국내 도로 포장설계법인 KPRP와 미국의 포장설계법인 AASHTOWare Pavement·TxCRCP-ME를 CRCP에 대해서 비교해보았다. CRCP 는 강성포장 중 하나로 줄눈이 없고 콘크리트 슬래브 내에 종방향 연속 철근을 삽입한 것이 특징이다. 줄눈부가 없으므로 줄눈부에서 발생하는 파손과 균열이 없어 주행성이 좋고 공용성이 우수하다. 또한 수명이 길어 장수명 포장에 적합하다. 이러한 특징으로, 국내 CRCP의 수요가 증가할 것으로 예상되어 CRCP를 기준으로 비교해보았다. 국내 포장설계법 개발 이전 AASHTO 설계법을 사용해왔지만, 여러 문제점과 한계가 존재하여 국내 실정에 맞는 포장설계법의 개발 이 필요해졌고, 결과적으로 오랜 연구 끝에 2011년 KPRP가 개발되었다. 이후 꾸준히 업데이트를 통해서 현재는 2016년 버전의 KPRP 를 사용하고 있다. 미국에서는 텍사스주의 TxCRCP-ME와 같이 주마다 각기 다른 포장설계법도 있지만, 보편적으로 AASHTOWare Pavement를 사용하여 역학적-경험적 설계를 하고 있다. 분석결과, 공용성 해석 결과 지표의 차이가 가장 컸으며, 이 외에도 피로하중 허용반복횟수, PunchOut 전이함수도 계산 방법과 로직의 계수가 조금씩 달랐다.

PURPOSES : This study was conducted to investigate the stress distribution and resulting effects in the joint between CRCP and JCP when temperature deformation occurs. METHODS : The tie bars, CRCP and JCP pavements, and lean concrete base were created as three-dimensional finite element models using ABAQUS, a general-purpose finite element analysis program. Contact stress analysis was performed between rebar and JCP and between JCP and lean concrete base layer. In the section where stress concentration occurred, the degree of damage was estimated using the CDP model. RESULTS : Since the domestic CRCP does not have a separation layer between the base layer and the surface layer, it was found that when connected to a JCP where the base layer and the surface layer are completely separated, stress concentration occurs around the tie bar at the connection point. Analysis results using the CDP model showed that 25 to 32 mm around the reinforcing bar exceeded the elastic range of concrete. CONCLUSIONS : At the point where CRCP and JCP are connected, local stress concentration is inevitable because the friction and bonding conditions with the base layer and the degree of curling deformation restraint by CRCP rebars are different, and design improvement is expected through life cycle cost and long-term measurement analysis.

PURPOSES : In this study, the initial behaviors of shoulder concrete slabs and tiebars at the longitudinal construction joints between the shoulder JCP and mainline CRCP are investigated. METHODS : The strains of concrete and tiebars were measured at the longitudinal construction joint between the CRCP and JCP. Measurements were performed using data accumulated over a month after concrete placement. The contact conditions were investigated by comparing the strains at each location. RESULTS : The longitudinal construction joints between the shoulder JCP and mainline CRCP exhibited the composite behavior of bonding and friction, and a virtual neutral axis was formed inside the JCP. At the connection of the shoulder concrete, the strain and temperature of the concrete were inversely proportional. The tiebars connecting the CRCP and JCP exhibited different behaviors depending on the bonding conditions around the tiebars of the construction joints. In the presumed state in which the bonding condition was maintained, the concrete temperature and tiebar strain were directly proportional; however, the presumed state of the separation condition exhibited an inversely proportional relationship. In the 24-h behaviors of the tiebars, the effects of the horizontal and curling movements overlapped, and the strains of the measured tiebars increased at the minimum and maximum temperatures of the shoulder JCP. CONCLUSIONS : The strains in the tiebars and concrete slabs primarily depended on the boundary conditions (bonding and friction) of the longitudinal construction joint between the shoulder JCP and mainline CRCP.

PURPOSES : The purpose of this study was to investigate the long-term trend of internal strain within the continuously reinforced concrete pavement (CRCP) based on measurements. METHODS : The strains of the concrete and reinforcing bars were measured at two induced cracks and one construction joint. The analysis was performed using data accumulated over five years from the concrete placement. The effects of the initial construction conditions were investigated by comparing the strains and stresses at each location. RESULTS : In the long-term behavior, the highest tensile strains of the concrete and rebar were observed from December to January, and the lowest tensile or the highest compressive strain was observed from July to August. A lower rebar stress was measured in the construction joint, which has a higher steel ratio than that of cracks. As the distance from the crack and joint increased, the rebar strains decreased. Higher tensile strains of the concrete and rebar were measured where a higher concrete setting temperature occurred. A gradual decrease in the maximum concrete tensile strain was observed in the five-year measurements. However, in the case of reinforcing bars, stress reduction with time was not observed in the long-term behavior. CONCLUSIONS : Although a gradual decrease in concrete strain was revealed by long-term measurements, it is predicted that minimizing the concrete setting temperature to reduce the initial tensile strain could effectively increase the fatigue strength of CRCP

