납고무받침의 비선형성을 고려한 벤치마크 사장교의 복합제어

Park Kyu Sik,Jung, Hyung Jo,Lee In Won 한국지진공학회 2002 한국지진공학회논문집 Vol.6 No.4

본 논문에서는 지진하중을 받는 사장교의 진동제어 기법 개발을 위해 제공된 벤치마크 사장교에 복합제어 기법을 적용하였다. 이 벤치마크 문제는 2003년 완공 예정으로 미국 Missouri 주에 건설중인 Cape Girardeau 교를 대상 구조물로 고려하였다. Cape Girardeau 교는 New Madrid 지진구역에 위치하고 Mississippi 강을 횡단하는 주요 교량이라는 점 때문에 설계 단계에서부터 내진 문제를 중요하게 고려하였다. 벤치마크 문제에는 사장교의 상세한 설계도면에 기초해 교량의 복잡한 거동을 나타낼 수 있는 3자원 선형모델과 각 제어기법의 성능을 평가하기 위한 18개의 평가기준이 제시되어 있다. 본 연구에서 적용한 복합제어 기법은 지진하중으로 인해 구조물에 발생되는 하중을 줄이기 위한 수동제어 기법과 상판변위와 같은 구조물의 응답을 추가적으로 제어하기 위한 능동제어 기법이 결합된 제어 방법이다. 수동제어 장지로는 납고무받침을 사용하였고 Bouc-Wen 모델을 사용하여 비선형 거동을 고려 할 수 있도륵 모델링 하였다. 능동제어 장치로는 이상적인 hydraulic actuators 가 사용되었으며 제어 알고리듬은 H_2/LQG 를 적용하였다. 수치해석 결과 제안방법의 성능은 수동제어 방법에 비해 매우 효과적이며, 능동제어 방법에 비해서는 약간 좋은 제어성능을 나타내었다. 복합제어 방법은 수동제어 부분 때문에 능동제어 방법에 비해 보다 신뢰할 수 있는 제어 방법이다. 따라서 제안된 제어방법은 지진하중을 받는 사장교의 제어를 위해 효과적으로 사용될 수 있다. This paper presents a hybrid control strategy for seismic protection of a benchmark cable-stayed bridge, which is provided as a testbed structure for the development of strategies for the control of cable-stayed bridges. This benchmark problem considers the cable-stayed bridge that is scheduled for completion in Cape Girardeau, Missouri, USA in 2003. Seismic considerations were strongly considered in the design of this bridge due to the location of the bridge in the New Madrid seismic zone and its critical role as a principal crossing of the Mississippi river. Based on detailed drawings of this cable-stayed bridge, a three-dimensional linearlized evaluation model has been developed to represent the complex behavior of the bridge. A set of eighteen evaluation criteria has been developed to evaluate the capabilities of each control strategy. In this study, a hybrid control system is composed of a passive control system to reduce the earthquake-induced forces in the structure and an active control system to further reduce the bridge responses, especially deck displacements. Conventional base isolation devices such as lead rubber bearings are used for the passive control design and Bouc-Wen model is used to simulate the nonlinear behavior of these devices For the active control design, ideal hydraulic actuators are used and on H_2/LQG control algorithm is adopted. Numerical simulation results show that the performance of the proposed hybrid control strategy is quite effective compared to that of the passive control strategy and slightly better than that of the active control strategy. The hybrid control method is also more reliable than the fully active control method due to the passive control part. Therefore, the proposed hybrid control strategy can effectively be used to seismically excited cable-stayed bridges.

Stochastic modelling and optimum inspection and maintenance strategy for fatigue affected steel bridge members

Hua-Peng Chen,Tian-Li Huang,Hao Zhou,Wei-Xin Ren 국제구조공학회 2016 Smart Structures and Systems, An International Jou Vol.18 No.3

This paper presents a method for stochastic modelling of fatigue crack growth and optimising inspection and maintenance strategy for the structural members of steel bridges. The fatigue crack evolution is considered as a stochastic process with uncertainties, and the Gamma process is adopted to simulate the propagation of fatigue crack in steel bridge members. From the stochastic modelling for fatigue crack growth, the probability of failure caused by fatigue is predicted over the service life of steel bridge members. The remaining fatigue life of steel bridge members is determined by comparing the fatigue crack length with its predetermined threshold. Furthermore, the probability of detection is adopted to consider the uncertainties in detecting fatigue crack by using existing damage detection techniques. A multi-objective optimisation problem is proposed and solved by a genetic algorithm to determine the optimised inspection and maintenance strategy for the fatigue affected steel bridge members. The optimised strategy is achieved by minimizing the life-cycle cost, including the inspection, maintenance and failure costs, and maximizing the service life after necessary intervention. The number of intervention during the service life is also taken into account to investigate the relationship between the service life and the cost for maintenance. The results from numerical examples show that the proposed method can provide a useful approach for cost-effective inspection and maintenance strategy for fatigue affected steel bridges.

