• Journal of the Society of Naval Architects of Korea
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• v.30 no.3
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• pp.100-115
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• 1993

In this paper, the extent of use of three kinds of the existing idealized structural units, namely the idealized beam-column unit, the idealized unstiffened plate unit and the idealized stiffened plate unit, is expanded to deal with the excessive tension-deformation effects, in which a simplified mechanical model for the stress-strain relation of steel members under tensile load is suggested. The 1/3-scale hull model for a leander class frigate under sagging moment tested by Dow is analyzed, and it is shown that the excessive tension-de-formation is a significant factor affecting the progressive collapse behavior, particularly in the post-collapse range.

• Nuclear Engineering and Technology
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• v.51 no.3
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• pp.884-893
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• 2019

Spent fuel racks are steel structures used in the storage of the spent fuel removed from the nuclear power reactor. Rack units are submerged in the depths of the spent fuel pool to keep the fuel cool. Their free-standing design isolates their bases from the pool floor reducing structural stresses in case of seismic event. However, these singular features complicate their seismic analysis which involves a transient dynamic response with geometrical nonlinearities and fluid-structure interactions. An accurate estimation of the response is essential to achieve a safe pool layout and a reliable structural design. An analysis methodology based on the hydrodynamic mass concept and implicit integration algorithms was developed ad-hoc, but some dispersion of results still remains. In order to validate the analysis methodology, vibration tests are carried out on a reduced scale mock-up of a 2-rack system. The two rack mockups are submerged in free-standing conditions inside a rigid pool tank loaded with fake fuel assemblies and subjected to accelerations on a unidirectional shaking table. This article compares the experimental data with the numerical outputs of a finite element model built in ANSYS Mechanical. The in-phase motion of both units is highlighted and the water coupling effect is detailed. Results show a good agreement validating the methodology.

• Structural Engineering and Mechanics
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• v.90 no.3
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• pp.287-299
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• 2024

Composite skew plates are aesthetically appealing light weight structural units finding wide applications in floors and roofs of commercial buildings. Although bending and vibration characteristics of these units have received attention from researchers but the domain of first and progressive failure has not been explored. Confident use of these plates necessitates comprehensive understanding of their failure behavior. With this objective, the present paper uses an eight noded isoparametric finite element together with von-Kármán's approach of nonlinear strains to study first ply and progressive failure up to ultimate damage of skew plates being subjected to uniform surface pressure. Parameters like skew angles, laminations and boundary conditions are varied and the results are practically analyzed. The novelty of the paper lies in the fact that the stiffness matrix of the damaged plate is calculated by considering material degradation locally only at failed points at each stage of first and progressive failure and as a result, the present outputs are so close to experimental findings. Interpretation of results from practical angles and proposing the relative performances of the different plate combinations in terms of ranks will be of much help to practicing engineers in selecting the best suited plate option among many combinations.

• Proceedings of the Computational Structural Engineering Institute Conference
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• 2002.10a
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• pp.346-353
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• 2002

The risk of bearing failure is evaluated through the seismic response analysis of a bridge considering the probabilistic characteristics of structural properties such as the mass of superstructure, the stiffness of pier, and the translational and rotational stiffness of the foundation as well as seismic loadings during the bridge service lift. The effect of pounding between adjacent vibration units on the risk of bearing failure is also investigated. The probabilistic characteristics of structural properties are obtained by the Monte Carlo simulations based on the probabilistic characteristics of basic random variables included in the structural properties. From the simulation results, the failure probability of fixed bearings attached on the abutment is found to be much higher than those placed on the piers. It is also found that the pounding effect significantly increases the failure probability of bearings. In the simply supported bridges, the risk of bearing failure increases as the number of bridge spans increase. Therefore, the failure probability of fixed bearing due to the effects of pounding phenomena and the number of bridge spans should be considered in the seismic desist of bearings.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.526-529
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• 2004

Arches are one of the most important basic structural units as well as the beams, columns and plates. Most complicated structures consist of only these basic units and therefore it is very attractive research subject to analysis both the static and dynamic behavior of such units including the arches. This study deals with the free vibration of arbitrary shaped arches. In order to obtain the exactly arch shape, which surveyed (x, y) of neutral axis of arbitrary shaped arches are compared to various shape of arch: circular, parabolic, sinusoidal, elliptic, spiral and cartenary. The differential equations governing free vibrations of arches are merely adopted in the open literature rather than deriving the equations in this study. The Taylor series method is used as the numerical differential scheme. The Runge-Kutta method and the Regula-Falsi method, respectively, are used to integrate the governing differential equations and to compute the natural frequencies It is expected that results obtained herein can be practically utilized in the fields of vibration control.

