• 대한조선학회논문집
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• 제55권5호
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• pp.438-447
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• 2018

For a fixed jacket type offshore structure directly supported by the seabed, the structural behavior of offshore structure depends on the soil properties. Soil properties affect on the stiffness of the piles and the boundary condition in the structural analysis. The structural analysis is performed using PSI (Pile-Soil Interaction) suggested in the code and design rule. PSI analysis of the jacket structure is carried out after various soil types are selected according to the soil properties like internal friction angle, undrained shear strength, unit weight and so on. Three types of soil are selected by varying strength for a clay and sand, respectively. The structural analysis of the jacket structure is performed using these soils. The results about axial and lateral reaction force and the stress and displacement on the structure are compared. As a results, the structural response is smaller as the soil becomes more stiff. In conclusion, it is confirmed that the structural response of fixed jacket type offshore platform supported by seabed is sensitive to the change of soil properties.

• Structural Engineering and Mechanics
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• 제33권3호
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• pp.325-337
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• 2009

Structural damage detection, damage localization and severity estimation of jacket platforms, based on calculating modal strain energy is presented in this paper. In the structure, damage often causes a loss of stiffness in some elements, so modal parameters; mode shapes and natural frequencies, in the damaged structure are different from the undamaged state. Geometrical location of damage is detected by computing modal strain energy change ratio (MSECR) for each structural element, which elements with higher MSECR are suspected to be damaged. For each suspected damaged element, by computing cross-modal strain energy (CMSE), damage severity as the stiffness reduction factor -that represented the ratios between the element stiffness changes to the undamaged element stiffness- is estimated. Numerical studies are demonstrated for a three dimensional, single bay, four stories frame of the existing jacket platform, based on the synthetic data that generated from finite element model. It is observed that this method can be used for damage detection of this kind of structures.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2006년도 춘계 학술발표회 논문집
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• pp.1237-1244
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• 2006

This research discussed about method for basis construction of sea jacket construction. Several access ways of method for foundation construction of sea jacket construction are used. Accompany many efforts of design and build process to overcome the form of construction work and application equipment, special quality of construction and restriction and so on of sea environment in the case of pile foundation. Therefore, great many factor of sea condition, construction special quality, base condition, construction time, equipment composition, worker composition etc. shows other work form in spot at sea jacket construction process.

• 대한토목학회논문집
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• 제32권6A호
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• pp.389-398
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• 2012

이 연구에서는 빠른 조류 환경에서의 재킷식 해양구조물인 울돌목 시험조류발전소 구조물에 대한 시공 중 및 운영 중 변형률을 장기 계측하여, 계측 자료를 다양하게 분석하였다. 우선 구조물 시공 단계별 변형률 응답의 변화를 분석하여, 양중, 블록재하, 파일 인발 및 근입 등의 작업 시 변형률에 큰 변화가 발생함을 제시하였다. 또한 재킷 레그 절단과 같은 구조변경 후의 고정하중 및 조류하중에 의한 변형률 변화를 분석하여, 조류하중보다는 고정하중에 의한 변형률의 변화가 크게 발생함을 확인하였으며, 운영 중 계측 결과로부터 주요 변동 주기 성분을 분석하여, 변형률 계측 자료에 M2 및 M4 조석 성분과 동일한 주기를 갖는 장주기 성분이 가장 크게 존재함을 확인하였다. 마지막으로 변형률 기반의 구조 건전성 모니터링에 있어 중요한 변형률 예측 모델을 신경망 기반으로 작성하여, 조류 유속 및 조위에 따른 변형률을 합리적인 수준에서 예측할 수 있음을 확인하였다.

• 복식문화연구
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• 제14권1호
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• pp.142-152
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• 2006

The purpose of the study was to demonstrate how to recreate Spencer jacket of Empire Style in an attempt to apply this historic style to theatrical costumes and other high fashion items in modern times. The study was carried out through 2 steps. First, Literature, films and other visual information were utilized in order to classify the designs of Spencer jacket. Second, Production of Spencer jacket using patterns shown in literatures and those commercially used and commercial patterns were investigated to find out design characteristics of jackets. Results and discussions are as follows: The results showed that Spencer jacket can be categorized into following three styles: (1) Jackets having front opening without button stands and standing collar, (2) Double breasted opening and notched collar, (3) Single breasted opening and flat collar with waist band. The characteristics of Spencer jacket design were as follows: (1) Short jacket length, (2) Armhole line moved inwards, (3) Long fit shaped puff sleeves, whose puff being distributed more heavily over back of the sleeve, (4) Diamond shaped back bodice, which are consisted with princess lines and shoulder lines moved backwards.

