• 한국해양공학회지
• /
• 제26권4호
• /
• pp.37-41
• /
• 2012

Due to global warming, the need to secure alternative resources has become more important nationally. Because of the very strong current on the west coast, with a tidal range of up to 10 m, there are many suitable sites for the application of TCP (tidal current power) in Korea. In the southwest region, a strong current is created in the narrow channels between the numerous islands. A rotor is an essential component that can convert tidal current energy into rotational energy to generate electricity. The design optimization of a rotor is very important to maximize the power production. The performance of a rotor can be determined using various parameters, including the number of blades, shape, sectional size, diameter, etc. There are many offshore jetties and piers with high current velocities. Thus, a VAT (vertical axis turbine) system, which can generate power regardless of flow direction changes, could be effectively applied to cylindrical structures. A VAT system could give an advantage to a caisson-type breakwater because it allows water to circulate well. This paper introduces a multi-layer vertical axis tidal current power system. A Savonius turbine was designed, and a performance analysis was carried out using CFD. A physical model was also demonstrated in CWC, and the results are compared with CFD.

• 한국해안해양공학회지
• /
• 제17권1호
• /
• pp.32-40
• /
• 2005

방파제 구조물에 대한 기존의 내진설계 및 내진성능검토에서는 주로 설계지진에 대하여 구조물의 변위 및 응력을 검토함으로써 지진 안전성을 평가한다. 그러나 이러한 검토가 주로 결정론적 접근방법에 의한 것으로 지진의 가장 큰 특성이라 할 수 있는 불확실성을 제대로 반영하기 어렵다. 본 연구에서는 지진발생과 지반계수의 화률론적 분포 특성을 고려한 확률론적 지진위험도 평가에 대해 연구하였다. 우선 항만구조물의 지진에 대한 구조적 취약성을 다수의 지진자료를 이용하여 평가하였고, 지진재해지도를 이용하여 해당 지역에서의 지진재해도를 산정하였으며, 이들을 조합함으로써 방파제 구조물의 확률론적 지진위험도를 평가하였다.

• 한국해안해양공학회지
• /
• 제16권2호
• /
• pp.64-74
• /
• 2004

SCP공법(Sand Compaction Pile Method)은 안벽구조물 하부 지반이 연약할 경우에 압밀침하 속도를 증가시키고, 침하를 감소시키며, 지지력을 증가시키기 위하여 널리 적용되어 왔다. 연약지반에 타설 된 모래말뚝과 주변 연약지반으로 구성된 SCP 개량지반 상부에 상부 캐이슨과 상치구조물이 설치됨에 따라, SCP 복합지반에서는 모래말뚝에 의한 즉시침하와 함께 주변 점토지반의 압밀침하가 복합적으로 유발하게 된다. 본 연구에서는 SCP 복합지반에 대한 기존의 탄성침하 및 압밀이론에 근거하여 침하 예측기법을 제안하였다. 제안된 침하모델의 모델정수값들의 산정하기 위하여 유전자 알고리즘에 근거한 역해석 기법을 적용하여 최적화 과정을 수행하였다. 국내 SCP 복합지반에 대한 예제해석을 수행하여 제안된 침하예측기법의 적용성을 검토하였다.

• 기술사
• /
• 제15권4호
• /
• pp.12-24
• /
• 1982

East Parts of Bangladesh have been benifited by low cost energy generated by domestic natural gas but West parts where energy generated by imported fuel. Bangladesh Government authority has very much concerned to transmit the low cost electricity to the West from the East for past several years. To solve such concerns, cross-country 230kv double circuits Power transmission line was proposed, however there was a big obstacle for the realization of this line to cross the Jamuna river which has 12 km long width with a deep muddy river bed. A consultant engineering firm named Merz-Mclellan anyway finalized this plan and a world-wide bid was announced on June 31, 1979. Due to the expected difficulty to construct the towers on sea like area, only three construction groups have participated. including a Korean joint venture organization of Samsung-Korean Developement corporation-Kolon Electric Machinery company. After 3 months bid evaluation, contract was awarded to Korean Consosium and KEM Co was in charge of designing steel towers with anchor bolts and base plates beside to electrical engineering field. Then KEM Co have faced and over-comed many unenpected technical difficulties such as forced eccentricity joint on base plate, distorsion issue of 60mm thick plates welding, threading anchor bolts, tad heat treatment of some anchor bolts, disagreement from Consultant Engineer on multiplying factor of leg stresses for 45$^{\circ}$ wind and on reducing O.L.F for wind loads on cables for such 1220km long spans. After spending two years long period for designing and engineering towers, base plates, and anchor bolts, first shipment of tower was finally realized on Nov. 8, 1981 and on the other hand KDD has proceeded concrete caisson work on schedule at Jamuna river site and expected to complete tower erection and stringing of cables within this year of 1982 which was original completion target.

• 산업기술연구
• /
• 제24권B호
• /
• pp.95-105
• /
• 2004

This paper is an experimental and numerical research works about the effects of the b earing capacity of sloped rubble mound on the density of rubble mound and the position of footing. Centrifuge model tests were performed to investigate the bearing capacity of rubble m ound by changing the density of rubble mound and the location of loading in forms of s trip loading to simulate the caisson. Materials of rubble mound used in the model tests were crushed rocks having similar value of uniformity coefficient to the value in field. Two different relative densities of 80% and 90% were prepared during tests. The dimens ions of centrifuge model were trapezoidal shape of model mound having the bottom wid th of mound, 30cm and height of mound, 10cm. Gravity level applied during the centrif uge test was 50G. Surcharge loading in the forms of strip loading was applied on the t op of the sloped model mound. Tests were carried out by changing the position of loadi ng. The rigid model footing was located in the center of top of the model rubble mound and the edge of model footing was at the crest of mound. Test results were analyzed by using the limit equilibrium methods proposed by Meyer hof(1957) and Bowles(1982) and the numerical approach with FLAC being available com mercially software. For the numerical estimations with FLAC, the rubble mound was si mulated with the constitutive relationship of Mohr-Coulomb elasto-plastic model.

