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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 28, Issue 3 - Jun 2016
Volume 28, Issue 2 - Apr 2016
Volume 28, Issue 1 - Feb 2016
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Development of Stochastic Decision Model for Estimation of Optimal In-depth Inspection Period of Harbor Structures
Lee, Cheol-Eung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 63~72
DOI : 10.9765/KSCOE.2016.28.2.63
An expected-discounted cost model based on RRP(Renewal Reward Process), referred to as a stochastic decision model, has been developed to estimate the optimal period of in-depth inspection which is one of critical issues in the life-cycle maintenance management of harbor structures such as rubble-mound breakwaters. A mathematical model, which is a function of the probability distribution of the service-life, has been formulated by simultaneously adopting PIM(Periodic Inspection and Maintenance) and CBIM(Condition-Based Inspection and Maintenance) policies so as to resolve limitations of other models, also all the costs in the model associated with monitoring and repair have been discounted with time. From both an analytical solution derived in this paper under the condition in which a failure rate function is a constant and the sensitivity analyses for the variety of different distribution functions and conditions, it has been confirmed that the present solution is more versatile than the existing solution suggested in a very simplified setting. Additionally, even in that case which the probability distribution of the service-life is estimated through the stochastic process, the present model is of course also well suited to interpret the nonlinearity of deterioration process. In particular, a MCS(Monte-Carlo Simulation)-based sample path method has been used to evaluate the parameters of a damage intensity function in stochastic process. Finally, the present stochastic decision model can satisfactorily be applied to armor units of rubble mound breakwaters. The optimal periods of in-depth inspection of rubble-mound breakwaters can be determined by minimizing the expected total cost rate with respect to the behavioral feature of damage process, the level of serviceability limit, and the consequence of that structure.
Development of a Moving Body Type Wave Power Generator using Wave Horizontal Motions and Hydraulic Experiment for Electric Power Production
Hwang, Seong Su ; Lee, Dong Soo ; Yang, Kyong Uk ; Byun, Jung Hwan ; Park, Il Heum ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 73~80
DOI : 10.9765/KSCOE.2016.28.2.73
To reduce the mechanical energy loss and to get the high energy efficiency, an apparatus of wave power generation inducing a consistent one way rotating motion from the wave reciprocation motions was developed and the hydraulic experiments for the real electric power production were conducted and the results were discussed. In the experiments for the shape of the buoyant tank, the efficiency of the fixed 9 cm diameter type enduring the wave plate weight was 14.6% and this was the best result for all shapes. But although the free sliding type was expected to represent a high efficiency, the experiments did not show a good result as 8.5% efficiency. Therefore, the shape of buoyant tank was decided as the fixed 9 cm diameter type in the next all tests. In the experiments for the various incident waves, when the water depth was 90 cm, the average efficiencies were measured as 3.9% in the 2nd gear, 4.9% in the 3rd gear, 4.9% in the 4th gear, 12.0% in the 5th gear, 10.0% in the 6th gear, 3.1% in the 7th gear, and 3.0% in the 8th gear. Also, when the water depth was 80 cm, the average efficiency was shown as 15.0% with 5th gear condition. Therefore the high average efficiency as 13.5% was given with 80~90 cm water depth and the 5th gear in the model.
Inter-annual Variation of Tides on the Western Coasts of Korea
Jung, Tae Sung ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 81~91
DOI : 10.9765/KSCOE.2016.28.2.81
Harmonic analysis of tide data observed on the western coasts has been conducted. The changing trends of harmonic constants were reviewed. Overall, amplitudes of semidiurnal tide are not changed and present phases are faster than in the past. In Mokpo located in a semi-enclosed bay, the amplitudes have been greatly increased and the phases have become earlier due to construction of sea-dike and seawalls. Harmonic constants of diurnal tide have not been changed except Mokpo. In Mokpo the phases of diurnal tide have been earlier. Tidal ranges in spring tide and neap tide have not been significantly changed except Mokpo. In Mokpo tidal ranges have been increased and tidal flats widened. Approximate higher high water has been overall rising. Therefore, Korean western coasts can be easily inundated than before.
Reliability Analysis of Tripod Support Structure for Offshore Wind Turbine using Stress Concentration Factor
Lee, Sang Geun ; Kim, Dong Hyawn ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 92~100
DOI : 10.9765/KSCOE.2016.28.2.92
Reliability analysis of tripod support structure for offshore wind turbine was performed. Extreme distribution function of peak response due to wind and wave loads was estimated by applying peak over threshold(POT) method. Then, stress based limit state function was defined by using maximum stress of support structure which was obtained by multiplying beam stress and concentration factor. The reliability analysis result was compared when maximum stress was calculated from shell element. Reliability index was evaluated using first order reliability method(FORM).
Analysis on the Estimation Error of the Lowest and Highest Astronomical Tides using the Wido Tidal Elevation Data
Jeong, Shin Taek ; Yoon, Jong Tae ; Cho, Hongyeon ; Ko, Dong Hui ; Kang, Keum Seok ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 101~108
DOI : 10.9765/KSCOE.2016.28.2.101
In designing of the wind power facilities, the highest and lowest astronomical tides (HAT and LAT) are needed in terms of an international design tidal water levels. The AHHW and ALLW, however, have been used as the design tidal levels in Korea. The HAT and LAT in the Wido coastal sea should be estimated to satisfy the standard because the pilot wind power facilities will be located in the adjacent Wido coastal sea. In this study, the HAT and LAT are estimated using the 31-years hourly tidal elevation data of the Wido tidal gauging station and the nodal variation patterns of the major lunar components, such as
, are analysed to check the expected long-term lunar cycle, i.e., 18.61-year's nodal variation patterns. The temporal amplitude variations of the
clearly show the 18.61-years periodic patterns in case of the no-nodal correction condition. In addition, the suggested HAT and LAT elevations, estimated as the upper and lower confidence limits of the yearly HAT and LAT elevations, show 40 cm greater than AHHW and 35 cm lower than ALLW, respectively.
Trends of the Storm Wave Appearance on the East Coast Analyzed by using Long-term Wave Observation Data
Jeong, Weon Mu ; Ryu, Kyong-Ho ; Oh, Sang-Ho ; Baek, Won-dae ;
Journal of Korean Society of Coastal and Ocean Engineers, volume 28, issue 2, 2016, Pages 109~115
DOI : 10.9765/KSCOE.2016.28.2.109
The trend in appearance of storm waves on the east coast of Korea was investigated based on long-term wave data observed at six different stations. At the four wave stations of KIOST (Sokcho, Mukho, Hupo, and Jinha), no notable trend was found during the observation period with respect to the annual average and maximum values of the significant wave height. In addition, the annual number of the appearance of storm waves showed decreasing trend at the three stations except Jinha, where slightly increasing trend of the quantity was recognized. In contrast, at Donghea ocean data buoy of KMA, abruptly increasing trend was found for the annual average and maximum of the significant wave height and for the annual number of the appearance of storm waves as well, demonstrating lack of consistency in the observation data from Donghea buoy of KMA.