• Title/Summary/Keyword: L-moment diagram

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Estimation of Drought Rainfall by Regional Frequency Analysis using L and LH-Moments(I) - On the Method of L-Moments - (L 및 LH-모멘트법과 지역빈도분석에 의한 가뭄우량의 추정(I) - L-모멘트법을 중심으로 -)

  • 이순혁;윤성수;맹승진;류경식;주호길
    • Magazine of the Korean Society of Agricultural Engineers
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    • v.45 no.5
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    • pp.97-109
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    • 2003
  • This study is mainly conducted to derive the design drought rainfall by the consecutive duration using probability weighted moments with rainfall in the regional drought frequency analysis. It is anticipated to suggest optimal design drought rainfall of hydraulic structures for the water requirement and drought frequency of occurrence for the safety of water utilization through this study. Preferentially, this study was conducted to derive the optimal regionalization of the precipitation data that can be classified by the climatologically and geographically homogeneous regions all over the regions except Cheju and Ulreung islands in Korea. Five homogeneous regions in view of topographical and climatological aspects were accomplished by K-means clustering method. Using the L-moment ratio diagram and Kolmogorov-Smirnov test, generalized extreme value distribution was confirmed as the best fitting one among applied distributions. At-site and regional parameters of the generalized extreme value distribution were estimated by the method of L-moments. Design drought rainfalls using L-moments following the consecutive duration were derived by the at-site and regional analysis using the observed and simulated data resulted from Monte Carlo techniques. Relative root-mean-square error (RRMSE), relative bias (RBIAS) and relative reduction (RR) in RRMSE for the design drought rainfall derived by at-site and regional analysis in the observed an simulated data were computed and compared. In has shown that the regional frequency analysis procedure can substantially more reduce the RRMSE. RBIAS and RR in RRMSE than those of at-site analysis in the prediction of design drought rainfall. Consequently, optimal design drought rainfalls following the regions and consecutive durations were derived by the regional frequency analysis.

Parametric study on eccentrically-loaded partially encased composite columns under major axis bending

  • Begum, Mahbuba;Driver, Robert G.;Elwi, Alaa E.
    • Steel and Composite Structures
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    • v.19 no.5
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    • pp.1299-1319
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    • 2015
  • This paper presents a detailed parametric study, conducted using finite element tools to cover a range of several geometric and material parameters, on the behaviour of thin-walled partially encased composite (PEC) columns. The PEC columns studied herein are composed of thin-walled built-up H-shaped steel sections with concrete infill cast between the flanges. Transverse links are provided between the opposing flanges to improve resistance to local buckling. The parametric study is confined to eccentrically-loaded columns subjected to major axis bending only. The parameters that were varied include the overall column slenderness ratio (L/d), load eccentricity ratio (e/d), link spacing-to-depth ratio (s/d), flange plate slenderness ratio (b/t) and concrete compressive strength ($f_{cu}$). The overall column slenderness ratio was chosen to be the primary variable with values of 5, 10 and 15. Other parameters were varied within each case of L/d ratio. The effects of the selected parameters on the behaviour of PEC columns were studied with respect to the failure mode, peak axial load, axial load versus average axial strain response, axial load versus lateral displacement response, moment versus lateral displacement behaviour and the axial load-moment interaction diagram. The results of the parametric study are presented in the paper and the influences of each of the parameters investigated are discussed.

Regional Frequency Analysis for Rainfall Data using the Burr XII Distribution (Burr XII 분포형을 이용한 강우자료 지역빈도해석)

