콘크리트 슬래브 상하부간 부등건조수축 예측모델 개발

최기효,임진선,남영국,김연복,정진훈 한국도로학회 2008 한국도로학회 학술대회 발표논문 초록집 Vol.2008 No.10

재령초기 콘크리트포장 줄눈거동에 미치는 온도의 영향

최기효,정진훈,천성한,박문길,Choi. Ki-Hyo,Jeong. Jin-Hoon,Chun. Sung-Han,Park. Moon-Gil 한국방재학회 2007 한국방재학회 학술발표대회논문집 Vol.2007 No.1

The temperature variation of concrete pavement at early-age significantly affects the initiation and movement of joint cracks. For this analysis, we have built on IIA(Incheon International Airport) concrete pavement construction zone, and we measured the temperature and movement of the concrete slabs by using thermocouples, moisture sensors, V/W strain gages, and Demac discs. The analysis results showed that pavement`s temperature significantly affected the joint movement. The widths of the joint cracks increased at evening and early in the morning when the temperature dropped but, those decreased in the day time when the temperature rose because of the effect of thermal expansion of the concrete slabs. The movements of the joints where the cracks never developed showed opposite trend to the cracked joints. 콘크리트포장의 줄눈의 초기균열발생과 움직임에 영향을 주는 중요한 인자는 콘크리트 내부의 초기온도이므로 이를 측정하고 분석하는 것은 매우 중요하다. 이를 연구하기 위해 인천국제공항 포장공사 지역에 써머커플과 습도센서, 진동형스트레인게이지, 디멕디스크 등을 설치하였다. 초기균열 거동은 디멕게이지를 이용하여 측정하였고, 초기균열 및 줄눈분 균열은 육안으로 확인 하였다. 분석결과, 콘크리트포장의 온도는 줄눈거동에 크게 영향을 주는 것으로 나타났다. 줄눈에 발생한 균열의 폭은 콘크리트슬래브의 열팽창의 영향으로 온도가 하강하는 야간이나 새벽에 증가하고, 온도가 상승하는 주간에는 줄어드는 것을 확인할 수 있었다. 균열이 발생하지 않은 줄눈의 거동은 이와는 반대의 경향을 나타내었다.

고속도로 콘크리트 포장의 균열율 변화량 예측모형 개발

최기효,이상직,김하영,김동혁,문기훈,정진훈 한국도로학회 2020 한국도로학회 학술대회 발표논문 초록집 Vol.2020 No.09

콘크리트 포장 슬래브 부등 건조수축 등가 온도차이의 모형화

임진선,최기효,이창준,정진훈 한국도로학회 2009 한국도로학회논문집 Vol.11 No.4

Torsional behavior of concrete pavement slabs due to temperature and moisture effects is constrained by self weight and friction etc, and causes stress as the result. The stress due to humidity variation in the slab is difficult to calculate while that due to temperature variation can easily be calculated by a commercial structural analysis program. Thus, the slab behavior can be predicted more accurately if the humidity effect is converted to equivalent temperature and is used as an input of structural analysis. In this study, a concrete pavement slab was constructed and strains of the slab due to environmental loadings were measured for long-term period. Thermal strains were subtracted from the measured strains by using thermal expansion coefficient of the concrete measured in a laboratory. Shrinkage strains, the remained strains, was supposed as additional thermal strains to calculate imaginary temperature with equivalent effect of the shrinkage by dividing the shrinkage with the thermal expansion coefficient. An existing shrinkage model was modified by considering the self weight and friction to be used in another model which can convert differential shrinkage between top and bottom of the slab to equivalent temperature difference. Addition research efforts on tensile stress reduction according to steady increase in the compressive strains are warranted for more accurate stress calculation. 온도 및 수분의 영향에 의하여 발생한 콘크리트 포장 슬래브의 컬링(curling)과 와핑(wraping)의 비틀림 거동은 자중이나 마찰력 등에 의하여 구속되며 이로 인하여 응력이 발생된다. 슬래브 내부의 온도 변화에 의해 발생한 응력은 상용 구조해석 프로그램으로 쉽게 계산할 수 있지만 습도 차이에 의하여 발생되는 응력은 기존 프로그램으로는 계산하기 어렵다. 따라서, 슬래브의 거동에 미친 습도의 영향이 등가의 온도로 환산되어 구조해석에 입력값으로 사용된다면 보다 정확하게 환경하중에 의한 슬래브의 거동을 예측할 수 있을 것이다. 본 연구에서는 콘크리트 슬래브를 현장에 시공하여 환경하중에 의해 발생된 변형률을 장기적으로 측정하였으며 실내에서 측정된 콘크리트 시편의 열팽창 계수를 사용하여 열변형률을 추출하였다. 나머지 변형률인 건조수축변형률을 추가적인 열변형률이라고 가정하고 이를 열팽창 계수로 나누어 줌으로써 건조수축과 등가의 영향을 갖는 가상의 온도가 계산되었다. 자중이나 마찰력 등이 고려되도록 기존 건조수축 모형을 수정하였으며, 이를 이용하여 슬래브 상부와 하부 상이에 발생한 건조수축의 차이를 등가의 온도차이로 환산할 수 있는 모형을 개발하였다. 보다 정확한 응력계산을 위하여 압축 변형률의 지속적 증가에 따른 인장응력 감소에 관한 추가적인 연구가 이어질 것이다.

