• Journal of the Korean Geotechnical Society
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• v.34 no.10
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• pp.61-74
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• 2018

In this study, the pull-out behavior of tunnel type anchorage of suspension bridges was analyzed based on results from laboratory size model tests and numerical analysis. Tunnel type anchorage has found its applications occasionally in both domestic and oversea projects, therefore design method including failure mode and safety factor is yet to be clearly established. In an attempt to improve the design method, scaled model tests were conducted by employing simplified shapes and structure of the Ulsan grand bridge's anchorage which was the first case history of its like in Korea. In the model tests, the anchorage body and the surrounding rocks were made by using gypsum mixture. The pull-out behavior was investigated under plane strain conditions. The results of the model tests showed that the tunnel type anchorage underwent wedge shape failure. For the verification of the model tests, numerical analysis was carried out using ABAQUS, a finite element analysis program. The failure behavior predicted by numerical analysis was consistent with that by the model tests. The result of numerical analysis also showed that the effect of Poisson's ratio was negligible, and that a plugging type failure mode could occur only when the strength of the surrounding rocks was 10 times larger than that of anchorage body.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1992.10a
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• pp.25-30
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• 1992

최근 전자계산기를 이용한 진동해석 방법이 눈부시게 발달하여, 일반 구조물 이나 기계 구조물 등의 동특성을 설계 단계에서 정도 높게 예측하는 것이 가능하게 되었다. 그러나 종래의 구조해석은 주어진 시스템의 동특성을 위한 것으로 얻어진 동특성으로부터 질량, 관성제원 및 스프링상수값 등의 설계상 수값을 규명하는 연구는 미미한 실정이다. 이것에 대한 해결방법으로 크게 해석적인 방법과 실험적인 방법으로의 접근이 있어 왔다. 해석적인 방법으로 유한요소해석에서 얻은 모드좌표를 물리좌표로 변환하는 방법으로 Guyan의 정축소와 같은 절점축소를 행하는 방법이 고찰되었다. 실험적인 방법으로 가 진실험에서 얻은 전달함수나 모드파라미터로부터 [M], [K] 행렬을 결정하는 연구가 있었지만 어떤것도 질량, 스프링상수 등의 설계상수를 완전히 규명하 지는 못하였다. 또한, 설계 단계에서 필요한 질량, 관성제원 또는 스프링상수 등의 최적한 값이나, 원하는 시스템특성을 얻을 수 있는 설계상수의 적정한 폭을 구하는 연구는 설계자의 경험과 반복된 시행착오에 의존하는 실정이다. 감도해석은 이러한 문제점을 개선하는 수단으로 설계변수에 대한 동특성의 변화율을 구하는 것이다. 감도해석을 수행하는 것은 어느 설계변수를 수정하 는 것이 주어진 동특성에 부합되는 지를 알려주고, 어느 것을 수정하는 것이 원하는 방향의 동특성변화에 가장 효과적인지를 알려주는 것이다. 따라서 감 도해석을 이용하여 설계의 최적화 프로그램을 만들수 있고, 이것은 설계자가 요구하는 동특성을 목적함수로 하여 주어진 구조물을 최적화하는 설계상수 값을 얻을 수 있게 한다. 본 논문에서는 강체모델의 동특성으로부터 모델의 설계 상수를 규명하고, 동특성의 개선을 위하여 설계변수의 변경량을 물리좌 표계에서 얻는것을 목적으로 한다. 강체 마운트계의 관성제원 및 마운트강성 의 규명을 위하여 임으로 주어진 설계상수를 모델데이타로 하여 관성제원과 스프링 강성을 구하였다. 관성제원의 규명은 주어진 모델의 관성값을 모르는 것으로 하여 임의의 초기 관성값으로 감도해석에 의해 주어진 계의 관성값 을 물리 좌표계에서 규명하였다. 마운트 강성의 규명도 관성제원의 규명과 같은 방법으로 임의의 강성값으로 감도해석을 하여 강성값을 규명하였다. 또 한 감도해석에 의한 동특성 변경은 특정한 고유진동 수의 변경이 필요할 때, 고유진동수의 이동을 위한 관성제원의 변경 및 마운트 강성변경값을 예측할 수 있다. 본 연구수행의 기본적인 흐름도는 Fig.1.1과 같다. 위와 같은 작업 으로 엔진 마운트와 같은 강체 모델의 시스템 규명을 행하는 경우에 유한요 소해석 및 가진 실험으로 얻은 고유진동수의 정보 또는 원하는 고유진동수 의 특성을 기본으로 실제 설계에서 사용이 가능하도록 물리 좌표계에서 관 성 제원 및 스프링상수를 구할 수 있을 것이다.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.25 no.4
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• pp.339-346
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• 2012

In this paper, equivalent models for active control devices are proposed so that building structures with such devices are analyzed using commercial structural analysis programs for the assessment of the structural members under active vibration control. Equivalent link models represent active control device with a virtual linear spring and dashpot, and equivalent force models are control force history acting at the installation point in structural models. Active controllers are designed based on the reduced-order models for a vertical cantilever model and a high-rise building model and corresponding equivalent models are determined from control gain matrices. Based on acceleration, displacement and member force responses, the effectiveness of the equivalent models is verified. As a result, proposed equivalent models, of which equivalent link model showed better performance, appear to enable detailed investigation of structural behavior to the extent of member force level.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2003.05a
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• pp.183-188
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• 2003

The present work was conducted to build a propulsion system for an airship. For this purpose, free shaft gas-turbine was modified to produce electrical power. he experiments were carried out to analyze the driving rotor condition at various power shaft loads. From this analysis, an appropriate damping device was required, and the changeable inertial moment from the fly-wheel was applied. Without the appropriate damping device, instability was found, and it was resulted as power loss. Also the amount of inertial moment was certified by the performance of dynamic transient effects from the engine test results. Knowledge gained from this research could benefit the propulsion and power conversion community by increasing the better understanding of shaft loads and inertial effects.

