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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of the Earthquake Engineering Society of Korea
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Journal DOI :
Earthquake Engineering Society of Korea
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Volume & Issues
Volume 10, Issue 6 - Dec 2006
Volume 10, Issue 5 - Oct 2006
Volume 10, Issue 4 - Aug 2006
Volume 10, Issue 3 - Jun 2006
Volume 10, Issue 2 - Apr 2006
Volume 10, Issue 1 - Feb 2006
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Vehicle Load Analysis using Bridge-Weigh-in-Motion System in a Cable Stayed Bridge
Park, Min-Seok ; Lee, Jung-Whee ; Kim, Sung-Kon ; Jo, Byung-Wan ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 1~8
DOI : 10.5000/EESK.2006.10.6.001
This paper describes the procedures developing the algorithm for analyzing signals acquired from the Bridge Weigh-in-Motion (BWIM) system installed in Seohae Bridge as a part of the bridge monitoring system. Through the analysis procedure, information about heavy traffics such as weight, speed, and number of axles are attempted to be extracted from time domain strain data of the BWIM system. One of numerous pattern recognition techniques, artificial neural network (ANN) is employed since it can effectively include dynamic effects, bridge-vehicle interaction, etc. A number of vehicle running experiments with sufficient load cases are executed to acquire training and/or test set of ANN. Extracted traffic information can be utilized for developing quantitative database of loading effect. Also, it can contribute to estimate fatigue lift or current health condition, and design truck can be revised based on the database reflecting recent trend of traffic.
Signal Analysis from a Long-Term Bridge Monitoring System in Yongjong Bridge
Kim, Sung-Kon ; Koh, Hyun-Moo ; Lee, Jung-Whee ; Bae, In-Hwan ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 9~18
DOI : 10.5000/EESK.2006.10.6.009
This paper presents schematically the monitoring system installed in Yongjong Bridge, a self-anchored suspension bridge located in the expressway linking Seoul and Incheon International Airport. Automatic measurement of instrumented civil engineering structures is now widely applied for behavior monitoring during construction in field as well as long-term monitoring for lifetime assessment of bridge structures. A representative example of results that can be acquired through structural health monitoring system is presented by means of data measured during a few years after the opening of the bridge. In order to effectively measure the tension force for hangers that have relatively short length or high tension force, a static tension measurement device has been explored. Newly equipped railway system on the existing bridge results in change of dead load, consequently dynamic characteristics have also been changed. This result can be detected by the monitoring system during and after railway construction.
Numerical Verification of Hybrid Optimization Technique for Finite Element Model Updating
Jung, Dae-Sung ; Kim, Chul-Young ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 19~28
DOI : 10.5000/EESK.2006.10.6.019
Most conventional model updating methods must use mathematical objective function with experimental modal matrices and analytical system matrices or must use information about the gradient or higher derivatives of modal properties with respect to each updating parameter. Therefore, most conventional methods are not appropriate for complex structural system such as bridge structures due to stability problem in inverse analysis with ill-conditions. Sometimes, moreover, the updated model may have no physical meaning. In this paper, a new FE model updating method based on a hybrid optimization technique using genetic algorithm (GA) and Holder-Mead simplex method (NMS) is proposed. The performance of hybrid optimization technique on the nonlinear problem is demonstrated by the Goldstein-Price function with three local minima and one global minimum. The influence of the objective function is evaluated by the case study of a simulated 10-dof spring-mass model. Through simulated case studies, finally, the objective function is proposed to update mass as well as stiffness at the same time. And so, the proposed hybrid optimization technique is proved to be an efficient method for FE model updating.