교량 안전등급 분석을 통한 유지관리전략 개선 방안 연구

황윤국(Yoon-Koog Hwang),선종완(Jong-Wan Sun),최영민(Young-Min Choi),박경훈(Kyung-Hoon Park) 한국산학기술학회 2021 한국산학기술학회논문지 Vol.22 No.3

교량은 국가 주요 기반시설물 중의 하나로서 ‘시설물의 안전 및 유지관리에 관한 특별법’에 따라 정기적인 안전점검 또는 진단이 실시되고 있다. 이를 통해 교량의 상태평가 및 안전성평가 결과에 의해 각각 상태등급과 안전성등급이 개별적으로 산정되고, 두 등급의 결과 중 상대적으로 낮은 등급이 해당 교량의 안전등급으로 결정된다. 본 연구에서는 교량 안전등급의 핵심인 상태등급과 안전성등급의 상관관계를 일반국도 상에 위치한 교량의 대표적인 상부구조형식인 RC슬래브교, PSCI거더교, 강박스거더교, 라멘교 및 프리플렉스거더교를 대상으로 분석하였다. 또한 분석 대상 교량의 형식별로 각각의 등급 간의 상관현황, 상관범위 등을 파악하고, 교량 상부구조형식별 점검 및 진단의 적정 수행주기 변경방안을 제안하여 국내의 기존 유지관리 정책 수립의 합리적인 개선 방향을 제시하고자 하였다. 연구 결과에 근거하여 교량은 상부구조형식, 안전등급에 따라 기존 점검 및 진단 주기의 일부 조정이 필요할 것으로 판단되며, 향후 보다 다양한 교량형식에 대한 세부적인 연구를 통해 유지관리 정책의 개선이 지속적으로 이루어져야 할 것으로 판단된다. Because bridges are major national infrastructure, regular safety inspections or diagnoses for bridges have been conducted in accordance with the "Special Act on the Safety and Maintenance of Facilities." Accordingly, the condition and safety assessments of the bridge are conducted to derive the condition and safety rating, respectively. A lower result is determined to be the safety grade of the bridge. In this study, the relationship between the condition rating and safety rating, which are the core of the bridge safety grade, was analyzed by the representative superstructure types of bridges, such as RC slab, PSCI girder, Steel box girder, Rhamen, and Preflex girder, to identify the correlation status and range between each rating. A reasonable improvement direction for establishing existing maintenance policies was suggested by proposing an alternative plan to change the proper implementation cycle of the inspection and diagnosis of bridge superstructure types. As a result of the research, it is necessary to adjust the inspection and diagnosis cycle according to the superstructure type and safety grade. In addition, maintenance policies need to be improved through detailed research on more diverse bridge types in the future.

China’s Search for Grand Strategy after the Cold War and the Future of the Korean Peninsula

안병준 한국사회과학협의회 2012 Korean Social Science Journal Vol.39 No.2

The nature of China’s rise in the 21st century world is one of the most important questions for East Asia and the future of the Korean peninsula. Judging from various signs of Chinese assertiveness emerging after America’s Great Recession broke out in 2008, Chinese grand strategy, if any, seems to be shifting from Peaceful Rise advocated to ensure a smooth economic development to Near-shore Balancing toward Regional Hegemony designed to deter the U.S. from approaching near Chinese shores in Asia. This shift may well reflect China’s rising power itself and its perceptions about a relative decline of American power especially in the wake of the sudden financial crisis. I have selected four most important constraints on Chinese grand strategy: history, geopolitics, economy and domestic politics. In comparative terms, Chinese history and politics set more constraints on intentions and styles of Chinese grand strategy whereas Chinese geopolitics and economy set more constrains on power and capabilities. From these I also have discerned four contending visions of Chinese grand strategy: Sino-centric nationalism, realism, globalism, and Confucianism as soft power. Of these, nationalism and realism seems to exert more influence than globalism and Confucianism insofar as the overall direction of Chinese grand strategy is concerned. The direction of Chinese grand strategy evolving from these diverse trends can best be described as what I call Near-shore Balancing toward Regional Hegemony. The advent of this new strategy may conflict with America’s grand strategy called Offshore Balancing in East Asia which is designed to keep one power from dominating the region especially when the U.S. now tries to “come back to Asia” by reinforcing its forward deployments. South Korea finds itself in increasing rivalry between these “two dreams sharing the same bed”: China’s quest for a unipolar Asia via building a Sino-centric and exclusive East Asian Community and America’s quest for a multipolar Asia via fostering a Trans-Pacific Partnership (TPP) toward a Pacific Community. South Korea has little choice but strengthening its security alliance with U.S. and expanding its thrusts for economic globalization via free trade agreements while attempting by all means to build strong bridges with China and other powers by deepening common economic and strategic interests.

