• Smart Structures and Systems
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• 제15권2호
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• pp.245-258
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• 2015

A methodology based on distributed fiber optic sensors is proposed to detect the lateral buckling for subsea pipelines in this study. Uncontrolled buckling may lead to serious consequences for the structural integrity of a pipeline. A simple solution to this problem is to control the formation of lateral buckles among the pipeline. This firms the importance of monitoring the occurrence and evolution of pipeline buckling during the installation stage and long-term service cycle. This study reports the experimental investigations on a method for distributed detection of lateral buckling in subsea pipelines with Brillouin fiber optic sensor. The sensing scheme possesses the capability for monitoring the pipeline over the entire structure. The longitudinal strains are monitored by mounting the Brillouin optical time domain analysis (BOTDA) distributed sensors on the outer surface of the pipeline. Then the bending-induced strain is extracted to detect the occurrence and evolution of lateral buckling. Feasibility of the method was validated by using an experimental program on a small scale model pipe. The results demonstrate that the proposed approach is able to detect, in a distributed manner, the onset and progress of lateral buckling in pipelines. The methodology developed in this study provides a promising tool for assessing the structural integrity of subsea pipelines.

• Advances in aircraft and spacecraft science
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• 제3권4호
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• pp.427-445
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• 2016

Star sensors are the attitude estimation sensors of the satellite orbiting in its path. It gives information to the control station on the earth about where the satellite is heading towards. It captures the images of a predetermined reference star. By comparing this image with that of the one captured from the earth, exact position of the satellite is determined. In the process of imaging, stray lights are eliminated from reaching the optic lens by the mechanical enclosures of the star sensors called Baffles. Research in space domain in the last few years is mainly focused on increased payload capacity and reduction in launch cost. In this paper, a star sensor baffle made of Aluminium is considered for the study. In order to minimize the component weight, material wastage and to improve the structural performance, an alternate material to Aluminium is investigated. Carbon Fiber Reinforced Polymer is found to be a better substitute in this regard. Design optimisation studies are carried out by adopting suitable design modifications like implementing an additional L-shaped flange, Upward flange projections, downward flange projections etc. A better configuration of the baffle, satisfying the design requirements and achieving manufacturing feasibility is attained. Geometrical modeling of the baffle is done by using UNIGRAPHICS-Nx7.5(R). Structural behavior of the baffle is analysed by FE analysis such as normal mode analysis, linear static analysis, and linear buckling analysis using MSC/PATRAN(R), MSC-NASTRAN(R) as the solver to validate the stiffness, strength and stability requirements respectively. Effect of the layup sequence and the fiber orientation angle of the composite layup on the stiffness are also studied.

• 국제초고층학회논문집
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• 제4권1호
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• pp.9-25
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• 2015

Field measurements of various structures have been conducted for many purposes. Measurement data obtained by field measurement is very useful to determine vibration characteristics including dynamic characteristics such as the damping ratio, natural frequency, and mode shape of a structure. In addition, results of field measurements and modal identification can be used for modal updating of FEM analysis, for checking the efficiency of damping devices and so on. This paper shows some examples of field measurements and modal identification for structural health monitoring. As the first example, changes of dynamic characteristics of a 15-story office building in four construction stages from the foundation stage to completion are described. The dynamic characteristics of each construction stage were modeled as accurately as possible by FEM, and the stiffness of the main structural frame was evaluated and the FEM results were compared with measurements performed on non-load-bearing elements. Simple FEM modal updating was also applied. As the next example, full-scale measurements were also carried out on a high-rise chimney, and the efficiency of the tuned mass damper was investigated by using two kinds of modal identification techniques. Good correspondence was shown with vibration characteristics obtained by the 2DOF-RD technique and the Frequency Domain Decomposition method. As the last example, the wind-induced response using RTK-GPS and the feasibility of hybrid use of FEM analysis and RTK-GPS for confirming the integrity of structures during strong typhoons were shown. The member stresses obtained by hybrid use of FEM analysis and RTK-GPS were close to the member stresses measured by strain gauges.

