• Structural Engineering and Mechanics
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• 제61권5호
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• pp.675-684
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• 2017

In this paper, a hybrid seismic response control (HSRC) system was developed to control bridge behavior caused by the seismic load. It was aimed at optimum vibration control, composed of a rubber bearing of passive type and MR-damper of semi-active type. Its mathematical modeling was driven and applied to a bridge model so as to prove its validity. The bridge model was built for the experiment, a two-span bridge of 8.3 meters in length with the HSRC system put up on it. Then, inflicting the EI Centro seismic load on it, shaking table tests were carried out to confirm the system's validity. The experiments were conducted under the basic structure state (without an MR-damper applied) first, and then under the state with an MR-damper applied. It was also done under the basic structure state with a reinforced rubber bearing applied, then the passive on/off state of the HSRC system, and finally the semi-active state where the control algorithm was applied to the system. From the experiments, it was observed that pounding rather increased when the MR-damper alone was applied, and also that the application of the HSRC system effectively prevented it from occurring. That is, the experiments showed that the system successfully mitigated structural behavior by 70% against the basic structure state, and, further, when control algorithm is applied for the operation of the MR-damper, relative displacement was found to be effectively mitigated by 80%. As a result, the HSRC system was proven to be effective in mitigating responses of the two-span bridge under seismic load.

• 한국전산구조공학회논문집
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• 제21권2호
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• pp.127-133
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• 2008

본 연구는 일반 철골구조물에서 사용되는 구조용 프리캐스트 콘크리트 외부벽판과 연결부재로 인하여 건물 전체의 내진성능을 조사하였고, 벽판의 높이 변화에 따른 건물 전체의 횡방향 강성 변화량을 파악하였다. 외부벽판과 연결부재를 구조 부재로 간주할 경우 수동형 제진장치와 같이 지진에너지를 소산할 뿐 아니라 추가로 전체 건물의 횡방향 강성을 제공하는 것을 확인하였다. 이력거동 성능을 가진 연결부재를 비선형 유한요소해석 프로그램인 ABAQUS를 이용하여 조사한 결과, 건물의 내진성능 향상에 연결부재가 가장 중요한 역할을 하는 것으로 확인되었다.

• Earthquakes and Structures
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• 제9권3호
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• pp.563-576
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• 2015

Over the past few decades, seismic retrofitting of structural systems has been significantly improved by the adoption of various methods such as FRP composite wraps, base isolation systems, and passive/active damper control systems. In parallel with this trend, probabilistic risk assessment (PRA) for structural and nonstructural components has become necessary for risk mitigation and the achievement of reliable designs in performance-based earthquake engineering. The primary objective of the present study was to evaluate the effect on piping fragility at T-joints due to seismic retrofitting of structural systems with passive energy-dissipation devices (i.e., linear viscous dampers). Three mid-rise building types were considered: without any seismic retrofitting; with distributed damper systems; with optimal placement of dampers. The results showed that the probability of piping system failure was considerably reduced in a Multi Degree of Freedom (MDOF) building retrofitted with optimal passive damper systems at lower floor levels. This effect of damper systems on piping fragility became insignificant as the floor level increased.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 가을 학술발표회 논문집
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• pp.476-483
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• 2004

This paper presents a hybrid system combining lead rubber bearings and hydraulic actuators controlled by a μ-synthesis method for seismic response control of a cable-stayed bridge. A hybrid system could alleviate some of restrictions and limitations that exist when each system is acting alone because multiple control devices are operating. Therefore, the overall control performance of a hybrid system may be improved compared to each system, however the overall system robustness may be negatively impacted by active device in the hybrid system or active controller may cause instability due to small margins. Therefore, a f-synthesis method that guarantees the robust performance is considered to enhance the possibility of real applications of the control system. The control performances of the proposed control system are compared with those of passive, active, semiactive control systems and hybrid system controlled by LQG algorithm and an extensive robust analysis with respect to stiffness and mass matrices perturbation and time delay of actuator is performed. Numerical simulation results show that the control performance of the proposed control system is superior to that of the passive system and slightly better than that of the active and semiactive systems and two hybrid systems show similar control performances. Furthermore, the hybrid system controlled by a μ-synthesis method shows the good robustness without loss of control performances. Therefore, the proposed control system could effectively be used to seismically excited cable-stayed bridge which contains many uncertainties.

