• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.45 no.5
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• pp.376-385
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• 2017

In this paper, a method for the estimation of structural displacements using structure's mode shapes and accelerations is suggested to reduce the disadvantages of acceleration time integration method. Acceleration time integration method requires accurate information on initial conditions, and errors caused by noise can be accumulated during time integration. To avoid these problems, the method for the estimation of structural displacements based on mode superposition method is developed and two vibration experiments for cantilever beam are conducted to verify this method. Static displacements and dynamic displacements of beam structure are estimated using measured accelerations from experiments and mode shapes of cantilever beam, and they are compared with measured displacements using laser displacement sensor. From these results, the validity and usefulness of this method are verified.

• Journal of the Earthquake Engineering Society of Korea
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• v.14 no.2
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• pp.37-47
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• 2010

In order to attain enhanced seismic performance of RC bridges, premature shear failure prior to the achievement of target ductilities of the piers should be prevented. For this purpose, a reliable shear strength evaluation is required. The shear strength of an RC column subjected to a lateral force decreases with an increase in ductility. Many empirical equations for the shear strength have been proposed by many researchers. However, there are many discrepancies in the initial shear strength in the low ductility range, and in the decrease rate according to the ductility. In this study, a new empirical equation of shear strength considering the displacement ductility effect has been proposed, in which the initial shear strength equation proposed by the authors was revised on the basis of the investigation of many other researchers' test results. The resulting improvement in accuracy is confirmed by comparison with other empirical equations.

• Tunnel and Underground Space
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• v.13 no.2
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• pp.77-86
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• 2003

The finite element method and statistics of the convergence measurement are useful method of the stability analysis of the tunnel adjacent to the pier. It is the purpose of the this case study to certificate of validity of the application of those methods. The safety of the pilot tunnel method and LW pre-grouting has been evaluated from the FEM analysis. The three-dimensional finite element method is carried out for the decision of the level of stress redistribution at the two-dimensional numerical analysis. An analysis of the convergence is carried out by the estimation of preceding convergence at tunnel excavation. F-examination is applied for this estimation. As results of that analysis, The F-value is from 10.81 to 158.74 and the coefficient of determination is from 0.82 to 0.99. An analysis of convergence is carried out by using regression analysis. Consequently, it is shown that the convergence can be modeled as following function C(t)=a[1-exp(-bt)].

• Journal of the Korean Geophysical Society
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• v.7 no.4
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• pp.313-324
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• 2004

The finite element method and statistics of the convergence measurement are useful method of the stability analysis of the tunnel adjacent to the pier. It is the purpose of the this case study to certificate of validity of the application of those methods. The safety of the pilot tunnel method and LW pre-grouting has been evaluated from the FEM analysis. The three-dimensional finite element method is carried out for the decision of the level of stress redistribution at the two-dimensional numerical analysis. An analysis of the convergence is carried out by the estimation of preceding convergence at tunnel excavation. F-examination is applied for this estimation. As results of that analysis, The F-value is from 10.81 to 158.74 and the coefficient of determination is from 0.82 to 0.99. An analysis of convergence is carried out by using regression analysis. Consequently, it is shown that the convergence can be modeled as following function C(t) = a[1-exp(-bt)].

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.563-580
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• 1998

This study was designed to analysis the displacement and stress distribution of individual tooth by orthodontic force during distal on masse movement of the maxillary dentition. In this study, three dimensional finite element analysis was used. Author made the finite element model of maxillary teeth, periodontal ligament, alveolar bone and bracket with anatomic and physiologic characteristics on computer. Author analysed and evaluated the displacement and stress distribution of individual tooth when extraoral force, Class II intermaxillary elastics, ideal arch wire, MEAW and tip back bend were used for distal on masse movement of the maxillary dentition. These analyses were also applied in the case of the maxillary second molar were not extracted. Author compared the results of the cases which maxillary second molar were extracted or not. The results were expressed quantitatively and visually. Author obtained following results, 1. When anterior headgear was applied, the posterior translation, posterior tipping, and vertical displacement of teeth were produced more in the anterior segment of the dentition. 2. When Class II intermaxillary elastics were applied in the ideal arch wire, the teeth displacement were usually produced in the anterior segment. But when tip back bend were added in the ideal arch wire, the orthodontic force produced by elastics were transmitted to the posterior segment. As increasing the tip back bend, posterior translation and lingual tipping of anterior teeth were decreased, posterior translation and tipping displacement of posterior teeth were increased, and extrusion of anterior teeth by Class II elastics were decreased 3. When MDAW and Class II elastics were applied, the teeth movement were sir flu with the case of ideal arch wire and Class II elastics, but more small and uniform teeth displacement were produced Compared with the ideal arch wire, posterior tipping of the posterior segment were more produced than lingual tipping displacement of the anterior segment. 4. When the maxillary second molar without orthodontic appliance existed, the displacement of maxillary first molar were decreased.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.29 no.6
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• pp.563-569
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• 2016

