• Journal of Korea Water Resources Association
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• v.49 no.4
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• pp.315-325
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• 2016

Generally, a natural river discharge is highly regulated by the hydraulic structures, and the regulated flow is substantially different from natural inflow characteristics for the use of water resources planning. The natural inflow data are necessarily required for hydrologic analysis and water resources planning. This study aimed to develop an integrated model for more reliable simulation of daily dam inflow. First, a piecewise Kernel-Pareto distribution was used for rainfall simulation model, which can more effectively reproduce the low order moments (e.g. mean and median) as well as the extremes. Second, a Bayesian Markov Chain Monte Carlo scheme was applied for the SAC-SMA rainfall-runoff model that is able to quantitatively assess uncertainties associated with model parameters. It was confirmed that the proposed modeling scheme is capable of reproducing the underlying statistical properties of discharge, and can be further used to provide a set of plausible scenarios for water budget analysis in water resources planning.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.33 no.4
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• pp.1271-1279
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• 2013

In this paper, a study on the prediction method of basic wind speed at the construction site of long-span bridge using short-term measurements was conducted. To determine the basic wind speed in the wind resistant design for the long-span bridge away from the weather station, statistical analysis of long-term data at site is required. Wind observation mast was installed at site, and short-term measurements were gathered and the correlation analysis between the site and the station was done using regression analysis and MCP(Measure-Correlate-Predict). The long-term wind data of the site was obtained from correlation formula after topographical revision of long-term data of the station. And basic wind speed could be estimated by extreme probability distribution analysis. The research results show that the wind speed by regression analysis is predicted lower than by MCP and after this study a series of correlation analyses at several sites will show clearly the difference two methods. And also a quality control of long-term wind data is very important in estimation of wind speed.

• Proceedings of the Korea Water Resources Association Conference
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• 2009.05a
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• pp.1316-1320
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• 2009

최근 한반도지역의 시공간적 수문변화 및 지속시간 연최대강우 추세분석을 위하여 기상청에서 제공 되어지는 관측자료를 이용하여 분석을 실시하였다. 분석을 위하여 서울, 인천, 속초, 부산, 군산등 전국적인 분포를 보이는 60개소의 일강수량, 일평균기온, 일최고 및 최저기온, 일평균풍속, 일습도 자료를 수집하였다. 더불어 지속시간별 연최대강우 추세분석을 위하여 동일기간에 대한 시간자료를 수집하여 분석을 실시하였다. 일자료를 이용한 분석결과 분석기간의 년평균강수량은 1998년 이전 1342.2mm였으나, 1998년 이후는 1,511.6mm로서 최근의 강수량 증가를 확인할 수 있었다. 계절적으로는 비홍수기에 비하여 홍수기에 강수량 증가가 더욱 두드러졌으며, 수계별로는 낙동강과 섬진강의 경우가 한강과 금강등 기타 수계에 비하여 최근의 강수량 증가추세가 상대적으로 뚜렷한 것으로 분석되었다. 내륙과 해안지역의 분석결과에서는 해안지역의 년강수량이 내륙에 비하여 90mm 정도 높게 나타났으며, 지역별로는 동해안지역이 서해안과 남해안에 비하여 변화경향이 크게 나타났다. 일최고강수량 및 집중호우빈도 분석결과 수계별 분석의 경우 한강수계가 다른 수계에 비하여 상대적으로 큰 증가경향을 보였으며, 한편 섬진강수계는 다소 완만한 경향을 나타내고 있었다. 집중호우빈도 분석결과 역시 년강수량과 마찬가지로 동해안지역에서의 변화경향이 크게 나타나고 있었다. 무강수일수는 전국적으로 감소경향을 보이고 있어, 강수발생일당 강수량은 증가하는 경향을 보이고 있었다. 이러한 수문학적 변화경향을 세부적으로 살펴보기 위하여 수계별 대표지점을 선정하여 지속시간별(1hr, 2hr, 3hr, 4hr, 6hr, 12hr) 강우강도 추세분석을 실시하였다. 분석결과 지속시간에 따른 강우강도 역시 증가하는 경향을 나타내는 것을 확인하였으며 짧은 지속시간이 상대적으로 큰 증가경향을 나타내는 것으로 확인하였다. 하지만 정확한 분석을 위하여 보다 많은 관측소에 대한 추가분석이 필요할 것으로 판단되어 진다.

