• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2003년도 가을 학술발표회 논문집
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• pp.509-516
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• 2003

In tile design of base isolation system for building and short-span bridge, shift of the natural period of the structure is main objective. But, most long-span bridges such as a cable-stayed bridges have a number of long-period modes due to their flexibility and small structural damping. thus the design concept of base isolation system for building and short-span brigde may be difficult to use directly to these structures. However, the effectiveness of LRB for cable-stayed bridges is indicated by Ali and Abdel-Ghaffar. In this study, the design procedure and guidelines of LRB for a seismically excited cable-stayed bridge are investigated. The design properties of LRB are chosen that the design index(DI) is minimized or little changed for variation of properties. This result show that the stiffer rubber and bigger lead core size are need to cable-stayed bridges. And the seismic performance of designed LRB is also investigated. The consequences show that the perforamnce of designed LRB is better than that of Naeim-Kelly mettled designning LRB for general building structures. Moreover, the design properties of LRB are researched to several diffrent dominant frequency of earthquake. The results present that the plastic and elastic stiffness of LRB are affected by the dominant frequency of earthquake.

• Transactions on Electrical and Electronic Materials
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• 제3권1호
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• pp.9-13
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• 2002

In this work, the surface of inorganic fillers were modified with some functional groups such as stearic acid, aliphatic long chain, vinylsilane and aminosilane to control the interaction between inorganic fillers and polymer matrix. Ethylene-vinyl acetate copolymers (EVA) with various amount of vinyl-acetate and copolyether-ester elastomer were used as polymer matrix. The addition of inorganic fillers increases flame retardancy, but results in steep drop of electrical and mechanical properties, which may be caused by the defects in the interface between organic/inorganic hybrid composites. The hybrid composites are found to show better mechanical properties and higher volume resistivities as inorganic fillers are well dispersed and have good adhesion with polymer matrix. Also, the most effective type of functional group coated on fillers depends on the chemical structure of polymer.

• Smart Structures and Systems
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• 제21권4호
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• pp.421-433
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• 2018

Carbon fiber reinforced polymer (CFRP) cable has good mechanical properties and corrosion resistance. However, the anchorage of CFRP cable is a big issue due to the anisotropic property of CFRP material. In this article, a high-efficient bonding anchorage with novel configuration is developed for CFRP cables. The acoustic emission (AE) technique is employed to evaluate the performance of anchorage in the fatigue test and post-fatigue ultimate bearing capacity test. The obtained AE signals are analyzed by using a combination of unsupervised K-means clustering and supervised K-nearest neighbor classification (K-NN) for quantifying the performance of the anchorage and damage evolutions. An AE feature vector (including both frequency and energy characteristics of AE signal) for clustering analysis is proposed and the under-sampling approaches are employed to regress the influence of the imbalanced classes distribution in AE dataset for improving clustering quality. The results indicate that four classes exist in AE dataset, which correspond to the shear deformation of potting compound, matrix cracking, fiber-matrix debonding and fiber fracture in CFRP bars. The AE intensity released by the deformation of potting compound is very slight during the whole loading process and no obvious premature damage observed in CFRP bars aroused by anchorage effect at relative low stress level, indicating the anchorage configuration in this study is reliable.

• Smart Structures and Systems
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• 제23권5호
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• pp.449-466
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• 2019

Cable-stayed bridges are attractive due to their beauty, reducing material consumption, less harm to the environment and so on, in comparison with other kinds of bridges. As a massive structure with long period and low damping (0.3 to 2%) under many dynamic loads, these bridges are susceptible to fatigue, serviceability disorder, damage or even collapse. Tuned Mass Damper (TMD) is a suitable controlling system to reduce the vibrations and prevent the threats in such bridges. In this paper, Multi Tuned Mass Damper (MTMD) system is added to the Ahvaz cable stayed Bridge in Iran, to reduce its seismic vibrations. First, the bridge is modeled in SAP2000 followed with result verification. Dead and live loads and the moving loads have been assigned to the bridge. Then the finite element model is developed in OpenSees, with the goal of running a nonlinear time-history analysis. Three far-field and three near-field earthquake records are imposed to the model after scaling to the PGA of 0.25 g, 0.4 g, 0.55 g and 0.7 g. Two MTMD systems, passive and active, with the number of TMDs from 1 to 8, are placed in specific points of the main span of bridge, adding a total mass ratio of 1 to 10% to the bridge. The parameters of the TMDs are optimized using Genetic Algorithm (GA). Also, the optimum force for active control is achieved by Fuzzy Logic Control (FLC). The results showed that the maximum displacement of the center of the bridge main span reduced 33% and 48% respectively by adding passive and active MTMD systems. The RMS of displacement reduced 37% and 47%, the velocity 36% and 42% and also the base shear in pylons, 27% and 47%, respectively by adding passive and active systems, in the best cases.

• Journal of Power Electronics
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• 제16권5호
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• pp.1743-1751
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• 2016

The increasing demand for high voltage DC grids resulting from the continuous installation of offshore wind farms in the North Sea has led to the concept of multi-terminal direct current (MTDC) grids, which face some challenges. Power (current) flow control is a challenge that must be addressed to realize a reliable operation of MTDC grids. This paper presents a reduced switch count topology of a current flow controller (CFC) for power flow and current limiting applications in MTDC grids. A simple control system based on hysteresis band current control is proposed for the CFC. The theory of operation and control of the CFC are demonstrated. The key features of the proposed controller, including cable current balancing, cable current limiting, and current nulling, are illustrated. An MTDC grid is simulated using MATLAB/SIMULINK software to evaluate the steady state and dynamic performance of the proposed CFC topology. Furthermore, a low power prototype is built for a CFC to experimentally validate its performance using rapid control prototyping. Simulation and experimental studies indicate the fast dynamic response and precise results of the proposed topology. Furthermore, the proposed controller offers a real solution for power flow challenges in MTDC grids.

