이송 아스팔트 혼합물의 냉각 특성 기초 평가

윤태영 한국도로학회 2021 한국도로학회논문집 Vol.23 No.1

PURPOSES : The cooling characteristics of the asphalt mixture in a moving dump truck were analyzed using a numerical simulation method. The cooling characteristic can be used to determine the optimum transport path for minimizing the temperature drop of the asphalt mixture. METHODS : In this research, a coupled analysis of the discrete element method (DEM) with computational fluid dynamics (CFD) was applied for cooling characteristic analysis of asphalt mixtures in transit. Two different transit speeds, 30 km/h and 60 km/h, were considered to evaluate the effect of speed on the temperature drop of the asphalt mixture. Velocity, pressure, and temperature contours were plotted and temperature variations were compared. RESULTS : Most of the temperature drops in the asphalt mixture were observed in the middle of the dump box in the longitudinal direction. It was confirmed that a faster speed causes a greater temperature drop for the same travel time and a slower speed causes the more temperature to reach the same travel distance as expected. CONCLUSIONS : It is concluded that the coupled analysis method can be used to quantitatively evaluate the effect of vehicle speed on temperature drop in asphalt mixtures. In addition, the method can be used to determine the optimum travel path considering environmental conditions and traffic congestion.

골재배합설계법 개발을 위한 다짐밀도모형의 특성평가

윤태영,전성일,남정희,유평준 한국도로학회 2013 한국도로학회 학술대회 발표논문 초록집 Vol.2013 No.09

골재의 다짐모형(Packing Density Model)은 다양한 최적다짐밀도를 통하여 혼합물 내에서 골재의 역 할을 최대화하거나 다른 고가의 재료를 절감하기 위하여 다양한 건설분야에서 연구되고 있다. 다짐밀도모형은 1929년에 Furnas에 의하여 제시된 단순한 모형으로부터, Aim and Goff 모형, Toufar 모형, Linear Packing Density 모형 등 다양한 연구자들에 의하여 그 형태가 제시되고 발전되어 왔으나, 기본 적으로 굵은골재에 잔골재가 포함되는 경우와 잔골재에 굵은골재가 포함되는 경우로 단순화될 수 있으며, 모형의 정밀도를 향상시키거나 물리적 현상을 반영하기 위한 함수 또는 계수의 조합으로 보완되는 것이 일반적이다. 본 연구에서는 다양한 다짐밀도모형을 고찰하여 잔골재와 굵은골재의 부피비에 따른 다짐밀도예측결과 를 평가하였으며, 향후 이산요소법(Discrete Element Method, DEM)을 이용하여 개발될 골재배합설계법에 필요한 변수를 고려한 모형의 형태를 제시하였다. 다짐밀도모형의 재해석을 통하여 확인된 다짐밀도 모형의 주요변수는 개별 골재의 단위중량, 지름 및 개별골재더미의 다짐밀도이며, 다짐의 최적화를 저해하는 Wall Effect와 Loosening Effect를 고려하기 위하여 통계적함수를 적용하거나 다짐에너지를 고려 하기 위한 변수도 조건에 따라 적용될 수 있음을 확인하였다. 또한 대부분의 이론적 다짐밀도모형에서 개별 골재더미의 다짐밀도는 골재 혼합물의 다짐밀도에 큰 영향을 미치는 변수이지만, 그 영향이 작지 않을 것으로 예측되는 개별골재더미 사이의 물리적 상호작용은 대부분의 기존다짐밀도모형에 고려되어 있지 못한 것으로 확인되었다. 이상의 기존 수학적 다짐모형의 검토를 통하여 DEM을 활용하여 개발될 다짐밀도예측모형의 형태를 제안하였다.

