• Geotechnical Engineering
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• v.14 no.2
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• pp.93-106
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• 1998

The behavior of axially loaded pile was analyzed by two methodologies: one is the finite difference method using load transfer curves recommended by API(1993) , and the other is the numerical analysis using the FLAC program. From both analyses, load-displacement curves and load distributions along the depth were evaluated appropriately for the measured. The analysis using the FLAC could capture the nonlinearity of load-displacement curve even for unloading and reloading cases, since the unloaded stress paths of fill layer elements occurred on the failure envelop. Futhermore, the measured load transfer curves were compared with the API recommendations and with the calculations obtained front the results of the FLAC analysis for the interpretation of the transfer behavior between the soil and the pile under axial loadings. It was concluded that the atrial behavior of open ended piles at Pusan could be evaluated by both the finite difference analysis using API load transfer curves and the numerical analysis using FLAC.

• Journal of Bio-Environment Control
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• v.17 no.3
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• pp.188-196
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• 2008

Single span pipe greenhouses (pipe houses) are widely used in Korea because these simple structures are suitable for construction by farmers thus reducing labor cost. However, these pipe houses are very weak and frequently damaged by heavy snow and strong wind. Pipe house is constructed by pipe fabricator, which is anchored to the ground by inserting each pipe end into ground to $30\sim40cm$, so the ground support condition of pipe end is not clear for theoretical analysis on greenhouse structure. This study was carried out to find out the suitable ground support condition needed f3r structural analysis when pipe house was designed. The snow and wind loading tests on the actual size pipe house were conducted to measure the collapsing shape, displacement and strain. The experimental results were compared with the structural analysis results for 4 different ground support conditions of pipe ends(fixed at ground surface, hinged at ground surface, fixed under ground and hinged under ground). The pipe house under snow load was collapsed at the eaves as predicted, and the actual strain at the windward eave and ground support under wind load was larger than that under snow load. The displacement was the largest at the hinged support under ground, followed by the hinged at ground surface, the fixed under ground and then the fixed at ground surface independent of displacement direction and experimental loading condition. The experimental results agreed most closely with the results of theoretical analysis at the fixed condition under ground among 4 different ground support conditions. As the results, it was recommended that the pipe end support condition of single span pipe greenhouse was the fixed under ground for structural analysis.

• Elastomers and Composites
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• v.39 no.3
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• pp.228-233
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• 2004

A bushing is a device used in automotive suspension systems to reduce the load transmitted from the wheel to the frame of the vehicle. A bushing is a hollow cylinder, which is bonded to a solid steel shaft at its inner surface and a steel sleeve at its outer surface. The relation between the force applied to the shaft and the relative deformation of a bushing is nonlinear and exhibits features of viscoelasticity. Since a force-displacement relation for bushings is important for multibody dynamics numerical simulations, the relation is expressed in terms of a force relaxation function and a method of determination by experiments on bushings has been developed. For the nonlinear viscoelastic axial response, Pipkin-Rogers model, the direct relation of force and displacement, has been derived from experiment. It is shown that the predictions by the proposed force-displacement relation are in very good agreement with the experimental results.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.9
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• pp.859-869
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• 2009

The sharp indenters such as Berkovich and conical indenters have a geometrical self-similarity in theory, but different materials have the same load-depth curve in case of single indentation. In this study, we analyze the load-depth curves of conical indenter with angles of indenter via finite element method. From FE analyses of dual-conical indentation test, we investigate the relationships between indentation parameters and load-deflection curves. With numerical regressions of obtained data, we finally propose indentation formulae for material properties evaluation. The proposed approach provides stress-strain curve and the values of elastic modulus, yield strength and strain-hardening exponent with an average error of less than 2%. It is also discussed that the method is valid for any elastically deforming indenters made of tungsten carbide and diamond for instance. The proposed indentation approach provides a substantial enhancement in accuracy compared with the prior methods.

• Journal of Korean Association for Spatial Structures
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• v.6 no.3 s.21
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• pp.103-110
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• 2006

This study presents a technique to control quantitatively lateral drift of RC tall frameworks subject to lateral loads. To this end, lateral drift constraints are established by introducing approximation concept that preserves the generality of the mathematical programming and can efficiently solve large scale problems. Also the relationships of sectional properties are established to reduce the number of design variables and resizing technique of member is developed under the 'constant-shape' assumption. Specifically, the methodology of dynamic displacement sensitivity analysis is developed to formulate the approximated lateral displacement constraints. Three types of 10 and 50 story RC framework models are considered to illustrate the features of dynamic stiffness-based optimal design technique proposed in this study.

• Transactions of the Korean Society of Mechanical Engineers
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• v.10 no.3
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• pp.427-431
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• 1986

3점 굽힘 시험편, 중앙균열 인장 시험편, 콤팩트 인장 시험편에 대한 J적분식을 하나의 일반화된 형태로 유도한다. 이 일반식은 Eftis와 Liebowitz에 의해 제안된 하중과 하중점 변위 사이의 관계와 Sumpter에 의한 탄성과 소성성분 J적분의 중첩개념을 이용함으로써 유도된다. 일반식에 포함된 .eta.계수를 위 3가지 시험편에 대해서 결정한다. 위 3가지 시험편에 대한 J적분의 최종식은 하중과 하중점 변위곡선 아래의 면적을 측정하지 않아도 되는 형태로 나타난다. 본 연구의 결과식은 Landes등에 의한 실험치와 비교하여 매우 잘 일치함을 보인다.

