• The Journal of the Acoustical Society of Korea
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• v.12 no.4
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• pp.39-46
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• 1993

조화집중이동하중을 받는 무한보에서의 음향방사에 대한 연구는 선박, 비행기, 타이어 트레드 밴느 등과 같은 계의 설계시 계의 구조물로부터 발생하는 소음에 대한 해결방안을 제시해 준다. 구조물 표면에 발생하는 음향파워는 svktnqusghks방법을 이용하여 보의 전길이에 분포된 음향 인텐시티를 적분하여 구한다. 보의 표면에서 발생하는 음향파원는 미하수, 장력, 감쇠계수, 기초강성계수, 그리고 파수비에 의해서 결정된다. 각 인자에 따른 음향파워에 대한 정성적인 분석을 수행하기 위해 심프슨 적분방법을 이용하여 수치적분을 하였다. 무한보에 작용하는 유체하중에 3다라 진동에너지가 음향에너지로 변환되는 비율이 달라진다. 밀도가 큰 유체는 등가감쇠로 작용하여 보로부터 방사된 음향에너지는 빠르게 감소된다. 하중의 이동에 의하여 도플러이동효과가 발생하여 무한보의 공진부근에서의 음향파워 파크가 분리되고 보의 기초감쇠의 영향으로 음향에너지는 감소된다.

• Transactions of the Korean Society of Mechanical Engineers
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• v.14 no.5
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• pp.1104-1111
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• 1990

A method to identify nonlinear elements position of a nonlinear system is presented. Nonlinear elements position can be identified by an equivalent error damping and stiffness matrices which are based on the equivalent linearization technique. The procedures of this technique are: (1) Obtain input force and system response. (2) Define error between the actual and linearized restoring forces. (3) Calculate linearized damping and stiffness coefficients to minimize the square error sum. Several examples are tested and found that these methods are very effective not only to locate the nonlinear elements position but also to identify the degree of nonlinearity qualitatively. Nonlinear type can be qualitatively identified by examining the plots of restoring force vs equivalent state values.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.28 no.2
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• pp.145-152
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• 2015

In the study, the effects of damping devices on damping ratio increase and wind-load reduction were investigated based on the computational platform, which is one of the parametric modeling methods. The computational platform helps the designers or engineers to evaluate the efficacy of the numerous alternative structural systems for irregular Super-Tall building, which is crucial in determining the capacity and the number of the supplemental damping devices for adding the required damping ratios to the building. The inherent damping ratio was estimated based on the related domestic and foreign researches conducted by using real wind-load records. Two types of damping devices were considered: One is inter-story installation type passive control devices and the other is mass type active control devices. The supplemental damping ratio due to the damping devices was calculated by means of equivalent static analysis using an equation suggested by FEMA. The optimal design of the damping devices was conducted by using the computational platform. The structural element quantity reduction effect resulting from the installation of the damping devices could be simply assessed by proposing a wind-load reduction factor, and the effectiveness of the proposed method was verified by a numerical example of a 455m high-rise building. The comparison between roof displacement and the story shear forces by the nonlinear time history analysis and the proposed method indicated that the proposed method could simply but approximately estimate the effects of the supplemental damping devices on the roof displacement and the member force reduction.

• Journal of the Earthquake Engineering Society of Korea
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• v.8 no.3
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• pp.33-42
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• 2004

While transforming the inelastic system into the equivalent elastic one gives an advantage of simpler analysis, the actual inelastic behavior of the system is hardly modeled in the capacity spectrum method (CSM). Therefore, the accuracy of CSM depends on the precise estimation of equivalent period and damping ratio as well as the modification of the elastic response spectrum and the corresponding demand spectrum. In this paper, the effect of demand spectrums on the accuracy of CSM is evaluated. First, the response reduction factors provided in ATC-40 and Euro Code are evaluated. Numerical analysis results indicated that the acceleration responses obtained using the factor of Euro Code are closer to the actual response than those obtained using the factors of ATC-40. Next, the accuracy of CSM is evaluated constructing the demand spectrum using the absolute acceleration responses and pseudo acceleration responses. The results obtained using the absolute acceleration responses were found to be generally larger than those obtained using the pseudo ones. Since CSM often underestimates the response, the use of absolute acceleration response gives the response relatively closer to the exact ones. However, the difference becomes negligible as the hardening ratio and the yield strength ratio become larger.

• 한국방재학회:학술대회논문집
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• 2011.02a
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• pp.29-29
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• 2011

