• Steel and Composite Structures
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• 제10권4호
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• pp.317-329
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• 2010

According to the results of 9 circular concrete filled steel tube (CFT) push-out tests, a new theoretical model for average bond stress versus free end slip curve is proposed. The relationship between verage bond stress and free end slip is obtained considering some varying influential parameters such as slenderness ratio and diameter-to-thickness ratio. Based on measured steel tube strain and relative slip at different longitudinal positions, the distribution of bond stress and relative slip along the length of steel tube is obtained. An equation for predicting the varying bond-slip relationship along longitudinal length and a position function reflecting the variation are proposed. The presented method can be used in the application of finite element method to analyze the behavior of CFT structures.

• Computers and Concrete
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• 제3권1호
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• pp.17-28
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• 2006

Replacement of actual stress distribution in a reinforced concrete (RC) flexural member with a simpler geometrical shape, which maintains magnitude and location of the resultant compressive force, is an acceptable conceptual trick. This concept was originally perfected for normal strength concrete. In recent years, high strength concrete (HSC) has been introduced and widely used in modern construction. The stress block parameters require updating to account for special features of HSC in the design of flexural members. In future, more varieties of concrete may be developed and a corresponding design procedure of RC flexural members will be required. The usual practice is to conduct large number of experiments on various sizes of specimen and then evolve an empirical relation. This paper presents a numerical procedure through which the stress block parameters can be numerically derived for a given strain ratio variation. The material model for concrete is presented and computational procedure is described. This procedure is illustrated with several variations of strain ratio. The advantages of numerical procedure are that it costs less and it can be used with new material models for any new variety of concrete.

• 한국도로학회논문집
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• 제9권2호
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• pp.63-76
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• 2007

본 연구에서는 콘크리트 포장에 덧씌우기를 하였을 때 다축차륜하중에 의한 응력분포특성을 분석하기 위하여 변환영역에서의 해석법을 개발하였다. 덧씌우기는 기존의 슬래브와 완전히 부착이 되었을 경우와 전혀 부착이 되지 않았을 때의 두 가지 극한 조건을 기준으로 분석을 하였다. 차륜하중은 복륜단축, 복륜복축, 복륜삼축 등 복륜다축하중을 고려하였으며 덧씌우기의 두께, 탄성계수, 포아송비 등이 응력분포에 미치는 영향을 분석하였다. 변환영역에서의 해석법을 이용하여 덧씌우기 포장을 분석하는 방법에 대하여 상세히 설명하였으며 해석결과의 정확성은 유한요소법을 이용한 해석결과와 비교하여 검증하였다. 해석을 수행한 결과 덧씌우기의 두께, 탄성계수, 포아송비의 증가는 기존 슬래브 하부의 최대인장응력을 감소시키며 감소 정도는 부착 덧씌우기가 비부착 덧씌우기에 비해 더 큰 것을 알 수 있었다. 또한 덧씌우기의 포아송비가 응력에 미치는 영향은 그리 크지 않은 것을 알 수 있었으며 부착과 비부착 덧씌우기 포장에서 덧씌우기의 두께 및 탄성계수의 증가에 따른 기존슬래브의 최대응력 감소특성도 분석하였다. 그리고 하중의 축수에 따른 부착과 비부착 덧씌우기 포장의 응력분포 및 최대응력특성도 분석하였다.

• Coupled systems mechanics
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• 제9권6호
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• pp.575-597
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• 2020

Equilibrium equations of a porous FG plate resting on Winkler-Pasternak foundations with various boundary conditions are derived using a new refined shear deformation theory. Different types of porosity distribution rate are considered. Governing equations are obtained including the plate-foundation interaction. This new model meets the nullity of the transverse shear stress at the upper and lower surfaces of the plate. The novel rule of mixture is proposed to describe and approximate material properties of the FG plates with different distribution case of porosity. The validity of this theory is studied by comparing some of the present results with other higher-order theories reported in the literature. Effects of variation of porosity distribution rate, boundary conditions, foundation parameter, power law index, plate aspect ratio, side-to-thickness ratio on the deflections and stresses are all discussed.

• 전자공학회논문지T
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• 제35T권1호
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• pp.75-81
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• 1998

본 논문은 장방형 다이아프램 형상과 단일형 피에조저항 전단응력 스트레인 게이지 와의 관계를 해석하여 최적의 전단응력 압력센서를 설계하기 위한 것이다. 다이아프램상의 전단응력을 시뮬레이션 하기 위하여 유한요소법 분석 프로그램 ANSYS 5.1를 사용하였다. 시뮬레이션 결과는 다이아프램 형상비가 3일때 스트레인 게이지의 위치는 중앙에서, 크기는 전체 장방형 다이아프램 크기의 8%를 점유할때 온도에 안정적이고, 최대 감도를 가진다는 것을 조사하였다.