• 한국방재학회 논문집
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• 제10권4호
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• pp.9-16
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• 2010

구조물 상시모니터링에서 센서위치 최적화는 모니터링 결과에 중요한 영향을 준다. 따라서 본 논문은 구조계수 또는 손상도를 추정하기 위한 목적으로 동특성 자료를 계측하고자 할 때, 충분한 정보를 획득할 수 있는 최적의 계측점을 선정하는 방법을 제안하였다. 제안된 방법은 유전자 알고리즘을 계측점 선정을 위한 최적화 기법으로 사용하는 것이다. 유전자 알고리즘의 핵심인 적합도함수를 구조계수에 의한 모드벡터의 민감도와 모드벡터의 직교성을 고려할 수 있도록 구성하였다. 간단한 타워 구조물에 대한 예제 해석을 통해 제안된 방법의 타당성을 확인하였다. 적합도함수를 구성하고 있는 모드 민감도와 모드 직교성이 최적 계측점 선정에 어떤 영향을 주는지 예제해석을 통하여 분석하였다. 결론적으로, 제안된 적합도 함수를 사용하면 계측 목적에 타당한 계측점을 선정할 수 있음을 확인하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제12권1호
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• pp.81-90
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• 2008

본 연구에서는 유한 요소법과 고도화된 손상 탐지 기법을 결합하여 구조적 손상을 규명하는 방법을 다룬다. 본 연구의 특징은 충격하중을 받는 구조물의 동적 거동 특성을 분석하여 이를 임의의 손상 형태를 갖는 판에 적용한다는 것이다. 이러한 방법은 손상된 부위의 강성 분포를 추정할 뿐만 아니라 손상의 정도도 파악할 수 있는 장점을 갖으며 분할 요소수의 제한을 두지 않는다. 제안된 방법을 검증하기 위하여 본 알고리즘은 임의의 손상을 갖는 박판에 대하여 적용하기 한다. 수치해석 결과로부터 제안된 알고리즘은 수치적 효율성과 함께 임의의 손상 분포를 규명할 수 있음을 보여준다.

• 한국공간구조학회논문집
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• 제5권2호
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• pp.73-79
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• 2005

텐서그러티는 연속인장-불연속압축 구성요소에 기반한 상대적으로 새로운 구조시스템이다. 좀 더 상세한 구조적 고찰이 필요하지만, 연구목적에 접근하기 위해서는 최소한 텐서그러티의 구조원리와 근본적인 역학관계를 파악하는 것이 필수적이다. 일단 이점을 확인하고 난 후에, 이러한 구조물의 특성뿐만 아니라 건축에서의 적용성을 다룬다. 그리고 이런 시스템을 규정하는 정의에 이견이 없지는 않으나, 경량구조물로써 텐서그러티의 가능성을 설명하기 위하여 구조디자인연구소(iESD)에서 제작한 텐서그러티 모듈(기본형)의 몇 가지 예를 제시한다. 따라서, 본 연구에서는 기본 정의(규정)뿐 아니라 기본 모듈의 유형을 소개하고, 건축에서 텐서그러티 모듈의 변형성과 응용성을 탐색한다.

• 대한조선학회논문집
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• 제34권3호
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• pp.38-52
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• 1997

초고속선의 구조설계에 있어서 가장 중요한 요소중의 하나가 구조부재에 대한 경량화이며, 이점에서 최근 알루미늄하니콤 샌드위치판이 초고속선의 선각재료로서 주목을 받고있다. 본 논문에서는 80미터급 초고속 카훼리에 대한 시설계를 통하여 알루미늄 샌드위치판의 초고속선의 선각재료로서의 유용성을 확인코져 한다. 이를위해, 먼저 사례연구 대상선박의 사양을 정하고, 기존의 알루미늄 보강판 방식과 샌드위치 방식으로 구조설계를 수행, 이들의 설계결과를 비교함으로써 샌드위치구조의 구조경량화 가능성을 검증코져 한다. 선박의 경제성을 검토하기 위해서 선박건조비 및 운항비를 포함한 전체비용을 두가지 방식에 대하여 정량적 비용분석을 수행코져 한다. 끝으로, 현재 초고속대형선의 선각재료로서 알루미늄하니콤 샌드위치판이 사용되지 못했던 원인과 앞으로 해결해야할 과제들에 대해서 고찰하였다.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2007년도 정기 학술대회 논문집
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• pp.62-67
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• 2007

