• Computational Structural Engineering
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• v.9 no.1
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• pp.125-132
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• 1996

This study is to propose a practical and realistic reliability analysis by ETCM (Expected Total Cost Minimization). One of the main objectives is intended to propose the safety assessment and capacity rating of existing reinforced concrete members by evaluation index, that is RF(Rating Factor) from the results of the field test and inspection for reinforced concrete bridge. ETCM method is used for the reliability analysis of the proposed models. The proposed reliability model and method are applied to the safety assessment and system factors of reinforced concrete members.

• Computational Structural Engineering
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• v.29 no.2
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• pp.8-11
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• 2016

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2001.09a
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• pp.187-193
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• 2001

The object of this research is to evaluate the seismic performance of existing circular reinforced concrete bridge piers by the Quasi-static test. Existing reinforced concrete bridge piers, which were non-seismical]y designed in accordance with the conventional provisions of Korea Highway Design Specification, are needed to rating evaluate seismic performance fur probable earthquake motions in future by developing a seismic analysis computer program with estimation algorithm. This study has been performed to verify the effect of lap spliced longitudinal steel, confinement steel type and confinement steel ratio for the seismic behavior of reinforced concrete bridge piers. Quasi-static test has been done to investigate the physical seismic performance of RC bridge piers, such as displacement ductility, energy absorption, strength degradation etc.

• Proceedings of the Korea Concrete Institute Conference
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• 2000.04a
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• pp.470-475
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• 2000

This research covers the resting of precast/prestressed concrete I-Girder bridge. The research was designed to examine processes for improving the condition evaluation and rating of prestressed concrete bridge. To establish procedures that allow for the full utilization of prestressed concrete bridge capacity, a 28-year old sample was loaded to failure in site. The bridge was constructed with 12 spans, and girders of each span were simply supported. At each loading stage, the deflections, reinforcement strains, prestressing wire strains and concrete strains were examined. Failure behavior was analyzed, and failure load was also evaluated. The test results wee compared to the analytical results from the non-linear finite element analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.4
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• pp.326-333
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• 2004

This research proposes a high frequency resonant inverter for high power conversion apparatus, which is consist of two L-C linked full-bridge inverter using MOSFET in order to distribute voltage and current of the devices. As an output power control strategy, the time sharing control method is applied. From the computer simulation results, the inverters and devices can be shared properly voltage and current rating of the system. And also, theoretical characteristics of the proposed circuit are compared with experimental results.

• Structural Engineering and Mechanics
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• v.41 no.1
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• pp.83-94
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• 2012

Assessment of a monumental concrete arch bridge with a total length of 210 meters having three major spans of 30 meters and a height of 65 meters, which is located in an earthquake-prone region in southern part of the country is presented in this study. Three-dimensional finite element model of the bridge was generated using a commercially available general finite element analysis software and based on the outcomes of a series of in-depth acceleration measurements that were conducted on-site, the model was refined. By using the structural parameters obtained from the dynamic and the static tests, calibrated model of the bridge structure was obtained and this model was used for necessary calculations regarding structural assessment and evaluation.

• Structural Engineering and Mechanics
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• v.53 no.1
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• pp.89-104
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• 2015

In current bridge management systems (BMSs), load and speed restrictions are applied on unhealthy bridges to keep the structure safe and serviceable for as long as possible. But the question is, whether applying these restrictions will always decrease the internal forces in critical components of the bridge and enhance the safety of the unhealthy bridges. To find the answer, this paper for the first time in literature, looks into the design aspects through studying the changes in demand by capacity ratios of the critical components of a bridge under the train loads. For this purpose, a structural model of a simply supported bridge, whose dynamic behaviour is similar to a group of real railway bridges, is developed. Demand by capacity ratios of the critical components of the bridge are calculated, to identify their sensitivity to increase of speed and magnitude of live load. The outcomes of this study are very significant as they show that, on the contrary to what is expected, by applying restriction on speed, the demand by capacity ratio of components may increase and make the bridge unsafe for carrying live load. Suggestions are made to solve the problem.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2512-2514
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• 1999

A new zero voltage and zero current switching(ZVZCS) full bridge DC-DC converter with transformer isolation is proposed for arc welding machines. The proposed DC-DC converter uses an auxiliary transformer to obtain ZCS for leading leg, which provides load current control capability even in short circuit condition. The auxiliary circuit also operates in ZVZCS mode. The power rating of the auxiliary transformer is about 10% of the main transformer. The operation is verified by experiments for 12[KW] prototype.

• Journal of the Korea institute for structural maintenance and inspection
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• v.25 no.1
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• pp.67-74
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• 2021

This paper evaluated the structural safety of an aging PSC I-girder bridge with rebar corrosion in the deck. The geometry and rebar of the bridge were designed based on an actual PSC I-girder bridge, and the numerical analysis was performed considering the crack of concrete and yielding of steel rebar. According to the evaluation criteria of Korea Infrastructure Safety and Technology Corporation, this study defined two criteria of rebar exposure and corrosion rates to construct a total of 32 corrosion scenarios. Rebar exposure was defined as the exposure of tensile rebars in the bridge deck due to the removal of cover concrete. The results of the analysis showed that the safety and rating factors of the bridge decreased with increasing rebar exposure and corrosion rates. For the rebar corrosion rate more than 50%, the safety grade of the bridge should be carefully evaluated for all the rebar exposure rate. When the rebar corrosion rate exceeds 57%, the bridge was evaluated as E grade regardless of rebar exposure rate. A correlation analysis for a 2% of rebar exposure rate found that the bridge was evaluated as A grade up to 55.8% corrosion rate, C grade up to 56.9%, D grade up to 58.5%, and E grade for corrosion rate greater than 58.5%. This study indicates the necessity of a quantitative evaluation of rebar corrosion for evaluating the structural safety of aging bridges.

• Journal of Power Electronics
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• v.12 no.1
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• pp.113-119
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• 2012

This paper describes the design and control of a phase shift full bridge converter with a current doubler, which can be used for the on-board charger for the lead-acid battery of electric forklifts. Unlike the common resistance load, the battery has a large capacitance element and it absorbs the entire converter output ripple current, thereby shortening the battery life and degrading the system efficiency. In this paper a phase shift full bridge converter with a current doubler has been adopted to decrease the output ripple current and the transformer rating of the charger. The charge controller is designed by using the small signal model of the converter, taking into consideration the internal impedance of the battery. The stability and performance of the battery charger is then verified by constant current (CC) and constant voltage (CV) charge experiments using a lead-acid battery bank for an electric forklift.