국내에서 기존건축물의 내진성능평가 기법이 연구되기 시작한지 20여 년간 다양한 평가방법이 제안되었다. 그러나, 제안된 평가방법은 미국이나 일본의 평가 방법을 도입 및 수정하는 내용이 주가 되어 국내실정에 맞지 않는 부분도 많이 발견되었다. 따라서 국내에서 제안된 기존 건축물의 내진성능 평가기법, 지진피해예측에 근거한 보강건축물의 합리적인 선정방법 및 이들 건축물에 적합한 내진보강방법 등의 연구는 아직까지 초보적인 단계라고 할 수 있다. 이에 본 연구의 목적은 이러한 평가 기법을 적용한 국내 저층구조물의 내진성능을 평가하는 것이다. 저층구조물의 내진성능을 평가하기 위하여 1988년 내진설계가 도입되기 이전에 건립된 4층 규모의 학교구조물을 해석대상 구조물로 선정하였다. 대상 해석구조물의 내진성능평가는 일본의 내진성능 평가법을 참고하여 평가절차가 다소 복잡한 부분을 국내 실정에 맞게 개선시킨 내진화 우선도 평가방법과 정밀한 내진성능을 평하는 방법으로 세계적으로 널리 사용되고 있는 ATC-40 성능평가방법에서 등가단자유 모델로 변환 과정에서 등가유효감쇠 및 등가유효주기 산정 관계식의 문제점을 개선한 FEMA-440의 선형화 성능평가방법(Linearization Method)을 사용하여 구조물의 성능을 평가하였다. 내진 성능 평가를 위해 현재 전 세계적으로 널리 사용되고 있는 구조물 비선형 전용 해석 프로그램인 Perform-3D를 이용하여 해석을 수행하였다. 본 연구를 통해 기존 저층구조물로 선정한 학교구조물에 대한 내진성능을 평가한 결과, 내진화 우선도 평가법 및 FEMA-440의 내진성능 평가는 유사한 경향의 결과를 나타내었고, 두 평가결과를 요약하면 Y방향은 보와 기둥에 끼인 조적벽체의 영향으로 별도의 내진성능이 향상 보강이 필요없으나, X방향은 창문하부 허리 조적벽 등의 영향으로 다소 취성적인 내진성능을 보유하고 있어 충분한 내진성능 확보를 위한 추가적인 보강이 필요한 것으로 판단된다.

• Proceedings of the KSR Conference
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• 2000.11a
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• pp.374-381
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• 2000

본 논문에서는 지진 발생시, LRB가 설치된 교량의 시간이력 해석을 수행하였다 이를 위해 LRB의 비선형 거동특성을 Bi-linear로 모형화 하였으며, 기존의 방법인 등가선형으로 모형화된 해석결과와 비교하였다. 또한 LRB받침만 설치된 경우와, LRB받침과 일반탄성받침이 함께 사용된 경우를 해석하여, 받침이 혼합된 경우, 상시하중과 지진하중시 발생할 수 있는 문제점을 검토하였다. 4경간 연속교량에 적용된 해석결과를 보면, LRB만을 설치한 경우, Pot-Bearing만 설치된 경우에 .비해, 고유주기 상승과 이력감쇠에 의한 지진력의 감소와 함께, 지진력의 효과적인 분배를 볼 수 있었으며, 일반탄성받침과의 적절한 조합에 의해서도, 충분한 면진성능을 얻을 수 있었다. 또한 LRB의 등가선형 모델이 Bi-linear 모델에 비해 보수적인 해석결과를 나타내었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.7 no.3
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• pp.23-30
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• 2003

The seismic base isolation design approach has been reviewed and modified to fit the nonlinear static analysis procedure for determination of the performance point of structures in a simpler way, such an adaptation may be possible for the fact that a structural system under development of damage due to earthquake loading keeps softening to result in period shifting toward longer side. The superiority of the proposed method to the state-of-the-practice approach is that the reasonably accurate performance point can be obtained without constructing the so-called acceleration displacement response spectrum required in application of capacity spectrum method. The validity of the proposed approach was verified by comparing the predicted values to the exact ones presented in the literature.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.20 no.6
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• pp.691-697
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• 2007

Numerical eigen analysis of beam-like structure can be easily and effectively done by various conventional beam theory-based methods. However, in case of the structures composed of composite-sectioned beams, the application of conventional numerical methods requires one to derive both equivalent material and geometry properties. In the present paper, these equivalent properties are derived by the transformed section method and the test FEM program is coded. The numerical accuracy of the proposed method is verified through the comparison with the ANSYS 3-D model.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.5
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• pp.35-45
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• 2001

Recently, the floor systems those require large open space may have low inherent damping due to the decline of the use of curtain walls. Furthermore, the use of the high strength materials has resulted in more flexible and longer spanning in floor systems. The long span structures such as shopping malls, offices and large assembly rooms may lead to significant dynamic response due to human activities. Excessive vibrations make the occupants uncomfortable and deteriorate the serviceability of buildings. It is now proved that footfall loading is the major source of floor vibrations. The common method of application of walking loads for the vibration analysis of structures subjected to walking loads is to inflict measured walking loads and periodic function at a node. But this method could not account for the moving effect of walking. In this study, natural frequency and damping ratio of example structure are evaluated by heel drop tests. And the application of equivalent walking loads is used for on efficient vibration analysis of the plate structures subjected to walking loads.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.29 no.11
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• pp.851-856
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• 2018

In this study, we analyze the characteristics of wireless power transfer(WPT) based on magnetic resonance in an underwater environment and propose an equivalent model suitable for underwater WPT. The proposed underwater WPT equivalent model is constructed by expanding the free-space WPT T-model reflecting characteristics change according to media. Considering the water salinity, we propose a method to extract the parameters of the proposed model based on the S parameters. To verify the proposed model, a 6.78-MHz underwater WPT system was constructed and compared with the predicted power transfer efficiency of the model. As a result, it was confirmed that the proposed model predicts the variation of characteristics with an average error of less than 3 %.