Structural Health Monitoring (SHM) for a Cable Stayed Bridge under Typhoon

주민관,박철우,김규선 대한토목학회 2015 KSCE JOURNAL OF CIVIL ENGINEERING Vol.19 No.4

Long span bridges have usually experienced natural disaster during service age. A typhoon is very specific natural phenomenon which has a great impact on human life, including civil structures themselves. Combined with IT, operation of these monitoring systems enables reasonable, scientific, and economic maintenance based on measured data. IN particular, as climate has changed due to global warming, unexpected natural disasters have occurred more frequently. Structural Health Monitoring (SHM) for the cable supported bridges in a typhoon can reduce maintenance efforts and costs. Scientific verification for cable supported bridge structural performance is also possible using SHM data. This can ensure a more efficient maintenance strategy is developed for bridges. This study analyzed the SHM data of a cable stayed bridge during a typhoon, with the structural capacity evaluated respective to the safety ratio for Fracture Critical Member (FCM). Finally, some strategies for cable supported bridge maintenance during a typhoon were suggested and its applicability was discussed.

Pulse-width Adjustment Strategy for Improving the Dynamic Inductor Current Response Performance of a Novel Bidirectional DC-DC Boost Converter

Li, Mingyue,Yan, Peimin The Korean Institute of Power Electronics 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a pulse-width adjustment (PWA) strategy for a novel bidirectional DC-DC boost converter to improve the performance of the dynamic inductor current response. This novel converter consists of three main components: a full-bridge converter (FBC), a high-frequency isolated transformer with large leakage inductance, and a three-level voltage-doubler rectifier (VDR). A number of scholars have analyzed the principles, such as the soft-switching performance and high-efficiency characteristic, of this converter based on pulse-width modulation plus phase-shift (PPS) control. It turns out that this converter is suitable for energy storage applications and exhibits good performance. However, the dynamic inductor current response processes of control variable adjustment is not analyzed in this converter. In fact, dc component may occur in the inductor current during its dynamic response process, which can influence the stability and reliability of the converter system. The dynamic responses under different operating modes of a conventional feedforward control are discussed in this paper. And a PWA strategy is proposed to enhance the dynamic inductor current response performance of the converter. This paper gives a detailed design and implementation of the PWA strategy. The proposed strategy is verified through a series of simulation and experimental results.

Characteristics analysis of micro‑source half‑bridge converter series Y‑connection based microgrid systems

Xinggui Wang,Yingjie Ding,Jinjian Li,Yongji Guo 전력전자학회 2023 JOURNAL OF POWER ELECTRONICS Vol.23 No.10

Due to the problems of serious circulation current, large switching loss, high harmonic content, unstable voltage, and high engineering cost in existing microgrid structures, a micro-source half-bridge converter series Y-connection-based microgrid (HCSY-MG) is proposed in this paper. On the basis of the equivalent circuit in the system islanding state, the output characteristics of the system and the corresponding influencing factors under both square wave modulation and phase-shifted pulse width modulation (PS-PWM) are analyzed. Under single-cycle square wave modulation, since the DC-side capacitors of some micro-source half-bridge converters are affected by reactive power, which can result in system output voltage fluctuations or even an in-phase imbalanced state, a multi-period cycle modulation strategy is applied to solve this problem. Under the PS-PWM strategy, if the modulation degree and capacitance of the micro-source half-bridge converters are reasonably set, the output voltage of the system can be guaranteed to be in an in-phase equilibrium state. A simulation model and an experimental platform are built to verify the feasibility of the system and the effectiveness of the proposed strategy.

Pulse-width Adjustment Strategy for Improving the Dynamic Inductor Current Response Performance of a Novel Bidirectional DC–DC Boost Converter

Mingyue Li,Peimin Yan 전력전자학회 2018 JOURNAL OF POWER ELECTRONICS Vol.18 No.1

This paper presents a pulse-width adjustment (PWA) strategy for a novel bidirectional DC–DC boost converter to improve the performance of the dynamic inductor current response. This novel converter consists of three main components: a full-bridge converter (FBC), a high-frequency isolated transformer with large leakage inductance, and a three-level voltage-doubler rectifier (VDR). A number of scholars have analyzed the principles, such as the soft-switching performance and high-efficiency characteristic, of this converter based on pulse-width modulation plus phase-shift (PPS) control. It turns out that this converter is suitable for energy storage applications and exhibits good performance. However, the dynamic inductor current response processes of control variable adjustment is not analyzed in this converter. In fact, dc component may occur in the inductor current during its dynamic response process, which can influence the stability and reliability of the converter system. The dynamic responses under different operating modes of a conventional feedforward control are discussed in this paper. And a PWA strategy is proposed to enhance the dynamic inductor current response performance of the converter. This paper gives a detailed design and implementation of the PWA strategy. The proposed strategy is verified through a series of simulation and experimental results.

