• 한국지진공학회논문집
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• 제23권5호
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• pp.239-248
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• 2019

In this study, the out-of-plane seismic resistance of lightly-reinforced existing walls strengthened with thick RC jacket was investigated. The thick RC jacket with a thickness of 500 mm was placed at one side of the thin existing wall with a thickness of 150 mm. At the interface between the wall and RC jacket, a tee-shaped steel section with a number of anchor bolts and dowel bars was used as the shear connector. To investigate the connection performance and strengthening effects, the cyclic loading tests of four jacketed wall specimens were performed. The tests showed that the flexural strength of the jacketed walls under out-of-plane loading was significantly increased. During the initial behavior, the tee shear connector transferred forces successfully at the interface without slip. However, as the cracking, spalling, and crushing of the concrete increased in the exiting walls, the connection performance at the interface was significantly degraded and, consequently, the strength of the jacketed walls was significantly decreased. The flexural strength of the jacketed walls with tee shear connector was estimated considering the full and partial composite actions of the tee shear connector.

• Structural Engineering and Mechanics
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• 제84권4호
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• pp.517-530
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• 2022

In re-assessing the Jacket-type fixed steel structures, the current standards often allow the simplicity of corrosion sections using local buckling or equivalent section approach to applying empirical formulae of frame stress and resistance analyses. However, those approaches can lead to significant errors for non-uniform corroded frames in a specific area, including force distribution, stress, and allowable strength of the tubular section, compared to the actual cases. This paper investigates a suitable approach to determine the actual stress on non-uniform corroded tubular frames under compression through the non-linear ABAQUS model by considering the effect of large deformation on the frame axis and the frame section. There are 3 scenarios of interest. In the 1st and 2nd scenarios with simple corrosion cases, the stress ratios using the numerical model and theoretical formulae correspond to the calculation of allowable strength reduction ratios in standards. However, scenario 3, which describes non-uniform corroded sections based on survey data, provides considerable differences in results. Therefore, it proves the reliable and effective results when using this method to analyze the resistance of the actual corroded section in the Jacket platforms.

• 한국지진공학회논문집
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• 제5권5호
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• pp.13-23
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• 2001

연계논문 에서는 해양환경하중을 받는 스틸자켓의 기하학적 비선형을 고려한 정적 동적해석을 위한 유한요소 정식화 과정을 제시하였다. 또한, 스틸자켓의 극한거동을 추적하기 위하여 뼈대구조의 소성힌지 해석법을 적용하였다. 본 연구에서는 스틸자켓의 통합해석 프로그램 OSA2000을 개발한다. 연계논문에서 제시된 주처리 프로그램의 내용을 제외하고, visual basic과 OpenGL 그래픽 라이브러리를 사용하여 데이타 입력을 효과적으로 수행하기 위한 전처리 프로그램과 해석결과 분석을 위한 후처리 프로그램을 개발한 내용을 요약한다. 또한, 다양한 예제해석을 통하여 프로그램의 검증 및 해석결과를 제시한다.

• 한국전산구조공학회논문집
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• 제35권2호
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• pp.93-100
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• 2022

본 논문에서는 한국의 서남해상에 건설예정인 해상풍력발전타워의 지지구조물로 고려되고 있는 세발구조와 자켓구조의 선박충돌 거동을 비선형동적해석을 통하여 비교·분석하였다. 이 구조물은 3MW용량의 풍력타워를 지지하기 위하여 설계되었다. 두 지지구조는 쉘요소를 이용하여 비선형 거동을 고려할 수 있도록 모델링하였고, 발전기를 포함하는 상부의 타워구조물은 탄성재료를 이용하여 보요소와 집중질량으로 모델링하였다. 전체 질량은 세발구조가 자켓구조에 비하여 약 1.66배 정도였다. 바지선과 상선을 충돌선박으로 선정하여 모델링하였다. 조수차의 조건을 고려하여 충돌선박의 충돌위치를 평균해수면의 상하로 3.5m변동하는 것으로 고려하였다. 또한 각 선박의 최소충돌속도(=2.6m/s)에서의 충돌에너지를 각각 4배까지 증가시키면서 충돌거동을 산정하였다. 해석결과 지지구조 충돌부위의 강성이 클수록 선박의 소성에너지 소산량이 상대적으로 증가하였다. 충돌조건에 따라 풍력타워의 변형은 진동에서 붕괴까지 발생하였다. 세발구조가 자켓구조에 비하여 큰 충돌저항력을 보였다. 이는 중앙부에 강성이 집중된 구조적 특성과 상대적으로 많은 강재의 사용량에 기인한 것으로 판단된다.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.637-642
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• 2008

The concept of district heating involves centralised heat production where heat is distributed to consumer via a piping network. The objective of this work is to identify the Flexible Pipe from an economy, execution, maintenance point of view. Flexible Pipe has in some countries, especially in Europe, been used for many years in district heating. In spite of years of experience, there still exist doubts about the possibilities of using flexible pipes in district heating applications, mostly because of no experiences in domestic market. The advantage of flexible pipe systems is their flexibility. This holds not only for the inner pipe but also for the total pipe system including insulation and jacket. Even for the largest diameter the minimum radius of curvature is given to 1.5m. The most important difference between flexible pipe systems and preinsulated steel pipes is their simple and quick assembly. Such information could provide a basis for making reasonable hypotheses about consumer preferences, to foam a basis for making future marketing more effective.

