• Title/Summary/Keyword: traffic condition

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A Hardening and Strength Properties of Magnesium Phosphate Mortars for Rapid Repair Materials (급속 보수용 마그네슘 인산염 모르타르의 경화 및 강도특성)

  • Oh, Hongseob;Lee, Inhee
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.23 no.3
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    • pp.103-110
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    • 2019
  • Damage to the pavement system due to various causes will be required rapid repair work for reopening the vehicle traffic. The magnesium oxide phosphate composite(MPC) has a short curing time and is capable of early compressive strength development, is suitable for rapid repair materials. The aim of this study was to evaluate the hardening and compressive strength characteristics of MPC according to the water-binder (W / B) ratio and magnesium-phosphate(M / P) ratio in order to develop repair materials consisted with light burned magnesia and potassium dihydrogen phosphate. In order to ensure the workability in the field application, the difference of mechanical properties according to standard sand and ordinary sand and performance of retards were evaluated. The mix proportion with W/B ratio was about 35% and the M/P ratio was about 1.0 ~ 1.2 has a superior perfomance with strength and hardening condition. Especially, the strength of composite at only 1 day curing with W/B ratio of 0.35 and the M/P ratio of 1.2 was shown the higher than 25.0 MPa. Boric acid as a retarder was found to be suitable for ensuring the working time, and the purity of magnesium oxide was about 90 ~ 95%, which is effective for ensuring curing time and strength.

Estimation of installation spacing by analyzing the lateral behavior of the safety fence fixed to rail bottom (레일저부고정형 안전펜스의 횡 방향 거동 분석을 통한 설치간격 산정)

  • Park, Seonghyeon;Sung, Deokyong;Lee, Changho;Jung, Hyuksang;Youg, Seungkyong
    • Journal of The Korean Society For Urban Railway
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    • v.6 no.4
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    • pp.249-257
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    • 2018
  • The number of deaths for railway traffic accidents is mainly caused by working close to the track, or when unauthorized passage pass through the track. The safety fences are being used to ensure safety for workers close to the track, and to improve the efficiency of the work, without interfering with the passage of trains. However, a safety fence for railway tracks needs to be examined to see if it will interfere with the passage of trains. The purpose of this study is to analyze the safe distance between train and safety fence developed in Korea. In addition, the lateral load condition of wind pressure by trains is estimated and numerical analysis is carried out according to the installation intervals of railway safety fences. It has been confirmed that the proper spacing between the train and the railway safety fence should be at least 200 mm from the vehicle limit, and that the proper spacing of railway safety fence must be calculated in consideration of the wind pressure by trains.

A Study on Behavior of Post-integrated Abutment Bridge When Abutment and Bridge Decks are Jammed (교대 협착 발생 시 무조인트화 교량의 거동 분석 연구)

  • Park, Yang Heum;Nam, Moon S.;Jang, Il Young
    • Journal of the Korean GEO-environmental Society
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    • v.22 no.3
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    • pp.31-35
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    • 2021
  • The expansion joints installed on the bridge for the accommodation of expansion and contraction of the supper structure are essential members of the bridge. However, the expansion joints are deteriorated over time and the waterproof function weakens, causing rainwater to penetrate and deteriorate the structure. In order to solve the traffic congestion caused by frequent replacement of the old expansion joints along with the deterioration of the structure, a post-integrated abutment bridge in which the existing expansion joints are removed and replaced with reinforced concrete link connection has been applied to highway bridges since 2016. After the post-integrated abutment method was applied, it was partially applied to bridges in which the superstructure and abutment were jammed. In this study, the causes of problems that may occur when the post-integrated abutment method is applied to the jammed bridge were analyzed numerically. It was analyzed that damage occurred in the link connection part. Based on the results of this study, the application condition for the post-integrated abutment method is reinforced as it is not possible to apply the post-integrated abutment method to bridges are already jammed.

Performance of Feature-based Stitching Algorithms for Multiple Images Captured by Tunnel Scanning System (터널 스캐닝 다중 촬영 영상의 특징점 기반 접합 알고리즘 성능평가)

