• 한국도로학회지:도로
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• v.5 no.4 s.18
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• pp.36-46
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• 2003

포장구조체에서 요구되는 강도를 갖게 하는 구조 설계의 방법은 경험적 절차부터 반역학적 절차까지 발전되어 왔다. 재생 가열아스팔트혼합물이 기존의 가열아스팔트혼합물(HMA)과 비교하여 비슷하거나 때에 따라 더 좋은 성능을 가져오므로, AASHTO설계지침서에서는 본질적으로 재생(recycled) HMA 재료와 신생(virgin) HMA 재료간의 차이가 없다고 기술하고 있으며, 기존 HMA 재료에 사용되는 덧씌우기설계법의 구조회복 분석방법(structural rehabilitation analysis method)을 재생포장설계에도 권장하고 있다. 재생 가열아스팔트의 설계를 위한 AASHTO 방법은 설계교통량, 교통량 및 수행능력예측의 신뢰수준, 공용기간, 그리고 포장상태 평가지수에 의하여 결정된 포장구조체에서 요구되는 포장두께지수(SN)에 기초한다. 포장두께지수(SN)는 포장층 두께, 상대강도계수, 각 층의 배수조건들의 곱의 조합으로서 나타내어질 수 있다. 덧씌우기로 간주될 수 있는 재생된 층의 포장두께지수(SN)는 기존 포장에서의 포장두께지수와 보강된 포장에서 요구되는 포장두께지수의 차이에 의하여 계산되어질 수 있다. 상대강도계수의 값은 AASHTO 설계지침에 명시되어 있다. AI 방법은 교통량, 노상의 회복탄성계수, 그리고 설계두께를 계산하기 위한 표층과 기층의 종류를 사용한다. 이 방법은 재생된 가열혼합물질과 기존의 가열혼합물질과는 거의 비슷한 성능을 나타낸다고 본다. 또다른 AI 방법에 의하면 재생된 층은 덧씌우기층이라고 간주하고, 현재의 포장두께와 요구되어지는 포장두께 사이의 차를 이용하여 재생될 층의 두께를 산정한다. 소요되는 덧씌우기 두께는 포장의 현장 상태지수(condition rating)와 각 종류에 따른 포장체와 포장재료가 아스팔트 콘크리트층의 등가두께로 전환되어 나타나는 방법에 근거하여 결정될 수 있다. 또 다른 방법은 포장체 각 층의 물성과 하중을 이용한 컴퓨터 프로그램에 의하여 산정된 하중-변형 응답에 의한 설계 방법을 포함한다. 이런 방법들에서는 포장체는 탄성이나 점탄성층 위에서 탄성이나 점탄성 거동을 보인다고 가정한다. 재생 상온혼합물에서의 AASHTO 설계 방법은 가열혼합물의 설계방법과 유사하다. 그러나, 재생 상온혼합물에서의 상대강도계수는 시공방법에 좌우되므로, 기술자의 판단을 근거로 하여 결정되어져야 한다. AI방법에서는 포장구조체를 다층탄성구조라고 보고, 노상의 강도와 설계 교통량을 근거로 요구되는 포장두께를 결정한다. 재생 상온혼합물 기층의 두께는 재생 상온혼합물 기충 위에서 가열아스팔혼합물에 대하여 산정된 덧씌우기 두께를 이용하여 결정할 수 있다. 아스팔트 표면의 재생은 기존 포장의 구조적 능력을 정상적으로 개선할 수 없으므로, 표면 재생의 두께를 설계하는 방법은 없다. 그러나, 임의의 덧씌우기 두께는 기존의 덧씌우기 설계법에 기초하여 산정 할 수 있다. 만약 덧씌우기가 승차감만을 개선시킨다고 여겨진다면, 혼합물에서 사용되어지는 최대 골재 크기에 기초한 최소 두께를 결정할 수 있다.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2011.04a
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• pp.627-630
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• 2011

