• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.1
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• pp.71-83
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• 2004

The purpose of this study is to present an analysis method for the prediction of the changes m ground conditions. To this end, three dimensional convergence displacements are analyzed in several ways to estimate the trend of displacement changes. Three-dimensional arching effect is occurred around the unsupported excavation surface including tunnel face when a tunnel is excavated in a stable rock mass. If the ground condition ahead of tunnel face changes or a weak zone exists, a diagnostic trend of displacement change is observed by the 3 dimensional measurement and numerical analysis. Therefore, the change of ground condition and the existence of a weak zone ahead of tunnel face can be predicted by monitoring 3-dimensional absolute displacements during excavation, and applying the methodology (the ratio of L/C, $C/C_o$, etc.) presented in this study.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.579-582
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• 2011

본 논문에서는 9 % Ni강 LNG 저장탱크 조사를 통해서 유한요소해석을 수행하여 구조건전성을 평가하였으며 실용에서 활용할 수 있는 자료를 제시하였다. 과거의 LNG 저장탱크의 설계는 2차원 선에서만 유한요소해석이 수행되었으나 보다 진보된 하드웨어와 소프트웨어의 발전으로 3차원 유한요소해석이 가능케 되었다. 본 연구에서는 9 % Ni 강 LNG 저장탱크 내조의 정적 구조 해석이 상용 유한 요소 해석 프로그램인 ABAQUS를 통해 수행되었다. LNG 저장 탱크 내조 시공 시 용접부 형상을 참고하여 용접부 모델을 고려한 해석을 각각 수행하였다. 용접부의 탄성계수의 변화를 통하여 최대응력과 최대변위를 계산하였다. 실제 LNG tank의 운용 시 발생하는 하중은 자중과, 수두 압과, 온도차에 의한 열응력이며 이들이 복합적으로 작용하였을 시, 용접선을 고려하지 않은 모델에 대해서는 최대응력이 207 MPa이며, 동일 조건에서 용접선을 포함한 모델에 대해 해석을 수행한 결과로서 최대응력이 그보다 약 100 MPa 정도 상승한 결과가 나타났다. 하중조건에서 온도차에 의한 열응력을 고려함과 고려하지 않음을 비교함으로서 실제 열응력에 대해서는 내조에 큰 영향을 미치지 않음을 확인하였다.

• Computational Structural Engineering
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• v.11 no.1
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• pp.179-190
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• 1998

A geometrically nonlinear finite element formulation of spatial cable networks is presented using two cable elements. Firstly, derivation procedures of tangent stiffness and mass matrices for the space truss element and the elastic catenary cable element are summarized. The load incremental method based on Newton-Raphson iteration method and the dynamic relaxation method are presented in order to determine the initial static state of cable nets subjected to self-weights and support motions. Furthermore, static non-linear analysis of cable structures under additional live loads are performed based on the initial configuration. Challenging example problems are presented and discussed in order to demonstrate the feasibility of the present finite element method and investigate static nonlinear behaviors of cable nets.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.66-69
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• 2004

본 논문에서는 트레드밀의 풀리 벨트를 통해 회전하는 앞 롤러와 러닝 벨트를 통해 회전하는 뒤 롤러의 경계조건과 하중조건을 적용하여 ANSYS로 구조해석을 수행하여, 변위(displacement), 응력 (stress), 변형률(strain)을 구하여 구조적 타당성을 검토하는데 있으며, 각각의 롤러를 모달해석을 통해 고유진동수(natural frequency)를 알아보고 얻어진 데이터 값을 통해 진동 발생 요소인 모터의 회전을 제어함으로서 공진(resonance) 현상을 피하는데 있다.

• Proceedings of the KAIS Fall Conference
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• 2004.11a
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• pp.80-82
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• 2004

본 논문에서는 폐목재의 재활용을 위한 파쇄기의 경계조건과 하중조건을 적용하여 유한요소법에 의한 ANSYS로 구조해석과 모달해석을 수행하여 변위(displacement), 응력(stress), 변형률(strain)을 구하고 구조적 타당성을 검토하였다. 이는 안전성을 고려한 설계의 기초자료가 되며 고유진동수(natural frequency)를 구하여 모터의 회전을 제어함으로서 공진(resonance) 현상을 피하는데 있다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.35 no.4
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• pp.863-874
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• 2015

The use of pile reinforcement is considered as one of the most promising techniques for improving load carrying capacity of piles in offshore area. In this study, to consider the horizontal and uplift bearing capacity of submerged breakwater bearing pile, exclusive analysis on load-transfer behaviour of pile was conducted. First of all, check the reinforcing effect from the three-dimensional finite element method, and estimate load transfer curve (ground reaction force). Based on these results, the reinforcing effect was quantified by estimating the coefficients of horizontal and uplift reinforcement of reinforced piles. Load transfer function with consideration of the reinforcing effect was proposed from estimated coefficients. A comparison of the analysis using the proposed load transfer function with three-dimensional finite element analysis has resulted that the proposed load transfer function is displaying good accuracy of predicting behavior of the load transfer between the pile and soil reinforcement. Interpretation of the submerged structure by applying a load transfer function considering the reinforcing effect, has shown that the reinforced pile's shear, bending moment and displacement are less than that of non-reinforced piles, while the subgrade reaction modulus arises greater. Thus, it is expected to be relatively cost effective in terms of design.