Hybrid modulation strategy of three-phase dual-active-bridge converter to improve power conversion efficiency under light load conditions in LVDC applications

Choi, Hyunjun,Jung, Jeehoon The Korean Institute of Power Electronics 2020 JOURNAL OF POWER ELECTRONICS Vol.20 No.4

A hybrid control strategy for the three-phase dual-active-bridge (3P-DAB) converter of LVDC applications is presented to improve the power conversion efficiency under light load conditions. The 3P-DAB converter is an attractive topology for high-power applications such as railway traction and aircraft due to its inherent the zero voltage switching (ZVS) capability and reduction of conduction loss due to an interleaved structure with seamless bi-directional power transitions. However, conventional phase shift modulation (PSM) applied to a 3P-DAB converter has disadvantages such as ZVS failure under light load conditions. In this paper, an asymmetrical pulse width modulation is inserted into PSM to replace the existing modulation algorithm of a 3P-DAB converter with a simple control approach. In the proposed control, the transferred power can be calculated according to the mode changes. In addition, the soft switching area of the power switches can be expanded by the proposed hybrid control strategy. Finally, experimental results validate the proposed hybrid modulation strategy using a 3-kW prototype 3P-DAB converter.

국내 중국인 유학생의 문화적응과 선교적 접근전략

김성엽(Kim Sung-Reup) 한국로고스경영학회 2011 로고스경영연구 Vol.9 No.2

한국에서 중국인 유학생들이 가지고 있는 정체성에 따른 기존의 가치관과 세계관이 낯선 한국의 문화적응에 많은 어려움을 겪으면서 스트레스가 발생하였다. 이러한 상태에서 교회공동체가 선교방향과 전략을 설정하는데 있어서 중국인 유학생들의 문화 스트레스 해소를 위한 다각적인 노력이 요구되고 있다. 중국인 유학생들에게 문화적응에 도움을 주기 위한 제도적 장치 및 정책마련과 함께 개인의 정서적 심리적 스트레스 해소에 도움을 제공할 수 있는 사회적 지지를 지역 교회와 대학 등의 공동 노력 차원에서 해결해야할 과제를 안겨 주었다. 따라서 대학과 교회 및 기타 선교기관들 모두가 선교 비견을 실현하는데 따른 다양한 장애요소를 식별하고 이를 극복할 수 있는 선교자원을 조성하고, 사회적 지지를 통해 해결할 수 있는 총체적인 선교 접근전략이 필요하다. 첫째, 선교전략을 수행하기 위한 사회적 지지의 주체가 되는 대학과 교 회, 선교기관의 협력에 따른 제도적 장치와 둘째, 대학과 자원봉사자들의 상담 역할, 셋째, 가깝게 접근 가능한 또래의 기독 대학생과의 교우관계, 넷째, 중국인 유학생 당사자의 노력 등이 요구 된다. 더 나아가서 선교대상인 중국인 유학생들을 중국 현지교회의 재자원화 할 수 있는 계기가 마련되어야 할 것이다. While the existing values according to the identity which the Chinese student have in the process of doing Korean college life and world view underwent a lot of difficulties in strange Korean cultural adaptation, the stress was generated. In this condition, when the church community sets the bridge direction and strategy, the many-sided effort for the cultural stress relaxation of the Chinese student studying abroads is required. The technical goal of the invention to the joint effort aspect including the local church and university, and etc. has to solve the institutional device and for giving aid to the Chinese student studying abroads to the cultural adaptation the Social Support providing the help to the personal emotional psychological stress relaxation with the preparation of policy was imposed. Firstly, the effort of the Chinese student studying abroad person concerned, and etc. is required with the university and church and institutional device according’ to the cooperation of’ the missionary institution and second with the consultation role of the university and volunteer and third with the relation of friends with the Christ college student of the peer and fourth nearly accessible it becomes the subject of the Social Support for performing the bridge strategy. More, furthermore, the opportunity of which can be made resources again China field church should be the bridge merchant prince Chinese student studying abroads prepared.