RMIc-3.0 Program Development to Prioritize Concrete Pavement Sections for Large-scale Repair Works

김동혁,최기효,문기훈,정진훈 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.7

Large-scale repair works (LSRW) are expensive and time-consuming, and therefore cannot becarried out simultaneously for all deteriorated pavements; hence, they are performed basedon urgency. In Korea, the re-modeling index (RMI) program versions 1.0 and 2.0 weredeveloped to predict the urgency of the LSRW on expressway concrete pavements. In thisstudy, version 3.0 of the RMI program was developed to address the drawbacks found inversion 2.0 of the program. The model used in the program was improved by using theequivalent single-axle load instead of the annual average daily traffic used in the previousversion, to consider the damage to pavement caused by heavy vehicles. In addition, anothermodel was modified by combining the winter climate conditions with the annual deicing saltusage, which was used as the only variable considering the environmental factors in theprevious version. The international roughness index and surface distress prediction models,which were not separated by pavement type in version 2.0 of the program, were separatedinto jointed concrete pavement and continuously reinforced concrete pavement. The logic forpredicting future RMI was also reasonably improved. In addition, the logic of categorizing theentire expressway concrete pavement section into homogeneous sections was objectivelyimproved for more effective LSRW. Consequently, for 2023, the Korea Expressway Corporationselected for LSRW those homogeneous sections that were evaluated as urgent by the RMI3.0program.

고속도로 콘크리트 포장 리모델링 구간 우선순위 결정방법 개발

김동혁,김하영,최기효,문기훈,정진훈 한국도로학회 2021 한국도로학회 학술대회 발표논문 초록집 Vol.2021 No.03

대규모 보수공사를 위한 고속도로 아스팔트 포장의 대표구간 선정

김하영,김동혁,최기효,정진훈 한국도로학회 2021 한국도로학회논문집 Vol.23 No.1

PURPOSES : The type and degree of structural conditions and influencing factors distributed across representative sections should be similar to those distributed across entire sections as the representative sections have been predominantly used for developing performance prediction models, which substitute entire sections of road pavement. Therefore, a logic that selects the representative sections with similar distributions of structural conditions and the influencing factors with those of entire expressway asphalt pavement sections requires development. METHODS : The logic developed in this study to select the representative sections of asphalt pavements comprised three steps. First, the data on the structural conditions of the pavement and the influencing climate conditions and pavement materials were collected and organized. Consequently, in the second step, the candidate sections were selected, with the severity of the structural conditions of the pavement distributed widely and evenly. Finally, in addition to the widely and evenly distributed pavement conditions, the representative sections with climatic conditions and pavement materials were selected. RESULTS : A total of 6,352 ordinary asphalt pavement sections and 596 composite asphalt pavement sections were selected as entire expressway asphalt pavement sections and the data were collected and organized according to the logic developed in this study. Three times the representation sections were selected as candidate sections and, finally, 85 sections were selected as representative sections. The distribution of structural conditions and influencing climate conditions and pavement materials in the representative sections were similar to those in the entire sections. In addition, the representative sections were spread evenly across the country. CONCLUSIONS : The sections presenting similar distributions of structural conditions and the influencing factors of entire expressway asphalt pavement sections could be selected in this study. Using the representative sections selected in this study, a remodeling index model will be developed for predicting the asphalt pavement sections that require large-scale repair.

