• 한국도로학회논문집
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• 제17권1호
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• pp.105-118
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• 2015

PURPOSES : This study aims to evaluate the road safety of the super-elevation transition section of a left turn curve and suggest the minimum longitudinal grade of a super-elevation transition section to be used before and after a left curved section. METHODS : We evaluated the road condition by means of the safety-criterion-evaluation method involving side friction factors, and then solve the problem by introducing the minimum longitudinal grade criterion based on conditions described in the hydraulics literature. RESULTS : It was calculated that when a road satisfies hydroplaning conditions, the difference between side friction assumed and side friction demanded is less than -0.04. In this case, the safety criterion for the condition is unsatisfied. Conversely, when a road is in a normal state under either wet or dry conditions, it was calculated that the difference between side friction assumed and side friction demanded is more than 0.01. Thus, the safety criterion for this condition is found to be satisfied. After adjusting the minimum longitudinal grade applied to a super-elevation transition section, the hydroplaning condition can be eliminated and the safety criterion can be met for all sections. CONCLUSIONS : It is suggested that a minimum longitudinal grade should be provided on super-elevation transition sections in order to prevent hydroplaning.

• 대한토목학회논문집
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• 제38권3호
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• pp.467-475
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• 2018

지자체 도로예산 절감을 위해 소규모 지역도로의 통행환경을 고려한 소규모 지역도로 포장상태 평가 기준을 제시하고자 하였다. 지방 지자체에서 관리하는 지역도로의 경우 설계속도가 낮고 일정하지 않으며 중차량 통행량이 작아 비교적 중요도가 떨어지는 구간이다. 일반적으로 포장상태 조사에는 조사장비를 이용하나 고가의 운영비가 소요되어 소규모 지역도로 적용에는 효율성 문제가 발생한다. 본 연구에서는 소규모 지역도로에 적합한 새로운 포장상태 평가지수를 제시하였다. 소규모 지역도로의 포장상태 평가는 제시된 평가지수에 따라 3등급으로 구분하였으며, 전문가 설문조사를 통해 타당성을 검토하였다. 제시된 평가지수는 포장상태 설문조사 결과와 $R^2$가 0.88로 매우 높은 상관성이 높은 것으로 나타났다. 제한된 조건에서 육안 균열조사를 통해 산출된 포장상태평가지수는 소규모 지역도로에 활용이 가능하다. 또한 보다 경제적인 포장상태평가방법으로 지역도로 관리뿐 아니라 도로관리 예산절감에도 효과가 있을 것으로 기대된다.

• 한국도로학회논문집
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• 제13권4호
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• pp.167-175
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• 2011

효율적인 도로의 설계와 관리를 위해서는 도로건설의 경제성 분석이 중요하며 이를 위해서는 도로 상태별 차량별 유류소모량의 평가가 필요하다. 도로에서는 초기 건설비용, 유지보수비용, 차량운행비용, 지정체비용 등이 발생되는데, 도로의 경제성 분석을 위해서는 초기 건설비용, 유지보수비용 등과 같은 관리자비용과 차량운행비용, 지정체비용 등과 같은 이용자비용을 모두 포함한 사회적 비용이 고려되어야 한다. 이 중 차량운행비용은 교통량에 따라 그 비용이 변화되므로 차량운행비용 항목의 큰 부분을 차지하는 유류소모량 또한 교통량에 따라 변화하게 된다. 그런데 유류소모량은 차량의 주행속도 및 도로포장의 상태, 특히 평탄성에 따라 크게 변화되므로 도로의 경제성 분석을 위한 차량운행비용의 산정을 위해서는 주행차량에 대해 도로 상태에 따른 유류소모량을 평가하여 경제성 분석에 반영해야 할 필요가 있으나 아직 이를 고려하지 못하고 있는 상황이다. 본 연구에서는 국내에서 운행되는 승용차에 대해서 도로 상태별 유류소모량 추정모델을 개발하였다. 우선 우리나라의 교통시설 투자평가 및 도로건설의 예비타당성 조사에서 차량운행비용 산정을 위해 사용되고 있는 주행속도와 유류소모량의 관계식을 고찰하고, 승용차를 대상으로 도로포장의 평탄성에 따른 유류소모량 변화의 관계를 실제 도로에서 실측하여 평탄성과 유류소모량 변화의 관계를 분석하였다. 실험 결과, 평탄성에 따른 유류소모량의 변화는 평탄성이 1m/km 증가하였을 경우 100km 주행시 약 $80m{\ell}$ 정도의 비율로 유류소모량이 증가하는 것으로 확인되었다. 따라서 도로의 설계 및 유지관리에 있어서 보다 정확한 경제성 분석을 수행하기 위해서는 도로포장의 평탄성에 따른 유류소모량 변화를 고려해야 할 필요가 있다.

