• Proceedings of the KSR Conference
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• 2004.06a
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• pp.955-960
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• 2004

In this study, three dimensional FE analysis of concrete slab track has been performed in order to develop the realistic design of precast concrete slab track. The precast slab track system including the precast concrete slab panel and the grout layer is modeled using the three dimensional solid element with crack softening effect. The input load is computed from the one dimensional beam element model constituting the rail and several discrete springs. To investigate the effect of the longitudinal connection of slab panels, two different systems-continuous and discrete systems - are modeled. The analytical results show that the stresses of both the slab panel and the grout layer are in the range of linear elastic, and, at the interface between two adjacent panels, the primary stresses of the grout layer of the discrete system are higher than those of the continuous system. However, The overall stress levels of the grout layer are very low relative to the strength of th grout.

• Proceedings of the KSR Conference
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• 2010.06a
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• pp.650-655
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• 2010

The ground vibration which is induced by train leads defect and crack of neighborhood structure. Consequently, in order to reduce the train vibration, it is need to appropriate countermeasure. Wave-guide typed roadbed induce the train vibration to a channel wave forms using the difference of the track layer's stiffness. Therefore train vibration is restrictively attenuated along the longitudinal direction of the track. 5 kind of wave-guide typed roadbed structure is selected in this paper. A finite element, time history, linear spectrum, transfer function and damping ratio analysis are performed to evaluate the vibration reduction efficiency as the wave-guide roadbed.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.10a
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• pp.633-638
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• 1997

This study was performed to investigate the fatigue behaviour and fatigue damage process of RC structures under repeated load. Especially, the behavior of RC beams subjected to flexure-shear force has been focused. The test results show that the deflections of beam and the strains of longitudinal steels and stirrups under cyclic loads increase with constant rate, and these increases depend on diagonal crack openings and strain increases. The present study provides useful data for the analysis of damage accumulation of reinforced concrete beams under repeated loadings.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.878-883
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• 2003

To modify some problems of ACI shear provisions, ultimate shear strength equation considering size effect and arch action to compute shear strength in high-strength concrete beams without stirrups is presented in this research. Three basic equations, namely size reduction factor, rho factor, and arch action factor, are derived from crack band model of fracture mechanics, analysis of previous some shear equations for longitudinal reinforcement ratio, and concrete strut described as linear function in deep beams. Constants of basic equations are determined using statistical analysis of previous shear testing data. To verify proposed shear equation for each variable, namely d, , ρ, f/sub c/' and aid, about 250 experimental data are used and proposed shear equation is compared with ACI 318-99 code, CEB-FIP Model code, Kim & Park's equation and Zsutty's equation. While proposed shear equation is simpler than other shear equations, it is shown to be economical predictions and reasonable safety margin. Hence proposed shear strength equation is expected to be applied to practice shear design.

• Restorative Dentistry and Endodontics
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• v.20 no.1
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• pp.173-182
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• 1995

The purpose of this study was to evaluate the adaptability of light-cured glass ionomer cement to cavity walls. Class V cavities were prepared on the labial surfaces of extracted bovine incisor teeth. The cavities were restored with Fuji II as self-cured glass ionomer cement and Fuji II LC, Vitremer as light-cured glass ionomer cement. Fluorescent markers (fluoreceine and rhodamin B) were incorperated into liquid and primer for a better image of microscopic observation. Restored teeth were sectioned by longitudinal and labiolingual direction. The adaptability at the tooth-restoration interface was assessed incisally, axially and cervically by confocal scanning laser microscope. Following results were obtained : 1. Chemical-cured glass iomomer cement restoration showed close adaptation on the all of the cavity walls, but, cracks formed within the cement. 2. Light-cured glass ionomer cement restoration was well adapted to the cavity walls, but showed crack in the cement adjacent to axial dentinal wall. 3. There' was no significant difference in adaptability between two light-cured glass ionomer cement restorations.

• Proceedings of the Korea Concrete Institute Conference
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• 2005.05a
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• pp.131-134
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• 2005

Until recently tensile stresses in concrete have not been considered, since it does not affect the ultimate strength of reinforced concrete flexural members significantly. However, to verify the load-deflection relationship, the effect of tensile stresses between reinforcing bars and concrete, so-called tension stiffening effect must be taken into account. Main parameters of the tension stiffening behavior are known as concrete strength, and bond between concrete and reinforcing bars. In this study a total of twenty specimen subject to bending was tested with different concrete strength, coverage, and de-bonding length of longitudinal bars. The effects of these parameters on the flexural rigidity, crack initiation and propagation were carefully checked and analyzed.

• Journal of Ocean Engineering and Technology
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• v.18 no.1
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• pp.22-27
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• 2004

An orthotropic steel deck system is widely adapted form for a long-span bridge. It has many advantages, such as the big reduction of dead weight, the simplicity for erection, and the reduction of the construction period. However, an orthotropic steel deck system requires a lot of welding work, which may result in defects and deformation of connection. Therefore, the research for the general behavior and fatigue strength of the several details in orthotropic steel deck bridge is necessary. The fatigue failure with distortion results from secondary stress by out-of-plane deformation; these kinds of cracks are very difficult to measure, and can not be precisely calculated through finite element analysis. This stress concentration phenomenon generates the fatigue failure around the lower scallop of the transverse rib. This paper presents improved details of the intersection between the longitudinal rib and the transverse rib of an orthotropic steel deck bridge by the third dimensional hit size test, and the finite element method, which can minimize local stress through parametric study.

• Structural Engineering and Mechanics
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• v.15 no.4
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• pp.437-449
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• 2003

The aim of this study is to develop an analytical model of a beam with open cracks and external strengthening which is able to predict its modal scheme components (natural frequencies and mode shapes). The model is valid as far as the excitation level is low enough not to activate non linear effects. The application field of the model are either the prediction of the efficiency of the reinforcement or the non destructive assessment of the structural properties. The degrees of freedom associated to the fault lips must be taken into account in order to introduce the effect of the external strengthening. In a first step, an analytical formulation of a beam with thin notches is proposed according to the references. The model is then extended to incorporate the strengthening consisting in a longitudinal stiffness applied in the vicinity of the cracks. In a second step, the analytical results are compared with these obtained from a finite element simulation.

• Earthquakes and Structures
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• v.7 no.5
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• pp.861-875
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• 2014

This paper studies the response of seismic behavior of reinforced concrete exterior beam-column joints under reversal loading with different anchorages and joint core details. The joint core was detailed without much confinement (group-I) and/or with proposed X-cross bars in the core (group-II). The beam longitudinal reinforcement's anchorages were designed as per ACI 352 (headed bars), ACI 318 (conventional $90^{\circ}$ bent hooks) and IS 456 ($90^{\circ}$ bent hooks with extended tails). The nonlinear finite element analysis response of the beam-column joints was studied, along with initial and progressive cracks up to failure. The experimental and analytical results were compared and presented in this paper to make more scientific conclusions.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.41-44
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• 2004

This experimental investigation was conducted to examine the behaviour of eight one-third scale columns made of high-strength concrete (HSC). The columns were subjected to a constant axial load corresponding to 30 per cent of the column axial load capacity and a cyclic horizontal load-inducing reversed bending moment. The variables studied in this research are the volumetric ratio of transverse reinforcement, tie configuration and tie yield strength. Columns with 42 per cent higher amounts of transverse reinforcement than that required by seismic provisions of ACI 318-02 showed ductile behaviour. Relationships between the calculated damage index and the observed damage such as initial crack, spalling of concrete, buckling of longitudinal bar, and crushing of concrete are propose.