• Journal of Welding and Joining
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• 제14권2호
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• pp.36-45
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• 1996

Fatigue strength of the spot welded lap joint is considerably influenced by corrosive environments. Particularly, the chloride and the sulfide are most injurious to strength of the spot welded lap joint. Therefore, there is a need to evaluate its effect to corrosion fatigue strength for safe life design of spot welded structures. In order to evaluate their corrosion fatigue strength, corrosion fatigue tests on the spot welded lap joints of the uncoated and the coated high strength steel sheets were conducted in air and in 10% NaCl solution. Corrosion fatigue strength of the uncoated specimens were entirely lower than the coated one in NaCl solution, but those of the coated specimens in NaCl solution were lower than in air. And stress distribution in single spon welded lap joint subjected to tension-shear load was investigated by the finite element method. Using these results, we tried to evaluate corrosion fatgue strength of the various spot welded lap joints with maximum stress $\sigma_{max}$ at edge on loading side of the spot welded lap joint. We could find that corrosion fatigue strength could be quantitatively and systematically rearranged by $\sigma_{max}$.

• 한국재료학회지
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• 제29권4호
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• pp.264-270
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• 2019

As a case study on aspect ratio behavior, Kaolin, zeolite, $TiO_2$, pozzolan and diatomaceous earth minerals are investigated using wet milling with 0.3 pai media. The grinding process using small media of 0.3 pai is suitable for current work processing applications. Primary particles with average particle size distribution D50, ${\sim}6{\mu}m$ are shifted to submicron size, D50 ${\sim}0.6{\mu}m$, after grinding. Grinding of particles is characterized by various size parameters such as sphericity as geometric shape, equivalent diameter, and average particle size distribution. Herein, we systematically provide an overview of factors affecting the primary particle size reduction. Energy consumption for grinding is determined using classical grinding laws, including Rittinger's and Kick's laws. Submicron size is obtained at maximum frictional shear stress. Alterations in properties of wettability, heat resistance, thermal conductivity, and adhesion increase with increasing particle surface area. In the comparison of the aspect ratio of the submicron powder, the air heat conductivity and the total heat release amount increase 68 % and 2 times, respectively.

• Structural Engineering and Mechanics
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• 제31권6호
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• pp.679-696
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• 2009

The paper aims at analyzing the stress distribution around an underground opening that is subjected to non-symmetrical surface loading with emphasis on opening shapes with sharp corners and the stress concentrations developed at these locations. The analysis is performed utilizing the BIE method coupled with the Neumann's series. In order to implement this approach, the special recurrent relations for half plane were proven and the modified Shanks transform was incorporated to accelerate the series convergence. To demonstrate the capability of the developed approach, a horseshoe shape opening with sharp corners was investigated and the location and magnitude of the maximum hoop stress was calculated. The dependence of the maximum hoop stress location on the parameters of the surface loading (degree of asymmetry, size of loaded area) and of the opening (the opening height) was studied. It was found that the absolute magnitude of the maximum hoop stress (for all possible surface loading locations) is developed at the roof points when the opening height/width ratio is relatively large or when the pressure loading area is relatively narrow (compared to the roof arch radius), and contrarily, when the opening height/width ratio is relatively small or when the surface pressure is applied to a relatively wide area, the absolute magnitude of the maximum hoop stress is developed at the bottom sharp corner points.

• Geomechanics and Engineering
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• 제20권1호
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• pp.75-86
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• 2020

This study aims to simulate the stabilization process of fibrous peat samples using end-bearing Cement Deep Mixing (CDM) columns by three area improvement ratios of 13.1% (TS-2), 19.6% (TS-3) and 26.2% (TS-3). It also focuses on the determination of approximate stress distribution between CDM columns and untreated fibrous peat soil. First, fibrous peat samples were mechanically stabilized using CDM columns of different area improvement ratio. Further, the ultimate bearing capacity of a rectangular foundation rested on the stabilized peat was calculated in stress-controlled condition. Then, this process was simulated via a FEM-based model using Plaxis 3-D foundation and the numerical modelling results were compared with experimental findings. In the numerical modelling stage, the behaviour of fibrous peat was simulated based on hardening soil (HS) model and Mohr-Coulomb (MC) model, while embedded pile element was utilized for CDM columns. The results indicated that in case of untreated peat HS model could predict the behaviour of fibrous peat better than MC model. The comparison between experimental and numerical investigations showed that the stress distribution between soil (S) and CDM columns (C) were 81%C-19%S (TS-2), 83%C-17%S (TS-3) and 89%C-11%S (TS-4), respectively. This implies that when the area improvement ratio is increased, the share of the CDM columns from final load was increased. Finally, the calculated bearing capacity factors were compared with results on the account of empirical design methods.

• 응용통계연구
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• 제9권1호
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• pp.53-73
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• 1996

일정형 및 계단형 가속수명시험의 시험설계에 대한 일반적인 모형과 최적설계에 대한 최근의 연구결과를 소개하고, 수명분포가 와이블인 경우에 대하여 두가지 시험방법에 대한 최적설계를 점근분산의 행태, 설계변수의 효과, 최적시험조건에서 시험종결 시점까지의 기대고장개수 및 기대시험종결시간, 점근분산의 상대적효율과 설계변수의 사전추정치에 대한 둔감성의 측면에서 비교, 분석하였다.