• Steel and Composite Structures
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• 제25권3호
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• pp.287-298
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• 2017

The present study aims to determine the structural response of full scaled rectangular columns under both of vertical and lateral loads using numerical methods. In the study, the composite columns considering full concrete filled circular steel tube (FCFRST) and concrete filled double-skin rectangular steel tube (CFDSRST) section types are numerically modelled using ANSYS software. Vertical and lateral loads are applied to models to assess the structural response of the composite elements. Also similar investigations are done for reinforced concrete rectangular (RCR) columns to compare the results with those of composite elements. The analyses of the systems are statically performed for both linear and nonlinear materials. In linear static analyses, both of vertical and lateral loads are applied to models as only one step. However in nonlinear analyses, while vertical loads are applied to model as only one step, lateral loads are applied to systems as step by step. The displacement and stress changes in some critical nodes and sections and contour diagrams are reported by graphs and figures. At the end of the study, it is demonstrated that the nonlinear models reveal more accurate result then those of linear models. Also, it is highlighted that composite columns provide more and more safety, ductility compared to reinforced concrete column.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 추계 학술발표회 2차
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• pp.3-12
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• 2010

Vertical drains have been commonly used to increase the rate of the consolidation of dredged material. The installation of vertical drains additionally provides a radial flow path in the dredged foundation. The objective of this study develops a numerical model for 2-D axisymmetric non-linear finite strain consolidation considering self-weight consolidation to predict the effect of vertical drain in dredged foundation which is in process of self-weight consolidation. The non-linear relationship between the void ratio and effective stress and permeability during consolidation are taken into account in the numerical model. The results of the numerical analysis are compared with that of the self-weight consolidation test in which an artificial vertical drain is installed. In addition, the numerical model developed in this paper is the simplified analytical method proposed by Ahn et, al (2010). The comparisons show that the developed numerical model can properly simulate the consolidation of the dredged material with the vertical drains installed.

• 한국산학기술학회논문지
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• 제16권7호
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• pp.5009-5014
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• 2015

사질토 지반 위에 놓여 있는 점토지반에 대한 좁은굴착시 간극수압에 의한 융기현상이 발생할 수 있다. 간극수압에 의한 융기현상의 평가는 지반보를 고려해서 하게 되는데 좀 더 엄밀한 평가를 위해서는 지반보에 발생하는 응력분포의 결정이 필요하다. 본 연구에서는 탄성론에 근거하여 지반보에 발생하게 되는 응력분포와 변위분포 산정식을 제시하였다. 지반보의 자중에 의해 지반보내에 발생하는 응력분포를 5차 다항식으로 표현되는 응력함수로부터 유도하였는데 지반보의 깊이에 따른 연직응력의 분포는 포물선 분포를 나타내었으며 연직하향으로 작용함을 알 수 있었다. 단위중량이 $16kN/m^3이고 두께와 폭이 1m인 지반보인 경우 보의 내부에 발생하는 최대 연직응력의 크기는 1.7kPa 정도였다. 지반보 바닥면에 간극수압이 작용하는 경우의 응력분포를 자중에 의한 응력분포에 중첩시켜 구하였는데 지반보 자중의 5배에 해당하는 간극수압이 작용하는 경우 지반보의 깊이를 따라 곡선형태의 연직방향 압축응력분포를 나타내었다. 간극수압이 작용하는 경우에 대해 유도된 지반보의 응력분포로부터 변위분포를 유도하고 그 예측식을 제시하였다.

• Journal of Periodontal and Implant Science
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• 제36권2호
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• pp.531-554
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• 2006

Oral implants must fulfill certain criteria arising from special demands of function, which include biocompatibility, adequate mechanical strength, optimum soft and hard tissue integration, and transmission of functional forces to bone within physiological limits. And one of the critical elements influencing the long-term uncompromise functioning of oral implants is load distribution at the implant- bone interface, Factors that affect the load transfer at the bone-implant interface include the type of loading, material properties of the implant and prosthesis, implant geometry, surface structure, quality and quantity of the surrounding bone, and nature of the bone-implant interface. To understand the biomechanical behavior of dental implants, validation of stress and strain measurements is required. The finite element analysis (FEA) has been applied to the dental implant field to predict stress distribution patterns in the implant-bone interface by comparison of various implant designs. This method offers the advantage of solving complex structural problems by dividing them into smaller and simpler interrelated sections by using mathematical techniques. The purpose of this study was to evaluate the stresses induced around the implants in bone using FEA, A 3D FEA computer software (SOLIDWORKS 2004, DASSO SYSTEM, France) was used for the analysis of clinical simulations. Two types (external and internal) of implants of 4.1 mm diameter, 12.0 mm length were buried in 4 types of bone modeled. Vertical and oblique forces of lOON were applied on the center of the abutment, and the values of von Mises equivalent stress at the implant-bone interface were computed. The results showed that von Mises stresses at the marginal. bone were higher under oblique load than under vertical load, and the stresses were higher at the lingual marginal bone than at the buccal marginal bone under oblique load. Under vertical and oblique load, the stress in type I, II, III bone was found to be the highest at the marginal bone and the lowest at the bone around apical portions of implant. Higher stresses occurred at the top of the crestal region and lower stresses occurred near the tip of the implant with greater thickness of the cortical shell while high stresses surrounded the fixture apex for type N. The stresses in the crestal region were higher in Model 2 than in Model 1, the stresses near the tip of the implant were higher in Model 1 than Model 2, and Model 2 showed more effective stress distribution than Model.

