• Smart Structures and Systems
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• v.19 no.1
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• pp.39-46
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• 2017

Finite element model updating is very effective procedure to determine the uncertainty parameters in structural model and minimize the differences between experimentally and numerically identified dynamic characteristics. This procedure can be practiced with manual and automatic model updating procedures. The manual model updating involves manual changes of geometry and analyses parameters by trial and error, guided by engineering judgement. Besides, the automated updating is performed by constructing a series of loops based on optimization procedures. This paper addresses the ambient vibration based finite element model updating of long span reinforced concrete highway bridges using manual model updating procedure. Birecik Highway Bridge located on the $81^{st}km$ of Şanliurfa-Gaziantep state highway over Firat River in Turkey is selected as a case study. The structural carrier system of the bridge consists of two main parts: Arch and Beam Compartments. In this part of the paper, the arch compartment is investigated. Three dimensional finite element model of the arch compartment of the bridge is constructed using SAP2000 software to determine the dynamic characteristics, numerically. Operational Modal Analysis method is used to extract dynamic characteristics using Enhanced Frequency Domain Decomposition method. Numerically and experimentally identified dynamic characteristics are compared with each other and finite element model of the arch compartment of the bridge is updated manually by changing some uncertain parameters such as section properties, damages, boundary conditions and material properties to reduce the difference between the results. It is demonstrated that the ambient vibration measurements are enough to identify the most significant modes of long span highway bridges. Maximum differences between the natural frequencies are reduced averagely from %49.1 to %0.6 by model updating. Also, a good harmony is found between mode shapes after finite element model updating.

• Journal of the Korea institute for structural maintenance and inspection
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• v.27 no.5
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• pp.120-129
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• 2023

Hanger cable tension is a major response that can determine the integrity and safety of suspension bridges. In general, the vibration method is used to estimate hanger cable tension on operational suspension bridges. It measures natural frequencies from hanger cables and indirectly estimates tension using the geometry conditions of the hanger cables. This study estimated the hanger cable tension of the Palyeong Bridge using a vision-based system. The vision-based system used digital camcorders and tripods considering the convenience and economic efficiency of measurement. Measuring the natural frequencies for high-order modes required for the vibration method is difficult because the hanger cable response measured using the vision-based system is displacement-based. Therefore, this study proposed a back analysis technique for estimating tension using the natural frequencies of low-order modes. Optimization for the back analysis technique was performed by defining the difference between the natural frequencies of hanger cables measured in the field and those calculated using finite element analysis as the objective function. The direct search method that does not require the partial derivatives of the objective function was applied as the optimization method. The reliability and accuracy of the back analysis technique were verified by comparing the tension calculated using the method with that estimated using the vibration method. Tension was accurately estimated using the natural frequencies of low-order modes by applying the back analysis technique.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.13 no.5
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• pp.327-333
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• 2003

Several tests are performed to evaluate road booming noise. Baseline test delivers the information of road noise characteristics. Coupling effect between structure and acoustics is obtained from the mode shapes and the natural frequencies by the modal test. Equivalent stiffness at joint areas between chassis and car-body system can be determined by the input point inertance test. Noise sensitivity of body mounting point of a chassis part can be obtained from the noise transfer function test with input point inertance test. Operational deflection shape makes us analyze the actual vibration modes of the chassis system under actual leading and find noise sources very easily. Finally, the transfer path analysis is used to Identify noise Paths through the chassis system. The objectives and the procedures of the tests are described in this Paper Also, the guideline for efficient road noise evaluation test can be found.

• Structural Engineering and Mechanics
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• v.7 no.5
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• pp.503-512
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• 1999

Practicing a hole or an orifice through a plate or a slab constitutes a very frequent engineering situation due to operational reasons imposed on the structural system. From a designer's viewpoint it is important to know the effect of this modification of the mechanical system upon its elastodynamic characteristics. The present study deals with the determination of the lower natural frequencies of the structural element described in the title of the paper using a variational approach and expressing the displacement amplitude of the plate in terms of the double Fourier series which constitutes the classical, exact solution when the structure is simply supported at its four edges.

