device is tested and the corresponding test results are provided. Since fast data processing is very important in the active vibration control of the structures, achieving the fast loop times of the control system is focused. The control algorithm using PPF in addition to FIR filter is implemented. Finally, numerous experiments were carried out on the aluminum plate to validate the superior performance of the vibration control system at different control loop times.