강바닥판 교면포장의 파손방지를 위하여 윤하중을 받는 강박스형 강바닥판의 변형도를 조사하였다. 이를 위하여 강바닥판과 거더는 쉘요소, 포장은 고체요소로 각각 모델링하고 정밀유한요소해석을 수행하였다. 탄성비, 포장의 두께, 그리고 방수층의 두께 및 물성치 변화에 따른 교면 포장된 강바닥판의 계면, 포장상면 그리고 포장 두께에서의 교축, 교직 그리고 중력방향에 대한 변형도를 측정하였다. 그 결과 방수층의 두께 및 물성치의 변화에 대해 강바닥판과 포장은 거의 영향을 받지 않았고, 대체적으로 포장의 두께가 강바닥판과 포장사이의 탄성비보다 포장의 변형에 더 기인하는 것으로 나타났다.

• International Journal of Highway Engineering
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• v.7 no.2 s.24
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• pp.23-31
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• 2005

This study is a part of research for developing the technologies of long life pavements having more than 40-year design life. The objective of this study is to develop the simplified design procedure for determining the layer thickness and modulus of the long life pavement. A synthetic database was established using the finite element program of a pavement structure with various combinations of layer thickness and modulus. The synthetic database includes the structural and material information, surface deflection, and critical pavement responses. Using the developed synthetic database, this paper suggests the minimum layer thickness and modulus for long life pavements bared on the limited strain level concept. Results demonstrate that the pavement greater than 410mm of total AC layer thickness is considered as the long life pavements regardless of the material characteristics and thickness in each layer. To become a long life pavement, a total thickness of AC layer should be greater than 250mm. The design procedure for determining the layer thickness and modulus of the pavements with AC layer thickness ranging from 250 to 410mm is also presented in this paper.

• International Journal of Highway Engineering
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• v.9 no.2 s.32
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• pp.141-151
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• 2007

The current standards and specifications for the road pavement construction have been developed based on materials and construction methods. The pavements constructed in accordance with those specifications do not guarantee high performance of pavements since they do not consider long-term performance of pavements. Therefore, as part of the study to develop performance-based construction standards for pavements, the payment adjustment methods based on the pavement performance are currently being developed. This paper presents preliminary studies performed to develop the payment adjustment methods when there is deficiency in the concrete slab thickness that is one oi the most important factors for the pavement design and construction. First, the payment adjustment methods in USA were investigated. Then, the AASHTO failure equation, the relationship between slab thickness and stress, and the relationship between stress level and pavement life were employed to propose the payment adjustment concepts based on the pavement performance for the deficient slab thickness. The variation in the slab thickness according to measurement locations was investigated by taking cores. In addition, the measurement methods of slab thickness and the variation of measured thicknesses depending on performers were analyzed, and finally the methodology to develop the thickness deficiency ranges for the use in the payment adjustment methods was proposed.

• 한국방재학회:학술대회논문집
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• 2010.02a
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• pp.47.2-47.2
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• 2010

빗물을 노상 침투시키는 투수성포장은 물순환 보전과 차량 주행 안전성 확보와 같은 효과를 기대할 수 있다. 지금까지 보도나 주차장 같이 비교적 교통조건이 열악하지 않은 구간에 적용되고 있지만 우수 침투로 인해 노상이 연약화 될 것을 우려하여 현재까지 차도에 적용하지 못하고 있으며 설계 방법 또한 정립되어 있지 못한 실정이다. 본 연구에서는 투수성포장의 포장단면을 설계하기 위한 방안으로 단지내 포장을 투수성포장으로 설계할 경 물의 침투로 인해 노상의 지지력이 약화 된다고 가정하고 노상 지지력의 약화에 따른 포장층의 역학적 거동 특성을 유한요소 해석을 통하여 분석하여 구조적 안정성을 확보할 수 있는 포장두께를 분석하였다. 또한 설계 개념에서 노상의 지지력 저하에 따른 포장두께의 할증방안과 할증두께를 분석하였다.

