• 한국지반공학회논문집
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• 제21권5호
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• pp.15-24
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• 2005

본 논문에서는 교량 말뚝기초의 모델링기법에 관한분류 및 단부 지점조건의 영향을 분석하였다. 연성스프링 방법은 모델링 형태가 간편하면서도 복잡한 군말뚝 거동을 효과적으로 나타낼 수 있으므로 실제 설계에 유용한 방법이다. 다양한 말뚝 배열, 말뚝 간격, 선단지지조건, 그리고 하중크기에 따라 3차원 해석기법(YSGroup)을 통해 영향인자 분석을 수행하였으며, 그 결과 횡방향 변위, 최대 말뚝 휨응력, 그리고 군말뚝의 횡방향 스프링강성을 산정, 이를 비교$\cdot$분석하였다. 영향인자 분석을 통해 3차원 해석기법(YSGroup)을 통해 횡방향 스프링강성을 산정한 경우는 다른 단독말뚝 해석을 통해 산정한 경우에 비하여 복잡한 군말뚝 거동을 보다 적절히 예측함을 알 수 있었다.

• Geomechanics and Engineering
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• 제9권3호
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• pp.313-328
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• 2015

In the present study, a CPT-based p-y analysis method was proposed for offshore mono-piles embedded in sands. Static and cyclic loading conditions were both taken into account for the proposed method. The continuous soil profiling capability of CPT was an important consideration for the proposed method, where detailed soil profile condition with depth can be readily incorporated into the analysis. The hyperbolic function was adopted to describe the non-linear p-y curves. For the proposed hyperbolic p-y relationship, the ultimate lateral soil resistance $p_u$ was given as a function of the cone resistance, which is directly introduced into the analysis as an input data. For cyclic loading condition, two different cyclic modification factors were considered and compared. Case examples were selected to check the validity of the proposed CPT-based method. Calculated lateral displacements and bending moments from the proposed method were in good agreement with measured results for lateral displacement and bending moment profiles. It was observed the accuracy of calculated results for the conventional approach was largely dependent on the selection of friction angle that is to be adopted into the analysis.

• Geomechanics and Engineering
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• 제19권1호
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• pp.79-91
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• 2019

Renewed interest in the long-term pile foundations has been driven by the increase in offshore wind turbine installation to generate renewable energy. A monopile subjected to repetitive loads experiences an evolution of displacements, pile rotation, and stress redistribution along the embedded portion of the pile. However, it is not fully understood how the embedded pile interacts with the surrounding soil elements based on different pile geometries. This study investigates the long-term soil response around offshore monopiles using finite element method. The semi-empirical numerical approach is adopted to account for the fundamental features of volumetric strain (terminal void ratio) and shear strain (shakedown and ratcheting), the strain accumulation rate, and stress obliquity. The model is tested with different strain boundary conditions and stress obliquity by relaxing four model parameters. The parametric study includes pile diameter, embedded length, and moment arm distance from the surface. Numerical results indicate that different pile geometries produce a distinct evolution of lateral displacement and stress. In particular, the repetitive lateral load increases the global lateral load resistance. Further analysis provides insight into the propagation of the shear localization from the pile tip to the ground surface.

• Earthquakes and Structures
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• 제16권5호
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• pp.533-546
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• 2019

This study presents an experimental investigation on six beam-column joint specimens under the lateral cyclic loading. The aim was to explore the effectiveness of steel fiber-reinforced concrete (SFRC) in reducing the transverse shear stirrups in beam-column joints of the reinforced concrete (RC) frames with strong-columns and weak-beams. Two RC and four SFRC specimens with different types of reinforcement detailing and steel fibers of volume fraction in the range of 0.75-1.5% were tested under gradually increasing cyclic displacements. The main parameters investigated were lateral load-resisting capacity, hysteresis response, energy dissipation capacity, stiffness degradation, viscous damping variation, and mode of failure. Test results showed that the diagonally bent configuration of beam longitudinal bars in the beam-column joints resulted in the shear failure at the joint region against the flexural failure of beams having straight bar configurations. However, all SFRC specimens exhibited similar lateral strength, energy dissipation potential and mode of failure even in the absence of transverse steel in the beam-column joints. Finally, a methodology has been proposed to compute the shear strength of SFRC beam-column joints under the lateral loading condition.

• Geomechanics and Engineering
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• 제24권6호
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• pp.531-543
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• 2021

Freezing and thawing of pore water within backfill can affect the stability of retaining wall as the phase change of pore water causes changes in the mechanical characteristics of backfill material. In this study, the effects of freezing and thawing on the mechanical performance of retaining wall with granular backfill were investigated for various temperature and groundwater level (GWL) conditions. The thermal and mechanical finite element analyses were performed by assigning the coefficient of lateral earth pressure according to phase change of soil for at-rest, active and passive stress states. For the at-rest condition, the mobilized lateral stress and overturning moment changed markedly during freezing and thawing. Active-state displacements for the thawed condition were larger than for the unfrozen condition whereas the effect of freezing and thawing was small for the passive condition. GWL affected significantly the lateral force and overturning moment (Mo) acting on the wall during freezing and thawing, indicating that the reduction of safety margin and wall collapse due to freezing and thawing can occur in sudden, unexpected patterns. The beneficial effect of an insulation layer between the retaining wall and the backfill in reducing the heat conduction from the wall face was also investigated and presented.