PURPOSES : The purpose of this study is to analyze the crack and vertical behaviors of a continuously reinforced concrete pavement (CRCP) under three different steel ratios (0.6%, 0.7%, and 0.8%) using field measurement data acquired from isolated concrete slabs with transverse cracks. METHODS : Using an LVDT and a crack gauge, CRCP behavior data are acquired by segmenting a concrete slab into multiple sections based on the similarity in the longitudinal steel ratio of each section. To examine the vertical behavior of CRCP based on longitudinal steel ratios, three field experiments are conducted in February, May, and September three years after project completion. The minimum and maximum ambient temperature data for each section are acquired during the experiments. Using the data acquired, the vertical and crack behaviors of CRCP with 0.6% of longitudinal steel ratios are analyzed. In addition, the effect of the steel ratio on the vertical behavior as well as seasonal vertical behaviors are examined. RESULTS : Analysis of the vertical behavior of concrete slabs with a 0.6% steel ratio shows that the minimum vertical displacement occurred at the center of the slab, whereas a significant vertical displacement is detected on the edges of the slab. Based on examining vertical displacements formed along the direction of transverse cracks, it is observed that the vertical behavior is prominent around the shoulders, whereas similar vertical behaviors are observed at the center and joints of the slab. Furthermore, it is discovered that the minimum crack occurred at the center of the transverse cracks, whereas the maximum crack occurred on the shoulders and joints. Furthermore, it appears that the daily displacements of the vertical behavior at the center of the slab constitute approximately one-half of the daily displacements on the joints. Based on the results of vertical behavior as a function of the longitudinal steel ratios, it is discovered that steel ratios of 0.7% and 0.8% yield the most prominent vertical behaviors around the edge of the shoulder in the winter, spring, and fall seasons. The seasonal deviations of the vertical behaviors based on the measuring positions of the longitudinal steel ratios appear less significant at the center of the slab than those on the shoulder. In particular, for the slab with a steel ratio of 0.8%, subtle vertical behaviors are observed at the center. It is discovered that the seasonal deviation of the vertical behavior measurements varying by the measuring locations of the steel ratios appears less significant at the center of the slab than at the shoulder, and that it decreases with the steel ratio. CONCLUSIONS : CRCP generates cracks on the slab; however, they are managed by rebars in the CRCP. This study reveals that the major vertical and crack behaviors of CRCP occur around the shoulders than at the center of the CRCP slab. Therefore, new methods for managing cracks on the CRCP shoulder should be developed to improve the performance of CRCP. It is hoped that the results presented herein will be useful for the advanced analysis of CRCP behaviors.

PURPOSES : The Korea Expressway Corporation has been working on an early remodeling project for the Jungbu Expressway, to prepare techniques for the rehabilitation of the old CRCP. In this study, a literature review, field survey, and thickness design using MEPGD were conducted. This is to provide a procedure for the pre-treatment, or repair of the existing pavement in the JungBu Expressway. METHODS : To evaluate the pavement condition of the JungBu Expressway, the existing PMS data were analyzed, and field surveys were conducted for each pavement condition. The SMA overlay thickness design was performed using the pavement thickness design program (MEPGD). In addition, the repair procedure was reviewed considering the characteristics of the old CRCP in Korea. RESULTS : From the analysis of existing PMS, field surveys, and laboratory tests, it was discovered that the old CRCP condition of the Jungbu Expressway was not satisfactory. Using MEPDG, the SMA thicknesses for each scenario were proposed as 5, 8, and 10 cm. In addition, appropriate repair procedures for each distress type(punchpout, multiple repair, re-failure, failure of longitudinal joint, etc.) of damaged CRCP in Korea were proposed. CONCLUSIONS : For the remodeling project of the Jungbu Expressway, appropriate repairs should be performed for each type of distress in the old CRCP. In this study, an appropriate overlay thickness and pre-treatment method are suggested.