Determination of Optimal Accelerometer Locations using Mode-Shape Sensitivity
Kwon, Soon-Jung ; Shin, Soo-Bong ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 29~36
DOI : 10.5000/EESK.2006.10.6.029
This paper proposes a new algorithm of MS-EIDV (modal sensitivity-effective independence distribution vector) for determining optimal accelerometer locations (OAL) by using the Fisher Information Matrix (FIM) derived from mode-shape sensitivities. Also, the paper provides a reasonable guideline for selecting OAL which can reflect dynamic responses of a structure effectively. Since OAL should be determined with known values of structural parameters but since the parameters can be estimated by applying an inverse method such as SI (system identification) using measured response, the paper proposes a statistical method to overcome the paradox by considering the error bound of the structural parameters. To examine the proposed methods, a frequency-domain SI method has been applied. By using the identified results, the minimum necessary number of accelerometers could be selected depending on the number of target measurable modes. Through simulation studies, the results by applying EIDV method directly using the information of mode shapes were compared with those by applying the proposed MS-EIDV.
Seismic Performance Improvement of Base Isolated Buildings using Smart Passive Control System
Jung, Hyung-Jo ; Jung, Chan-Kuk ; Choi, Kang-Min ; Lee, In-Won ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 37~46
DOI : 10.5000/EESK.2006.10.6.037
In this study, the efficacy of the newly developed smart passive control system to improve seismic performance of base isolated building structures is numerically verified. The smart passive control system consists of a magnetorheological (MR) damper and an electromagnetic induction (EMI) part. The damping characteristics of an MR damper can be controlled by the current generated in an EMI part according to the Faraday's law of electromagnetic induction. An EMI part consisting of a permanent magnet and a solenoid coil could substitute a control system including sensors, a controller and an external power supply in a conventional smart control system. The benchmark control problem for a base isolated building presented by the american society of civil engineers is considered for numerical simulation. The control performance of the smart passive control system is compared to that of the conventional smart control system using MR dampers. It is demonstrated from the numerical simulation results that the smart passive control system is useful to improve the seismic performance of base isolated buildings.
A Study on Cost-Effectiveness Evaluation and Optimal Design of ant dampers for Cable-Stayed Bridges
Park, Won-Suk ; Hahm, Dae-Gi ; Koh, Hyun-Moo ; Park, Kwan-Soon ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 47~56
DOI : 10.5000/EESK.2006.10.6.047
A method is presented for evaluating the economic efficiency of a semi-active magneto-rheological (MR) damper system for cable-stayed bridges under earthquake loadings. An optimal MR damper capacity maximizing the cost-effectiveness is estimated for various seismic characteristics of ground motion. The economic efficiency of MR damper system is addressed by introducing the life-cycle cost concept. To evaluate the expected damage cost, the probability of failure is estimated. The cost-effectiveness index is defined as the ratio of the sums of the expected damage costs and each device cost between a bridge structure with the MR damper system and a bridge structure with elastic bearings. In the evaluation of cost-effectiveness, the scale of damage cost is adopted as parametric variables. The results of the evaluation show that the MR damper system can be a cost-effective design alternative. The optical capacity of MR damper is increased as the seismic hazard becomes severe.
Hybrid Damage Monitoring Technique for Bridge Connection Via Pattern-Recognition of Acceleration and Impedance Signals
Kim, Jeong-Tae ; Na, Won-Bae ; Hong, Dong-Soo ; Lee, Byung-Jun ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 57~65
DOI : 10.5000/EESK.2006.10.6.057
This paper presents hybrid structural damage monitoring system which performs both global damage assessment of structure and damage detection of local structural joints. Hybrid damage monitoring system is composed of vibration-based technique and electro/mechanic impedance technique. Vibration-based technique detects global characteristic change ot structure using modal characteristic change of structure, and electro/mechanical impedance technique detects damage existence of local structural joints using impedance change of PZT sensor. For the verification of the proposed hybrid monitoring system, a series of damage scenarios are designed to loosened bolts situations of the structural joints, and acceleration response and impedance response signatures are measured. The proposed hybrid monitoring system is implemented to monitor global damage-state and local damages in structural joints.
