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Assessment of the Impact Factor and the Stress Histogram of Railway Bridges in Korea (국내 강철도 교량의 충격계수 및 응력빈도분포의 평가)

  • Choi, Jun Hyeok;Cho, Sun Kyu;Chang, Dong Il
    • Journal of Korean Society of Steel Construction
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    • v.9 no.4 s.33
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    • pp.489-500
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    • 1997
  • The number of railway bridges in Korea reaches to about 3,000. Among them, the ratio of steel bridges is about 47%. Most of the long span railway bridges take the truss type, its number is 15 in Korea. These bridges have more than 30 years service life, it is expected that the damages of cracks and corrosion is going. Therefore, the estimation of fatigue life with random stress is considered as significant subject in maintenance. In this paper, the random stress was measured in bridges and counted the stress cycles using the rainflow counting method So, the stress range frequencies and their equivalent stress are obtained and the amplification factor for the span length, bridge types and traveling speed is assessed by the dynamic testing. From the results, the stress range of the stringer and the lower chord is higher than the other members and the characteristics of the stress histogram is varied to the loading system and the amount of the passing through trains. And the impact effects are depended on the traveling speed as well as the span length.

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A Study on the Flexural Fatigue Behavior of R/C Beams Repaired with Concrete-Polymer Composites (유기 및 유기재료로 보수된 R/C 보의 휨 피로거동에 관한 연구)

  • 심종성;황의승;배인환;이은호
    • Magazine of the Korea Concrete Institute
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    • v.7 no.6
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    • pp.233-241
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    • 1995
  • In this thesis, the fatigue tests were performed on a series of R /C beams repaired with co& crete-lmlyrner composites to investigate the fatigue bahavior. The three point loading system is used in the fatigue tests. In these tests, relations between the repeated loading cycles and mid-span deflections, number of repeated loading cycles when repaired beams were fractured, the bonding performance of repair materials were observed. On this basis, the mid-span deflections, the crack growth and failure mode of repaired R /C beams were studied. A S-N curve was drawn to present the fatigue strength of repaired beams. From the test results, it was shown that behavior of R /C beams repaired with polymer-cement series were very sirnillar to control beam about bonding performance, mid-span deflections and fatigue strength according to S-N curve drawn by the regression anlysis on the fatigue test results.

Analysis on the Ventilation Performance of Single-span Tomato Greenhouse with Roof Windows (천창을 설치한 토마토 재배 단동 온실의 환기성능 분석)

  • Nam, Sang-Woon;Kim, Young-Shik;Both, Arend-Jan
    • Journal of Bio-Environment Control
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    • v.20 no.2
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    • pp.78-82
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    • 2011
  • Ventilation rates, inside and outside weather data were measured in a arch-shape single-span plastic greenhouse growing tomatoes. On the roof of the experimental greenhouse, round windows which have a diameter of 0.6 m were installed at intervals of 8m. It showed that the number of air changes in this greenhouse were average 0.17 volumes per minute and in the range of 0.02 to 0.32 volumes per minute. These air changes are insufficient to meet the recommended ventilation rate for commercial greenhouses, and it is estimated that interval of 6 m is appropriate for spring or fall season. For summer season, it is necessary to narrow the space or to enlarge the open area of roof windows. Using the heat balance model, the evapotranspiration coefficients of greenhouse tomatoes were estimated from experimental ventilation data, overall heat transfer and solar radiation. It showed that the evapotranspiration coefficients were average 0.62 and in the 0.39 to 0.85 range. We suggest applying 0.6 as the evapotranspiration coefficient in design of ventilation for the single-span tomato greenhouses.

Mining Maximal Frequent Contiguous Sequences in Biological Data Sequences (생물학적 데이터 서열들에서 빈번한 최대길이 연속 서열 마이닝)