• 대한토목학회논문집
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• 제26권5D호
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• pp.813-819
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• 2006

미끄럼 저항은 타이어와 도로노면의 마찰저항을 나타내는 지수로 차량의 주행 안전성에 지대한 영향을 미친다. 타이어의 상태, 노면의 마모도, 주행속도, 노면의 건조, 습윤, 결빙 등에 따라 미끄럼저항의 크기는 달라진다. 특히 겨울철 도로노면의 경우 강설 후 기온강하에 도로포장표면이 결빙이 발생할 경우 미끄럼저항이 급격히 저하되며, 미끄럼저항을 회복하고자 제설 작업을 수행하게 된다. 제설작업 후에는 습윤상태로 노면조건이 바뀌게 되는데, 제설제가 노면에 잔류하게 되면 일반적인 습윤상태에서의 미끄럼저항을 확보치 못할 수 있다. 본 연구에서는 국내 포장도로의 대다수를 차지하는 밀입도 아스팔트와 타이닝 콘크리트 포장노면에 대하여 실험실 조건에서 노면 결빙시, 제설중 제설후 잔류물이 노면에 있을 경우의 조건에서의 미끄럼저항을 정량적으로 평가하였다. 연구 결과 노면 결빙시 미끄럼저항 회복시간은 수용액 살포방법이 고체염 살포방법 보다 빠르며 제설제 중에는 소금이 가장 빠르게 나타났다. 노면에 잔류한 제설제는 콘크리트 시편이 아스팔트 시편보다 미끄럼저항 값이 높게 나타났으며 습윤 노면 상태와 비교시 미끄럼저항 확보율은 54~80% 이다.

• 한국전산유체공학회:학술대회논문집
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• 한국전산유체공학회 2003년도 The Fifth Asian Computational Fluid Dynamics Conference
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• pp.84-85
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• 2003

A parallelized FEM code based on domain decomposition method has been recently developed for a large scale computational fluid dynamics. A 4-step splitting finite element algorithm is adopted for unsteady computation of the incompressible Navier-Stokes equation, and Smagorinsky LES(Large Eddy Simulation) model is chosen for turbulent flow computation. Both METIS and MPI library are used for domain partitioning and data communication between processors respectively. Tiburon of Hyundai-motor is chosen as the computational model at $Re=7.5{\times}10^{5}$, which is based on the car height. It is confirmed that the drag under road condition is smaller than that of wind tunnel condition.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.473-476
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• 2005

Mobility of tracked vehicles is dependent on performance of its power equipment and suspension systems. Especially, its road wheels, components of its suspension systems, play an important role in distributing the vehicle weight on the ground and preventing from misguiding tracks. In this study, the maximum force acted on multipurpose tracked vehicles driven on the worst condition was calculated. And then FE analyses were carried out to evaluate the strength of the road wheels under the maximum force condition. For quality evaluation of the road wheels, FE simulations and experimental works were carried out under specific slant loads. Residual deformation for the slant loads was investigated and commented upon.