• 한국전자파학회논문지
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• 제28권9호
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• pp.698-706
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• 2017

디지털 제어 시스템에서 주로 사용되는 설비인 PLC(Programmable Logic Controller)와 통신선로에 대한 HPEM(High Power Electromagnetic) 펄스의 노출 위험이 최근 증가되고 있다. 본 연구에서는 서로 다른 주파수 대역을 가지는 HPEM 발생장치를 이용하여 분리된 독립 객체로써 전자 장치의 HPEM에 대한 취약성을 평가하였다. 전자장치가 어떠한 영향을 받는지 상황별로 나누어 비교하였고, HPEM에 노출된 피 시험 기기의 취약성을 분석하였다. 피 시험 기기는 특정 이상의 HPEM에 노출되면, 제어 장치의 전압 및 통신 파형에 왜곡된 특성을 보였으며, UTP(Unshielded Twisted Pair) 케이블에 연결된 장치는 유도전압에 의해 작동 불량을 나타났다. 그러나 FTP(Foiled Twisted Pair) 케이블에 연결된 장치인 경우에는 HPEM 노출로부터 효율적으로 보호되었다. 따라서 현재 전력설비 및 산업현장에서 이용되고 있는 디지털 제어시스템에 대한 HPEM 노출 취약성과 보호대책의 필요성을 입증하였다.

• 한국구조물진단유지관리공학회 논문집
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• 제18권5호
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• pp.87-95
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• 2014

사장교는 다수의 케이블에 의해 지지되어 복잡한 거동을 하는 구조체이며, 측경간 케이블에 의해 단부교각에서 부반력이 발생한다. 이를 해결하기 위해 적절한 측경간비를 설정해야 하고 앵커교각의 부반력 대책을 강구해야 한다. 부반력 제어 대책으로는 중간교각, 카운터 웨이트 등을 설치하는 방안이 있으며 이에 따라 사장교의 구조계가 결정된다. 밤콩교량은 타당성 검토 단계에서 5경간 사장교로 계획되었다. 하지만 시공성 및 경제성 등의 문제로 실시설계 단계에서 3경간 사장교로 변경되었다. 시공성을 확보하기 위하여 중간교각을 배제하였고, 이에 따른 부반력을 제어하기 위해 측경간비를 증가시켰다. 그 결과, 원안 설계에 비하여 시공성, 구조적 안전성, 효율성을 확보할 수 있었다.

• 한국구조물진단유지관리공학회 논문집
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• 제27권2호
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• pp.58-66
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• 2023

이 연구에서는 진동법을 이용하여 케이블 장력을 추정하고 비접촉 방식으로 케이블의 변위 응답을 측정하기 위한 센서로 영상기반시스템을 적용하였다. 영상기반시스템에서 카메라는 대상 구조물과 카메라의 시야를 고려한 위치에 설치된다. 그러나 설치하려는 위치의 이미지에는 대상 구조물과 차량 등의 다른 구조물이 포함될 수 있어 구조물의 변위 응답 측정에 필요한 기준점을 인식하기 어려울 수 있다. 영상기반시스템의 설치 위치로 인해 차량이 포함된 왜곡된 이미지는 이미지 해석에서 부정확한 결과를 나타내므로 두 이미지 사이의 유사성을 산정하여 차량이 포함된 이미지를 제거하였다. 제안된 방법을 이용한 사장교 케이블의 장력을 측정하는 방법의 타당성을 확인하기 위해 공용 중인 사장교에서 진동법을 적용하여 장력을 측정하였다.

• 한국지진공학회논문집
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• 제6권2호
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• pp.63-71
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• 2002

본 논문에서는 미국토목학회(ASCE)의 사장교에 대한 첫번째 벤치마크 문제를 이용하여 제어-구조물 상호작용을 고려한 새로운 반능동제어 기법을 제안하였다. 이 벤치마크 문제에서는 2003년 완공 예정으로 미국 Missouri주에 건설 중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고, Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계단계에서부터 내진 문제를 중요하게 고려하였다. 본 연구에서는 MR 유체 감쇠기를 제어 장치로 제안하였고, clipped-optimal 알고리듬을 제어 알고리듬으로 사용하였다. 또한, 대용량 MR 유체 감쇠기 실험 결과를 이용하여, Bingham 모델, Bouc-Wen 모델, 수정된 Bouc-HWen 모델과 같이 수치해석에 이용할 수 있는 다양한 동적 모델을 개발하였다. MR 유체 감쇠기는 제어가능한 에너지 소산장치이며 구조물에 에너지를 가하지 않기 때문에 제안된 제어기법은 한정입출력 안정성이 보장된다. 수치해석을 통해, MR 유체 감쇠기를 이용한 반능동제어 기법이 사장교의 응답 감소에 효과적인 방법임을 증명하였다.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2001년도 ICCAS
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• pp.25.4-25
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• 2001

In this paper, a five degree-of-freedom haptic device is proposed. The proposed haptic device has a pen which is suspended by tensioned six strings. Human operator handles the pen. Six DC motors are used as actuators to generate tensions in six strings to make resultant force feedback at the pen to the human operator Six encoders are used for calculating the movement of the pen. A digital controller is used for generate control signals for the suitable tension in the six strings. A current amplifiers is used for amplifying the control signals. Cable-suspended system has advantages of structure simplicity (only with several strings driven by motors without using other tensioning mechanisms), low inertia, and high force-to-weight ratio. Pen-based system has advantages of compactness and ...