• Journal of the Korea institute for structural maintenance and inspection
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• v.20 no.4
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• pp.1-8
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• 2016

Recently, buildings tend to be large size, complex shape and functional. As the size of buildings is becoming massive, the need for structural health monitoring(SHM) technique is ever-increasing. Various SHM techniques have been studied for buildings which have different dynamic characteristics and are influenced by various external loads. Generally, the visual inspection and non-destructive test for an accessible point of structures are performed by experts. But nowadays, the system is required which is online measurement and detect risk elements automatically without blind spots on structures. In this study, in order to consider the response of non-linear structures, proposed a signal feature extraction and the adaptive threshold setting algorithm utilized to determine the abnormal behavior by using statistical methods such as control chart, root mean square deviation, generalized extremely distribution. And the performance of that was validated by using the acceleration response of structures during earthquakes measuring system of forced vibration tests and actual operation.

• Proceedings of the Korea Water Resources Association Conference
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• 2018.05a
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• pp.183-183
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• 2018

최근 국지성 호우와 홍수, 그리고 극심한 가뭄과 같은 기후변화로 인한 극치수문현상이 빈번하게 관측되고 있다. 이는 과거와는 다른 양상의 강우사상으로 광화문(2010), 강남역(2010), 청계천(2010), 청주(2017), 부산(2017) 등 주요 도심지역에 내수침수로 인한 막대한 인명, 재산 피해를 발생시켰으며, 피해의 빈도와 강도가 증가되고 있는 추세이다. 특히 기후변화에 따른 강우강도의 증가는 설계홍수량의 변화를 초래하며, 그로 인해 홍수 위험도 증가와 치수안전도 감소 등 수공구조물의 설계기준에 불확실성을 증가시키는 원인이 되고 있다. 최근 국내에서도 기후변화에 따른 수공시설물 설계빈도 상향에 대한 필요성이 대두되고 있으나 기후변화의 불확실성 및 기후시나리오의 한계로 인해 정량적 분석결과가 제시되지 않아 정책 수립에 반영하기 현실적으로 어려운 상황이다. 본 연구에서는 기후변화에 따른 홍수특성에 대한 도시유역의 영향을 평가하기 위하여 서울 효자배수분구를 대상유역으로 선정하고, 과거관측자료 기준 S0 대비 상세화 기법(Downscaling) 및 편의보정(Bias Correlation)으로 생성된 RCP 4.5 기후시나리오 HadGEM3-RA(RCM)모델을 통해 생산된 S1, S2, S3 기간의 확률강우량의 변화를 평가하였다. 이때 확률분포형은 Gumbel, 매개변수 추정은 최우도법(ML)을 사용하였고, 도시유출모형을 이용하여 최대첨두홍수량 및 침수면적 산정하고 기후변화 기간별 변동성을 분석하였다. 평가 결과 대부분의 도시배수시설물의 설계빈도인 10년빈도를 3사분위값을 기준으로 할 때 50년과 70년 이상의 미래를 가정할 경우 각각 약 10%, 20%의 확률 홍수량이 증가가 예상되었다. 이러한 결과 현재 구축되어 있는 배수시스템의 설계빈도를 크게 상회하는 값으로 도시배수시스템에 많은 어려움을 줄 것으로 예상되며, 정량적 평가 결과가 기후변화 적응 대책 신규 시설물 설계시 참고할 수 있는 기초자료로 활용될 것으로 판단된다.

