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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korean Society of Coastal and Ocean Engineers
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Korean Society of Coastal and Ocean Engineers
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Volume & Issues
Volume 24, Issue 6 - Dec 2012
Volume 24, Issue 5 - Oct 2012
Volume 24, Issue 4 - Aug 2012
Volume 24, Issue 3 - Jun 2012
Volume 24, Issue 2 - Apr 2012
Volume 24, Issue 1 - Feb 2012
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Development of Time-Dependent Reliability-Based Design Method Based on Stochastic Process on Caisson Sliding of Vertical Breakwater
Kim, Seung-Woo ; Cheon, Sehyeon ; Suh, Kyung-Duck ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 305~318
DOI : 10.9765/KSCOE.2012.24.5.305
Although the existing performance-based design method for the vertical breakwater evaluates an average sliding distance during an arbitrary time, it does not calculate the probability of the first occurrence of an event exceeding an allowable sliding distance(i.e. the first-passage probability). Designers need information about the probability that the structure is damaged for the first time for not only design but also maintenance and operation of the structure. Therefore, in this study, a time-dependent reliability design method based on a stochastic process is developed to evaluate the first-passage probability of caisson sliding. Caisson sliding can be formulated by the Poisson spike process because both occurrence time and intensity of severe waves causing caisson sliding are random processes. The occurrence rate of severe waves is expressed as a function of the distribution function of sliding distance and mean occurrence rate of severe waves. These values simulated by a performance-based design method are expressed as multivariate regression functions of design variables. As a result, because the distribution function of sliding distance and the mean occurrence rate of severe waves are expressed as functions of significant wave height, caisson width, and water depth, the first-passage probability of caisson sliding can be easily evaluated.
Development of the Inter-tidal Exposure Duration Formulae Using Tidal Harmonic Constants
Jeong, Shin Taek ; Cho, Hongyeon ; Ko, Dong Hui ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 319~325
DOI : 10.9765/KSCOE.2012.24.5.319
A new formulae for the estimation of the exposure duration in the inter-tidal zone are developed. The exposure duration is one of the most important factors influencing the habitat distribution of the benthic organisms. The formulae can estimate the exposure duration only using the four major tidal harmonic constants available in almost coastal areas. It is easier than the existing method using the frequency analysis of the hourly tidal elevation data. The estimation results by using the formulae suggested in this study are compared with the value by using the observed tidal elevation data analysis in the west coast, Korea. The mean RMS (root-mean squared) errors ranged form 0.8 to 1.4%. It can be used to simply estimate the accurate exposure duration in the region not having the longterm hourly tidal elevation data.
Error analysis on the Offshore Wind Speed Estimation using HeMOSU-1 Data
Ko, Dong Hui ; Jeong, Shin Taek ; Cho, Hongyeon ; Kim, Ji Young ; Kang, Keum Seok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 326~332
DOI : 10.9765/KSCOE.2012.24.5.326
In this paper, error analyses on the calculation of offshore wind speed have been conducted using HeMOSU-1 data to develop offshore wind energy in Yeonggwang sea of Korea and onshore observed wind data in Buan, Gochang and Yeonggwang for 2011. Offshore wind speed data at 98.69 m height above M.S.L is estimated using relational expression induced by linear regression analysis between onshore and offshore wind data. In addition, estimated offshore wind speed data is set at 87.65 m above M.S.L using power law wind profile model with power law exponent(0.115) and its results are compared with the observed data. As a result, the spatial adjustment error are 1.6~2.2 m/s and the altitude adjustment error is approximately 0.1 m/s. This study shows that the altitude adjustment error is about 5% of the spatial adjustment error. Thus, long term observed data are needed when offshore wind speed was estimated by onshore wind speed data. because the conversion of onshore wind data lead to large error.