• Earthquakes and Structures
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• 제15권3호
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• pp.227-241
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• 2018

The present paper deals with the optimum performance of the passive hybrid control system for the benchmark highway bridge under the six earthquakes ground motion. The investigation is carried out on a simplified finite element model of the 91/5 highway overcrossing located in Southern California. A viscous fluid damper (known as VFD) or non-linear fluid viscous spring damper has been used as a passive supplement device associated with polynomial friction pendulum isolator (known as PFPI) to form a passive hybrid control system. A parametric study is considered to find out the optimum parameters of the PFPI system for the optimal response of the bridge. The effect of the velocity exponent of the VFD and non-linear FV spring damper on the response of the bridge is carried out by considering different values of velocity exponent. Further, the influences of damping coefficient and vibration period of the dampers are also examined on the response of the bridge. To study the effectiveness of the passive hybrid system on the response of the isolated bridge, it is compared with the corresponding PFPI isolated bridges. The investigation showed that passive supplement damper such as VFD or non-linear FV spring damper associated with PFPI system is significantly reducing the seismic response of the benchmark highway bridge. Further, it is also observed that non-linear FV spring damper hybrid system is a more promising strategy in reducing the response of the bridge compared to the VFD associated hybrid system.

• Smart Structures and Systems
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• 제4권6호
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• pp.741-757
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• 2008

The research field of structural control has evolved from the development of passive devices since 1970s, through the intensive investigation on active systems in 1980s, to the recent studies of semi-active control systems in 1990s. Currently semi-active control is considered most promising in civil engineering applications. However, actual implementation of semi-active devices is still limited due mainly to their system maintenance and associated long-term reliability as a result of power requirement. In this paper, the concept of functionally upgraded passive devices is introduced to streamline some of the state-of-the-art researches and guide the development of new passive devices that can mimic the function of their corresponding semi-active control devices for various applications. The general characteristics of this special group of passive devices are discussed and representative examples are summarized. Their superior performances are illustrated with cyclic and shake table tests of two example devices: mass-variable tuned liquid damper and friction-pendulum bearing with a variable sliding surface curvature.

• 한국지진공학회논문집
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• 제19권6호
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• pp.273-282
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• 2015

In this study, shaking table test has been carried out for the dual frame passive control system for seismic performance verification of the proposed system. The proposed system was separated into two independent frameworks that are strength resistant core and frame structure by connecting to the damper. Moreover, the seismic performance improvement of the proposed system has been verified by comparing and analyzing the experimental results of the proposed system with an existing core system. As a result of the shaking table test, acceleration and displacement responses of dual-frame vibration control system are decreased than those of the existing strength resistant type core system. In the case of the core system, while the damage was concentrated on the column of first floor, the damage of the dual system was dispersed in each layer. The damage also was concentrated on the damper, almost no damage occurs to the structural members. It has been emphasized that installed dampers in the proposed dual system reduce the input energy of whole structure by absorbing seismic input energy, which leads overall system damage to be reduced.

• Earthquakes and Structures
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• 제11권6호
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• pp.1077-1099
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• 2016

One of the main shortcomings in the current passive base isolation system is lack of adaptability. The recent research and development of a novel adaptive seismic isolator based on magnetorheological elastomer (MRE) material has created an opportunity to add adaptability to base isolation systems for civil structures. The new MRE based base isolator is able to significantly alter its shear modulus or lateral stiffness with the applied magnetic field or electric current, which makes it a competitive candidate to develop an adaptive base isolation system. This paper aims at exploring suitable control algorithms for such adaptive base isolation system by developing a close-loop semi-active control system for a building structure equipped with MRE base isolators. The MRE base isolator is simulated by a numerical model derived from experimental characterization based on the Bouc-Wen Model, which is able to describe the force-displacement response of the device accurately. The parameters of Bouc-Wen Model such as the stiffness and the damping coefficients are described as functions of the applied current. The state-space model is built by analyzing the dynamic property of the structure embedded with MRE base isolators. A Lyapunov-based controller is designed to adaptively vary the current applied to MRE base isolator to suppress the quake-induced vibrations. The proposed control method is applied to a widely used benchmark base-isolated structure by numerical simulation. The performance of the adaptive base isolation system was evaluated through comparison with optimal passive base isolation system and a passive base isolation system with optimized base shear. It is concluded that the adaptive base isolation system with proposed Lyapunov-based semi-active control surpasses the performance of other two passive systems in protecting the civil structures under seismic events.

• 한국지진공학회:학술대회논문집
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• 한국지진공학회 2006년도 학술발표회 논문집
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• pp.495-502
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• 2006

Seismic performance of semi-active fuzzy control algorithm to operate MR dampers for coupling adjacent building is investigated in this paper. In the proposed semi-active control technique, the fuzzy logic is used as a method to adjust input voltage to MR damper. In order to validate control performance of proposed technique, the seismic performance of the semi-active fuzzy control system is compared with that of passive control system where the input voltage to MR damper is set to display maximum damping force. The simulated results show that the semi-active fuzzy control technique effectively regulates the trade-off existing between seismic responses of two buildings subject to various earthquake excitations.

• 한국지진공학회논문집
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• 제6권4호
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• pp.51-63
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• 2002

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.