• Journal of the Earthquake Engineering Society of Korea
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• v.5 no.6
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• pp.55-64
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• 2001

Industrial machines are sometimes exposed to the danger of earthquake. In the design of a mechanical system, this factor should be accounted for from the viewpoint of reliability to analyze a complex nonlinear structure system under random excitation is proposed. First, the actual random excitation, such as earthquake, is approximated to the corresponding Gaussian process for the statistical analysis. The modal equations of overall system are expanded sequentially. Then, the perturbed equations are synthesized into the overall system and solved in probabilistic way. Several statistical properties of a random process that are of interest in random vibration are evaluated in each substructure. Comparing with the results of the numerical simulation proved the efficiency of the proposed method.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.20 no.5
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• pp.25-32
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• 2006

This paper proposes a regeneration inverter system, which can regenerate the excessive power form do bus line to ac source for traction system. The proposed regeneration inverter system for dc traction can reduce harmonics which are included to ac current source. The regeneration inverter is operated as two modes. In the regeneration inverter mode, it can recycle regenerative energy caused by decelerating tractions and in the active power filter mode, it can compensate harmonic distortion produced by the rectifier substation. In this paper, the regeneration inverter uses PWM DC/AC inverter algorithm and the active power filter uses p-q theory. From the informative simulation and experimental results, which are performed wiith a prototype rated 3.7[kw], it can expected that the proposed system can be effectively applied in the real traction system rated 100[kw].

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.39 no.3
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• pp.218-224
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• 2011

A modal method is presented for the investigation of the effects of measurement errors in damage detection for dynamic structural systems. The structural modifications to the baseline system result in the response changes of the perturbed structure, which are measured to determine a unique system in the inverse problem of damage detection. If the numerical modal data are exact, mathematical programming techniques can be applied to obtain the accurate structural changes. In practice, however, the associated measurement errors are unavoidable, to some extent, and cause significant deviations from the correct perturbed system because of the intrinsic instability of eigenvalue problem. Hence, a self-equilibrating inverse system is allowed to drift in the close neighborhood of the measured data. A numerical example shows that iterative procedures can be used to search for the damaged structural elements. A small set of selected degrees of freedom is employed for practical applicability and computational efficiency.

• The Journal of the Acoustical Society of Korea
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• v.21 no.5
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• pp.503-509
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• 2002

Cylindrical chamber silencers with an extended inlet and outlet are extensively used in many application fields to reduce the propagated noise in ducts. The basic attenuation effectiveness in the low frequency region can be explained by the reactive wave action inside the expansion chamber associated with the geometric configurations of the inlet and outlet locations, and the area expansion of the jacket. In this study. an acoustic analysis is carried out for a concentric extended pipe inserted into a simple expansion chamber. An algebraic equation is derived by using the eigenfunction expansion and orthogonality principle in which the acoustic pressures and particle velocities defined on each subdivided surface are expressed by the separable coordinates. By using the proposed analytical method, transmission losses are predicted for several configurations of the concentric extended systems and they agree very well with experimental results.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.11 no.1
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• pp.64-72
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• 2001

This paper is on a design of the high-speed cipher IC using IDEA algorithm. The chip is consists of six functional blocks. The principal blocks are encryption and decryption key generator, input data circuit, encryption processor, output data circuit, operation mode controller. In subkey generator, the design goal is rather decrease of its area than increase of its computation speed. On the other hand, the design of encryption processor is focused on rather increase of its computation speed than decrease of its area. Therefore, the pipeline architecture for repeated processing and the modular multiplier for improving computation speed are adopted. Specially, there are used the carry select adder and modified Booth algorithm to increase its computation speed at modular multiplier. To input the data by 8-bit, 16-bit, 32-bit according to the operation mode, it is designed so that buffer shifts by 8-bit, 16-bit, 32-bit. As a result of simulation by 0.25 $\mu\textrm{m}$ process, this IC has achieved the throughput of 1Gbps in addition to its small area, and used 12,000gates in implementing the algorithm.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.217-224
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• 2005

A methodology of selecting an optimal model is proposed for applying a frequency-domain SI method effectively. Instead of using a reduced finite element model, a reasonably detail finite element model is established first and then the model is identified. To satisfy the identifiability criterion, a parameter grouping scheme is applied to control the number of unknowns. Among the simulated member grouping cases, an optimal model is selected as the one with the minimal statistical error. The proposed approach has been examined through simulation studies on a single span box-girder bridge.