  • Kang, Tae-Ho;Yoo, Jae-Soo
    • The KIPS Transactions:PartD
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    • v.15D no.2
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    • pp.155-162
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    • 2008
  • Biological sequences such as DNA sequences and amino acid sequences typically contain a large number of items. They have contiguous sequences that ordinarily consist of hundreds of frequent items. In biological sequences analysis(BSA), a frequent contiguous sequence search is one of the most important operations. Many studies have been done for mining sequential patterns efficiently. Most of the existing methods for mining sequential patterns are based on the Apriori algorithm. In particular, the prefixSpan algorithm is one of the most efficient sequential pattern mining schemes based on the Apriori algorithm. However, since the algorithm expands the sequential patterns from frequent patterns with length-1, it is not suitable for biological dataset with long frequent contiguous sequences. In recent years, the MacosVSpan algorithm was proposed based on the idea of the prefixSpan algorithm to significantly reduce its recursive process. However, the algorithm is still inefficient for mining frequent contiguous sequences from long biological data sequences. In this paper, we propose an efficient method to mine maximal frequent contiguous sequences in large biological data sequences by constructing the spanning tree with the fixed length. To verify the superiority of the proposed method, we perform experiments in various environments. As the result, the experiments show that the proposed method is much more efficient than MacosVSpan in terms of retrieval performance.

A study on the stability of pile bridge abutment on soft ground undergoing lateral flow (연약지반에서의 말뚝기초 교대의 측방유동 대책공법 적용에 관한 연구)

  • 오일록;채영수
    • Proceedings of the Korean Geotechical Society Conference
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    • 2003.03a
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    • pp.753-760
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    • 2003
  • An existing studies concern about movement of pile bridge abutments. However, lateral displacement cause the serious failure of bridge by embankment under soft soil lateral flow A intention is obtained by analyzing the relationship between the safety factor of evaluation for lateral movements. Precise investigation and analysis are performed, in which the lateral movement of bridge abutments has occurred, and construct design strut-slab between bridge abutments in order to restraint lateral flow. As a result of this study, it was found that when evaluation for lateral movements is allowed to use Tschebotarioff's method and lateral flow decision number (I) and revision lateral flow decision number (M$_{I}$) by Korea Highway Corporation. Most important thing is decision of pressure of lateral flow at this case. Tschebotarioff's isoscales triangle method have no trouble analysis of pressure of lateral flow. Strut-slab method are nearly not have constructed case in this field site study that applied method. The method are between abutments combined steel strut and reinforced concrete slab. This method are effective restraint lateral flow but have little difficulty if long span bridge between abutments.s.

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A Study on the Determinants of Utilization of Family Health Worker in Rural Korea (일부농촌주민의 가정건강요원 이용에 영향을 주는 요인에 관한 연구 -연세 강화보건시범사업지역을 중심으로-)

  • Park, Jong-Ku
    • Journal of Preventive Medicine and Public Health
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    • v.12 no.1
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    • pp.38-42
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    • 1979
  • The objectives of this study were to identify the determinants of the 1. Home visiting activities by FHWs 2. Utilization of village Family Health Workers(FHWs) 3. Attitudes towards FHWs 4. Knowledge about FHW's activities] among housewives in the Kang Wha Community Health Project area This study was analysed by using path analysis Exogenous variables were 1. Distance between the housewives' houses and that of their local FHW 2. Duration of work of each FHW as FHW in her village 3. Number of preschool children in the households Endogenous variables were 1. Home visiting frequency to each household by FHW 2. Knowledge about FHW's activities 3. Attitude towards FHWs 4. Utilization of FHW] by the housewives The results were as follows: The shorter the distance between client's and FHW's house, the higher the number of preschool children in the household, and the longer the duration of work of FHW as FHW, the higher is the number of her household visits in a given time span. The more frequently the FHW visits a household and the higher the knowledge about FHW's activities in the household, the more positive is the attitude of the housewives to the FHW and the more frequently she visits and utilizes the FHW on her own initiative.

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L(3, 2, 1)-LABELING FOR CYLINDRICAL GRID: THE CARTESIAN PRODUCT OF A PATH AND A CYCLE

  • Kim, Byeong Moon;Hwang, Woonjae;Song, Byung Chul
    • Korean Journal of Mathematics
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    • v.25 no.2
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    • pp.279-301
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    • 2017
  • An L(3, 2, 1)-labeling for the graph G = (V, E) is an assignment f of a label to each vertices of G such that ${\mid}f(u)-f({\upsilon}){\mid}{\geq}4-k$ when $dist(u,{\upsilon})=k{\leq}3$. The L(3, 2, 1)-labeling number, denoted by ${\lambda}_{3,2,1}(G)$, for G is the smallest number N such that there is an L(3, 2, 1)-labeling for G with span N. In this paper, we compute the L(3, 2, 1)-labeling number ${\lambda}_{3,2,1}(G)$ when G is a cylindrical grid, which is the cartesian product $P_m{\Box}C_n$ of the path and the cycle, when $m{\geq}4$ and $n{\geq}138$. Especially when n is a multiple of 4, or m = 4 and n is a multiple of 6, then we have ${\lambda}_{3,2,1}(G)=11$. Otherwise ${\lambda}_{3,2,1}(G)=12$.