• 대한인간공학회지
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• 제19권2호
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• pp.15-31
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• 2000

The aim was to evaluate the prevailing ergonomic and psychosocial conditions regarding low back injury in an automobile assembly system. This study consisted of two parts. In the first part of the study, analytic biomechanical model and NIOSH guidelines were applied to evaluate risk levels of low back injury for automobile assembly jobs. Total of 246 workers were analysed. There were 20 jobs having greater back compressive forces than 300kg at L5/S1. Also, there were 44 jobs over Action Limit with respect to 1981 NIOSH guidelines. This might in part be explained by the ergonomic conditions of the company analysed generally being good, with a relatively low duration of 'combined' extreme work posture. The relationship between psychosocial factors and low back injury was examined in the second part of the study. It has recently been recognized that overall reaction to working conditions was influenced by a range of factors, some of which were physical and some psychosocial. The psychosocial environment surrounding the work place may contribute to the perception of risk and eventual ill-health. A battery of questionnaires concerning the psychosocial stress based on PWI(Psychosocial Well-being Index) and musculoskeletal pain symptoms at low back was completed by 246 workers at the same plant. Results showed that 207 out 246 workers experienced the symptoms and 27 workers were diagnosed as patients. Two groups(low stressed, high stressed) based on PWI score had no significant relationships with both symptoms and results of diagnosis. However, sensitivities for symptoms and diagnosis by PWI were 91.3% and 92.6% respectively. Finally, relationships between physical work load and psychosocial stress were analysed. Specifically, some postural factors {vertical deviation angle of forearm, horizontal deviation angle of upperarm, vertical deviation angle of thigh, etc) were highly correlated with psychosocial stress. The results illustrated that PWI scores were associated with some physical workloads. However, psychosocial stress levels couldn't be well related with the pain symptom as well as the actual incidence of low back injury since pain or discomfort regarding low back injury were more complex than that of other musculoskeletal disorders.

• 한국지반환경공학회 논문집
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• 제11권1호
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• pp.27-34
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• 2010

본 연구에서는 유한요소해석을 실시하여 지반굴착으로 인해 융기(heaving)가 발생하는 지반에 사전에 근입된 말뚝의 거동에 대한 분석을 실시하였다. 수치해석에서는 말뚝과 점토사이 경계면에서의 미끄러짐(소성항복)을 고려하여 그 상호거동에 대하여 고찰하였다. 본 연구에서는 말뚝의 상향변위, 말뚝과 인접지반의 상대변위, 말뚝에 작용하는 전단응력 및 인장력을 분석하였다. 특히, 수직응력의 감소로 인해 말뚝과 인접지반에서의 전단응력이 전이되는 메커니즘에 대한 심도있는 분석을 실시하였다. 굴착에 의해 수직응력이 감소하여 말뚝과 인접지반 사이에서의 상대변위 및 전단응력이 변화하였다. 말뚝 대부분의 위치(Z/L=0.0-0.8)에서는 상향의 전단응력이 발생하였으나, 말뚝 선단부 부근(Z/L=0.8-1.0)에서는 하향의 전단응력이 발생하였고, 이로 인해 말뚝에는 인장력이 발생하였다. Z는 임의의 심도, L은 말뚝의 길이이다. 수치해석을 통해서 분석된 말뚝의 거동에 대하여 상세히 보고하였다.

• 한국도로학회논문집
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• 제3권1호
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• pp.151-163
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• 2001

아스팔트포장층내에 보강용 토목섬유를 설치하여 포장층의 응력-거동특성을 연구한 예는 매우 드물다. 본 연구에서는 유한요소법을 사용하여 지오그리드와 유리섬유로 보강한 층의 응력-변형 특성을 연구하였다. 유리섬유와 지오그리드의 강성이 다른 두가지 종류를 사용하고 설치위치, 포장단면층의 두께 변화를 주어 아스팔트포장층에 미치는 영향을 분석하였다. 포장층내에 발생하는 수직응력, 수직변위, 최대전단응력을 분석한 결과 수직응력, 수직변위 보다 최대전단응력을 크게 감소시키는 경향이 나타났다. 최대전단응력 감소효과가 약 15$\sim$20% 정도 있음을 알 수 있었다. 보강재의 탄성계수가 큰 유리섬유가 가장 효과가 좋으며 깊이 3cm$\sim$5cm에 설치하는 것이 가장 효과가 좋은 것으로 나타났다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2010년도 춘계 학술발표회
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• pp.1458-1465
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• 2010