• Steel and Composite Structures
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• 제45권1호
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• pp.101-118
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• 2022

The seismic performance of the reinforced concrete (RC) special-shaped column to steel beam connections with steel jacket used in the RC column to steel beam fabricated frame structures was investigated in this study. The three full-scale specimens were subjected to cyclic loading. The failure mode, ultimate bearing capacity, shear strength capacity, stiffness degradation, energy dissipation capacity, and strain distribution of the specimens were studied by varying the steel jacket thickness parameters. Test results indicate that the RC special-shaped column to steel beam connection with steel jacket is reliable and has excellent seismic performance. The hysteresis curve is full and has excellent energy dissipation capacity. The thickness of the steel jacket is an important parameter affecting the seismic performance of the proposed connections, and the shear strength capacity, ductility, and initial stiffness of the specimens improve with the increase in the thickness of the steel jacket. The calculation formula for the shear strength capacity of RC special-shaped column to steel beam connections with steel jacket is proposed on the basis of the experimental results and numerical simulation analysis. The theoretical values of the formula are in good agreement with the experimental values.

• 대한조선학회지
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• 제23권2호
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• pp.33-45
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• 1986

In the present paper, the nonlinear analysis of dynamic response of the jacket type offshore structures subject to nonlinear fluid force is performed. Furthermore, several analysis methods, such as quasi-static analysis, Newmark-$\beta$ method and state vector time integration technique, and described and compared with each others in order to investigate the efficiency numerical of the schemes for this kind of nonlinear structural analysis. In the problem formulation, various environmental forces acting on the jacket type offshore structure have been studied and calculated. Particularly, hydrodynamic forces are calculated by using the Morison type formula, which contains the interaction effect between the motion of the structure and the velocity of fluid particles. Also, Stokes' 5th order wave theory and Airy's linear wave theory are used to predict the velocity distribution of the fluid particles. Finally, the nonlinear equation of motion of the structure is obtained by using three-dimensional finite element formulation. Based on the above procedures, two examples, i.e. a single pile and a typical offshore jacket platform, are studied in details.

• Ocean Systems Engineering
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• 제8권2호
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• pp.201-221
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• 2018

In this paper a comprehensive study for the structural control of Jacket platform with Magneto-Rheological (MR) damper is presented. The control is implemented as a closed loop feedback of the applied voltage in the MR Damper using fuzzy logic. Nine cases of combinations with MR damper are presented to complete the work. The selection of the MR damper (RD 1005-3) is based on the operating parameters (i.e., the range of frequency and displacement). Bingham model is used to obtain the control forces. The damping co-efficient of the model is obtained using empirical relationship between the voltage in the MR damper and input velocity from the structural members. The force acting on the structure is obtained from Morison equation using P-M spectrum. The results show that the reliable control was obtained when there was a continuous connection of multiple MR dampers with the lower levels of the structure. Independent MR dampers at different levels provided control within a range, while the MR dampers placed at alternate positions gave very high control.

• 한국해양공학회:학술대회논문집
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• 한국해양공학회 2003년도 춘계학술대회 논문집
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• pp.203-207
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• 2003

As the upending is one of the critical steps in the installation of offshore structure, datail procedure of upending operation is studied in the paper. For larger offshore structure installation, launching method is often applied. However after launching, the upending process is to be followed. To ensure successful upending operation, datail process is analysed considering various factors affecting on the operation including reserved buoyancy, free flotation position, seabed clearance, ballast and hook load. To investigate the influence of each factor on the procedure, twelve numerical jacket models with various dimensions are simulated and studied. From the study, it is revealed that the increase of buoyance and decrease of self weight generate a large seabed clearance. The law seabed clearance during flooding creates higher hook load and height. The paper also introduces a guideline for the related structure design and construction with the effects of contribution factors in the upending operation.

• 한국해양공학회지
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• 제28권3호
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• pp.218-226
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• 2014

Since the support structure of an offshore wind turbine has to withstand severe environmental loads such as wind, wave, and seismic loads during its entire service life, the need for a robust and reliable design increases, along with the need for a cost effective design. In addition, a robust and reliable support structure contributes to the high availability of a wind turbine and low maintenance costs. From this point of view, this paper presents a design process that includes design optimization and reliability analysis. First, the jacket structure of the NREL 5-MW offshore wind turbine is optimized to minimize the weight and stresses, while satisfying the design requirements. Second, the reliability of the optimum design is evaluated and compared with that of the initial design. Although the present study results in a new optimum shape for a jacket support structure with reduced weight and increased reliability, the authors suggest that the optimum design has to be accompanied by a reliability analysis during the design process, as well as reliability based design optimization if needed.