• Steel and Composite Structures
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• v.29 no.2
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• pp.257-272
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• 2018

The research of shear connectors composed from mechanical couplers with rebar anchors, embedded in concrete, and steel bolts, as a mean of shear transfer in composite connections is presented in the paper. Specific issues related to this type of connections are local concrete pressure in the connector vicinity as well as the shear flow along the connector axis. The experimental research included 18 specimens, arranged in 5 series. Nonlinear numerical analyses using Abaqus software was conducted on corresponding FE models. Different failure modes were analysed, with emphasis on concrete edge failure and bolt shear failure. The influence of key parameters on the behaviour of shear connector was examined: (1) concrete compression strength, (2) bolt tensile strength and diameter and (3) concrete edge distance. It is concluded that bolted shear connectors with mechanical couplers have sufficient capacity to be used as shear connectors in composite structures and that their behaviour is similar to the behaviour of post installed anchors as well as other types of connectors anchored without the head.

• Computational Structural Engineering
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• v.7 no.1
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• pp.83-90
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• 1994

This study presents the nonlinear dynamic analysis method of the bridge with the seismic isolation bearing. Also the numerical analyses are performed for investigating the response characteristics of the bridge isolated with the lead-rubber bearing under the ground motions compatible to Korea bridge design response spectra. It is found that the pier design force can be considerably smaller than the one for the bridge with the fixed bearing. It is observed that the lead-rubber bearing has the great effectiveness for reducing the longitudinal seismic force in case of the bridges with low and medium periods. Therefore the seismic isolation bearing can be used instead of the fixed bearing for the economic and safe design of the bridge.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.18 no.4 s.70
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• pp.385-393
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• 2005

This paper established the dynamic model of a flexible Timoshenko beam capable of geometrical nonlinearities subject to large overall motions by using the finite element method. Equations of motion are derived by using Hamilton principle and are formulated in terms of finite elements in which the nonlinear constraint equations are adjoined to the system using Lagrange multipliers. The Newmark direct integration method and the Newton-Raphson iteration are employed here for the numerical study which is to demonstrate the efficiency of the proposed formulation.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.1
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• pp.54-62
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• 2008

A new solution method was developed to solve the free surface flow around a hull and named as 'Variable Free Surface Panel Method'. In the method the non-linearity of the free surface boundary conditions was fully taken into account and the raised panel method was employed to effectively solve the problem. The transom stern flow was also considered and the panel on the hull was generated using the panel cutting method. Numerical calculations were performed for KCS(KRISO Container Ship) hull form and compared with the experimental data to confirm the validity of the method. The comparison with the conventional free surface panel method was also accomplished. It is confirmed that new method gives more reliable results than the conventional method.

• Journal of the Society of Naval Architects of Korea
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• v.45 no.5
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• pp.538-546
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• 2008

In this paper, the constitutive equation is developed to analyze the characteristics of strain-induced plasticity in the range of low temperature of 316 stainless steel. The practical usefulness of the developed equations is evaluated by the comparison between experimental and numerical results. For 316 stainless steel, constitutive equations, which represent the characteristics of nonlinear material behavior under the cryogenic temperature environment, are developed using the Bodner's plasticity model. In order to predict the material behaviour such as damage accumulation, Bodner-Chan's damage model is implemented to the developed constitutive equations. Based on the developed constitutive equations, 3-D finite element analysis program is developed, and verified using experimental results.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.26 no.1
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• pp.55-62
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• 2016

Nuclear fuels are always exposed to hot temperature and high speed coolant flow during the reactor operation. Thus the fuel rod accompanies small amplitude vibration due to the turbulent flow. The random vibration causes friction between the fuel rod and the grid structure which provides the lateral supports. The friction is critical to the fuel rod fretting wear, and it degrades fuel performance when a severe wear is developed. LuGre friction model is introduced in the paper, and the performance was evaluated comparing to the classical Coulomb model. It is shown that the developed friction force considering the Coulomb friction is not enough to stop or delay the motion while the stick-slip can be simulated using LuGre friction model. Numerical solutions of the two dimensional spacer grid cell model with the modern friction are also reviewed, and it is discussed that the new friction model simulates well the nonlinear mechanism.

• The Korean Journal of Applied Statistics
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• v.27 no.6
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• pp.1029-1038
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• 2014

Bayesian experimental design is a useful concept in applied statistics for the design of efficient experiments especially if prior knowledge in the experiment is available. However, a theoretical or numerical approach is not simple to implement. We review the concept of a Bayesian experiment approach for linear and nonlinear statistical models. We investigate relationships between prior knowledge and optimal design to identify Bayesian experimental design process characteristics. A balanced design is important if we do not have prior knowledge; however, prior knowledge is important in design and expert opinions should reflect an efficient analysis. Care should be taken if we set a small sample size with a vague improper prior since both Bayesian design and non-Bayesian design provide incorrect solutions.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.377-381
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• 2006

Recently, as economy grow and population increase we need to develop our coastal area and make good use of it for various purposes. That's why large structures are being installed on the sea. Some samples are petroleum storage tanks, pier of sea bridges. These are large structures which have been installed at coastal area. When we design such vertical cylinder, we should avoid too much construction expense caused by excessive designing or by lack of sufficient design. In order to prevent excessive expenditure, it is important to correctly calculate the force of waves acting on structures and predict the wave transformation. In this study, apply to VOF method based on Navier-Stokes equation and then discussed that nonlinear wave force and wave transformation. A comparison between the numerical model and existing experimental results showed nice agreement among them.

• Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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• 2006.11a
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• pp.351-354
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• 2006

In underwater environment, the control of AUV is difficult, because of the existence of parameter uncertainties and disturbances as well as highly nonlinear and coupled system dynamics. The requirement for the simple and robust controller which works satisfactorily in those dynamical uncertainties, call for a design using the PD or sliding mode controller. The PD controller is very popular controller in the industrial field and the sliding mode controller has been used successfully for the AUV controller design. In this paper, the two controllers arc designed for ISiMI(Integrated Submergible Intelligent Mission Implementation) AUV and the performances are compared by numerical simulation under the modeling uncertainty and disturbances. The design process of PD and sliding mode controller for ISiMI AUV and simulation results are included to compare the performances of the two controllers.

• Structural Engineering and Mechanics
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• v.47 no.6
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• pp.741-756
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• 2013

Distributed-Steel Bar Reinforced Concrete (DSBRC) columns, a new and innovative construction technique for composite steel and concrete material which can alleviate the difficulty in the arrangement of the stirrup in the column, were studied experimentally and analytically in this paper. In addition, an ordinary steel Reinforced Concrete (SRC) column was also tested for comparison purpose. The specimens were subjected to quasi-static load reversals to model the earthquake effect. The experimental results including the hysteresis curve, resistance recession, skeleton curves and ductility ratio of columns were obtained, which showed well resistant-seismic behavior for DSBRC column. Meanwhile a numerical three-dimensional nonlinear finite-element (FE) analysis on its mechanical behavior was also carried out. The numerically analyzed results were then compared to the experimental results for validation. The parametric studies and investigation about the effects of several critical factors on the seismic behavior of the DSBRC column were also conducted, which include axial compression ratios, steel ratio, concrete strength and yield strength of steel bar.