유한요소해석을 통한 접착식 콘크리트 덧씌우기 포장의 거동분석

서진석,박해원,마경훈,김하영,최기효,정진훈 한국도로학회 2019 한국도로학회 학술대회 발표논문 초록집 Vol.2019 No.09

Application of Environmental Loading in Mechanistic Design of Airport Concrete Pavements

서진석,박해원,유주호,최민규,최기효,정진훈 한국도로학회 2019 한국도로학회논문집 Vol.21 No.6

PURPOSES : Almost every design method for airport concrete pavements considers only traffic loading and not environmental loading. This study proposes a mechanistic design method for airport concrete pavements, that considers both environmental and traffic loading simultaneously. METHODS: First, the environmental loading of concrete pavements in Korean airports was quantified. FEAFAA, a finite element analysis program for airport pavements, was used to calculate the maximum tensile stress (MTS) of the slab, caused by both environmental and traffic loadings. The factors that influence the MTS were identified via sensitivity analysis, and an MTS prediction model was developed using the statistical analysis program SPSS. The ratio of MTS to the tensile strength of slab was calculated using the prediction model. The fatigue model under the AC 150/5320-6E and AC 150/5320-6F standards of the FAA was corrected to make it suitable for the predicted stress-strength ratio. RESULTS : The MTS prediction model and corrected fatigue model were used to redesign the slab thickness and joint spacing of airport concrete pavements originally designed using the AC 150/5320-6D standard, which empirically considers traffic loading only. As a result, different slab thicknesses and joint spacings were redesigned with consideration for environmental loading, specifically the weather conditions of airports. . CONCLUSIONS: The slab thickness and joint spacing can be mechanistically designed at the same time, whereas previously, only the slab thickness was designed, and the joint spacing was determined empirically.

줄눈균열 유도장치를 사용한 콘크리트 포장의 줄눈거동

박문길(Park Moon Gil),최기효(Choi Ki Hyo),남영국(Nam Young Kug),정진훈(Jeong Jin Hoon) 대한토목학회 2008 대한토목학회논문집 D Vol.28 No.1D

콘크리트 포장의 줄눈은 초기 콘크리트 슬래브에 건조수축과 온도변화에 의한 무작위 균열이 발생하지 않도록 해주어 도로포장의 공용성 향상에 기여한다. 하지만 콘크리트가 충분히 양생되기 전에 수행된 줄눈 절단 작업은 줄눈 주변의 콘크리트에는 미세균열 등의 손상을 발생시키고 이로 인하여 반복적인 교통 및 환경하중에 의한 줄눈부의 파손이 장기적으로 발생한다. 본 연구에서는 이러한 인위적인 줄눈 절단작업 때문에 발생할 수 있는 줄눈부 파손을 감소시키기 위하여 선행연구를 통해 개발된 100㎜, 150㎜, 220㎜ 높이의 줄눈균열 유도장치와 다양한 깊이를 갖는 균열유도 홈을 시험시공 구간에 설치하고 줄눈균열의 발생과 거동을 약 5개월에 걸쳐 조사하였다. 그 결과, 줄눈균열 유도장치의 높이가 높을수록 균열유도 효과가 높은 반면 줄눈균열의 거동은 큰 것으로 나타났다. 향후 추가적인 조사와 줄눈균열 유도장치의 개선을 통하여 균열 유도 효율을 높이고 줄눈의 성능을 향상시켜야 할 것으로 판단되었다. Joint of concrete pavement contributes to improvement of pavement performance by preventing occurrence of random cracking due to drying shrinkage and temperature changes of concrete slabs at early age. However, saw-cutting operations performed prior to sufficient concrete hardening develop micro-cracking of the concrete near the joints, which may develop to long-term distresses due to repetitious traffic and environmental loadings. To reduce the distresses, the joint crack inducers with heights of 100 ㎜, 150 ㎜, and 220 ㎜ and the joint cracking slots with various depth were installed at a test section to investigate occurrence of the joint cracks and their behaviors over 5 months. As the results, higher efficiency of the crack inducing and larger behavior of the joint cracks were observed for the taller joint crack inducer. Higher efficiency of the crack inducing and improvement of the joint performance are warranted by additional investigation and reformation of the joint crack inducer.