A lot of dredging and reclaming projects are recently under way in Korea for the efficient use of limiting land space. Saemanguem area is special case of reclaiming by dredged soil. In case of a confined disposal of dredged soils by a pump dredger, generally coarse grained soils are separated from fines with dropping at the near part of the pump dredger. This kind of seperation of fine contents could be a factor of liquefaction by earthquake. In Korea, recently, earthquakes with magnitude of 3.0 or higher are distinctively increasing in 1990. In this study, cyclic shear characterics of Saemanguem Dredged sand depending on fine content were analyzed. A series of undrained cyclic triaxial test with cyclic stress ratio ($\sigma_d/{2\sigma_{{\upsilon}c}}'$) were performed on both isotropic consolidated specimen and sand with fine contents of 0%, 5%, 15%, 30%, 40% under the effective vertical stress of 100kPa and 50% and 60%, 70% of relative density for fine content of 0%, respectively. In the test results, cyclic shear strength increased by increasing of cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) with increasing the relative density at the same number of cyclic under the effective confining pressure of 100kPa. It is almost highest the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10% at fine content of 15% between Cyclic stress ratio($\sigma_d/{2\sigma_{{\upsilon}c}}'$) value at cyclic number five and fine content. Number of cyclic is 30 under the effective vertical stress of 100kPa, 70% of relative density for fine content of 15%. when the cyclic stress ratio at each relative density was compared at cyclic number five, the double amplitude(DA) 1%, 3%, 5%, 7.5% and 10%, and the pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value were compared; under the relative density of 70% and the effective confining pressure of 100kPa. The pore-pressure ratio (${\Delta}u/{\sigma'}_c$) 0.95 value showed a similar trend to the double amplitude (DA) 5% line.

• 한국지반공학회논문집
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• 제25권5호
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• pp.65-73
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• 2009

불연속성 암반에 건설된 2-아치 터널 지표면에 외력이 작용할 경우 지중응력의 분포 특성을 파악하기 위하여 대형 모형실험과 수치해석을 수행하였다 분석결과, 불연속면이 존재하는 경우에는 선형 탄성론에 근거한 응력보다 큰 지중응력이 분포하며, 불연속면의 경사도에 따라 압력구의 형상이 달라지는 것을 확인하였다. 불연속면이 수평이거나 연직인 경우에는 지중응력의 분포가 대칭적 이지만, 경사져 있으면 경사에 대해 수직과 평행한 양방향으로 나뉘어 분포되었다. 또한 불연속면의 경사가 고각일수록 불연속면에 평행인 방향의 지중응력이 더 크게 증가하였다. 연구결과, 불연속성 암반에서는 불연속면의 경사가 음력분포에 지대한 영향을 미치며, 필러에 전달되는 응력을 추정할 경우에는 재하위치와 불연속면의 경사 및 터널 구조물간 상호위치를 고려하는 것이 중요함을 확인하였다.

• 대한치과보철학회지
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• 제42권2호
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• pp.226-237
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• 2004

Purpose: Four finite element models were constructed in the mandible having a single implant fixture connected to the first premolar-shaped superstructure, in order to evaluate how the shape of the fixture and the implant-abutment connection would influence the stress level of the supporting tissues fixtures, and prosthethic components. Material and methods : The superstructures were constructed using UCLA type abutment, ADA type III gold alloy was used to fabricate a crown and then connected to the fixture with an abutment screw. The models BRA, END , FRI, ITI were constructed from the mandible implanted with Branemark, Endopore, Frialit-2, I.T.I. systems respectively. In each model, 150 N of vertical load was placed on the central pit of an occlusal plane and 150 N of $40^{\circ}$ oblique load was placed on the buccal cusp. The displacement and stress distribution in the supporting tissues and the other components were analysed using a 2-dimensional finite element analysis . The maximum stress in each reference area was compared. Results : 1. Under $40^{\circ}$ oblique loading, the maximum stress was larger in the implant, superstructure and supporting tissue, compared to the stress pattern under vertical loading. 2. In the implant, prosthesis and supporting tissue, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 3. In the superstructure and implant/abutment interface, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 4. In the implant fixture, the maximum stress was smaller with the internal connection type (FRI) and the morse taper type (ITI) when compared to that of the external connection type (BRA & END). 5 The stress was more evenly distributed in the bone/implant interface through the FRI of trapezoidal step design. Especially Under $40^{\circ}$ oblique loading, The maximum stress was smallest in the bone/implant interface. 6. In the implant and superstructure and supporting tissue, the maximum stress occured at the crown loading point through the ITI. Conclusion: The stress distribution of the supporting tissue was affected by shape of a fixture and implant-abutment connection. The magnitude of maximum stress was reduced with the internal connection type (FRI) and the morse taper type (ITI) in the implant, prosthesis and supporting tissue. Trapezoidal step design of FRI showed evenly distributed the stress at the bone/implant interface.