• The Journal of the Acoustical Society of Korea
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• v.12 no.1
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• pp.12-19
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• 1993

진동시험 동안 구조물은 진동시험기로부터 높은 진동에너지를 받게 되는데 공급되는 에너지를 시험물에 전달하기 위해서는 시험물에 따라 다양한 종류의 진동시험치구가 필요하게 된다. 이중에서 T-형상 진동시험치구는 진동시험축에 대해 3방향으로 시험물을 설치할 수 있고, 형상이 간단하며, 또한 값이 저렴하므로 많은 설계자들은 T-형상 치구를 설계하여 사용한다. 그러나 이 치구는 수직판이 어떤 주파수에서 평판처럼 공진현상을 일으키기 때문에 동역학적으로 설계하기가 어렵다. 본 논문에서는 진동시험치구의 기능을 향상시키기 위해 모우드 시험(Model Testing)기법을 사용하는 방법과 시험결과를 근거로 설계변경을 위해 수직보강판, 수평보강판, 그리고 천연 고무패드를 사용하여 이것들이 치구의 동특성에 미치는 영향을 기술하며 그 결과를 치구설계 때 응용 가능하도록 한다.

• Journal of The Korean Society For Urban Railway
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• v.6 no.4
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• pp.417-426
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• 2018

Piezoelectric shunt is an electric type damper capable of reducing the vibration of the structure. Vibration generated at the natural frequency of the structure are converted into electrical energy through the piezoelectric material attached to the structure. Electric energy can be dissipated by thermal energy using piezoelectric shunt composed of inductor and resistance to reduce vibration. In this paper, the equation for the optimum inductance required to reduce the vibration of the cantilever beam was examined and the vibration of the aluminum cantilever was reduced by using finite element analysis and experiments. In the finite element analysis, the mode shape and the strain energy distribution were calculated to examine the mounting position, and the vibration reduction of the cantilever was calculated by adjusting the inductance and resistance circuit values. In addition, in the experiment, a variable inductor module was used to reduce the vibration occurring at a specific frequency of the cantilever. Finally, based on the results of the finite element analysis and the experiment, it was verified that the piezoelectric shunt can effectively reduce the vibration of the cantilever.

• The Journal of the Acoustical Society of Korea
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• v.18 no.2
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• pp.32-39
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• 1999

In this paper, the characteristics of the ray tracing method (RTM) based on the cylindrical wave are discussed for the high frequency vibration analysis of two-dimensional structures. A ray tube describing the emanating cylindrical wave is used to derive the governing equation for incident reflected, and transmitted ray tubes which satisfies the condition at the coupled boundary. The suggested ray model is applied to panel array structures, and the predicted results for 2-panel, 3-panel, and 4-panel array structures are compared to those by Statistical energy analysis (SEA) and Wave intensity analysis(WIA). More enhanced prediction was obtained compared to the SEA, and similar prediction performance was observed to the WIA. Additionally, the RTM has a novel feature that it can estimate the spatially smoothed distribution of vibration energy and vibration intensity. It is expected that the present RTM can be used as one of the useful tools for the high frequency vibration analysis of two-dimensional coupled structures.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.1
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• pp.27-35
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• 2010

This paper presents the vibration control performance of the smart passive control system to suppress the undesired vibration of the structure subjected to the earthquake loadings. Smart passive control system is the MR damper-based control system augmented with electromagnetic induction(EMI) device which consists of permanent magnets and solenoid coils. According to the Faraday's law of electromagnetic induction, an EMI device produces electrical energy from the mechanical energy due to the reciprocal motions of the structure and provide it to the MR damper. The smart passive control system can be the simple and easy to implement and maintain control system by replacing the feedback control system including sensors, controllers and external power sources of the conventional MR damper-based semiactive control system with the EMI device. The control performance of the smart passive control system is evaluated through the set of shaking table test considering the various historical earthquake loadings.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.32 no.6
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• pp.375-381
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• 2019

Structural health monitoring to determine structural conditions at an early stage and to efficiently manage the energy requirements of buildings using systems that collects relevant data, is under active investigation. Structural monitoring requires cutting-edge technology in which construction, sensing, and ICT technologies are combined. However, the scope of application is limited because expensive sensors and specialized technical skills are often required. In this study, a Raspberry Pi module, one of the most widely used single board computers, a Lora module that is capable of long-distance communication at low power, and a high-performance accelerometer are used to construct a wireless edge computing system that can monitor building response over an extended time period. In addition, the Raspberry Pi module utilizes an edge computing algorithm, and only meaningful data is obtained from the vast amount of acceleration data acquired in real-time. The raw data acquired using Wi-Fi communication are compared to the Laura data to evaluate the accuracy of the data obtained using the system.