DEM을 이용한 굵은골재의 형상적 특성 정량화

윤태영,유평준,김연복 한국도로학회 2013 한국도로학회 학술대회 발표논문 초록집 Vol.2013 No.09

굵은골재의 입자 특성은 골재혼합물의 다짐도, 아스팔트 콘크리트 또는 시멘트 콘크리트 혼합물의 역 학적 특성에 큰 영향을 미치는 중요한 인자이다. 도로포장 재료로서 골재의 특성을 최대한 활용하기 위한 골재의 최적배합설계를 결정하기 위해서는 다양한 골재의 단위중량, 크기뿐만 아니라 역학적으로 설명될 수 있는 형상적 특성이 정량화할 필요가 있는데, 이를 위하여 사용되는 다짐밀도실험은 많은양의 실내실험을 요구하는 단점이 있다. 이산요소법 또는 개별요소법(Discrete Element Method, DEM)은 유한요소법(Finite Element Mehtod, FEM)과는 달리 이산되어 있는 재료의 거동을 수치적인 방법으로 모사할 수 있는 장점이 있으며, 이를 활용한 연구가 다양한 분야에서 이루어지고 있다. 그러나 아스팔트 혼합물에 관련된 분야에서는 골재자체의 특성이나 다짐밀도를 분석하기 위한 연구보다는 혼합물의 피로특성을 분 석하는 연구를 중심으로 이루어져 골재다짐에 관련된 연구는 많이 진행되지 못하였다. 본 연구에서는 골재의 형상적 특성을 반영한 역학적 물성을 정량화하고자 이미지 분석(Image Analysis)결과, 골재자체의 단위중량 및 무게 등의 기초물성 실험결과, 상용 DEM 소프트웨어, 문헌에서 확인된 역학적 인자 및 등가구형지름(Equivalent Sphere Diamter) 개념을 이용하여 골재슬럼프 실험에 서의 골재의 거동을 시뮬레이션하였으며, 높이 및 퍼진 골재의 지름을 기준으로 시뮬레이션 실험과 실제 실험결과와 유사한 것을 확인하였다. 본 연구의 결과는 x-ray CT 등을 이용한 향후 3D 골재형상 이미지 또는 혼합물 속의 골재의 분포 등을 이용한 골재다짐밀도 모형과 Flow Modeling Software 등과의 coupling을 통하여 시멘트 콘크리트의 배합설계법개발에 적용되기 위하여 지속적으로 수행될 예정이다.

키코판결과 설명의무

윤태영 한국민사법학회 2014 民事法學 Vol.66 No.-

'스콜라' 이용 시 소속기관이 구독 중이 아닌 경우, 오후 4시부터 익일 오전 9시까지 원문보기가 가능합니다.

The duty of explanation between contracting parties has been accepted in the academic circles in order to guarantee actual liberty of contract, although the Korean Civil Code does not have statutes that govern it. Nevertheless, there is few work providing an implication for defining the extent to which a duty of explanation can be applied. This shows how it is hard to find characteristics and circumstances of each individual contract cases that affect a scope of the explanation duty. As decided by the Korean Supreme Courts in November 2013, The KIKO(Knock-in Knock-out) case can be exemplified to shed light on definition of the explanation duty. KIKO’s contracts are the currency options designed to help companies hedge exchange rate risk associated with the appreciation of the Korean Won beginning in the middle of the 2000's. However, when the Korean Won depreciated precipitously against the dollar during the global financial crisis in 2008, companies that have signed the KIKO’s contracts filed lawsuits against the banks, claiming that the KIKO’s contracts are invalidated. In these cases, the duty of explanation was a big issue which involves difficult problems. For example, the issue about why business operators rather than consumers should be subject to explanation, and to what range should the bank explain about financial instrument. This study attempts to set a specific standard of explanation duty with recent four KIKO’s cases of the Korean Supreme Court. The Supreme Court recognized that the banks have high explanation obligation about KIKO because of complicated OTC derivative. According to the Supreme Court's decision, there is a finding that the plaintiff companies negotiated proper contract prices, had experience in forward exchange and foreign exchange risk insurance, and were actively involved in the negotiation of the execution time and contract terms with the banks; in this sense, thus, the banks did not violate the suitability rule or its explanation obligation. However, the question arises as to why the Supreme Court did not judge whether the banks explain the imbalanced risk of foreign exchange reserves and put-option or not. A financial instrument seller should not only provide information for the buyer, but also explain important factors on the risk in buyer’s view; and a key of explanation obligation in KIKO cases is the imbalanced risk of foreign exchange reserves between put-option.

아스팔트 혼합물 실린더 시편을 이용한 열역학적 이론의 적용 및 검증

윤태영,유평준 한국도로학회 2014 한국도로학회논문집 Vol.16 No.4

PURPOSES: Evaluation of thermal conductivity and convection properties of asphalt mixture by using thermodynamics. METHODS: In this research, temperature prediction model based on thermodynamics is derived for asphalt mixture in transient state and itis verified with laboratory test results. RESULTS: The derived temperature prediction model shows good agreement with laboratory test results. CONCLUSIONS: It is concluded that the derived model based on thermodynamics and thermal properties in the literature are good enoughto capture temperature variation in laboratory test. The approach based on thermodynamics can be applied to more complex temperaturesimulations.

