• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.2
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• pp.137-144
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• 2020

In this study, we propose a new truss deckplate system, which does not require temporary floor supports during construction, with ultra-high-performance concrete (UHPC) infilled top bars. The increased stiffness and strength of the proposed system were well retained as compared to those of the existing truss deckplate systems, thereby resulting in the reduction of maximum deflection at the span center. Four-point bending tests were performed on five specimens with a net span of 4.6 m to evaluate the structural performance of proposed system in the construction stage. In addition, the load-deflection curve was plotted for each specimen, and the effects of test parameters were analyzed. Further, a rigorous nonlinear three-dimensional finite element analysis was performed, and its results were compared with the test results. From the results, it was observed that the test specimens of the proposed system exhibited superior performance as compared to those of the existing one and also satisfied the serviceability requirement during construction provided by the Korea Building Code 2016.

• Journal of the Korean Society for Nondestructive Testing
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• v.29 no.4
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• pp.316-322
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• 2009

This paper presents a preliminary study to monitor the lateral behavior of pile foundation using multiplexed fiber Bragg grating(FBG) sensors. In the Preliminary study, an 1.7 meter long cantilever beam with the shape of square hollow box was fabricated and tested under the static loading. Four FBG sensors were multiplexed in a single optical fiber and installed into the top and bottom of the cantilever beam. The strains are directly measured from FBG sensors followed by curvature calculations based on the plane section assumption. Vertical deflections are then estimated using the regression analyses based on the geometric relationships. It has been found that excellent correlation with conventional sensing system was observed. The success of the test encourages the use of the FBG sensing system as a monitoring system for pile foundations. However, further consideration should be given in the case of the sensor malfunction for the practical purpose.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3A
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• pp.163-172
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• 2011

The CFTA girder developed is a concrete filled steel tubular system with arched shape and external post-tensioning (PT) tendons which control the initial camber and the bending stress of the girder. In the present study the effects of the PT tendons on the dynamic behavior of the girder subjected to a moving vehicle load are numerically investigated. Various levels for the tendon quantity and the tendon forces are considered, using the existing FE model of the girder. The vehicle considered is a DB-24 truck and is modeled with two tracks-three axles. Equivalent-load pulse time histories are applied to each node to simulate the moving vehicle, depending on the time of arrival and the discretization. The vehicle speeds are varied from 40 km/hr to 100 km/hr with increment of 20 km/hr. The analysis results show that the tendon forces do not produce any influences on the dynamic responses of the girder. However the dymamic deflection of the girder increases when a smaller amount of tendons is used. The Dynamic Amplification Factors (DAF) are evaluated based on the static and dynamic responses. Much lower values of the DAF are obtained, even no tendons applied, than those provided by the design criteria of the AASHTO LRFD and the Korea Highway Standard Specification.

• Transactions of the Korean Society of Mechanical Engineers
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• v.12 no.4
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• pp.694-704
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• 1988

A recursive parameter estimation scheme utilizing the variance perturbation method is applied to the workpiece deflection model during CNC turning process, in order to improve the cylindricity of slender workpiece. It features that it is based on exponentially weighted recursive least squares method with post-process measurement of finish surfaces at two locations and it does not require a priori knowledge on the time varying deflection model parameter. The measurements of finish surfaces by using two proximity sensors mounted face to face enable one to identify the straightness, guide-way, run-out eccentricity errors. Preliminary cutting tests show that the straightness error of the finish surface due to workpiece deflection during cutting is most dominant. Identifying the errors and recursive updating the parameter, the off-line control is carried out to compensate the workpiece deflection error, through single pass cutting. Experimental results show that the proposed method is superior to the conventional multi-pass cutting and the direct compensation control in cutting accuracy and efficiency.

• Computational Structural Engineering
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• v.2 no.1
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• pp.71-78
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• 1989

In this paper a computer program for displacement control method was developed, in which a certain displacement of the structure is increased and the applied loads and another displacements are obtained. To simplify the nonlinear structural analysis, the relationships of moment-curvature were linearized as elasto-softening model for over-reinforced concrete beam and as elasto-plastic-softening model for under-reinforced concrete beam. Since the result of the analysis of reinforced concrete beam depended on the element size beyond elastic zone, the relationship of moment-curvature was modified for each element by using the concept of fracture energy approach. Overall, analytical results accurately predicted the load-displacement behavior of reinforced concrete beams.