  • Seo, Jungho;Shin, Hongjoon;Ahn, Hyunjun;Heo, Jun-Haeng
    • Proceedings of the Korea Water Resources Association Conference
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    • 2017.05a
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    • pp.162-162
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    • 2017
  • 최근 우리나라는 전 지구적인 기후변화로 인하여 집중호우 및 돌발 홍수와 같은 극치 사상들이 증가하고 있는 추세이며, 이에 대한 분석을 위해 극치 분포를 이용한 수문통계적 특성에 대한 접근이 주로 이루어지고 있다. 이를 위해서는 충분한 수의 자료가 필요하나 우리나라 강우자료는 지점별로 자료 보유 년 수가 비교적 많지 않기 때문에, 이러한 문제를 극복하기 위하여 하나의 지역, 즉 주어진 지점을 포함하여 수문학적으로 동일한 조건을 만족하는 주변 지점의 자료를 모두 포함하여 빈도해석을 실시하는 지역빈도해석이 필요하다. 따라서 본 연구에서는 지역빈도해석과 두 개의 형상매개변수를 포함하여 다양한 극치 수문통계특성을 나타낼 수 있다고 알려진 Burr XII 분포를 이용하여 우리나라 강우자료에 대한 그 적용성을 살펴보았다. 이를 위해 군집분석을 통한 강우지점의 지역화 과정을 거치고 분류된 지역을 L-moment ratio diagram에 도시하여, Burr XII 분포 영역 내 포함여부를 통해 Burr XII 분포의 적합도를 도시적으로 살펴보고, Hosking and Wallis (1997)이 제안한 적합성 척도($^{IST}$)를 통한 적합성 여부를 판별하였다. 또한 우리나라 강우자료에 비교적 적합하다고 알려진 분포인 generalized extreme value, generalized logistic, Gumbel 분포와의 비교를 위해, 전체 지역에 대하여 재현기간에 따른 상대편의 (relative bias)와 상대평균제곱근오차 (relative root mean square error)를 산정하여 Burr XII 분포형의 적용 가능성을 살펴보았다.

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Estimation of Drought Rainfall by Regional Frequency Analysis Using L and LH-Moments (II) - On the method of LH-moments - (L 및 LH-모멘트법과 지역빈도분석에 의한 가뭄우량의 추정 (II)- LH-모멘트법을 중심으로 -)

  • Lee, Soon-Hyuk;Yoon , Seong-Soo;Maeng , Sung-Jin;Ryoo , Kyong-Sik;Joo , Ho-Kil;Park , Jin-Seon
    • Journal of The Korean Society of Agricultural Engineers
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    • v.46 no.5
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    • pp.27-39
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    • 2004
  • In the first part of this study, five homogeneous regions in view of topographical and geographically homogeneous aspects except Jeju and Ulreung islands in Korea were accomplished by K-means clustering method. A total of 57 rain gauges were used for the regional frequency analysis with minimum rainfall series for the consecutive durations. Generalized Extreme Value distribution was confirmed as an optimal one among applied distributions. Drought rainfalls following the return periods were estimated by at-site and regional frequency analysis using L-moments method. It was confirmed that the design drought rainfalls estimated by the regional frequency analysis were shown to be more appropriate than those by the at-site frequency analysis. In the second part of this study, LH-moment ratio diagram and the Kolmogorov-Smirnov test on the Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Logistic (GLO) and Generalized Pareto (GPA) distributions were accomplished to get optimal probability distribution. Design drought rainfalls were estimated by both at-site and regional frequency analysis using LH-moments and GEV distribution, which was confirmed as an optimal one among applied distributions. Design rainfalls were estimated by at-site and regional frequency analysis using LH-moments, the observed and simulated data resulted from Monte Carlotechniques. Design drought rainfalls derived by regional frequency analysis using L1, L2, L3 and L4-moments (LH-moments) method have shown higher reliability than those of at-site frequency analysis in view of RRMSE (Relative Root-Mean-Square Error), RBIAS (Relative Bias) and RR (Relative Reduction) for the estimated design drought rainfalls. Relative efficiency were calculated for the judgment of relative merits and demerits for the design drought rainfalls derived by regional frequency analysis using L-moments and L1, L2, L3 and L4-moments applied in the first report and second report of this study, respectively. Consequently, design drought rainfalls derived by regional frequency analysis using L-moments were shown as more reliable than those using LH-moments. Finally, design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were derived by regional frequency analysis using L-moments, which was confirmed as a more reliable method through this study. Maps for the design drought rainfalls for the classified five homogeneous regions following the various consecutive durations were accomplished by the method of inverse distance weight and Arc-View, which is one of GIS techniques.