• 한국해안·해양공학회논문집
• /
• 제31권6호
• /
• pp.478-484
• /
• 2019

용수 파력발전소의 해저케이블이 단락되는 사고가 2014년 겨울에 발생했다. 그 원인을 밝히기 위해서 재현기간 50년 이상의 고파랑 발생 가능성과 케이블 보호공의 설계중량 과소 산정 여부를 검토하였다. 기상청에서 운용하는 부이의 관측자료와 파랑추산자료를 검토하여 겨울동안 발생한 고파랑의 재현기간을 살펴보았다. 케이블 보호공의 설계중량을 검토하기 위해서 항만 및 어항 설계기준 뿐만 아니라 파의 입사각이 큰 경우의 연구결과를 참조해서 직접 안정중량을 계산하였다. 분석 결과, 2014년 겨울동안 재현빈도 50년 이상의 고파랑은 발생하지 않았으며, 경사지게 입사하는 파랑에 대한 케이블 보호공의 중량이 부족해서 보호공이 이탈한 것으로 나타났다.

• 한국구조물진단유지관리공학회 논문집
• /
• 제19권6호
• /
• pp.72-79
• /
• 2015

이 논문에서는 해안구조물에 대한 실질적이고 효율적인 구조신뢰성평가 기법을 제시하였다. 제안기법은 파랑, 조류 등의 하중관련 변수 그리고 콘크리트의 탄성계수와 압축강도, 지반정수 및 경계조건 등과 같은 저항관련 설계변수의 불확실성을 명확히 고려한 복잡한 해안구조물의 신뢰성을 평가할 수 있다. 라틴 하이퍼큐브 샘플링(LHS), 몬테카를로 시뮬레이션(MCS) 및 유한요소법을 합리적으로 결합한 제안기법에서 LHS기반 MCS는 신뢰성평가에 필요한 샘플링 수를 대폭 줄여주므로 계산노력이 획기적으로 감소된다. 검증예제를 통하여 제안기법이 상대적인 정확도를 보장하며 계산상의 효율성이 우수한 것으로 확인되었다. 또한 실제의 케이슨형식 방파제 구조물을 대상으로 한 수치예제를 통하여 그 적용성과 효율성을 입증하였다. 특히 유한요소법 또는 유한차분법과 같은 알고리즘 형태의 암시적 한계상태함수를 갖는 경우와 비선형해석, 복합재료, 다양한 기하형상 등을 복잡한 구조거동을 고려해야 하는 실제적인 구조물의 신뢰성평가에 적합한 것으로 판단된다.

• 한국지진공학회논문집
• /
• 제22권1호
• /
• pp.15-22
• /
• 2018

Pseudo-static approach has been conventionally applied for the design of gravity type quay walls. In this method, seismic coefficient ($k_h$), expressed in terms of acceleration due to gravity, is used to convert the real dynamic behavior to an equivalent pseudo-static inertial force for seismic analysis and design. Therefore, the calculation of an appropriate $k_h$ considering frequency characteristics of input earthquake is critical for representing the real dynamic behavior. However, the definitions of $k_h$, which is used for simplified analysis in Korea, focuses only on convenience that is easy to use, and the frequency characteristics of input earthquake are not reflected in the $k_h$ definitions. This paper evaluates the influences of the frequency characteristics of input earthquake on $k_h$ by initially reviewing the $k_h$ definitions in the existing codes of Japan for port structures and then by performing a series of dynamic centrifuge tests on caisson gravity quay walls of different earthquake input motions (Ofunato, Hachinohe). A review of the existing codes and guidelines has shown that the $k_h$ values are differently estimated according to the frequency characteristics of input earthquake. On the other hand, based on the centrifuge tests, it was found that the permanent displacements of wall are more induced when long-period-dominant earthquake is applied.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.815-826
• /
• 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%.

• 한국지반공학회:학술대회논문집
• /
• 한국지반공학회 2009년도 세계 도시지반공학 심포지엄
• /
• pp.545-553
• /
• 2009

A lot of long-span marine bridge, which connects land to island or island to island, are being designed and constructed lately in south-west coast in South Korea. In the past, caisson foundations in marine were mainly adopted in construction and stability aspect, however, nowadays with development of pile construction technology, drilled shaft foundations are mainly adopted. As the long span cable stayed bridge and suspension bridge applied with lots of loads are being designed, the scale of pile foundations are getting larger. As the construction cost of substructure including foundation in marine bridges is too high, the appropriate evaluation of the axial bearing capacity of pile becomes a core factor to decide the construction cost of foundation if the drilled shaft is adopted as foundation type of bridge. The evaluation values of skin friction and end bearing capacity of drilled shaft in weathered rock suggested in south Korea are only to introduce the foreign specifications, and most of them are designed in a kind of hard soil layer. Also the allowable load of pile section is less than the expected bearing capacity of pile in the soil condition since the allowable capacity of pile is undervalued. Recently in order to improve this factor the bi-axial hydraulic load test of pile was taken, the data of load transfer analysis of pile, unit of skin friction and end bearing capacity are accumulated. In our country, the design of piles are made with ASD, however, LRFD considering service, strength and extreme state was adopted in Incheon Grand Bridge implemented with BTL, and the research to systematize the resistance coefficient appropriate at home country are being progressed.