• Journal of Korean Society of Coastal and Ocean Engineers
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• v.31 no.6
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• pp.351-355
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• 2019

Load resistance factors for the limit state design of vertical caisson breakwaters are presented. Reliability analysis of 16 breakwaters in nationwide ports was conducted to calculate the partial safety factors and they were converted into load and resistance factors. The final load resistance factor was calibrated by applying the optimization technique to the individually calculated load resistance factors. Finally, the breakwater was redesigned using the optimal load resistance factor and verified whether the target level was met. The load resistance factor according to the change of the target reliability level is presented to facilitate the limit state design of breakwater.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.21 no.3
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• pp.224-229
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• 2009

Partial safety factors(PSFs) for Level I reliability based design of caisson type quay walls were calculated. First order reliability method(FORM) based PSFs are the functions of sensitivities of limit state function with respect to design random variables, target reliability index, characteristic values and first moment of random variables. Modified PSFs for water level and resilient water level are newly defined to keep consistency with the current design code. In the numerical example, PSFs were calculated by using a target reliability index. Seismic coefficient is defined to show extreme distribution. It was found that PSFs for seismic coefficient becomes smaller as the return period for design seismic coefficient grows longer.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.28 no.1
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• pp.27-33
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• 2016

A numerical analysis on deck wetness is carried out for a large caisson directly wet-towed by tugs in irregular waves. A constant panel method is used for linear analysis in frequency domain and a statistical post-processing for the deck wetness is presented. Hydrodynamic coefficients obtained from the frequency domain computation are imported for time domain analysis which enables complete modeling for towing equipment, environment, etc. Both frequency and time domain computations over two sea states are performed and comparison is made. In the time domain analysis, towing systems of various arrangements of tugs are investigated from short-term prediction for the largest deck wetness and the number of occurrences of deck wetness.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.79-92
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• 2011

In this study, wave pressure of short-period gravity waves and tsunami acting on the upright section of the horizontal-slit type caisson placed on the impermeable or permeable seabed, which is a well-known permeable breakwater with a good wave controlling ability, are investigated via numerical simulations. Further, the permeable seabed was modeled as the porous media with porosity of 0.4. Using the numerical results, the effects of the seabed conditions on the wave pressure on the front wall and inside wall of the chamber have been studied. In the numerical simulations, short-period gravity waves and tsunami(solitary wave or bore) with the same amplitude to the gravity wave are considered. A numerical wave tank is used, which is able to consider a gas-liquid two-phase flow in the same calculation zone. Numerical results show that the wave pressure of the tsunami was 3~5 times higher than the short-period gravity waves acting on the front wall and it was 2~4 times higher than the short-period gravity waves acting on the inner wall.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.32 no.5
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• pp.331-339
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• 2020

In this study, ways to reduce the edge pressure at the bottom plate of the caisson breakwater were considered. The water depth, freeboard, design wave height and period, and the location of the center of gravity on the super-structure of the breakwater were selected as key design variables that influence the edge pressure, and analyzed how the edge pressure changes according to the change of this key variables. The pressure distribution formulae suggested in the design standard was applied for the calculation of design wave forces. Based on the wave forces, the required effective self-weight of the super-structure and the minimum width of the caisson were determined to have a safety factor of 1.2 against sliding and overturning. From the results, it was found that the edge pressure rapidly increased as the water depth increased, and could exceed the allowable bearing capacity when it reached a certain water depth which is 20 m within the analysis conditions. It was also confirmed that the edge pressure gradually increased linearly as the freeboard increased, but decreased with the increase of the wave height and period. This edge pressure could be significantly reduced up to more than 20% by moving the center of gravity of the super-structure to the seaside, which is 5% of the caisson width. Based on the analysis results and the recently conducted research results, a method was proposed to reduce the edge pressure that can be used in the design.

• Journal of the Korean GEO-environmental Society
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• v.12 no.4
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• pp.33-41
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• 2011

In case of building up port facilities on soft ground, unsymmetrical surcharge of embankment, which make the excess pore water pressure to increase, causes to occur lateral displacement due to plasticity of soil. A study on lateral displacement and settlement of the caisson, which is installed on improved ground, was accomplished. The field measurement data and calculated values obtained from FEM program of Plaxis were compared and analyzed. For numerical analysis, the properties of soils, constructions stage and time were considered. Lateral displacement was measured at the point of inclinometers installed in front of caisson. Settlement was measured at the center of extra embankment behind of caisson. Comparison of measured and calculated for lateral displacement showed that the calculated value was greater than the measured, and increasing trend was different. The calculated value showed step increasing as step extra embankment applied, whereas the measured gradually was increased. For settlement of embankment, the amount of both measured and calculated were similar, but the trend was different like that of lateral movement.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.16 no.1
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• pp.27-38
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• 2004

In this study, the reliability design method developed by Shimosako and Takahashi in 1999 for calculation of the expected sliding distance of the caisson of a vertical breakwater is extended to take into account the variability in wave direction such as directional spreading of waves, obliquity of the deep-water design principal wave direction from the shore-normal direction, and its variation about the design value. To calculate the transformation of random directional waves, the model developed by Kweon et al. in 1997 is used instead of Goda's model, which was developed in 1975 for unidirectional random waves normally incident to a straight coast with parallel depth contours and has been used by Shimosako and Takahashi. The effects of directional spreading and the variation of deep-water principal wave directions were minor compared with those of the obliquity of the deep-water design principal wave direction from the shore-normal direction, which tends to reduce the expected sliding distance as it increases. Especially when we used the field data in a part of east coast of Korea, considering the variability in wave directions reduced the expected sliding distance to about one third of that not considering the directional variability. Reducing the significant wave height calculated at the design site by 6％ to correct the effect of wave refraction neglected in using Goda's model was found to be proper when the deep-water design principal wave direction is about 20 degrees. When it is smaller than 20 degrees, a value smaller than 6％ should be used, or vice versa. When we designed the caisson with the expected sliding distance to be 30㎝, in the area of water depth of 25 m or smaller, we could reduce the caisson width by about 30％ at the maximum compared with the deterministic design, even if we did not consider the variability in wave directions. When we used the field data in a part of east coast of Korea, considering the variability in wave directions reduced the necessary caisson width by about 10% at the maximum compared with that not considering the directional variability, and is needed a caisson width smaller than that of the deterministic design in the whole range of water depth considered (10∼30 m).

• Monthly Newsletter
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• s.215
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• pp.6-6
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• 2005

• Proceedings of the Korean Geotechical Society Conference
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• 1998.03a
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• pp.187-194
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• 1998

• 어항어장
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• s.80
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• pp.43-46
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• 2007

근래 패각이 공공사업 등에 이용되는 사례도 많아지고 있어 용지의 매립재나 연약지반의 개량재, 도로의 동파 억제재 등 여러 가지 용도로 이용되고 있다.