• Journal of the Korean Geotechnical Society
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• v.32 no.11
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• pp.43-50
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• 2016

A reinforcement is required to ensure the structural safety in case of railway embankment excavation under railway load. A large diameter soil nailing with concrete wall is applied as the reinforcement method instead of the conventional soil nailing system. In this study, a series of 3 dimensional numerical analyses are performed to investigate the optimum reinforcement considering 15 different conditions based on the length, lateral spacing, diameter, and inclination of the reinforcement. The interface between soil nail and perimetric grout is considered by means of cohesion, stiffness and perimeter of the grout. 0.3 m of reinforcement diameter is assessed as the most appropriate based on the economical viewpoint though ground displacement decreases with the increase of diameter, however the difference of displacement is negligible between 0.4 m and 0.3 m of diameter. Surface settlement, lateral displacement of wall, and stress of reinforcement are calculated and economic viewpoint to reinforce embankment considered. Consequently, the optimum reinforcement conditions considering those factors are evaluated as 3 m in length, 0.3 m in diameter, 1.5 m in lateral spacing, and 10 degree of inclination angle in the case of 3 m of excavation depth. Additionally, inclined potential failure surface occurs with approximately 60 degrees from the end of nails and the surface settlement and wall lateral displacement are restrained successfully by the large diameter soil nailing, based on the result of shear strain rate.

• Journal of the Korea institute for structural maintenance and inspection
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• v.9 no.2
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• pp.103-112
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• 2005

This study examines the stability of Sungsu bridge which was issued nine years ago because of its collapse accident and now is on the progress of extension work in each construction stage by construction monitoring system. From this study, the measured value in each construction stage of anchorage truss and suspended truss shows the agreement with the analytical values up to 60~110 percents, and the elements' stresses emanating from the pre-loading stage, are also similar to the analytical value. Regarding these results, it is expected that each member has enough stiffness and the construction condition is satisfactory. In addition, it is expected that the transverse members and sway bracing bolts integrate completely the existing truss and new attached truss as a one body from the result of the vibration test to find out the integration rates.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 1993.10a
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• pp.93-97
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• 1993

방진고무는 진동을 방지하여 다른 구조물의 진동전달 차단은 물론, 장비의 수명연장 및 효율을 증가시키기 위한 목적으로 사용되는데 이러한 방진고무 의 동적특성을 일반화하는 것은 어렵기 때문에 방진고무 시편의 동특성 해 석시험 결과치를 기준으로 원하는 성능에 부합하도록 방진고무의 재질을 선 정하고 사양에 의한 엔진마운트를 설계 제작하여야 한다. 이번에 제작한 UEM 엔진마운트는 해상용, 육상용 설비에 적용 가능하며, 특히 해상용에 적 용하고 외부 환경에 의한 부식으로부터 방진고무 및 기자재를 보호하기 위 하여 하우징을 특수재질로 제작하였고, 수직.수평력을 고려하여 큰 하중에 견딜 수 있도록 원추형 형상설계와 강성을 보강하였다. 특히, 원추형 형상으 로 제작하여 하중을 일정하게 분산시키고, 사용 가능한 선형영역을 확대 시 켰으며, Buffer(Steel Bar)를 이용하여 높은 파고 등에 의한 외부 충격량에 따른 큰 변위의 발생으로부터 설비를 보호할 수 있다. 본 논문에서는 물리적 특성이 같은 방진고무를 사용하고, 적층 수만 다르도록 두가지 모델 UEM-155와 UEM-255를 설계 제작하여 수직.수평방향의 정적시험, 동적시 험, 현장 장착시험 등을 수행함으로써 기업에서 요구한 사양에 적합한가를 고찰하였다.

• Journal of the Korea Concrete Institute
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• v.13 no.2
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• pp.161-167
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• 2001

It is difficult to obtain accurate fracture toughness values using three point bending test(TPB) proposed by RILEM committees because the shape of load-deflection curve is irregular and final crack propagation occurs after some slow stable cracking. However, fracture toughness is easily obtained from crack initiation load in the disk test. In this paper, the fracture properties of high strength concrete disks with center-crack was investigated. For this purpose, the experimental results were compared with the results by finite element analysis(FEA). And the experimental fracture locus was compared with theoretical fracture locus. Also, the results of fracture properties for the degree of concrete strength are presented. It is concluded from this study that results from FEA with maximum stress theory were compared well with the results from experiment. And the degree of concrete strength was contributed to the crack initiation load and fracture toughness, but was not contributed to the failure angle. Also, The discrepancy of fracture locus between the maximum stress theory and the experiment for concrete is considered to depend upon a large energy requirement for inducing the mixed-mode and sliding mode fractures.