연속철근 콘크리트 포장 시공 후 가로균열 순환거동 계측

유태석,조철민 한국도로학회 2018 한국도로학회논문집 Vol.20 No.5

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.

Effect of Cracking on Corrosion of Steel in Concrete

Faiz Uddin Ahmed Shaikh 한국콘크리트학회 2018 International Journal of Concrete Structures and M Vol.12 No.1

It is generally recognized that cracks provide easy access to ingress of chlorides in concrete and hence, the initiation of corrosion of steel in cracked concrete occurs at early stage. However, wide variety of results on the effect of crack widths on corrosion of steel in concrete are reported in many studies. Apart from crack width, the crack depths, cracking frequency and healing of cracks also influence the corrosion of steel in concrete. This paper presents a comprehensive review and summarised the results on the effect of cracking on corrosion of steel in concrete. The effect of crack widths on the diffusion of chlorides ions and carbon-dioxide is also discussed in this paper. Among all available results, a correlation between the corrosion current and the crack widths up to 0.3 mm can be established, however, no distinct trends are observed beyond that crack width. Conflicting results on the effect of crack widths on chloride ion diffusion are also reported. The longitudinal crack causes more severe corrosion of steel in concrete than transverse cracks of same width. Cracked concrete containing supplementary cementitious materials exhibited superior corrosion resistance than cracked ordinary Portland cement concrete of same width of transverse as well as longitudinal cracks. The same is also true in the case of lower water–binder ratios of cracked concrete. The increase in crack depth increased the chloride diffusion; however, the corrosion test shows an opposite trend. Conflicting results on the effect of crack frequency on corrosion of steel are also reported.

연속철근 콘크리트 슬래브 시스템의 균열진전 깊이와 균열폭 거동 관계 분석

조영교,김성민,오한진,최린,석종환 한국도로학회 2015 한국도로학회논문집 Vol.17 No.1

PURPOSES: The purpose of this study is to investigate the relationship between the crack propagation depth through a slab and crack width movement in continuously reinforced concrete slab systems (CRCSs). METHODS : The crack width movements in continuously reinforced concrete pavement (CRCP) and continuously reinforced concrete railway track (CRCT) were measured in the field for different crack spacings. In addition, the crack width movements in both CRCP and CRCT were simulated using finite element models of CRCP and CRCT. The crack width movements, depending on the unit temperature change, were obtained from both the field tests and numerical analysis models.. RESULTS: The experimental analysis results show that the magnitudes of the crack width movements in CRCSs were related to not only the crack spacing, but also the crack propagation depth. In CRCP, the magnitudes of the crack width movements were more closely related to the crack propagation depths. In CRCT, the crack width movements were similar for different cracks since most were through cracks. If the numerical analysis was performed to predict the crack width movements by assuming that the crack propagates completely through the slab depth, the predicted crack width movements were similar to the actual ones in CRCT, but those may be overestimated in CRCP. CONCLUSIONS: The magnitudes of the crack width movements in CRCSs were mainly affected by the crack propagation depths through the slabs.

연속철근 콘크리트 슬래브 시스템의 균열진전 깊이와 균열폭 거동 관계 분석

조영교,김성민,오한진,최 린,석종환 한국도로학회 2015 한국도로학회논문집 Vol.17 No.1

PURPOSES: The purpose of this study is to investigate the relationship between the crack propagation depth through a slab and crack width movement in continuously reinforced concrete slab systems (CRCSs). METHODS : The crack width movements in continuously reinforced concrete pavement (CRCP) and continuously reinforced concrete railway track (CRCT) were measured in the field for different crack spacings. In addition, the crack width movements in both CRCP and CRCT were simulated using finite element models of CRCP and CRCT. The crack width movements, depending on the unit temperature change, were obtained from both the field tests and numerical analysis models.. RESULTS: The experimental analysis results show that the magnitudes of the crack width movements in CRCSs were related to not only the crack spacing, but also the crack propagation depth. In CRCP, the magnitudes of the crack width movements were more closely related to the crack propagation depths. In CRCT, the crack width movements were similar for different cracks since most were through cracks. If the numerical analysis was performed to predict the crack width movements by assuming that the crack propagates completely through the slab depth, the predicted crack width movements were similar to the actual ones in CRCT, but those may be overestimated in CRCP. CONCLUSIONS: The magnitudes of the crack width movements in CRCSs were mainly affected by the crack propagation depths through the slabs.

Calculation Method of Early-Age Crack Width in Reinforced Concrete Bridge through a Nonlinear FEA Model

Shan Chang,Ming Yang,Yun Sun,Kui Liu 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.7

A prestressed concrete (PC) box girder with the total length of three span 130 m was constructed by the method of cast-in-place layer by layer with full framing, and the cracking of the top slab in the box room was found during the construction. Cracking is one of the main distresses for a reinforced concrete (RC) bridge, which also reduces the safety and service life of the structure. The existing calculation methods of crack width, which are used to evaluate the crack width induced by the external loads, are not suitable to calculate the early-age crack width. To evaluate the early-age crack width, a calculation method of early-age crack width was presented. The finite element analysis (FEA) model of the PC box girder being built was used to analyze two affecting parameters of early-age cracking by ABAQUS 2017 program. Through the nonlinear FEA model of the PC box girder, the calculation formula of early-age crack width was used to evaluate the crack width. The validity of the nonlinear FEA method has been verified by comparing the simulation results with the measured results.