PURPOSES : Korea Expressway Corporation has been working on an early remodeling project for the Jungbu Expressway to prepare methods for the rehabilitation of the old CRCP(Continuous Reinforced Concrete Pavement). In this study, the distress of the old CRCP was classified, and the engineering properties of the core specimens for each failure type were evaluated. Based on the test results, the concrete conditions of the existing CRCP were evaluated. This provides a basis for the pre-treatment or repair of the existing CRCP in the JungBu Expressway. METHODS : To evaluate the pavement condition of the Jungbu Expressway, existing PMS(Pavement Management System) data were analyzed, and field surveys were conducted for each pavement condition. The longitudinal rebar depth, rebar spacing, horizontal crack, and pavement thickness were examined through core sampling and non-destructive testing. In addition, the core specimens were used to evaluate the compressive strength, chloride penetration test, chloride ion penetration resistance, and freeze-thaw resistance. RESULTS : From the analysis of existing PMS data, field surveys, and laboratory tests, it was found that the old CRCP condition of the Jungbu Expressway was not good. Various types of failures occurred, and horizontal cracks at the rebar location, upward rebar locations, and rebar corrosion were confirmed. In addition, the compressive strength was considerably high, but the durability-related index was judged to be poor. CONCLUSIONS : For the remodeling project of the Jungbu Expressway, appropriate repairs should be carried out for each type of distress in the old CRCP.

PURPOSES : The purpose of this study was to suggest a quantitative trend of the daily and seasonal cyclic movement of transverse crackwidth based on measurements in CRCP(Continuously Reinforced Concrete Pavement) within the first year of construction. METHODS : Crack gauges were installed in eight normal cracks, two induced cracks, and two construction joints of newly constructed CRCP. Crack width movements were continuously collected for about a year to investigate the cyclic behavior after construction. The daily and seasonal crack width movements were quantitatively analyzed and compared. RESULTS: Crack width movement in hot weather was relatively less than in cold weather. As a result of frequency analysis of the daily cyclic behavior, it was revealed by measurement that the minimum crack width from 2 p.m. to 4 p.m. was caused by expansion of the concrete; and that the maximum width from 6 a.m. to 8 a.m. was caused by contraction. Average crack width movements were calculated for every month and showed seasonal cyclic behavior. Maximum crack width was measured from December to January. Average crack width was investigated from March to April. Daily crack width movement in relation to concrete temperature was calculated from -0.00017 to -0.03844 mm/℃ and showed gradual decrease in absolute value with time caused by change in the crack spacing. It was found that the relationships between the monthly average crack width and concrete temperature are from -0.004 to -0.012 mm/℃. CONCLUSIONS : Crack-width movement shows a daily and seasonal cyclic behavior. Crack-width measurement in any time or season will have variance caused by daily and seasonal cyclic movement. Variances and trends were obtained in this study based on measurements for various cracks. The long-term behavior of cracks should be surveyed and compared with these measurements to investigate trends of convergence with time, caused by convergence of crack spacing.

Domestic continuously reinforced concrete pavement has been built on a large scale on the Jungbu Expressway, which opened in 1987. Since then, there have been few application due to cost and construction difficulty. Currently, most of the expressway concrete pavements have been applied with jointed plain concrete pavement, but the interest in continuously reinforced concrete pavement has been increasing recently due to frequent premature failure in joints of JPCP. Accordingly, Korea Expressway Corporation has established design guidelines and details for continuously reinforced concrete pavements for expressway in 2014, based on the design method applied to the Jungbu Expressway, but incorporating foreign useful design methods. In terms of construction, pilot constructions were performed on Pyeongtaek~Jecheon Expressway Construction. The new design guidelines were applied to some sections of the Sangju~Yeongdeok Expressway Construction Project in 2016. This study conducted a survey and analysis of transverse cracks for one year after continuously reinforced concrete pavement construction in Sangju~Yeongdeok Expressway. This route was constructed with pavement thickness, base layer and longitudinal reinforcement according to domestic design guidelines. However, the transverse reinforcement was arranged differently according to the section. After construction, the transverse crack spacing was surveyed and the crack gauges were installed at the crack position to measure the movement. This compares the crack spacing according to the characteristics of longitudinal reinforcement and observes continuous movement of the crack width. The results showed that the crack spacing was more affected by the climate at the time of construction than the arrangement method of the transverse reinforcement. The crack width showed periodic changes according to the temperature change over 24 hours. However, due to seasonal changes, it showed a tendency of gradual increasing or decreasing in crack widths, and it was predicted that different measurement results will be shown depending on the time of crack width measurement. Generally, it is predicted that the crack spacing will be narrowed and the crack movement will tend to converge with the period after construction. This initial crack movement data is expected to be useful for comparing whether these predictions are valid.