Analysis on Characteristics of Variation in Flood Flow by Changing Order of Probability Weighted Moments (확률가중모멘트의 차수 변화에 따른 홍수량 변동 특성 분석)

  • Maeng, Seung-Jin;Hwang, Ju-Ha
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.10 no.5
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    • pp.1009-1019
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    • 2009
  • In this research, various characteristics of South Korea's design flood have been examined by deriving appropriate design flood, using data obtained from careful observation of actual floods occurring in selected main watersheds of the nation. 19 watersheds were selected for research in Korea. The various characteristics of annual rainfall were analyzed by using a moving average method. The frequency analysis was decided to be performed on the annual maximum flood of succeeding one year as a reference year. For the 19 watersheds, tests of basic statistics, independent, homogeneity, and outlier were calculated per period of annual maximum flood series. By performing a test using the LH-moment ratio diagram and the Kolmogorov-Smirnov (K-S) test, among applied distributions of Gumbel (GUM), Generalized Extreme Value (GEV), Generalized Logistic (GLO) and Generalized Pareto (GPA) distribution was found to be adequate compared with other probability distributions. Parameters of GEV distribution were estimated by L, L1, L2, L3 and L4-moment method based on the change in the order of probability weighted moments. Design floods per watershed and the periods of annual maximum flood series were derived by GEV distribution. According to the result of the analysis performed by using variation rate used in this research, it has been concluded that the time for changing the design conditions to ensure the proper hydraulic structure that considers recent climate changes of the nation brought about by global warming should be around the year 2002.

Estimation of Design Rainfall Considering the Change of the Number of Years for Observed Data (관측년수변화를 고려한 설계강우량 산정)

  • Ryoo, Kyong-Sik;Lee, Soon-Hyuk;Hwang, Man-Ha;Lee, Sang-Jin
    • Proceedings of the Korean Society of Agricultural Engineers Conference
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    • 2005.10a
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    • pp.284-287
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    • 2005
  • The objective of this study is to check into variation trends of design rainfall according to change of the number of years for observed data. To make comparative study of the relation between design rainfall and recorded year, this study was used maximum rainfall for 24-hr consecutive duration at Gangneung, Seoul, Incheon, Chupungnyeong, Pohang, Daegu, Jeonju, Ulsan, Gwangju, Busan, Mokpo and Yeosu rainfall stations. The tests for Independence, Homogeneity and detection of outliers were used Wald-Wolfowitz's test, Mann-Whitney's test and Grubbs and Beck test respectively. To select appopriate distribution, the distribution of genaralized pareto(GPA), generalized extreme value(GEV), generalized logistic(GLO), lognormal and pearson type 3 distribution is judged by L-moment ratio diagram and Kolmogorov-Smirnov (K-S) test. Design rainfall was estimated by at-site frequency analysis using L-moments and Generalized extreme value(GEV) distribution according to change of the number of years for observed data. Through the comparative analysis for design rainfall induced by L-moments and GEV distribution, relationship between design rainfall and recorded year is provided.

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Estimation of Frequency-Based Flood Using At-Site Frequency Analysis and Regional Frequency Analysis (지점빈도분석과 지역빈도분석을 이용한 확률홍수량 산정)

  • Lee, Kil-Seong;Park, Kyung-Shin;Chung, Eun-Sung;Kim, Sang-Ug
    • Proceedings of the Korea Water Resources Association Conference
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    • 2008.05a
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    • pp.2249-2253
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    • 2008
  • 본 연구에서는 지점빈도분석과 지역빈도분석을 이용하여 확률홍수량을 산정 하였다. 지점빈도 분석은 Annual Maximum Series(AMS) 및 Partial Duration Series(PDS)를 이용하여 자료를 추출하고 각 자료에 적합한 확률분포를 이용하여 확률홍수량을 산정하였다. 그러나 AMS를 이용한 확률홍수량의 산정은 표본의 개수가 부족하면 이에 따른 변동성(variability)이 커지게 되는 단점이 존재하며, PDS를 사용하면 임계값(threshold)에 따른 주관적 영향이 결과에 반영되는 단점이 존재하는 것으로 알려져 있다. 따라서 본 연구에서는 PDS를 사용하는 경우의 단점을 해결하기 위해 연 1.7회의 발생횟수를 갖는 자료를 추출하고 몬테카를로 모의시험을 통하여 주관적 영향을 제거하였다. 또한 두 가지 방법에 의해 산정된 확률홍수량의 비교검토를 위해 지역빈도분석을 수행하였다. 유역의 면적과 일평균강우량으로부터 확률홍수량을 산정할 수 있는 것으로 알려진 Bayesian-Generalized Least Square(B-GLS) 방법을 이용하여 확률홍수량을 산정하였다. 최종적으로 안양천 유역의 13개 소유역에 대한 세 가지 방법에 의해 산정된 확률홍수량을 비교 검토한 결과, 특정한 방법이 항상 우수하다는 결론은 얻을 수 없었으나 각 유역별로 AMS가 가장 크고 B-GLS가 가장 작은 확률홍수량을 갖는 경향을 나타내었다.