Crack Behaviour in the First Year after Construction of CRCP

Tae Seok Yoo,Cheol Min Cho 한국도로학회 2018 한국도로학회 학술대회 발표논문 초록집 Vol.2018 No.05

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.

Automated assessment of cracks on concrete surfaces using adaptive digital image processing

Yufei Liu,조수진,Jiansheng Fan,Billie F. Spencer, Jr. 국제구조공학회 2014 Smart Structures and Systems, An International Jou Vol.14 No.4

Monitoring surface cracks is important to ensure the health of concrete structures. However, traditional visual inspection to monitor the concrete cracks has disadvantages such as subjective inspection nature, associated time and cost, and possible danger to inspectors. To alter the visual inspection, a complete procedure for automated crack assessment based on adaptive digital image processing has been proposed in this study. Crack objects are extracted from the images using the subtraction with median filter and the local binarization using the Niblack\' s method. To adaptively determine the optimal window sizes for the median filter and the Niblack\' s method without distortion of crack object, an optimal filter size index (OFSI) is proposed. From the extracted crack objects using the optimal size of window, the crack objects are decomposed to the crack skeletons and edges, and the crack width is calculated using 4-connected normal line according to the orientation of the local skeleton line. For an image, a crack width nephogram is obtained to have an intuitive view of the crack distribution. The proposed procedure is verified from a test on a concrete reaction wall with various types of cracks. From the crack images with different crack widths and patterns, the widths of cracks in the order of submillimeters are calculated with high accuracy.

Automated assessment of cracks on concrete surfaces using adaptive digital image processing

Liu, Yufei,Cho, Soojin,Spencer, Billie F. Jr,Fan, Jiansheng Techno-Press 2014 Smart Structures and Systems, An International Jou Vol.14 No.4

Monitoring surface cracks is important to ensure the health of concrete structures. However, traditional visual inspection to monitor the concrete cracks has disadvantages such as subjective inspection nature, associated time and cost, and possible danger to inspectors. To alter the visual inspection, a complete procedure for automated crack assessment based on adaptive digital image processing has been proposed in this study. Crack objects are extracted from the images using the subtraction with median filter and the local binarization using the Niblack's method. To adaptively. determine the optimal window sizes for the median filter and the Niblack's method without distortion of crack object an optimal filter size index (OFSI) is proposed. From the extracted crack objects using the optimal size of window, the crack objects are decomposed to the crack skeletons and edges, and the crack width is calculated using 4-connected normal line according to the orientation of the local skeleton line. For an image, a crack width nephogram is obtained to have an intuitive view of the crack distribution. The proposed procedure is verified from a test on a concrete reaction wall with various types of cracks. From the crack images with different crack widths and patterns, the widths of cracks in the order of submillimeters are calculated with high accuracy.

UAV 사진측량법과 CNN을 이용한 콘크리트 균열폭 측정 및 3차원 재구성 방법

김구연,설동현,김태우,김홍진 한국풍공학회 2023 한국풍공학회지 Vol.27 No.4

본 연구는 추가적인 장비 없이 UAV만을 사용한 균열폭 측정 및 균열의 3차원 재구성 방법을 제안한다. UAV 사진측량법 및 CNN을이용한 균열의 3차원 재구성 및 균열폭 측정 검증을 위해 5곳의 균열이 존재하는 벽면을 대상으로 균열의 3차원 재구성을 하였으며 UAV와 균열 사이의 거리 4가지에 대해 균열폭을 측정하고 균열 현미경 측정값과 비교하여 정확성을 검증하였다. 대부분의 균열에서 균열폭을 정확히 측정하였으나 균열폭이 0.5mm보다 작은 경우와 벽면이 심하게 그늘져 어두운 곳에서는 측정 유효성이 떨어지는 결과를 보였다. This study proposes a method for crack width measurement and three-dimensional reconstruction of cracks using only Unmanned Aerial Vehicles (UAVs) without the need for additional equipment. Three-dimensional reconstruction of cracks using UAV photogrammetry and Convolutional Neural Networks (CNN) was conducted on a wall with five existing cracks to validate the measurement of crack width. Crack widths were measured at four distances between the UAV and cracks, and the accuracy was verified by comparing the measured crack widths with those obtained from crack microscopy. While accurate measurements were obtained for most cracks, results indicated reduced measurement effectiveness for cracks with widths less than 0.5mm and in areas where the wall was heavily shadowed, presenting darker conditions.

철근콘크리트 인장부재의 균열발생 후 철근부식에 따른 균열거동

김효혜(Kim Hyo-Hye),노삼영(Noh Sam-Young) 대한건축학회 2007 대한건축학회 학술발표대회 논문집 - 계획계/구조계 Vol.27 No.1

The formation of cracks in the reinforced concrete member is generally prerequisite. Therefore structural building codes suggest prediction formulas and limits of crack width for the durability and the serviceability of structures in which steel corrosion can be initiated through the cracks. The crack behavior of a reinforced tension member has been theoretically more or less mastered, although the accuracy of the prediction formulas for crack width suggested building codes is questionable. Additionally influence of steel corrosion indicated by concrete cracks on the crack width have not been referred. The aim of this study is the analysis of the crack behavior of a crack element between two cracks under steel corrosion after the crack formation. For this purpose a bond-slip relation was numerically modelled based on steel corrosion test results by other researchers. With the bond model and other effects due to the steel corrosion, the crack element was numerically analyzed. As results, bond stress, slip, steel stress and crack width in a crack element could be obtained in dependence on the corrosion duration of reinforced concrete structural members.