  • Lee, Tae-Hee;Park, Jin-Tae;Lee, Seung-Hun;Park, Sin-Zeon
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.5
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    • pp.30-42
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    • 2022
  • Due to the increase in construction of tunnels, the burdens of maintenance works for tunnel structures have been increasing in Korea. In addition, the increase of traffic volume and aging of materials also threatens the safety of tunnel facilities, therefore, maintenance costs are expected to increase significantly in the future. Accordingly, automated condition assessment technologies like image-based tunnel scanning system for inspection and diagnosis of tunnel facilities have been proposed. For image-based tunnel scanning system, it is key to create a planar image through stitching of multiple images captured by tunnel scanning system. In this study, performance of feature-based stitching algorithms suitable for stitching tunnel scanning images was evaluated. In order to find a suitable algorithm SIFT, ORB, and BRISK are compared. The performance of the proposed algorithm was determined by the number of feature extraction, calculation speed, accuracy of feature matching, and image stitching result. As for stitching performance, SIFT algorithm was the best in all parts of tunnel image. ORB and BRISK also showed satisfactory performance and short calculation time. SIFT can be used to generate precise planar images. ORB and BRISK also showed satisfactory stitching results, confirming the possibility of being used when real-time stitching is required.

Validation of Permanent Deformation Model for Flexible Pavement using Accelerated Pavement Testing (포장가속시험을 이용한 소성변형예측 모델의 검증)

  • Choi, Jeong Hoon;Seo, Youngguk;Suh, Young Chan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.29 no.4D
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    • pp.491-497
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    • 2009
  • This paper presents the results of accelerated pavement tests (APT) that simulate permanent deformation (rutting) of asphalt concrete pavements under different temperatures and loading courses. Also, finite element (FE) analysis has been conducted to predict the test results. Test section for APT is the same as one of test sections at Korea Expressway Corporation test road and is subjected to a constant moving dual tire wheel load of APT at three different temperatures: 30, 40, $50^{\circ}C$. The moving wheel is applied at different loading courses within a 75cm wide wheel path to account for traffic wandering. Also, the effect of wandering on permanent deformation development is investigated numerically with three wandering schemes. In this study, ABAQUS is adopted to model APT pavement section with plain stain elements and creep strain rate model is used to take into account viscoplastic stain of asphalt concrete mixtures, and elastic layer properties are back-calculated from FWD measurements. Plus, the effect of boundary condition and subgrade on FE permanent deformation predictions is investigated. A full FE model that accounted for subgrade provided more realistic rut depth predictions, indicating subgrade has contributed to surface rutting.

Small-cell Resource Partitioning Allocation for Machine-Type Communications in 5G HetNets (5G 이기종 네트워크 환경에서 머신타입통신을 위한 스몰셀 자원 분리 할당 방법)

  • Ilhak Ban;Se-Jin Kim
    • Journal of Internet Computing and Services
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    • v.24 no.5
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    • pp.1-7
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    • 2023
  • This paper proposes a small cell resource partitioning allocation method to solve interference to machine type communication devices (MTCD) and improve performance in 5G heterogeneous networks (HetNet) where macro base station (MBS) and many small cell base stations (SBS) are overlaid. In the 5G HetNet, since various types of MTCDs generate data traffic, the load on the MBS increases. Therefore, in order to reduce the MBS load, a cell range expansion (CRE) method is applied in which a bias value is added to the received signal strength from the SBS and MTCDs satisfying the condition is connected to the SBS. More MTCDs connecting to the SBS through the CRE will reduce the load on the MBS, but performance of MTCDs will degrade due to interference, so a method to solve this problem is needed. The proposed small cell resource partitioning allocation method allocates resources with less interference from the MBS to mitigate interference of MTCDs newly added in the SBS with CRE, and improve the overall MTCD performace using separating resources according to the performance of existing MTCDs in the SBS. Through simulation results, the proposed small cell resource partitioning allocation method shows performance improvement of 21% and 126% in MTCDs capacity connected to MBS and SBS respectively, compared to the existing resource allocation methods.

Episode Analysis of the Habit and Phase Changes of Snow Crystals in the Wintertime Yeongdong Region (겨울철 영동지역 눈 결정 습성과 성상 변화 에피소드 분석)