• Magazine of the Korea Concrete Institute
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• v.10 no.1
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• pp.143-151
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• 1998

최근들어 반복하중에 의한 철근콘크리트 구조물의 손상이 자주 발견되고 있으며 교량 등의 구조물 등은 때때로 과적차량에 의한 초과하중을 받아 이러한 피로손상이 심화되고 있다. 본 연구에서는 이러한 반복 하중을 받는 철근 콘크리트보의 누적피로손상에 대한 실험적 연구룰 수행하여 피로하중에 의한 철근콘크리트보의 손상과정을 규명하였다. 실험 변수를 전단철근의 양과 반복되는 하중의 크기 및 반복횟수로 하여 실험부재를 제작하였으며, 하중제어에 의한 휨시험법에 의해 3Hz의 반복하중을 시편에 재하하였다. 사인장 균열하중과 사인장 균열 후 반복하중에서의 보의 손상누적거동 즉 처짐. 전단철근의 변형도, 에너지 손실 등의 변화를 실험적으로 평가하였으며, 이를 통하여 반복하중에 의한 누적손상에 의해 철근 콘크리트보의처짐 및 전단변형도가 초기하중상태에서는 급격히 증가하다가 이후 점진적으로 증가하는 것을 규명하였다. 본 연구의 결과는 사용하중상태에서 점진적으로 발생할 수 있는 피로손상의 누적과정을 기술하여 주고 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2D
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• pp.295-303
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• 2009

The purpose of present study is to examine the effect of guideway characteristics on runnability of low and medium speed maglev vehicle. Dynamic governing equation for 2-dof vehicle and optimal feedback control scheme are developed. And then the effect of vehicle speed, rail roughness, guideway deflection, continuity of spans, each span length on dynamic response of the UTM-01 maglev vehicle are investigated. From the numerical simulation, it is found that the gap between bogie and guideway does not increase greatly within design velocity of the vehicle. The response of vehicle are mostly affected by the guideway deflection rather than rail roughness. As a result of the present study, the runnability of maglev vehicle can be improved by reducing the maximum deflection of guideway and adopting the continuous girder systems.

• Transactions of the Korean Society of Mechanical Engineers
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• v.9 no.5
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• pp.590-597
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• 1985

A recursive geometric adaptive control method to compensate for machining straightness error in the finished surface due to tool deflection and guideway error generated by end milling process is developed. The relationship between the tool deflection and the feedrate is modeled by a modified Taylor's tool life equation. Without a priori knowledge on the variations off cutting parameters, time varying parameters are then estimated by an exponentially windowed recursive least squares method with only post-process measurements of the straightness error. The location error is controlled by shifting the milling bed in the direction perpendicular to the finished surface and adding a certain amount of feedrate with respect to the tool deflection model before cutting. The waviness error is compensated by adjusting the feedrate during machining. Experimental results show that location error is controlled within a range of fixturing error of the bed on the guideway and that about 60% reduction in the waviness error can be achieved within a few steps of parameter adaption under wide operating ranges of cutting conditions even if the parameters do not converge to fixed values.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.1
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• pp.87-95
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• 2011

A rational method for determination of initial cable forces in cable-stayed bridges without complicated nonlinear analysis is presented. Initial shape analysis for cable-stayed bridges should be able to find optimizated initial cable forces and unstrained length that minimize deflection and vending moments of the deck and pylon. A presented method utilizing the idea of force equilibrium organizes initial shape analysis for each types of cable-stayed bridges. The results of that analysis were compared to several existing methods for 2D numerical examples. And for 3D actual bridges, the improved TCUD method was performed to demonstrate the accuracy of this study.

• Journal of the KSME
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• v.33 no.1
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• pp.22-32
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• 1993

본드선도는 물리적 등가가 적용되는 모든 상사 시스템을 대단히 조직이며 일관성 있게 모델링할 수있을 뿐만 아니라 시스템의 동적 방정식을 제어동역학 관점에 유리한 상태방정식으로 직접 유도할 수 있다. 또한 본드선도는 모델링 단계에서 무시된 각 요소들의 동적 특성 즉, 기계시스 템에서 회전축의 탄성처짐이나 운동 물체들 사이의 마찰 효과 전기 . 자기시스템에서 자속유출량, 그리고 유체 . 유압시스템에서 밀봉부분의 유량손실이나 압축성 유체 특성 등을 기곤에 구성된 본드선도의 변경 없이 각 특성들이 나타나는 본드상에 적절한 접합요소와 함께 단순히 첨가하여 고려할 수 있기 때문에 모델링 과정을 다시 반복하지 않고도 무시된 동적 특성들이 전체시스템에 미치는 영향을 파악할 수 있다. 특히 본드선도가 에너지 변환 장치나 에너지 유동 메카니즘이 복잡한 다에너지역 시스템 등에 거동이 전체시스템에 미치는 효과를 시각적으로 보다 세밀히 파악할 수 있을 뿐만 아니라 구성된 본드선도에 인과관계를 할당하여 본드선도의 접합요소를 통하여 유도된 최종적인 동적 방정식이 현실적으로 실현 가능한 물리시스템인지 파악할 수 있어 본드선도 모델링 단계에서 시스템을 묘사하는 동적 방정식의 옳고 그름을 평가할 수 있다. 이와 같이 본드선도는 기계, 전기 . 자기, 유체 . 유압, 열 시스템 및 이들이 조합된 복잡한 다에너지역 시스템 등을 효과적으로 모데링할 수 있는 매우 유용한 동적 시스템 모델링 방법이다.