연속철근 콘크리트 포장(CRCP)은 균열이 균일하게 발생하지 않을 경우 균열간격이 넓은 곳에서는 균 열폭이 과대하여 균열보수가 필요하며 균열간격이 너무 좁은 곳에서는 펀치아웃, 팝아웃 등의 파손이 발 생할 수 있어 일정한 균열간격을 유지할 필요가 있다. 본 연구에서는 균등한 간격으로 CRCP의 균열을 형 성할 수 있도록 실내실험을 통하여 유도균열장치의 최적 크기와 설치 위치를 선정하고자 하였다. 본 실험에서는 한국산업표준 KS F 2595의“콘크리트의 건조수축 균열 시험방법”에 사용되는 일축구 속시험체를 사용하였다. CRCP는 연속된 철근이 균열의 벌어짐을 구속하는 포장형식으로 CRCP를 모사하 기 위해서는 시험체의 길이가 길거나 양단을 고정할 수 있는 별도의 장치를 사용하여야 한다. 하지만 본 실험에 사용된 일축구속시험체는 양단에 앵커역할을 할 수 있는 강체가 있어 콘크리트의 수축 발생 시의 CRCP 거동 모사가 가능하다. 균열유도장치 높이 및 위치에 따라 유도균열 발생과정과 특성을 분석하기 위하여 유도균열장치의 높이 와 설치 위치에 따라 총 5개의 시험체를 제작하여 실험을 수행하였다. 그림 1과 같이 굳지 않은 콘크리트 내에 박막의 플라스틱 소재의 분리막을 삽입함으로써 균열을 유도하였다. 자연적인 건조수축에 의한 균열 의 발생은 과다한 시간이 소요되기 때문에 드라이아이스를 시험체 상부에 놓아 시험체의 온도를 인위적으 로 하강시켜 그림 2와 같은 균열의 발생을 앞당길 수 있도록 하였다. 균열유도장치 높이 및 위치에 따른 유도균열 발생 실험 결과 균열유도장치의 높이가 클수록 균열이 발 생하는 온도하강의 폭이 작아 균열을 유도하기 유리한 것으로 나타났다. 또한 균열유도장치의 높이가 클 수록 균열폭이 넓은 것으로 나타났으며, 이는 균열유도장치 높이가 클수록 균열진전 깊이가 더 깊기 때문 인 것으로 확인하였다. 또한 균열유도장치 설치를 상부에서 아래로 설치할수록 균열의 형태가 자연발생 균열과 유사한 형태로 발생하는 것으로 나타났다.

연속철근 콘크리트 포장(CRCP)에서 철근의 역할은 균열의 과도한 벌어짐을 구속하도록 하는 것이다. 따라서 본 연구에서는 그림 1(a)와 같이 슬래브 전체에 연속철근이 설치된 경우와 그림 1(b)와 같이 균열 부에만 부분적으로 철근이 설치된 경우의 거동을 비교함으로써 연속철근 콘크리트 포장의 철근감소를 위 한 기반을 마련하고자 하였다. 본 연구에서는 두 가지 실험을 통하여 연속철근과 부분철근이 설치된 시험체를 비교하였다. 첫 번째는 그림 1과 같이 시험체에 인위적인 온도하강을 통하여 균열을 발생시키고 이러한 균열의 거동 측정하는 것 이며, 두 번째는 각 시험체에 그림 2와 같이 하중재하를 함으로써 철근부착 정도를 비교하고자 하였다. 연속철근과 부분철근이 설치된 시험체에 대한 실내실험 결과 상부에만 균열이 발생 시의 균열폭 거동 을 측정한 결과 연속철근이 설치된 시험체와 부분철근이 설치된 시험체의 상부 균열폭 거동은 약 7%의 미소한 차이가 발생하여 두 시험체의 균열 거동은 유사한 것으로 확인되었다. 관통균열이 발생하였을 경 우에는 두 시험체의 상부 균열폭 거동이 2%의 미소한 차이가 발생하였다. 두 시험체에 하중을 재하함으 로써 철근부착실험을 진행한 결과 두 시험체의 파괴하중 차이가 10%로 미소하게 발생하여 두 시험체의 유도균열부에서 차량하중전달율은 유사할 것으로 판단되었다.

In a wide spectrum of pavement rehabilitation techniques, the application of thin asphalt overlay on existing concrete pavements have shown its ability to restore the functional capacity of the pavement system as well as maintain structural capacity. Although, prior researches stated that it does not add to the structural capacity of the existing pavement, the insulation generated by the asphalt overlay can affect the behavior of the discontinuities in the continuously reinforced concrete pavement (CRCP) system by reducing the magnitude of its movement. The investigation of crack movement behaviors of the CRCP in Chungbu Expressway was conducted in 2-phases: without overlay and with overlay. Crackmeters were installed at selected crack locations and measurements were collected. In the second phase of the investigation, crackmeters were installed at the concrete layer of the CRCP before a 2-inch asphalt overlay was applied. Results have shown that the crack movements under a thin asphalt overlay have reduced by 80% which indicates an effective insulation of the CRCP.