• 콘크리트학회논문집
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• 제22권1호
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• pp.11-18
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• 2010

이 연구에서는 변위-기반성능설계 개념에 의해 기존 철근콘크리트 기둥에 대하여 스틸재킷 보강에 의한 내진 성능개선의 성능설계 방법을 제시하였다. 스틸재킷 보강된 철근콘크리트 기둥에 대한 설계 변위 추정을 위해 스틸재킷 보강된 철근콘크리트 부재의 비선형 층상화 세그먼트 해석 모델을 제시하고, 성능기반설계에 의한 성능개선설계를 위하여 목표성능변위 및 설계지진가속도 조건에 대해 직접 변위-기반 설계 방법 및 변위계수법에 의한 내진성능개선 설계 방법을 제시하였다. 적용 예에서 이 방법은 기존 철근콘크리트 기둥과 비교하여 성능개선설계 결과 보강 전에 비해 변위 연성비 및 변위성능에서 크게 개선된 성능설계 결과를 제공해 주었다.

• Structural Engineering and Mechanics
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• 제63권3호
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• pp.293-302
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• 2017

This study deals with a numerical investigation of load transfer along interfaces of jacketed columns using finite element models. Appropriate plasticity and constitutive models are used to simulate the response of concrete and steel bars. Experimental data were used to calibrate the simulation of mechanical characteristics. The different compressive strength of core and jacket concrete, the confinement ratio, the dowels' diameter size and the load pattern shapes were considered. The path diagrams along the interfaces elucidate the areas around the dowel bars where due to stress concentration plastic hinges and intense discontinuities are created. The stress flow also depicts the contribution of confinement of the jacketed area to the overall resonant load capacity of the core column. The scope of the research is to identify and quantify the shear transfer along the interfaces of strengthened elements.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
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• pp.281-284
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• 2006

The marine Transmission tower infrastructure erected in the SI-HWA lake is deteriorated and damaged by the various environment effect, and then, there is a possibility of going bad in the safety. The appropriate maintenance to ensure the security of the structure during life cycle is necessary. Specially the Jacket or the steel file foundation in the sea is apt to be corroded quickly. In this research, to establish life management system of 345kV Yonghung marine transmission tower structure, the actual durability research facility which can obtain the actual proof data is constructed. the maintenance guideline and procedure of the structure are established. Hereafter, there is a plan which will advance the research against the composition of the life prediction model, which is based on the data acquired from the actual durability research facility.

• 대한심미치과학회지
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• 제12권2호
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• pp.31-38
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• 2003

Amelogenesis imperfecta patients suffered common clinical problems of poor esthetics, teeth sensitivity, and loss of occlusal vertical dimension. Amelogenesis imperfecta is a group of inherited disorders primarily affecting dental enamel. Variants of amelogenesis imperfecta generally classified hypoplastic, hypocalcified, or hypomaturation types based on the primary enamel defects. The mildest problems were found in the pitted hypoplastic type whereas the most severe problems were encountered in the hypocalcified type amelogenesis imperfecta. Management stragies include composite resin veneer and jacket crowns for anterior teeth as well as steel crowns for posterior teeth. Knowledge of the clinical features and dental complications of each variants if amelogenesis impecta helps in the diagnosis of the condition and allows institution of early preventive measures. The objective of this paper is to provide a review of the current concepts of the wide spectrum of etiological factors involved in the pathogenesis of this significance clinical entity in the primary dentition.

• Smart Structures and Systems
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• 제21권2호
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• pp.187-194
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• 2018

This paper focuses on the $H_{\infty}$ filter design problem for offshore steel jacket platforms. Its objective is to design a full-order state observer for offshore platforms in presence of unknown disturbances. To make the method more practical, it is assumed that the measured variables are available at discrete-time instants with time-varying sampling time intervals. By modelling the sampling intervals as a bounded time-varying delay, the estimation error system is expressed as a time-delay system. As a result, the addressed problem can be transformed to the problem of stability of dynamic error between the system and the state estimator. Then, based on the Lyapunov-Krasovskii Functional (LKF), a stability criterion is obtained in the form of Linear Matrix Inequalities (LMIs). According to the stability criterion, a sufficient condition on designing the state estimator gain is obtained. In the end, the proposed method is applied to an offshore platform to show its effectiveness.