Sensitivity Analysis of Global Wind-Wave Model
Park, Jong Suk ; Kang, KiRyong ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 333~342
DOI : 10.9765/KSCOE.2012.24.5.333
We studied the characteristics of spatial distribution of global wave height and carried out the modelsensitivity test by changing the input field, model resolution and physical factor (effective wind factor) since the spatial and temporal resolution in wind wave forecasting is one of most important factors. Comparisons among the different cases, and also between model, buoy and satellite data have been made. As a results of the wind-wave model run using the high resolution wind field, the bias of significant wave height showed the positive tendency and the Root-Mean Square Error(RMSE) was a bit decreased based on the comparison with buoy data. When the model resolution was changed to higher, the bias and RMSE was increased, and as the effective wind factor was smaller than default value(= 1.4) the bias and RMSE showed also decreasing pattern.
Shallow-water Design Waves at Gangreung Beach through the Analysis of Long-term Measured Wave Data and Numerical Simulation Using Deepwater Wave Conditions
Jeong, Weon Mu ; Jun, Ki Cheon ; Kim, Gunwoo ; Oh, Sang-Ho ; Ryu, Kyong-Ho ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 343~351
DOI : 10.9765/KSCOE.2012.24.5.343
In this study, shallow-water design waves are calculated for the return period of 10, 20, 30, and 50 years, based on the extreme value analysis of the wave measurement data at Gangneung beach. These values are compared with the results of SWAN simulation with the boundary condition of the deep-water design waves of the corresponding return periods at the Gangneung sea area provided by the Fisheries Agency (FA, 1988) and Korea Ocean Research & Development Institute (KORDI, 2005). It is found that the shallow-water wave heights at Gangneung beach calculated by the deep-water design waves were significantly less than the observation data. As the return period becomes higher, the significant wave heights obtained by the extreme value analysis becomes higher than those computed by SWAN with the deep-water design waves of the corresponding return periods. KORDI computed the hindcast wave data from January 2004 to August 2008 by WAM with a finer-grid mesh system than those of previous studies. Comparisons of the wave hindcast results with the wave observation show that the reproducibility of the winter-season storm wave was considerably improved compared to the hindcast data from 1979 to 2003. Hereafter, it is necessary to carry out hindcast wave data for the years before 2004 using WAM with the finer-grid mesh system and to supplement the deep-water design wave.
Near Real-time Immediate Forecasting of Storm Surge Based on Typhoon Advisories
Suh, SeungWon ; Lee, HwaYoung ; Kim, HyeonJeong ; Park, JinSoo ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 352~365
DOI : 10.9765/KSCOE.2012.24.5.352
A primary study on the rapid modeling of storm surge, which is one of typical coastal disasters, for immediate forecasting in conjunction with typhoon advisories is done and tested for the typhoons Bolaven, Tembin and Sanba which attacked to Korean Peninsula on August and September in this year 2012. Semi automatic rapid computations according to JTWC typhoon advisories were performed and uploaded to the web by models SLOSH in PC and ADCIRC in parallel clusters with 64 cores having 57k nodes encompassing the North-Western Pacific region. It only takes 1 and 2 hours from taking advisory to web uploading, respectively. By comparison with observed water surface elevations for the major tidal stations after Bolaven attack it shows within RMS error of 0.17~0.19 m for surge heights and only deviates 1 hour of peak surge time in ADCIRC model. Thus it is concluded that this approach provides a frame of near real-time immediate forecasting of storm surges with satisfactions.
Backshore Erosion due to High Swell Waves
Kim, Kyu Han ; Shim, Kyu Tae ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 24, issue 5, 2012, Pages 366~371
DOI : 10.9765/KSCOE.2012.24.5.366
High swell has been known for the one of the main causes of beach erosion in the east coast of Korea. In this study, coastal topography changes due to high swells are simulated to find its effect on the backshore by using movable bed experiments and numerical experiments. Sea bottom topographical changes due to various incident waves were investigated using CSHORE model in the numerical experiments. Furthermore, the mechanism and the phenomena of beach erosion due to waves and high swells on the foreshore and backshore were analyzed and compared with movable bed hydraulic experiments.