풍속에 따른 포설 아스팔트 혼합물의 온도변화에 대한 열전달 해석

윤태영,유평준 한국도로학회 2015 한국도로학회논문집 Vol.17 No.4

PURPOSES: Evaluation of the wind speed effect on the temperature drop of an asphalt mixture during construction, by using the transient heat transfer theory and dominant convective heat transfer coefficient model. METHODS: Finite difference method (FDM) is used to solve the transient heat transfer difference equation numerically for various wind speeds and initial temperature conditions. The Blasius convective heat transfer coefficient model is adapted to account for the effect of wind speed in the temperature predictions of the asphalt mixture, and the Beaufort number is used to select a reasonable wind speed for the analysis. As a function of time and depth, the temperature of the pavement structure is predicted and analyzed for the given initial conditions. RESULTS : The effect of wind speed on the temperature drop of asphalt mixture is found to be significant. It seems that wind speed is another parameter to be accounted for in the construction specifications for obtaining a better quality of the asphalt mixture. CONCLUSIONS: It is concluded that wind speed has a significant effect on the temperature drop of the asphalt layer. Although additional field observations have to be made to reflect the effect of wind speed on the construction specifications, it appears that wind speed is a dominant variable to be considered, in addition to the atmospheric temperature.

등가 구형입자를 이용한 DEM에서의 골재 슬럼프 실험 모사

윤태영,안상혁,남정희,유평준 한국도로학회 2013 한국도로학회논문집 Vol.15 No.5

PURPOSES: Simulation of aggregate slump test using equivalent sphere particle in DEM and its validity evaluation against lab aggregate slump test METHODS : In this research, aggregate slump tests are performed and compared with DEM simulation. To utilize spheric particles in YADE, equivalent sphere diameter concept is applied. As verification measures, the volume in slump cone filled with aggregate is used and it is compared with volume in slump cone filled with equivalent sphere particle. Slump height and diameter are also used to evaluate the suggested numerical method with equivalent concept RESULTS : Simulation test results show good agrement with lab test results in terms of loose packing volume, height and diameter of slumped particle clump. CONCLUSIONS : It is concluded that numerical simulation using DEM is applicable to evaluate the effect of aggregate morphological property in loose packing and optimum gradation determination based on the aggregate slump test simulation result.

DEM을 이용한 골재다짐모형 개발을 위한 기존 모형 분석

윤태영,김기현,유평준,김연복 한국도로학회 2013 한국도로학회논문집 Vol.15 No.5

PURPOSES: Determination of particle packing model variables that can be used for formulation of new DEM based particle packing model by examining existing particle packing models METHODS: Existing particle packing models are thoroughly examined by analytical reformulation and sensitivity analysis in order to set up DEM based new particle packing model and to determine its variables. All model equations considered in this examination are represented with consistent expressions and are compared to each others to find mathematical and conceptual similarity in expressions. RESULTS: From the examination of existing models, it is observed that the models are very similar in their shapes although the derivation of the models may be different. As well, it is observed that variables used in some existing models are comprehensive enough to estimate particle packing but not applicable to DEM simulation. CONCLUSIONS: A set of variables that can be used in DEM based particle packing model is determined

MSCR을 포함한 PG 실험법을 이용한 고분자 개질 바인더의 성능평가

윤태영,엄병식,유평준 한국도로학회 2012 한국도로학회논문집 Vol.14 No.5

PURPOSES : SUPERPAVE binder grade tests including Multiple Stress Creep and Recovery(MSCR) test are applied to evaluate rheological properties of four polymer modified binders. METHODS: To evaluate grade of four modified binders, PG testing protocols, such as DSR, BBR and MSCR are employed. RESULTS : It is observed that MSCR test shows different performance grades especially on modified binders. Both DMP and EG binder show similar high temperature performance to SBS 5% modified binder. CONCLUSIONS : Binder Grading system in Korea need to be reviewed to properly reflect the performnace of modified binders. The binders modified with DMP and EG can be possible alternatives SBS 5% modified binder considering its performance and cost.

동전단 마스터곡선을 이용한 아스팔트 바인더의 노화 특성 평가

윤태영,함상민,유평준 한국도로학회 2013 한국도로학회논문집 Vol.15 No.1

PURPOSES: To characterize the aging effect on asphalt binder, dynamic shear modulus mastercurve of two typical asphalt binders are developed. METHODS: To develop dynamic shear modulus mastercurve, dynamic shear modulus at high temperature and creep stiffness at low temperature are measured by temperature sweep test and bending beam rheometer test, respectively. RESULTS: It is observed that the aging effect on asphalt binder can be clearly observed from dynamic shear modulus mastercurve and the mastercurve can be utilized to predict behavior of asphalt binder at wide range of temperature CONCLUSIONS: It is confirmed that SBS 5% modified binder has more desirable mechanical property at low and high temperature as a pavement material comparing to PG64-22 binder and the mastercurve is an effective tool to evaluate the property of asphalt binder.