• 지질공학
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• 제20권2호
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• pp.191-202
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• 2010

본 연구에서는 부지조성을 위해 매립한 해성퇴적지반을 대상으로 성토량의 증가에 따라 발생되는 침하량과 측방유동량을 분석하여 연약지반의 깊이 및 성토하중을 고려한 침하량과 측방유동량 산정식을 제안하였다. 이를 위해 압성토공법이 적용된 해성퇴적지반 개량구간으로부터 현장조사와 실내시험 및 현장시험을 실시하였으며, 여러 계측기기를 설치하여 현장계측을 수행하였다. 그리고 이들 조사, 시험 및 계측결과로부터 지반의 분포상태, 물성 및 공학특성을 파악하였으며 회귀분석을 통한 침하량과 측방유동량을 산정하였다. 연구지역의 지층은 상부로부터 매립층, 퇴적층 및 기반암층으로 구성되어 있으며 자연적으로 형성된 점토층은 3.9~44.5 m 두께로 분포하고 있다. 그리고 지반개량을 위한 성토고는 4.7~7.8 m이고 이로 인해 발생된 침하량과 측방유동량은 각각 0.959~2.217 m 및 0.048~0.313 m 범위인 것으로 나타났다. 회귀분석을 실시한 결과 성토에 따른 침하량 및 측방유동량 산정식은 각각 $s=0.02h^2+0.11h$ 및 ${\delta}=0.01e^{0.37h}$와 같이 제시할 수 있다. 제안된 이들 경험식은 연구지역과 유사한 조건을 가진 해성퇴적지반에서 성토하중에 따른 침하량과 측방유동량을 개략적으로 산정할 시 적용이 가능할 것이다.

• 대한족부족관절학회지
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• 제9권1호
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• pp.94-98
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• 2005

Purpose: To compare the radiographic evaluations between two radiographic views (AP and lateral views) and four radiographic views (AP, lateral and both oblique views) in ankle fractures. Materials and Methods: From January 2000 to June 2002, 60 cases of ankle fractures were treated with open reduction and internal fixation and its followed up periods were at least 2 years. All cases were classified into three groups according to the method of preoperative radiographic evaluation. Two radiographic views (AP and lateral views) were taken in group A and four radiographic views (AP, lateral and both oblique views) were taken in group B. 12 Cases were evaluated with three dimensional computed tomography (3D CT). Four radiographic views and 3D CT were taken in group C. All cases were classified according to the Danis-Weber and Lauge-Hansen classification. Displacement of fracture fragment of medial, lateral, posterior malleolus and size of fracture fragment of posterior malleous were measured using picture archiving communication system (PACS). Results: Although kappa value between two or four radiographic views were good or excellent in Danis-Weber classification and Lauge-Hansen classification of ankle fractures, the displacements of medial and lateral malleoli were statistically different. Four radiographic views evalulated the degree of displacement of medial and lateral fragments more accurately compared to two radiographic views. Conclusion: Four radiographic views will be more useful than two radiographic views to decide the method of treatment and operation considering the displacement of fracture fragment.

• 한국전산구조공학회논문집
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• 제16권3호
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• pp.291-299
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• 2003

본 연구에서는 연속체해석을 토대로, 병렬코아를 갖는 아웃리거구조물의 수평하중에 대한 응력과 변위를 구하기 위한 방법을 제안하였고, 아웃리거의 위치에 따른 구조물의 거동에 대해 연구하였다. 아웃리거와 코아가 만나는 위치에서 코아의 회전병위가 아웃리거의 회전변위와 일치한다는 적합조건으로부터 아웃리거의 구속모멘트, 코아의 휨모멘트, 기둥의 축방향력, 그리고 구조물의 수평변위 등을 유도하였다. 구조모델들을 이용하여 MIDAS-GEN 프로그램에 의한 결과와 비교하였고, 병렬코아를 갖는 아웃리거구조물에 대해 만족할만한 결과를 얻었다. 구조물 최상단의 수평변위는 코아의 위치보다는 아웃리거의 위치에 의해 크게 영향을 받는 것으로 조사되었다. 비록, 이 논문에서 제시된 공식들이 이상적인 아웃리거구조물에 대한 것이지만 병렬코아를 갖는 실제 아웃리거구조물의 응력과 변위의 근사치를 추정하고, 구조물의 거동을 예측하기 위한 수단으로 유용하게 사용될 수 있을 것이다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2000년도 연약지반처리위원회 학술세미나
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• pp.79-92
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• 2000

In this paper, comparison of the observed and the predicted ground deformations due to the construction of road embankment with peck drain near the construction site was made. Measurement of the ground deformation at the gasoline stand due to the construction of road embankment was made and it was compared with the predicted deformation results of Finite Element Method analysis made with Elasto-plastic and Elastic visco-plastic models. A well agreement was obtained between the measured and predicted ground deformations.

• 한국철도학회:학술대회논문집
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• 한국철도학회 2007년도 춘계학술대회 논문집
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• pp.749-754
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• 2007

In this paper, the vibration of a rotating shaft with a thin rigid disk is considered. It is assumed that the shaft has uniform, circular cross-section. Based on the Timoshenko-beam theory, the transverse displacements and slops in two lateral directions, the axial displacement, and the torsional deformation are considered. The spectral element method is used for the vibration analysis of the rotating shaft with a thin rigid disk, which is modeled by two shaft elements and a thin rigid disk element.