  • Young-Gil Choi;Byung-Gon Kim;Ji-Yun Kim;Tae-Yeon Kim;Jin-Heon Han;GyuWon Lee;Kwonil Kim;Ki-Hoon Kim;Byung-Hwan Lim
    • Atmosphere
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    • v.34 no.2
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    • pp.139-151
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    • 2024
  • The Yeongdong region has suffered from severe snowstorms and the relevant damage such as traffic accidents on slippery roads, and the collapse of greenhouses and temporary buildings. While a lot of research on snowfall has been conducted, the detailed study of snow crystals' phase and habit through intensive observations and the relevant microphysical analysis is still lacking. Therefore, a snowflake camera, PARSIVEL, and intensive radiosonde soundings were utilized to investigate phase and habit changes in solid precipitation. Two remarkable episodes of phase and habit changes were selected such as 19 March 2022 and 15 February 2023. Both events occurred in the synoptic condition of the High in the north and the Low passing by the south, which was accompanied by rapid temperature cooling below 2.5 km. During the events of a short period between 3 to 6 hours, the temperature at 850 hPa decreased by about 4 to 6℃. This cooling led to a change in the main habit of snow particles from riming to aggregate, identified with both MASC and PARSIVEL. Meanwhile, the LDAPS model analyses do not successively represent the rapid cooling and short-term variations of solid precipitation, probably by virtue of overestimating low-level equivalent potential temperature during these periods. The underlying causes of these the low-level temperature variations within 6 hours, still remain unclear. It might be associated with mesoscale orographic phenomenon due to the mountains and East Sea effects, which certainly needs an intensive and comprehensive observation campaign.

Needs Accessment of Safety Education of High School Students in Seoul (서울시 고등학생의 안전교육 실태 및 요구도 조사)

  • 김민아;이명선
    • Korean Journal of Health Education and Promotion
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    • v.18 no.3
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    • pp.133-162
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    • 2001
  • Unexpected accidents in school has been gradually increased every year, and student's mistaken was the first reason of the accident. To preventing the students from Unexpected accidents in school, safety education is more important than having strong facilities to have much more strong protecting forces for the accidents. Therefore, systematic education of safety is needed most of all, and especially, strengthening safety education in school is needed. Hereby, this study is aimed at investigating and analysing the actual condition and demand of safety education. It also conducted a survey with the target of 1,255 students in the second grade of high school in Seoul from April 20 to May 19, and the result of this study is as follows. 1. In the general features of the subject of the survey, boy students and girl students occupied 50.8% and 49.2% each, and boys' high school (34.3%), girls' high school(32.2%) and co-ed(33.5%) participated in balance. In the location, north from Han river occupied 54.6%, south were 45.2%. 2. According to the status of experiencing an accident, boys were more experienced then girls(p〈0.05). From the section, home accident(56.8%) occupied most followed by school accident, traffic accident, sports accident and poisoning. The accident happening most often in detailed category is sports accident such as basket ball, foot ball and dodge ball. The actual condition of the subject's using a school health facility shows that boys students use it more often than girl students(p〈0.01) 3. In attitude toward safety, the subject showed lower interest in safety issues than other social issues. But attitude in seriality of safety problems were high. Also, they responded ‘individual citizen’(63.1%) as the one who should make efforts for safety. Regarding knowledge of preventing safety accidents in attitude toward individual safety, 42.2% answered ‘they know a little’ and 32.6% of respondents say ‘they do not know’. To a question of the degree of the subject's following safety rules, 36.4% were answered ‘keeping’ and the group using a school health facility shows more ‘keeping’ the others(p〈0.05). 4. To a question of asking if they have experienced safety education, 51.2% answered ‘yes’. Teachers who mainly take care of safety education are answered as training teacher(48.7%). As for education time, training class(51.3%) is said to have safety education most followed by health-related event and PE(Physical Education). Frequency of education shows once or twice a session (62.8%) most often, but in case of co-ed school, 5-7times a session or more(20.1%) are being practiced. Looking at education time, 1-2 hour(s)(22.1%) or for a short time(22.1%) during class are being practiced. As an education method, instruction(43.8%) and video education(32.5%) are being practiced, and when it comes to education evaluation method, ‘not practiced’(70.0%) answered. To the question if they are satisfied with school safety education, they answered more ‘no(43.1%)’ than ‘yes(6.7%)’, and the reason is that safety education class is just for formality's sake, and the fact they already know is being repeated. The contents of safety education is composed of school safety, home safety, and first aid. 5. It is turned out that 56.5% of the total boy students and 61.1% of the total girl students recognize the necessity of safety education. To the question if safety education is needed in an elementary and middle education course, 46.4% of the subject answer answered' it's necessary'. The most reason for their answers are ‘safety education is directly related to life’. 6. Regarding the requested time of safety education is ‘one hour a week’ by 55.9%. For safety education, safety education teachers(38.7%) are answered to be the most proper. As a request for safety education, video education is answered to be the most appropriate(30.6%), followed by practical skills, lecture and discussion(p〈0.05). Demand of educational evaluation, practical skills, interview and observation are answered to be needed. To the question if they want to participate in the way of demanded safety education, 41.9% of respondents answer ‘have a mind to participate in’ (41.9%). To benefits followed by completing safety education, 72.0% of respondents answer ‘agree’, and 24.7% ‘do not agree’, which means lout 4 disagrees with completing safety education. 7. Looking at demand of safety education according to the features of the subject, ‘our position for the person who has handicapped’ was answer to the most.

