• Tribology and Lubricants
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• 제30권1호
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• pp.1-8
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• 2014

In this study, a three-pad gas foil journal bearing with a diameter of 40 mm and an axial length of 35 mm was modeled to predict the static and dynamic performances with regard to an increasing mechanical preload. The Reynolds equation for an isothermal and isoviscous ideal gas was coupled with a simple elastic foundation foil model to calculate the hydrodynamic pressure solution iteratively. In the prediction results, the journal eccentricity, journal attitude angle, and minimum film thickness decreased, but the friction torque increased with the preload. A quick comparison implied a lower load capacity but higher stability for a three-pad gas foil bearing compared to a one-pad gas foil journal bearing. The direct stiffness coefficients increased with the preload, but the cross-coupled stiffness coefficients decreased. The direct damping coefficient increased in the horizontal direction but decreased in the vertical direction as the preload increased. These model predictions will be useful as a benchmark against experimental test data.

• Proceedings of the Korea Concrete Institute Conference
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• 한국콘크리트학회 2008년도 추계 학술발표회 제20권2호
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• pp.85-88
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• 2008

The purpose of this study was to investigate the seismic behavior of precast concrete segmental bridge piers with shear resistance connecting structure. A model of precast concrete segmental bridge columns with shear resistance connecting structure was tested under a constant axial load and a cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. The proposed numerical method for the seismic behavior of precast concrete segmental bridge piers with shear resistance connecting structure is verified by comparison with reliable experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• 제12권4호
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• pp.45-54
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• 2008

The purpose of this study was to investigate the performance of precast segmental PSC bridge columns with regard to P-delta effects. A model of precast segmental PSC bridge columns was tested under a constant axial load and a cyclically reversed horizontal load. A computer program, RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), was used for the analysis of reinforced concrete structures. In addition to the material nonlinear properties, an algorithm for the problem of large displacement that may result in additional deformation has been formulated using total Lagrangian formulation. This study documents the testing of precast segmental PSC bridge columns under cyclic loading, and presents conclusions based on the experimental and analytical findings.

• Journal of the Earthquake Engineering Society of Korea
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• 제15권6호
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• pp.81-90
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• 2011

The purpose of this study was to investigate the seismic performance of reinforced concrete bridge columns with interlocking circular hoops. Three interlocking columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology) was used for the analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated. Based on the experimental and analytical results, design recommendations are presented to improve the existing practice in the design and construction of reinforced concrete bridge columns with interlocking circular hoops.

• Journal of the Earthquake Engineering Society of Korea
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• 제14권1호
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• pp.51-62
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• 2010

The purpose of this study was to investigate the performance of hollow precast segmental PSC bridge columns. The proposed system can reduce work at a construction site and makes construction periods shorter. Shortened construction times, in turn, lead to important safety and economic advantages when traffic disruption or rerouting is necessary. Two hollow precast segmental PSC bridge columns were tested under a constant axial load and a quasistatic, cyclically reversed horizontal load. A computer program, RCAHEST (Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures, was used. The proposed numerical method gives a realistic prediction of performance throughout the loading cycles for several test specimens investigated.

• Journal of the Korean Society for Precision Engineering
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• 제27권2호
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• pp.94-101
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• 2010

Composite materials have a higher specific strength and modulus than traditional metallic materials. Additionally, these materials offer new design flexibilities, corrosion and wear resistance, low thermal conductivity and increased fatigue life. These, however, are susceptible to impact damage due to their lack of through-thickness reinforcement and it causes large drops in the load-carrying capacity of a structure. Therefore, the impact damage behavior and subsequently load-carrying capacity of impacted composite materials deserve careful investigation. In this study, the residual strength and impact characteristics of plain-woven CFRP composites with impact damage are investigated under axial tensile test. Impact test was performed using drop weight impact tester. And residual strength behavior by impact was evaluated using the caprino model. Also we evaluated behavior of residual strength by change of mass and size of impactor. Examined change of residual strength by impact energy change through this research and consider impactor diameter in caprino model.

• Journal of the Computational Structural Engineering Institute of Korea
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• 제24권2호
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• pp.201-210
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• 2011

This paper presents a nonlinear finite element analysis procedure for the seismic performance assessment of deep beam-and-interior column joints. A computer program, named RCAHEST(Reinforced Concrete Analysis in Higher Evaluation System Technology), for the analysis of reinforced concrete structures was used. Horizontal cyclic load tests were conducted to estimate the strength, ductility, and behavioral characteristics of deep beam-and-interior column joints. Experimental parameters are axial forces and amount of transverse reinforcement. The proposed numerical method for the seismic performance assessment of deep beam-and-interior column joints is verified by comparison of its results with reliable experimental results.

• Journal of the Earthquake Engineering Society of Korea
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• 제20권1호
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• pp.33-43
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• 2016

This study investigates the performance of hollow precast segmental bridge columns with reinforcement details for material quantity reduction. The proposed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. The precast segmental bridge columns provides an alternative to current cast-in-place systems. We tested a model of hollow precast segmental bridge columns under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of reinforced concrete structures. The used numerical method gives a realistic prediction of performance throughout the loading cycles for hollow precast segmental bridge column specimens investigated. As a result, proposed reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

• Journal of the Earthquake Engineering Society of Korea
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• 제20권1호
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• pp.21-31
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• 2016

This study investigates the seismic performance of new hollow reinforced concrete (RC) bridge piers with triangular reinforcement details. The developed triangular reinforcement details are economically feasible and rational, and facilitate shorter construction periods. We tested a model of new hollow RC bridge piers with triangular reinforcement details under a constant axial load and a quasi-static, cyclically reversed horizontal load. We used a computer program, Reinforced Concrete Analysis in Higher Evaluation System Technology (RCAHEST), for analysis of RC structures. The used numerical method gives a realistic prediction of seismic performance throughout the loading cycles for several hollow pier specimens investigated. As a result, developed triangular reinforcement details for material quantity reduction was equal to existing reinforcement details in terms of required performance.

• Journal of the Korea institute for structural maintenance and inspection
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• 제3권3호
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• pp.269-277
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• 1999

The purpose of this study is to investigate the structural behavior of reinforced concrete columns rehabilitated with epoxy-bonded steel plates subjected to axial load. Eleven specimens were made to evaluate structural capacity of reinforced concrete columns rehabilitated with steel plates. This study considers the change of the internal force and the deformation of reinforced concrete column with reinforcing steel plates, and analyzes the effect of the improvement of strength and ductility. Based on the test results, this study brings the following conclusions. In case of the effect of reinforcement by the ratio of the same volume, the internal force for the test model, which the width of the reinforcing steel plate is small, is effectively higher. The smaller the width and the thickness of reinforcing steel plate, the more effective the effect of reinforcement is. For applying the theorical equation by Uzumeri, the maximum load and the coefficient of effective crossing reinforcement by the width and the thickness of steel plate reflected the properties of reinforcing steel plate.