Application of Seismic Isolation and Vibration Control in Korea
Lee, Dong-Guen ; Kim, Tae-Ho ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 67~77
DOI : 10.5000/EESK.2006.10.6.067
Seismic activity of Korea is not so high as that of Japan or California and most of the structures were designed without considering the influence of earthquakes until the first seismic design code was enforced in 1988. Therefore, it was very hard to find seismically isolated structures in Korea until 1980's. Korean engineers assumed that the seismic isolation or vibration control would be useful only in a high seismicity region while such technologies can be quite useful in a low seismicity region for the efficient reduction of earthquake damages. Recently, Korean engineers began to have interest in the seismic isolation or vibration control and applied it to some important structures such as LNG storage tanks, many bridges and several buildings. However, design codes are not defining such useful advanced technologies for the design of building structures and several projects employing seismic isolation or vibration control in the design of structures had difficulties in obtaining construction permit from the local government. Therefore, it is an urgent requirement to introduce these advanced technologies in the seismic design code.
Baseline-Free Crack Detection in Steel Structures using Lamb Waves and PZT Polarity
Sohn, Hoon ; Kim, Seung-Bum ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 79~91
DOI : 10.5000/EESK.2006.10.6.079
A new methodology of guided wave based nondestructive testing (NDT) is developed to detect crack damage in civil infrastructures such as steel bridges without using prior baseline data. In conventional guided wave based techniques, damage is often identified by comparing the "current" data obtained from a potentially damaged condition of a structure with the "past" baseline data collected at the pristine condition of the structure. However, it has been reported that this type of pattern comparison with the baseline data can lead to increased false alarms due to its susceptibility to varying operational and environmental conditions of the structure. To develop a more robust damage diagnosis technique, a new concept of NDT is conceived so that cracks can be detected without direct comparison with previously obtained baseline data. The proposed NDT technique utilizes the polarization characteristics of the piezoelectric wafers attached on the both sides of the thin metal structure. Crack formation creates Lamb wave mode conversion due to a sudden change in the thickness of the structure. Then, the proposed technique instantly detects the appearance of the crack by extracting this mode conversion from the measured Lamb waves even at the presence of changing operational and environmental conditions. Numerical and experimental results are presented to demonstrate the applicability of the proposed technique to crack detection.
Stability of Saturation Controllers for the Active Vibration Control of Linear Structures
Moon, Seok-Jun ; Lim, Chae-Wook ; Huh, Young-Chul ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 93~102
DOI : 10.5000/EESK.2006.10.6.093
Control input's saturation of active control devices for large structures under large external disturbances are often occurred. It is more difficult to obtain the exact values of mass and stiffness as structures are higher. The modelling errors between mathematical models and real structures must be also included as parameter uncertainties. Therefore, in active vibration control of civil engineering structures like buildings and bridges, the robust saturation controller design method considering both control input's saturation and parameter uncertainties of system is needed. In this paper, stabilities of linear optimal controller LQR, modified bang-bang controller, saturated sliding mode controller, and robust saturation controller among various controllers which have been studied and applied to active vibration control of buildings are investigated. Especially, unstable phenomena of the LQR, the modified bang-bang controller and the saturated sliding mode controller when the control input is saturated or parameter uncertainties exist are presented to show the necessity of the robust saturation controller. The robust stability of the robust saturation controller are shown through a numerical example of a 2DOF linear vibrating system and an experimental test of the two-story structure with an active mass damper (AMD).
Forced Vibration Test of a Real-Scale Structure and Design of HMD Controllers for Simulating Earthquake Response
Lee, Sang-Hyun ; Park, Eun-Churn ; Youn, Kyung-Jo ; Lee, Sung-Kyung ; Yu, Eun-Jong ; Min, Kyung-Won ; Chung, Lan ; Min, Jeong-Ki ; Kim, Young-Chan ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 103~114
DOI : 10.5000/EESK.2006.10.6.103
Forced vibration testing is important for correlating the mathematical model of a structure with the real one and for evaluating the performance of the real structure. There exist various techniques available for evaluating the seismic performance using dynamic and static measurements. In this paper, full scale forced vibration tests simulating earthquake response are implemented by using a hybrid mass damper. The finite element (FE) model of the structure was analytically constructed using ANSYS and the model was updated using the results experimentally measured by the forced vibration test. Pseudo-earthquake excitation tests showed that HMD induced floor responses coincided with the earthquake induced ones which were numerically calculated based on the updated FE model.