• The Journal of Information Systems
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• v.11 no.2
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• pp.27-46
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• 2002

The main purpose of this paper is to study on the relation between utilization types of internet and performance at the small and medium firms in Korea. To accomplish the purpose of this paper effectively, first of all, theoretical background of the characteristics of chief executive officer are reviewed briefly. Second, research methodology is discussed with the following topics: (1) variables and operational definitions (2) research model and hypotheses (3) data analysis methods Third, research results are discussed with following topics: (1) characteristics of the sample (2) validity and reliability of variables (3) frequencies of the variables (4) resells of hypotheses tests Finally, this paper is summarized and future research areas are suggested briefly.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.1
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• pp.37-45
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• 1991

The electromagnetic field distribution within rectangular coaxial transmission lines (RCTL:TEM cells) is calculated using a numerical method. Boundary integral equations(BIE) considering equivalence theorem and extended boundary condition(EBC) in tapered region are used, thereby restricting the operational frequencies (0~130 MHz) below the cell cutoff frequency(130 MHz). The EM fields within NIST TEM cell ($1\times0.6\times2m$) are calculated by this method. The results of the numerical calcuation have a good agreement in the cross-sectional EM field distribution of TEM cell with 2-dimensional analysis results. Based on this method, the first cutoff freque- ncy in high order modes in the cell and the electric field polarization are considered.

• Journal of the Korean Institute of Telematics and Electronics
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• v.20 no.2
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• pp.29-34
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• 1983

A simulated inductance, with a phase parameter control circuit containing only two resistors and one operational amplifier, is realized as a two terminal network. Analytical results of the proposed circuit avow that we can realize a simulated inductance for constant inductance value, and experimental results confirm the theoretical predictions. Error of maximum 4%, between theoretical and experimental results of equivalent inductance, has been observed over a wide range of frequencies up to about 100 KHz.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.326-333
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• 2003

Railway system is consisted of resources such as rail-line, signalling system, and railcars. It is necessary to efficiently utilize these limited and expensive resources as much as possible up to given line capacity. So far, we treat the line capacity as the criteria for evaluating investment alternatives or for restricting train frequencies, and this criteria is calculated statical and experimental numerical formula. But, line capacity has special attribute that changes dynamically according to operational conditions, so there is a need of new line capacity estimation system. In this paper, we present systematic line capacity analysis model. The proposed model has three main components; TPS(tain performance simulator), PES(parameter evaluation simulator), LCS(line capacity simulator).

• 제어로봇시스템학회:학술대회논문집
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• 1993.10a
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• pp.1219-1226
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• 1993

A buck-boost zero current switched(ZCS) series resonant AC to DC converter for the DC output voltage regulation together with high power factor is proposed. The proposed single phase AC to DC converter enables a zero current switching operation of all the power devices allowing the circuit to operate at high swtiching frequencies and high power levels. A dynamic model for this Ac to DC converter is developed and an analysis for the internal operational characteristics is explored. Based on this analysis, a switched discrete sliding mode control(SDSMC) technique is investigated and its advantages over the other types of current control techniques are discussed. With the proposed control technique, the unity power factor without a current overshoot and a wide range of output voltage can be obtained.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.1 no.1
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• pp.123-129
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• 1997

This study is implementation of transmitter signal processing of MF/HF DSC Controller, obliligation system of GMDSS, focused on the technique of processing to encode the distress and general signal of the DSC message. We analyzed recommendation which prescribed frequencies, operational procedures and technical sequence of the DSC and suggested the basic circuit to be materialize the function of a distress alert and general calf of the DSC equipment using Microprocessor, constructed the algorithm of processing a message, programmed it using C language.