This paper presents the resizing method of columns and beams that considers column-to-beam strength ratios to simultaneously control the initial stiffness and ductility of steel moment frames. The proposed method minimizes the top-floor displacement of a structure while satisfying the constraint conditions with respect to the total structural weight and column-to-beam strength ratios. The design variable considered in this method is the sectional area of structural members, and the sequential quadratic programming(SQP) technique is used to obtain optimal results from the problem formulation. The unit load method is applied to determine the displacement participation factor of each member for the top floor lateral displacement; based on this, the sectional area of each member undergoes a resizing process to minimize the top-floor lateral displacement. Resizing members by using the displacement participation factor of each member leads to increasing the initial stiffness of the structure. Additionally, the proposed method enables the ductility control of a structure by adjusting the column-to-beam strength ratio. The applicability of the proposed optimal drift design method is validated by applying it to the steel moment frame example. As a result, it is confirmed that the initial stiffness and ductility could be controlled by the proposed method without the repetitive structural analysis and the increment of structural weights.

• Proceedings of the Korean Society of Broadcast Engineers Conference
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• 2016.06a
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• pp.1-4
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• 2016

효율적으로 깊이지도를 획득하기 위해 다양한 방법의 지역 기반스테레오 매칭 방법이 사용된다. 일반적인 지역기반 스테레오 매칭에 사용되는 비용값 계산 방법을 통해 깊이지도를 생성하게 되면 객체의 경계 영역이 무너지거나, 유사한 텍스쳐 정보가 연속적으로 나타나는 영역에서 부정확한 깊이값을 얻는 문제가 발생한다. 본 논문에서는 깊이지도의 정확성을 높이기 위해 2가지 단계를 거쳐 최종 깊이지도를 생성한다. 처음으로, 일반적으로 사용하는 지역기반 스테레오 매칭 비용 함수와 입력 영상의 기울기를 고려한 초기 비용값을 가이드 필터를 이용하여 최적의 비용값을 찾아 초기 변위지도를 생성한다. 스테레오매칭을 수행할 경우, 시점의 차이로 인해 보이지 않는 영역에서 정확한 변위값을 찾지 못하는 문제가 발생한다. 이러한 문제를 해결하기 위해 좌영상과 우영상을 기반으로 획득한 변위지도를 사용하여 교차검사를 함으로써 폐색영역을 찾아낸다. 폐색 영역을 이웃한 화소의 값을 사용하여 채울 경우 실선과 같은 오류가 결과 영상에 나타나게 된다. 이러한 오류 영역을 제거하기 위해 마지막으로 가중치를 적용한 중간값 필터를 적용한다. 실험 결과 제안한 방법을 사용하여 획득한 깊이지도가 기존의 방법보다 정확한 깊이값을 얻는 것을 확인할 수 있었다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.14 no.6
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• pp.1357-1363
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• 1994

A Monte-Carlo simulation model is developed to predict size distribution produced by the coalescence of air bubbles in turbulent shear f1ow. The simulation consists of generating a population of air bubbles into the initial positions at each time step and tracking them by simulating motions and checking collisions. The radial displacement of air bubbles in the simulation model is produced by numerically solving an advective diffusion equation. Longitudinal displacements are generated from the logarithmic flow velovity distribution and the bubble rise velocity. Collision of air bubbles for each time step is detected by a geometric test using their relative positions at the beginning of the time step and relative displacements during the time step. At the end of the time step, the total number of bubbles, their positions, and sizes are updated. The computer program is coded such that minimum storages for sizes and positions of bubbles are required.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.16 no.1
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• pp.87-94
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• 2003

A geometric non-linear finite element formulation of CRTS reflector subjected to displacement loads, corresponding to the successional assembly steps of the reflector, is presented in order to determine the initial static equilibrium state based on the displacement incremental method. Parametric analyses of the influence of cables and mechanical properties of the reflector on the shape error between reference and equilibrium surfaces have been studied. These results of the present study are compared with the others using Galerkin mothod and NASS 98 program to demonstrate the feasibility.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.332-335
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• 2011

바람에 의해 발생하는 장대교량의 진동현상은 버펫팅과 와류진동 그리고 플러터 등으로 구분할 수 있으며, 특히 설계풍속에 해당하는 강풍에 안전한 교량을 설계하는 것이 주된 관심사항이다. 이러한 장대교량의 공기역학적인 안정성 검토에 사용되는 플러터 계수를 풍동실험을 통하여 산정하였다. 본 논문에서는 일반적인 플레이트 거더교의 강풍에 대한 안정성을 검토하기 위하여 풍동실험을 수행하였으며, 자유진동 기법과 강제진동 기법을 사용하여 추출한 플러터 계수를 비교하였다. 자유진동 기법은 교량단면에 초기변위를 주어 상하 및 회전 진동을 하는 교량단면의 변위를 측정한 후 system identification 기법으로 플러터 계수를 구하게 된다. 그리고 강제진동 기법은 상하방향의 강제진동과 회전방향의 강제진동 실험을 독립적으로 수행하여 교량단면에 작용하는 풍하중과 단면의 진동을 분석함으로써 플러터 계수를 추정하게 된다. 그리고 플러터 계수의 비교를 통하여 강제진동 기법과 자유진동 기법의 장단점을 분석하였다.