Dynamic Characteristics of Seohae Cable-stayed Bridge Based on Long-term Measurements
Park, Jong-Chil ; Park, Chan-Min ; Kim, Byeong-Hwa ; Lee, Il-Keun ; Jo, Byung-Wan ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 115~123
DOI : 10.5000/EESK.2006.10.6.115
This paper presents long-term dynamic characteristics of a cable-stayed bridge where installed SHM (Structural Health Monitoring) system. Modal parameters such as natural frequencies and mode shapes are identified by modal analysis using three dimensional finite element model. The developed baseline model has a good correlation with measured natural frequencies identified from field ambient vibrations. By statistical data processing between measured natural frequencies and temperatures, it is demonstrated that the natural frequency is in linearly inverse proportion to the temperature. The estimation of temperature effects against frequency variations is performed. Mode shapes are identified from the TDD (Time Domain Decomposition) technique for ambient vibration measurements. Finally, these results demonstrate that the TDD method can apply to identify modal parameters of a cable-stayed bridge.
Development of a Lateral Mode Piezoelectric Oscillator Sensor to Detect Damages in a Structure
Roh, Yong-Rae ; Kim, Dong-Young ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 125~132
DOI : 10.5000/EESK.2006.10.6.125
This paper presents the feasibility of a lateral mode piezoelectric oscillator to detect damages in civil infrastructures. The lateral mode oscillator sensor is composed of an electronic feedback oscillator circuit and a piezoelectric lateral mode vibrator to be attached to a structure of interest. Damage to the structure causes a change in the impedance spectrum of the structure, which results in a corresponding change of a resonant frequency of the structure. The oscillator sensors can instantly detect the frequency change in a very simple manner. Feasibility of the piezoelectric oscillator sensor was verified in this work with a sample aluminum plate where artificial cracks of different lengths and number were imposed in sequence. Validity of the measurement was confirmed through comparison of the experimental data with the results of finite element analyses of a plate with cracks.
Fiber Optic Sensor for the Detection of Abnormal Structural Signals from Various Constructions
Kwon, Il-Bum ; Lee, Youn-Jae ; SeoMoon, Ung ; Jo, Jae-Heung ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 133~135
DOI : 10.5000/EESK.2006.10.6.133
We propose and fabricate a novel fiber optic sensor for the detection of abnormal structural signals from various constructions. It's advantages are highly sensitive. small in dimension and electro-magnetic immune. Since this sensor was simply constructed with a single-mode fiber at infra-red wavelength and a laser-diode with the wavelength of 625 nm, the modes in the end of the optical fiber were not show as Gaussian distributed. So, we used the change of the mode distribution to get the sensor output by the external abnormal effect of structures. We investigated the resonance by performing the bending test of an aluminum beam attached with the fiber sensor. In the test, we could obtained a feasible signal to sense the abnormal condition of structures.
Fiber Optic Sensors for Smart Monitoring
Kim, Ki-Soo ;
Journal of the Earthquake Engineering Society of Korea, volume 10, issue 6, 2006, Pages 137~145
DOI : 10.5000/EESK.2006.10.6.137
Recently, the interests in structural monitoring of civil infrastructures are increased. Especially, as the civil infrastructures such as bridges, tunnels and buildings become large-scale, it is necessary to monitor and maintain the safety state of the structures, which requires smart systems that can supply long-term monitoring during the service time of the structures. In this paper, we investigated the possibilities of fiber optic sensor application to the various structures. We investigate the possibility of using fiber optic Bragg grating sensors to joint structure. The sensors show good response to the structural behavior of the joint while electric gauges lack of sensitivity, durability and long term stability for continuous monitoring. We also apply fiber optic structural monitoring to the composite repaired concrete beam structure. Peel-out effects is detected with optical fiber Bragg grating sensors and the strain difference between main structure and repaired carbon sheets is observed when they separate each other. The real field test was performed to verify the behaviors of fiber Bragg grating sensors attached to the containment structure in Uljin nuclear power plant in Korea as a part of structural integrity test which demonstrates that the structural response of the non-prototype primary containment structures. The optical fiber Bragg grating sensor smart system which is the probable means for long term assessments can be applicable to monitoring of structural members in various civil infrastructures.