Galloping analysis of stranded electricity conductors in skew winds

  • Macdonald, J.H.G.;Griffiths, P.J.;Curry, B.P.
    • Wind and Structures
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    • v.11 no.4
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    • pp.303-321
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    • 2008
  • When first commissioned, the 1.6 km span 275kV Severn Crossing Conductor experienced large amplitude vibrations in certain wind conditions, but without ice or rain, leading to flashover between the conductor phases. Wind tunnel tests undertaken at the time identified a major factor was the lift generated in the critical Reynolds number range in skew winds. Despite this insight, and although a practical solution was found by wrapping the cable to change the aerodynamic profile, there remained some uncertainty as to the detailed excitation mechanism. Recent work to address the problem of dry inclined cable galloping on cable-stayed bridges has led to a generalised quasi-steady galloping formulation, including effects of the 3D geometry and changes in the static force coefficients in the critical Reynolds number range. This generalised formulation has been applied to the case of the Severn Crossing Conductor, using data of the static drag and lift coefficients on a section of the stranded cable, from the original wind tunnel tests. Time history analysis has then been used to calculate the amplitudes of steady state vibrations for comparison with the full scale observations. Good agreement has been obtained between the analysis and the site observations, giving increased confidence in the applicability of the generalised galloping formulation and providing insight into the mechanism of galloping of yawed and stranded cables. Application to other cable geometries is also discussed.

The Application of Genetic Algorithm for Optimum Virtual Path Network Design in ATM Network (ATM 망에서 최적 가상 경로망 설계를 위한 유전자 알고리즘 응용)

  • Kang, Ju-Rak;Kwon, Key-Ho
    • Journal of the Institute of Electronics Engineers of Korea CI
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    • v.38 no.5
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    • pp.86-92
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    • 2001
  • The Genetic algorithm is well known as an efficient algorithm which can solve a difficult optimization problems. Recently, there has been increasing interest in applying genetic algorithm to problems related to network design. In this paper, we propose a two step genetic algorithm for designing an optimum virtual path network(VPN) for a given physical network and traffic demand. The first step is to span route between every node pair in the network. The second step assigns VPs to minimize the total number of VPs, the number of VPs carried by a link, and the VPs hopcount. The propose algorithm is evaluated using computer simulation. The result shows that the VPN generated by the proposed algorithm is good in minimizing the number of VPs, the load on a link, and the VPs hopcount.

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Reynolds number effects on twin box girder long span bridge aerodynamics

  • Kargarmoakhar, Ramtin;Chowdhury, Arindam G.;Irwin, Peter A.
    • Wind and Structures
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    • v.20 no.2
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    • pp.327-347
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    • 2015
  • This paper investigates the effects of Reynolds number (Re) on the aerodynamic characteristics of a twin-deck bridge. A 1:36 scale sectional model of a twin girder bridge was tested using the Wall of Wind (WOW) open jet wind tunnel facility at Florida International University (FIU). Static tests were performed on the model, instrumented with pressure taps and load cells, at high wind speeds with Re ranging from $1.3{\times}10^6$ to $6.1{\times}10^6$ based on the section width. Results show that the section was almost insensitive to Re when pitched to negative angles of attack. However, mean and fluctuating pressure distributions changed noticeably for zero and positive wind angles of attack while testing at different Re regimes. The pressure results suggested that with the Re increase, a larger separation bubble formed on the bottom surface of the upstream girder accompanied with a narrower wake region. As a result, drag coefficient decreased mildly and negative lift coefficient increased. Flow modification due to the Re increase also helped in distributing forces more equally between the two girders. The bare deck section was found to be prone to vortex shedding with limited dependence on the Re. Based on the observations, vortex mitigation devices attached to the bottom surface were effective in inhibiting vortex shedding, particularly at lower Re regime.