• 한국기계가공학회지
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• 제10권3호
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• pp.47-52
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• 2011

A tracked vehicle is dependent on performance of power pack and suspension systems. Especially, road wheels which are components of suspension system contribute distributing vehicle weight on soil and preventing from misguiding tracks. In this study, the maximum force was calculated that a tracked vehicle is driven on the worst condition. And then, FE analyses were carried out to evaluate strength road wheel under maximum force condition. In standard of quality evaluation for road wheel, FE simulations and experimental works were carried out under thirty degree slant load of normal direction of shaft. And then, A relationship residual deformation for slant load was investigated. The result of this research is applicable to evaluate strength and to make use of basis data.

• 대한기계학회:학술대회논문집
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• 대한기계학회 2003년도 추계학술대회
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• pp.1127-1132
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• 2003

Suspension system of vehicle have enough endurance during its life time to protect passenger. Spring is one of major part of vehicle. Thus, a fatigue strength evaluation for leaf spring based on road load response was carried out. At first, strain of leaf spring is measured on the city condition and proving ground condition. And next, the damage analysis of road load response data was carried out. And fatigue test of leaf spring were also carried out. Based on -N life relation, fatigue life of leaf spring was evaluated at belgian mode, city mode and drawing test specification. After that, it is compared the design life of leaf spring and evaluated fatigue life by belgian mode, city mode and drawing test specification. From the above, the maximum load-fatigue life relation of leaf spring was defined by test. and new test target of belgian mode and city mode was proposed to accept design specification of leaf spring. It is expect that proposed test target can verify leaf spring fatigue endurance at specific road condition.

• 한국자동차공학회논문집
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• 제18권3호
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• pp.104-109
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• 2010

The fatality of pedestrian accounts for about 21.2% of all fatality at 2007 year in Korea. In car to pedestrian accident it is very important to inspect the throw distance of pedestrian after collision for exact reconstructing of the accident. The variables that influence on the throw distance of pedestrian can be classified into the factors of vehicle and pedestrian, and road condition. It was simulated by PC-CRASH, a kinetic analysis program for a traffic accident in sedan type vehicle and SPSS program was used for regression analysis. From the results, the throw distance of pedestrian increased with the increasing of vehicle velocity, and decreased with the increasing of impact offset. Also it decreased with the increasing of velocity of pedestrian at accident, and throw distance at the road condition of wet was longer than that at dry condition. Finally, the regression model of sedan type vehicle on the throw distance of pedestrian was as follows; $$dist_i=2.39-0.11offset_i+0.59speed_i-545height_i-0.25walk_i+2.78wet_i+{\epsilon}_i$$.

• Journal of Biosystems Engineering
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• 제35권4호
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• pp.231-238
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• 2010

The purpose of this paper was to investigate experimentally the steering torque characteristics of a tractor operated in various ground conditions. The experiments were conducted with the tractor reconstructed for steering torque test of the tractor at two different off-road conditions (ground-I and ground-II) and a on-road condition (ground-III), three different levels of tire inflation pressures (69 kPa, 138 kPa and 207 kPa), and four different levels of axle loads (4120 N, 4730 N, 5340 N and 5950 N). The results of this study are summarized as follows: 1) The steering torque was increased with the increase in steering angle for all experimental levels of ground conditions, axle loads and inflation pressures of tire. 2) As the axle load increased, the steering torque of the tractor increased for all ground conditions, and the increasing rate of the steering torque with the increase of axle load was greater at on-road than at off-road. 3) As the tire inflation pressure decreased, the steering torque increased. Also the increasing tendency of the steering torque with decreasing the tire inflation pressure showed that the harder the ground was, the larger the effect was. But for the soft ground condition, ground-I, no specific trend with inflation pressures was found. 4) Steering angle-steering torque relationship with ground conditions showed that the increasing rate of the steering torque was greater at on-road than off-road for small steering angle under 10 degree, and was greater at off-road than on-road for large steering angles over 10 degree.