• Proceedings of the Korean Society of Disaster Information Conference
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• 2022.10a
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• pp.311-312
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• 2022

최근 발생한 경주 및 포항 지진으로 인해 다수의 매립배관 손상이 보고되었다. 벨로우즈 신축관이음은 기하학적 특성으로 인해 진동 및 침하 등으로 인한 손상을 저감시킬 수 있다. 벨로우즈 신축관이음관의 내진 성능평가에 대한 실험적 혹은 해석적 연구는 미미한 상황이다. 본 연구는 벨로우즈 신축이음관의 내진성능을 분석하기 위해 반복하중 기반의 실험적 연구를 수행하였다. 또한 실험결과를 기반으로 3차원 유한요소 모델을 구축하였으며 실험과 해석에서 얻어진 하중-변위 관계를 비교하였다. 해석 모델에서 전체적인 강성이 큰 것으로 나타났으며 최대 변위가 작용할 때 에너지 소산량은 약 10% 가량 큰 것으로 나타났다.

• The Journal of Korean Academy of Prosthodontics
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• v.25 no.1
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• pp.281-302
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• 1987

의치상 재료 종류에 따라 의치, 점막 및 하악골에 발생되는 변위 및 응력을 연구하기 위하여 컴퓨터를 이용한 수치적 해석인 2차원 유한 요소법을 이용하였다. 2차원 유한 요소 모형으로선 표준 크기의 하악골 및 의치를 고려하여 231개의 사변형 요소 및 268개의 절점으로 분할한 후 각 구성 성분의 물리적 성질인 탄성률 및 프와송비를 대입시켰다. 사용된 의치로서는 일반 합성수지의치, 2mm후경의 탄성재를 의치상 하부에 이장한 합성수지의치, 2mm후경의 탄성재를 치아와 의치상 중앙에 삽입한 합성수지의치 및 0.5mm후경의 금속상의치의 4종류였으며, 하중시에 하악의 고정 부위로선 생체와 동일 조건을 부여하기 위하여 교근, 내측익돌근, 측두근등의 하악 폐구근이 부착되는 하악각 부위 및 하악 근돌기 부위의 16절점을 고정점으로 하였다. 하중 조건으로선 하악 제1대구치의 일점에 10kg의 수직 집중하중, 하악 중절치의 일점에 7kg의 수직 집중하중 및 하악 제 1소구치로 부터 하악 제2대구치까지의 교합면에 10kg의 수직 분산하중을 부여하여 분석한 결과는 다음과 같다. 1. 하중이 의치 교합면위의 가해진 부위에 따라 다양한 의치 회전 및 강하 현상을 보였으며, 탄성재를 이장 및 삽입한 합성 수지 의치의 변위가 일반 합성수지의치 및 금속상 의치의 변위보다 더 컸다. 2. 주응력을 고려할때 점막 부위에는 주로 압축 응력이 작용하였으며 치조제 부위는 압축응력과 인장 응력이 함께 작용하였다. 3. 탄성재를 삽입한 합성수지의치에 최고 등가 응력이 집중되었으며 그 다음은 탄성재를 이장한 합성수지의치, 일반 합성수지의치의 순이였으며 금속상의 경우는 금속을 따라서 높은 등가 응력이 넓게 분산되었다. 4. 의치상 종류에 관계없이 동일 하중 조건하에선 점막에 나타나는 등가 응력의 크기 및 분산양태는 유사하였다. 5. 하악골에서 등가 응력은 의치지지 부위에만 국한되지 않고 넓게 분산 되었으며 의치상 종류 및 하중 조건에 관계없이 치조제 후방 및 하악연의 후방 부위에 특히 높은 등가응력이 집중되었다. 6. 하악 중절치의 일점에 수직 하중을 가한 경우가 다른 하중 조건에 비하여 지지점과의 거리차이로 인하여 하악골에 가장 높은 등가 응력을 유발하였다. 7. 의치상 재료에 따른 하악 골에 발생되는 응력의 크기 및 분산에는 큰 차이가 없으나 금속상의 경우가 교합압을 분산하는데는 효과적이었다.

• Journal of the Earthquake Engineering Society of Korea
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• v.6 no.3
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• pp.11-21
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• 2002

The evaluation of displacement ductility is performed by direct method through tracking the inelastic hysteretic behavior of RC bridge columns subject to cyclic loading using a flexibility-based fiber element mode. To reasonably track the inelastic behavior until the RC bridge column reaches its ultimate state, the average stress-average strain relations and joint elements, which agree well with experiments, are modified and applied considering the tension stiffening behavior and discontinuous displacement between the column and its base. In addition the evaluation of displacement ductility is performed by a direct method easily applicable to numerical analysis. Locations for the integration points, values for the post-crushing concrete strength and low-cycle fatigue failure of longitudinal reinforcement that affect the calculation of yielding and ultimate displacements are proposed for the application to flexibility-based fiber element model. Since less than 10% of error occurs during the displacement ductility analysis, the yielding and ultimate displacements evaluated by the applied analysis method and model appear to be valid.

• Journal of the Korea Concrete Institute
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• v.25 no.5
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• pp.529-537
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• 2013

The aim of the current study is to develop a nonlinear isoparametric layered frame finite element (FE) analysis of FRP strengthened reinforced concrete (RC) beam or column members by a force-based FE formulation. In sections, concrete is modeled in the triaxial stress-strain relationship state and the FRP sheet is modeled as layered composite materials in two-dimension. The element stiffness matrix derived by the force-based FE has the force-interpolation functions without assuming the displacement shape functions. A lateral load test of RC column strengthened by GFRP sheets was analyzed by the developed force-based FE model. From comparative studies of the experimental and analysis results, it was shown to compare with the stiffness FE method that the force-based FE analysis could give more accurate predictions in the overall lateral load-deflection response as well as in nonlinear deformations and damages in the column plastic hinge region.