• International Journal of Highway Engineering
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• v.10 no.1
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• pp.11-18
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• 2008

The behavior of pavement and waterproofing layer on the steel bridge deck system under traffic loading was analyzed using a finite element method in this paper. In the finite element analysis, the othotropic steel bridge deck is represented by equivalent plate using solid element instead of shell element and the interface is assumed perfect bonding state. The effects of several parameters such as thickness of deck, Young's modulus of deck, thickness of pavement, different braking loading, and temperature on the stresses and strain in the interface are investigated for bridge deck pavement. The shear stress of waterproof layer increases with decrease of bridge deck thickness and stiffness. The change of shear stress is negligible when the bridge deck thictaess is greater than 150mm and stiffness is greater than $2{\times}10^{5}MPa$. As the pavement thickness and temperature decrease, the shear stress in the waterproof layer tends to be increased. The tensile strain at the bottom asphalt layer decreases as the temperature and thickness increase.

• Food Science and Preservation
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• v.9 no.2
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• pp.148-153
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• 2002

Effect of the thickness of low density polyethylene(LDPE) Film as packaging material on changes in physicochemical characteristics of mature-green mume (Prunus mume Sieb. et Zucc) fruits during storage at different temperatures(0, 10 and 25$\^{C}$) were investigated. Fruit samples stored in pouches with 30㎛ thickness of LDPE film maintained well not only external qualities such as Shape and firmness, but also internal chemical properties such as pH, acidity, the content of soluble solid and chlorophyll, and color, comparing with samples stored without packaging material or in other pouches with different film thickness(20 and 40㎛). From the results, it was found that the maintenance of quality of mature-green mume fruits during storage at 0, 10 and 25$\^{C}$ closely related to the changes in respiratory conditions for fruits affected by the film thickness of the packaging material.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.36 no.6
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• pp.1109-1116
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• 2016

There are various test methods for evaluating the reflective cracking resistance of asphalt concrete pavement. Repeated direct tensile test is cheap and simple compared to the other traditional experimental methods. Determination of failure criteria is needed to apply a repeated direct tensile test. Various methods were used to determine the number of failure of repeated direct tensile test. The number of failure was defined as the time to reach 10% of the initial load, this method can be satisfied with specified tolerance of 10%. When the thickness of specimen is increased to 50 mm from 30 mm, the failure number is increased by 13.6 times. Thus, this result shows that the thickness of pavement is a big influence on the reflective cracking resistance. Reflective cracking resistance of asphalt concrete is decreased according to the increase in opening displacement. The repeated direct tensile test can be used as a reflective cracking resistance factor in pavement design, because it can evaluate the reflective cracking resistance according to the pavement thickness, opening displacement, material properties etc.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.3
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• pp.2229-2233
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• 2015

The permeability of HMA(hot mixed asphalt) is a major influencing factor for long-term performance of the pavement. Especially, the lift thickness of the pavement during construction causes a wide range of physical properties of HMA. This study investigates the correlationship between the lift thickness and the physical properties of HMA through a series of laboratory experiments. The specimens were cored from a construction site of the dense graded asphalt pavement. The cored samples have various lift thickness and the number of compaction for the study. The results of the study show that the permeability of the sample decreases with the apperant density and t/NMAS, and the air void ratio. Therefore, the commonly used construction method as a constant lift thickness regardless of conditions needs to be reconsidered.

• International Journal of Highway Engineering
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• v.1 no.2
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• pp.155-168
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• 1999

Asphalt pavement tends to rut in high temperature and to crack in cold temperature. The performance of asphalt pavement can be deteriorated by korean weather condition which has the four distinct seasons. In this study, the typical sections that may minimize rutting and fatigue were analyzed through the numerical model tests. The layered elastic theory , finite element method and visco elastic theory were utilized for these numerical model tests. From the various numerical model tests, it is found that an optimum design procedure was recommended. It was increasing the thickness of asphalt stabilized base with fixing the wearing course as 5cm the minimum specified thickness. The section was most beneficial in resting rutting and fatigue. From the analysis of the relative index on tensile strain and cost analysis, it was recommended that the thickness ratio of subbase and asphalt concrete is 1.0$\sim$2.5.