• Korean Journal of Construction Engineering and Management
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• v.25 no.2
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• pp.36-44
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• 2024

This paper presents the application of Convolutional Neural Networks (CNNs) and Region of Interest (ROI) techniques for concrete crack analysis. Surfaces of concrete structures, such as beams, etc., are exposed to fatigue stress and cyclic loads, typically resulting in the initiation of cracks at a microscopic level on the structure's surface. Early detection enables preventative measures to mitigate potential damage and failures. Conventional manual inspections often yield subpar results, especially for large-scale infrastructure where access is challenging and detecting cracks can be difficult. This paper presents data collection, edge segmentation and ROI techniques application, and analysis of concrete cracks using Convolutional Neural Networks. This paper aims to achieve the following objectives: Firstly, achieving improved accuracy in crack detection using image-based technology compared to traditional manual inspection methods. Secondly, developing an algorithm that utilizes enhanced Sobel edge segmentation and ROI techniques. The algorithm provides automated crack detection capabilities for non-destructive testing.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.34 no.6
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• pp.211-221
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• 2022

The wave runup height is one of the most important parameters for affecting the design of coastal structures such as dikes, revetments, and breakwaters. In this study, SWASH (Zijlema et al., 2011), a non-hydrostatic pressure numerical model, was used to analyze the effect of reducing The wave runup height of solitary waves by submerged and floating rectangular obstacles. It was confirmed that the SWASH model reproduces the propagation, breaking, and runup of solitary waves quite well. In addition, it was confirmed that the wave deformation of the solitary wave by submerged and floating rectangular obstacles was well reproduced. Finally, we conducted an examination of the effect of reducing the runup height of submerged and floating rectangular obstacles. Reduced runup heights are calculated and the characteristics of runup height reduction according to the dimensions of the obstacle were analyzed. The energy attenuation effect of the floating obstacle is greater than the submerged obstacle, and it is shown to be more effective in reducing the runup height.

• The Korean Journal of Quaternary Research
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• v.9 no.1
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• pp.19-32
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• 1995

한반도 서해 만경강-동진강 하구역 조간대 퇴적층의 수직층서 퇴적상 변화를 분석 하여 퇴적과정을 기초해양환경의 관점에서 해석하였다. 본 연구해역 저 조선의 퇴적층은 사 질함량이 우세한 반면 방조제와 인접한 만조선의 퇴적층은 실트질이 우세하였고 상층과 하 층의 퇴적물이 뚜렷하게 구분되었다. 사질퇴적층의 내부퇴적구조는 괴상구조, 평행층리 및 사층리 구조등이 우세하며 니질퇴적층에서는 모래/니질 교호엽리구조가 우세하다. 본 연구 의 결과 만경강-동진강 조간대 퇴적층서는 인근의 방조제 축조에 다른 퇴적환경 변화에 크 게 영향받은 것으로 해석된다, 즉 방조제축소 이전 고에너지의 퇴적환경에서 집적되었던 사 질퇴적층이 방조제축조 이후에는 저에너지 환경조건에서 집적된 니질퇴적물로 피복된 것으 로 해석된다.

• 한국신재생에너지학회:학술대회논문집
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• 2011.11a
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• pp.37.2-37.2
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• 2011

Nowadays, offshore wind energy experiences a rapid development because of its wind condition and no noise impact problem. Different from Europe, offshore wind is just started in Asia. More work and research are needed in Korea. In this work, a three-bladed upwind variable speed pitch controlled 5MW wind turbine on a jacket support structure is used. During the simulation, several design load cases are investigated in two different fully coupled aero-hydro-servo-elastic codes. Some critical loads on the foundation are compared and analyzed.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2010.04a
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• pp.154-157
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• 2010

본 논문에서는 비선형 동적해석법을 이용하여 감쇠기의 적용이 철골조 건물의 연쇄붕괴 방지에 미치는 영향을 평가하였다. 단자유도 구조물에서 감쇠비의 변화에 따라 폭발하중이 구조물의 응답에 미치는 영향을 분석하였고, 15층 3경간 철골조 건물에서는 일정한 감쇠비 하에서 경간을 6m, 9m, 12m로 달리 하면서 감쇠기 설치 효과를 비교하였다. 단자유도 시스템의 경우 감쇠비가 증가 할수록 폭발하중에 의한 진동이 빠르게 감소하고 변위의 감소폭도 커지는 경향을 보였다. 15층 철골조 건물에서도 역시 감쇠기를 설치할 경우 수직 처짐 및 초기 진동을 제어하는 효과가 있었다. 구조물의 경간이 증가하여 수직 변위가 증가 할수록, 감쇠기에 의해 소산된 에너지도 증가하기 때문에 수직 처짐 제어효과가 큰 것으로 나타났다.