• Journal of Korea Water Resources Association
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• v.45 no.8
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• pp.815-826
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• 2012

The underestimating trend using existing ordinary regression (OR) based trend analysis has been a well-known problem. The existing OR method based on least squares approximate the conditional mean of the response variable given certain values of the time t, and the usual assumption of the OR method is normality, that is the distribution of data are not dissimilar form a normal distribution. In this regard, this study proposed a quantile regression that aims at estimating either the conditional median or other quantiles of the response variable. This study assess trend in annual daily maximum rainfall series over 64 weather stations through both in OR and QR approach. The QR method indicates that 47 stations out of 67 weather stations are a strong upward trend at 5% significance level while OR method identifies a significant trend only at 13 stations. This is mainly because the OR method is estimating the condition mean of the response variable. Unlike the OR method, the QR method allows us flexibly to detect the trends since the OR is designed to estimate conditional quantiles of the response variable. The proposed QR method can be effectively applied to estimate hydrologic trend for either non-normal data or skewed data.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.153-160
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• 2011

Recently there are many long span cable supported bridges like Cable Stayed Bridge and Suspension Bridge already constructed or planned. Reconsidering of proper design wind load of long span bridge is required since the meteorological value based on the data only from 1960s to 1995 has been used when we estimate the wind load for designing long span bridges. In this paper, the research area was confined to western and southern coasts where many long span bridges have constructed. The method of moment and the least-squares method were used to estimate the expected wind speeds of 100 year's return period for girder bridges and for 200 year's return period for long span bridges based on the Gumbel's distribution. As the return-period wind speed on the land face was revised because of recent high speed velocity, the revised return-period wind speed is increased by 17%. Compatibility of return-period wind speed was also evaluated using RMS (Root Mean Square) error method. Aa a result of this paper, the least-squares method is more compatible than the method of moment in the case of western and southern coasts in Korea.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.25 no.5
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• pp.317-326
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• 2013

Probabilistic design methods can consider uncertainties of design variables and are widely used in the design of vertical breakwaters. The probabilistic design methods include a partial safety factor method, reliabilitybased design method, and performance-based design method. Especially the performance-based design method calculates the accumulated sliding distance during the lifetime of the breakwater or during a design storm. Recently a time-dependent performance-based design method has been developed based on the first-passage probability of individual sliding distance during a design storm. However, because the allowable criteria in the first-passage probability method are not established, the stability of structures cannot be quantitatively evaluated. In this study, the allowable first-passage probabilities for two limit states are proposed by calculating the first-passage probabilities for the cross-sections designed with various water depths and characteristics of extreme wave height distributions. The allowable first-passage probabilities are proposed as 5% and 1%, respectively, for the repairable limit state (allowable individual sliding distance of 0.03 m) and ultimate limit state (allowable individual sliding distance of 0.1 m). The proposed criteria are applied to the evaluation of the effect of wave-height increase due to climate change on the stability of the breakwater.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.37 no.1
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• pp.29-41
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• 2017

Design rainfalls are one of the most important hydrologic data for river management, hydraulic structure design and risk analysis. The design rainfalls are first estimated by a point frequency analysis and the IDF (intensity-duration-frequency) curve is then constructed by a nonlinear regression to either interpolate or extrapolate the design rainfalls for other durations which are not used in the frequency analysis. It has been widely recognised that the more reliable approaches are required to better account for uncertainties associated with the model parameters under circumstances where limited hydrologic data are available for the watershed of interest. For these reasons, this study developed a hierarchical Bayesian based GLM (generalized linear model) for a regional frequency analysis in conjunction with a scaling function of the parameters in probability distribution. The proposed model provided a reliable estimation of a set of parameters for each individual station, as well as offered a regional estimate of the parameters, which allow us to have a regional IDF curve. Overall, we expected the proposed model can be used for different aspects of water resources planning at various stages and in addition for the ungaged basin.