The research team for the virtual construction development was established with the support of Korea Ministry of Construction and Transportation, and KICTEP (Korea Institute of Construction and Transportation Technology Evaluation and Planning). Its aims are to develop system that is to improve productivity & quality, to create a higher value-added business, and to cultivate international competitiveness in the construction industry. The virtual construction system is a design, engineering, and construction management information system that allows the project participants to effectively share the information throughout the construction life cycle with the support of 3D and design information. To achieve this, the research team focuses on developing several systems. First, the team focuses on developing for the pre-planning, the structural engineering, MEP, and the 3D based estimation system. Second, they focus on developing a simulation system for the construction process planning and feasibility study with help of the virtual reality technologies. Third, they focus on developing the CPLM (Construction Project Life-cycle Management) system for managing construction project data, and the decision support system that makes the collaboration among the project participants based on 3D technologies and information. We also focus on developing the SDAI (Standard Data Access Interface), the localized guideline for 3D design, and a training program. In addition, we focus on developing the undeveloped area of the commercial system and building an environment that can support the communication and collaboration in the construction life-cycle rather than developing the existing and commercialized system.

• Smart Structures and Systems
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• 제17권2호
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• pp.167-194
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• 2016

This paper investigates the Synergetics based Damage Detection Method (SDDM) for frame structures by using surface-bonded PZT (Lead Zirconate Titanate) patches. After analyzing the mechanism of pattern recognition from Synergetics, the operating framework with cooperation-competition-update process of SDDM was proposed. First, the dynamic identification equation of structural conditions was established and the adjoint vector (AV) set of original vector (OV) set was obtained by Generalized Inverse Matrix (GIM).Then, the order parameter equation and its evolution process were deduced through the strict mathematics ratiocination. Moreover, in order to complete online structural condition update feature, the iterative update algorithm was presented. Subsequently, the pathway in which SDDM was realized through the modified Synergetic Neural Network (SNN) was introduced and its assessment indices were confirmed. Finally, the experimental platform with a two-story frame structure was set up. The performances of the proposed methodology were tested for damage identifications by loosening various screw nuts group scenarios. The experiments were conducted in different damage degrees, the disturbance environment and the noisy environment, respectively. The results show the feasibility of SDDM using piezoceramic sensors and actuators, and demonstrate a strong ability of anti-disturbance and anti-noise in frame structure applications. This proposed approach can be extended to the similar structures for damage identification.

• 한국건축시공학회지
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• 제14권5호
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• pp.487-495
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• 2014

골조공사는 프로젝트의 전체 공사비 및 공사기간에서 차지하는 비율에 매우 높으며, 대형 프로젝트에서 골조공사 공기단축은 프로젝트의 성패를 결정하는 중요한 요소이다. 이에 공기단축을 위한 새로운 공법에 대한 연구가 지속적으로 이루어져 오고 있다. H형강 대신 앵글을 사용하는 PSRC 합성기둥은 기존의 SRC 기둥에 비해 높은 휨강도 및 연성도를 가지며 현장에서의 철근작업을 생략할 수 있다는 장점이 있으나, 여전히 거푸집작업이 필요하다는 한계점이 있다. 본 연구는 기존의 PSRC 기둥 공법을 개선하여 영구거푸집까지 선조립하는 Form-LPSRC 기둥 공법을 개발하는 것을 목적으로 한다. Mock-up test를 통해 발생 가능한 문제점을 사전에 검토함과 동시에 현장 적용을 통해 해당 공법의 적용효과를 분석하였으며, 기존 SRC 기둥에 공기, 원가, 품질, 안전, 환경 측면에서 우수한 것으로 나타났다.