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The Determination of Probability Distributions of Annual, Seasonal and Monthly Precipitation in Korea (우리나라의 연 강수량, 계절 강수량 및 월 강수량의 확률분포형 결정)

  • Kim, Dong-Yeob;Lee, Sang-Ho;Hong, Young-Joo;Lee, Eun-Jai;Im, Sang-Jun
    • Korean Journal of Agricultural and Forest Meteorology
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    • v.12 no.2
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    • pp.83-94
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    • 2010
  • The objective of this study was to determine the best probability distributions of annual, seasonal and monthly precipitation in Korea. Data observed at 32 stations in Korea were analyzed using the L-moment ratio diagram and the average weighted distance (AWD) to identify the best probability distributions of each precipitation. The probability distribution was best represented by 3-parameter Weibull distribution (W3) for the annual precipitation, 3-parameter lognormal distribution (LN3) for spring and autumn seasons, and generalized extreme value distribution (GEV) for summer and winter seasons. The best probability distribution models for monthly precipitation were LN3 for January, W3 for February and July, 2-parameter Weibull distribution (W2) for March, generalized Pareto distribution (GPA) for April, September, October and November, GEV for May and June, and log-Pearson type III (LP3) for August and December. However, from the goodness-of-fit test for the best probability distributions of the best fit, GPA for April, September, October and November, and LN3 for January showed considerably high reject rates due to computational errors in estimation of the probability distribution parameters and relatively higher AWD values. Meanwhile, analyses using data from 55 stations including additional 23 stations indicated insignificant differences to those using original data. Further studies using more long-term data are needed to identify more optimal probability distributions for each precipitation.

A Study of Rectangular-shaped Passive Row Piles in Horizontal Sand-ground under Lateral Soil Movement by Model Test (수평모래지반에서 측방변형을 받는 사각형 수동 열말뚝에 관한 실험적 연구)

  • Bae, Jong-Soon;Kwon, Min-Jea
    • Journal of the Korean Geotechnical Society
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    • v.24 no.4
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    • pp.23-36
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    • 2008
  • This study describes model tests on instrumented rectangular-shaped passive row piles embedded in horizontal sand-ground undergoing lateral soil movement. We tried to find the property of row piles dependent on the shape of pile, including the position of the pile in row, pile spacing, and soil movement. The results of test are as follows. The lateral earth pressure diagram variously appeared to be triangle, trapezoid and rectangular by shape and position of pile. The outer pile has a larger bending moment than the inner pile in the case of B-type, the inner piles has larger one than outer pile in case of H-type. $R_f$ (the ratio of resistance to lateral soil movement) was found to increase with increasing pile spacing irrespective of pile-shape. Y/L (location of action of lateral resistance force) for $d_s$ (displacement of soil) and $S_h$ (spacing of pile) appeared to be nearly regular position, and H-type is higher than B-type.

Estimating design floods for ungauged basins in the geum-river basin through regional flood frequency analysis using L-moments method (L-모멘트법을 이용한 지역홍수빈도분석을 통한 금강유역 미계측 유역의 설계홍수량 산정)

  • Lee, Jin-Young;Park, Dong-Hyeok;Shin, Ji-Yae;Kim, Tae-Woong
    • Journal of Korea Water Resources Association
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    • v.49 no.8
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    • pp.645-656
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    • 2016
  • The study performed a regional flood frequency analysis and proposed a regression equation to estimate design floods corresponding to return periods for ungauged basins in Geum-river basin. Five preliminary tests were employed to investigate hydrological independence and homogeneity of streamflow data, i.e. the lag-one autocorrelation test, time homogeneity test, Grubbs-Beck outlier test, discordancy measure test ($D_i$), and regional homogeneity measure (H). The test results showed that streamflow data were time-independent, discordant and homogeneous within the basin. Using five probability distributions (generalized extreme value (GEV), three-parameter log-normal (LN-III), Pearson type 3 (P-III), generalized logistic (GLO), generalized Pareto (GPA)), comparative regional flood frequency analyses were carried out for the region. Based on the L-moment ratio diagram, average weighted distance (AWD) and goodness-of-fit statistics ($Z^{DIST}$), the GLO distribution was selected as the best fit model for Geum-river basin. Using the GLO, a regression equation was developed for estimating regional design floods, and validated by comparing the estimated and observed streamflows at the Ganggyeong station.