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A Geographically Weighted Regression on the Effect of Regulation of Space Use on the Residential Land Price - Evidence from Jangyu New Town - (공간사용 규제가 택지가격에 미치는 영향에 대한 공간가중회귀분석 - 장유 신도시지역을 대상으로-)

  • Kang, Sun-Duk;Park, Sae-Woon;Jeong, Tae-Yun
    • Management & Information Systems Review
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    • v.37 no.3
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    • pp.27-47
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    • 2018
  • In this study, we examine how land use zoning affects the land price controlling other variables such as road-facing condition of the land, land form, land age after its development and land size. We employ geographically weighted regression analysis which reflects spatial dependency as methodology with a data sample of land transaction price data of Jangyu, a new town, in Korea. The results of our empirical analysis show that the respective coefficients of traditional regression and geographically weighted regression are not significantly different. However, after calculating Moran's Index with residuals of both OLS and GWR models, we find that Moran's Index of GWR decreases around 26% compared to that of OLS model, thus improving the problem of spatial autoregression of residuals considerably. Unlike our expectation, though, in both traditional regression and geographically weighted regression where residential exclusive area is used as a reference variable, the dummy variable of the residential land for both housing and shops shows a negative sign. This may be because the residential land for both housing and shops is usually located in the level area while the residential exclusive area is located at the foot of a mountain or on a gentle hill where the residents can have good quality air and scenery. Although the utility of the residential land for both housing and shops is higher than its counterpart's since it has higher floor area ratio, amenity which can be explained as high quality of air and scenery in this study seems to have higher impact in purchase of land for housing. On the other hand, land for neighbourhood living facility seems to be valued higher than any other land zonings used in this research since it has much higher floor area ratio than the two land zonings above and can have a building with up to 5 stories constructed on it. With regard to road-facing condition, land buyers seem to prefer land which faces a medium-width road as expected. Land facing a wide-width road may have some disadvantage in that it can be exposed to noise and exhaust gas from cars and that entrance may not be easy due to the high speed traffic of the road. In contrast, land facing a narrow road can be free of noise or fume from cars and have privacy protected while it has some inconvenience in that entrance may be blocked by cars parked in both sides of the narrow road. Finally, land age variable shows a negative sign, which means that the price of land declines over time. This may be because decline of the land price of Jangyu was bigger than that of other regions in Gimhae where Jangyu, a new town, also belong, during the global financial crisis of 2008.

Wetting-Induced Collapse in Fill Materials for Concrete Slab Track of High Speed Railway (고속철도 콘크리트궤도 흙쌓기재료의 Wetting Collapse에 관한 연구)

  • Lee, Sung-Jin;Lee, Il-Wha;Im, Eun-Sang;Shin, Dong-Hoon;Cho, Sung-Eun
    • Journal of the Korean Geotechnical Society
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    • v.24 no.4
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    • pp.79-88
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    • 2008
  • Recently, the high speed railway comes into the spotlight as the important and convenient traffic infrastructure. In Korea, Kyung-Bu high speed train service began in bout 400 km section in 2004, and the Ho-Nam high speed railway will be constructed by 2017. The high speed train will run with a design maximum speed of 300-350 km/hr. Since the trains are operated at high speed, the differential settlement of subgrade under the rail is able to cause a fatal disaster. Therefore, the differential settlement of the embankment must be controlled with the greatest care. Furthermore, the characteristics and causes of settlements which occurred under construction and post-construction should be investigated. A considerable number of studies have been conducted on the settlement of the natural ground over the past several decades. But little attention has been given to the compression settlement of the embankment. The long-term settlement of compacted fills embankments is greatly influenced by the post-construction wetting. This is called 'hydro collapse' or 'wetting collapse'. In spite of little study for this wetting collapse problem, it has been recognized that the compressibility of compacted sands, gravels and rockfills exhibit low compressibility at low pressures, but there can be significant compression at high pressures due to grain crushing (Marachi et al. 1969, Nobari and Duncan 1972, Noorany et al. 1994, Houston et al. 1993, Wu 2004). The characteristics of compression of fill materials depend on a number of factors such as soil/rock type, as-compacted moisture, density, stress level and wetting condition. Because of the complexity of these factors, it is not easy to predict quantitatively the amount of compression without extensive tests. Therefore, in this research I carried out the wetting collapse tests, focusing on various soil/rock type, stress levels, wetting condition more closely.