• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.461-464
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• 2006

The caisson of the inner wall type has a weak point that reflecting wave is big. Therefore it has been studied that the research of the decreasing reflecting wave using installation the perforated wall in front of caisson to decrease of that weak point. In this study, we analyzed the characteristic of reflection horizontal and diamond style vertical slit caisson using hydraulic model test. According to the results of experiments, we could confirm that diamond style vertical caisson has a reflection coefficient which has lower than horizontal caisson of the reflection coefficient of 5~10%.

• Journal of Ocean Engineering and Technology
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• v.23 no.1
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• pp.104-108
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• 2009

As the demands of ocean resource development increase, many offshore structures are required. To cope with the active ocean developments, many types of construction methods have been applied for offshore facilities, including oil, gas and harbors. One of the challenges is to transport and install the heave bridge caisson. Several construction methods are well understood. However, for the sake of safety and reliability, the F/D installation method can be utilized. While the caisson is carried by an F/D, the mooring force of the tug boat and the structure stability from exiting motions in the dock should be checked against external loadings and sea conditions. The external loads can be classified with wind force, current force, and wave force. In the stability analysis, transportation velocity and draft of F/D are important factors. The dynamic stability and hook load for crane barge installation for the same caisson are also studied. Considering external loads and dominant factors, the stability of caisson during transportation has been investigated.

• Journal of Ocean Engineering and Technology
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• v.24 no.4
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• pp.13-22
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• 2010

While a caisson used for breakwater is carried by a floating dock, accompanying stability problem by its existing motions in the dock is quite important and should be pre-checked against sea environmental condition. In the stability analysis, the acceleration, velocity, angle of roll and pitch motions are important to calculate frictional force and separation force. If separation force becomes bigger than frictional force, serious collision may be occurred between caisson and floating dock. In this study, stability evaluation during the transportation of a caisson on floating dock for breakwater was performed by using a commercial program, HydroD and CHARM3D/HARP.

• Proceedings of the Korean Geotechical Society Conference
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• 2010.09a
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• pp.825-839
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• 2010

The global and domestic market for offshore wind farm is expected to grow fast, and the design and installation of substructure and foundation is getting more important. As for the offshore wind farms located in the shallow(depth < 20m) water, the construction and installation of the substructure and foundation makes up about 1/4 ~1/3 of the offshore wind farm construction cost, and the portion is expected to increase because the turbine capacity is increasing from 2 ~ 3MW to 5MW or larger and the water depth of wind farms is also increasing over 30m. As a foundation for offshore wind turbine, the suction caisson foundation is being considered to be a highly competitive alternative to the conventional monopile or gravity based structure, because it has features suitable for the offshore construction such as quick installation, no heavy equipment for penetration and no hammering noise for driving. In order to study the installation behaviour of the suction caisson, laboratory tests were performed with sand. The pore water pressure and displacement were measured to analyze the suction pressure during penetration, the penetration speed and the amount of heaving.

• Journal of the Korean Society for Marine Environment & Energy
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• v.19 no.4
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• pp.259-265
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• 2016

The present study aims to design and utilize a model test system of a Caisson in wet towing condition, to assess towing stability of a 9,300 ton class caisson. The suggested towing system was designed to provide regular tension on the towline, whereas the previous model test system towed the model in constant speed. The new model test system was expected to reproduce the towing condition more realistically than the test system with constant speed condition, as the tugboat in actual towing condition tows the towline with constant power. Model tests were conducted in a towing tank with 1/30 scaled model. In the model tests, six-degrees-of-freedom motion of the caisson model and tension on the towline were measured and analyzed. By using the new system, fluctuation of the motion of model and tension on the towline decreased. The variation in the draft and initial trim was applied in the model tests. In the initial trim condition, the motion and towing force decreased.

• Journal of the Korean Society of Marine Environment & Safety
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• v.27 no.1
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• pp.172-178
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• 2021

In the ship repair market, interest in maintenance and repair is steadily increasing due to the reinforcement of prevention of environmental pollution caused by ships and the reinforcement of safety standards for ship structures. By reflecting this effect, the number of requests for repairs by foreign shipping companies increases to repair shipbuilders in the Southwest Sea. However, because most of the repair shipbuilders in the southwestern area are small and medium-sized companies, it is difficult to lead to the integrated synergy effect of the repair shipbuilding companies. Moreover, the infrastructure is not integrated; hence, using the infrastructure jointly is a challenge, which acts as an obstacle to the activation of the repair shipbuilding industry. Floating docks are indispensable to operating the repair shipbuilding business; in addition, most of them are operated through renovation/repair after importing aging caisson docks from overseas. However, their service life is more than 30 years; additionally, there is no structure inspection standard. Therefore, it is vulnerable to the safety field. In this study, the finite element analysis program of ANSYS was used to evaluate the structural safety of the modified caisson dock and obtain additional structural reinforcement schemes to solve the derived problems. For the floating docks, there are classification regulations; however, concerning structural strength, the regulations are insufficient, and the applicability is inferior. These insufficient evaluation areas were supplemented through a detailed structural FE-analysis. The reinforcement plan was decided by reinforcing the pontoon deck and reinforcement of the side tank, considering the characteristics of the repair shipyard condition. The final plan was selected to reinforce the side wing tank through the structural analysis of the decision; in addition, the actual structure was fabricated to reflect the reinforcement plan. Our results can be used as reference data for improving the structural strength of similar facilities; we believe that the optimal solution can be found quickly if this method is used during renovation/repair.

• Proceedings of the Korean Geotechical Society Conference
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• 2009.09a
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• pp.815-826
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• 2009

The paper presents a case study addressing the design and construction aspects for DCM(Deep Cement Mixing) method employed as the foundation of a caisson type breakwater with heavy weight(10,700 ton/EA) and a high design wave height($H_{1/3}$=8.7m). The DCM was designed for the project(Ulsan New Port North Breakwater Phase 1) by optimizing the pattern of DCM columns with a combination of short and long columns (i.e., block type(upper 3m)+wall type(lower)) and considering overlapped section between columns as a critical section against shear force where the coefficient of effective width of treated column($\alpha$) was estimated with caution. It was shown that the value can be 0.9 under the condition with the overlapped width of 30cm. In addition to that, a field trial test was performed after improving conventional DCM equipment (e.g., mixing blades, cement paste supplying pipes, multi auger motor, etc.) to establish a standardized DCM construction cycle (withdrawal rate of mixing blades) which can provide the prescribed strength. The result of the field strength test for cored DCM specimens shows that the averaged strength is larger than the target strength and the distribution of the strength(with a defect rate of 7%) also satisfies with the quality control normal distribution curve which allows defect rate of 15.9%.