• Structural Engineering and Mechanics
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• v.10 no.6
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• pp.621-633
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• 2000

Dynamic responses of a bridge system with several simple spans under longitudinal seismic excitations are examined. The bridge system is modeled as the multiple oscillators and each oscillator consists of four degrees-of-freedom system to implement the poundings between the adjacent oscillators and the friction at movable supports. Pounding effects are considered by introducing the impact elements and a bi-linear model is adopted for the friction force. From the parametric studies, the pounding is found to induce complicated seismic responses and to restrain significantly the relative displacements between the adjacent units. The smaller gap size also restricts more strictly the relative displacement. It is found that the relative displacements between the abutment and adjacent pier unit became much larger than the responses between the inner pier units. Consequently, the unseating failure could take a place between the abutment and nearby pier units. It is also found that the relative displacements of an abutment unit to the adjacent pier unit are governed by the pounding at the opposite side abutment.

• Nuclear Engineering and Technology
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• v.53 no.3
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• pp.967-973
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• 2021

In 2011, an earthquake and subsequent tsunami hit the Fukushima Daiichi Nuclear Power Plant, causing simultaneous accidents in several reactors. This accident shows us that if there are several reactors on site, the seismic risk to multiple units is important to consider, in addition to that to single units in isolation. When a seismic event occurs, a seismic-failure correlation exists between the nuclear power plant's structures, systems, and components (SSCs) due to their seismic-response and seismic-capacity correlations. Therefore, it is necessary to evaluate the multi-unit seismic risk by considering the SSCs' seismic-failure-correlation effect. In this study, a methodology is proposed to obtain the seismic-response-correlation coefficient between SSCs to calculate the risk to multi-unit facilities. This coefficient is calculated from a probabilistic multi-unit seismic-response analysis. The seismic-response and seismic-failure-correlation coefficients of the emergency diesel generators installed within the units are successfully derived via the proposed method. In addition, the distribution of the seismic-response-correlation coefficient was observed as a function of the distance between SSCs of various dynamic characteristics. It is demonstrated that the proposed methodology can reasonably derive the seismic-response-correlation coefficient between SSCs, which is the input data for multi-unit seismic probabilistic safety assessment.

• Structural Engineering and Mechanics
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• v.22 no.4
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• pp.449-467
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• 2006

Most existing concrete structures in Taiwan are considered nonductile due to insufficient transverse reinforcement and poor detailing of frame elements. Such features are fairly typical for buildings constructed prior to 1997, at which time the local building code was revised based on ACI 318-95. Among these structures, many contain perimeter or partition walls made of concrete or clay brick for architectural purposes. These walls, though treated as non-structural components in common design practice, could affect the structural behavior of the buildings during an earthquake. To study the behavior of such structures under seismic load, experiments were conducted on concrete frames of various configurations to show the force-deformation relationships, damage patterns, and other characteristics of the frames. For further interest, similar units with columns jacketed by carbon-fiber-reinforced-polymer (CFRP) were also tested to illustrate the effectiveness of this technique in the retrofit of concrete frames.

• Journal of Korean Clinical Nursing Research
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• v.25 no.3
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• pp.314-322
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• 2019

Purpose: The purpose of this study were to identify the influential factors of bullying of intensive care nurses and to suggest a final structural model based on identified relationships between nursing organizational culture, authentic leadership, self-esteem, and bullying in the workplace. Methods: Data were collected from 221 nurses at intensive care units in eight general hospitals using structured questionnaires and analyzed by structural equation modeling. Results: In this study, the average of bullying in the workplace was 1.34±0.40, nursing organizational culture was 3.31±0.47, self-esteem was 2.79±0.44, and authentic leadership was 3.61±0.60. The factors affecting nursing organizational culture were authentic leadership (β=.54, p<.001) and self-esteem (β=.24, p=.002) that had direct positive effects on the nursing organizational culture. The nursing organizational culture had also a direct effect on reducing workplace bullying (β=-.45, p<.001). Authentic leadership (β=-.24, p=.004) and self-esteem (β=-.11, p=.004) had indirect effects on workplace bullying, which was mediated by the nursing organizational culture. Conclusion: To understand and reduce workplace bullying, evaluating a nursing organizational culture should be preceded. Based on the finding of this study, an intervention for increasing authentic leadership and self-esteem of nurses can positively help to create the nursing organizational culture and then reduce workplace bullying.

• Polymer(Korea)
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• v.33 no.2
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• pp.183-188
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• 2009

Structural rearrangements of uni-axially deformed polyethylenes containing 1-octene comonomer and HDPE upon heating were investigated by time-resolved small and wide angle X-ray scattering techniques. During heating, structural changes including crystal transformation and lamellar rearrangement noted were very different depending on the comonomer contents. At low comonomer content below 2 wt%, inverse martensitic transformation of crystal lattice from monoclinic to orthorhombic cell and the rearrangement of broken lamellar units into more ordered and perfect lamellar stacks were noted with the temperature increase. At high contents above 9.5 wt%, however, polyethylene copolymers showed neither the crystal transformation nor lamellar rearrangement that can be attributed to low crystallinity and high content of branch units.