• Proceedings of the Korean Geotechical Society Conference
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• 2005.03a
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• pp.862-869
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• 2005

This study examined 233 cut slopes in Gyeongnam region; evaluated hazards and slope conditions involved in the slope; and determined the priority order for reinforcement. The conclusions are summarized in the following. (1) The slopes that need reinforcement or maintenance are 153, accounting for 65.6% of the entire slopes. Slopes with a length of $0{\sim}200m$ account for 70.9%; slopes with a height of $10{\sim}20m$ account for over 50%. (2) Slopes with slope of more than 1:0.5 account for 70.9% of the entire slopes. The steepness of the slope is owing to more rock slopes than soil slopes. (3) The percentages of rock slopes, soil slopes, complex slopes mixed with rocks and soil, and slopes comprised of igneous rocks are 54.4%, 24.9%, 20.7%, and 54.1%, respectively. (4) In the rock area occurred cave-in, plain failure, wedge failure, and overturning failure, in order. Slopes with volcanic rocks are the most unstable, while sedimentary rocks and metamorphic rocks are relatively stable. (5) When the slope height is over 20m, low grade slopes are more than 80%; leading to the conclusion that the higher the slope height is, the more unstable the slope is.

• Journal of Power System Engineering
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• v.10 no.2
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• pp.117-123
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• 2006

Woven fabrics composites are used as primary structural components in many applications because of their superior properties that offer high specific strength and stiffness. However, the complexity of the fabric structure makes understanding of their failure behavior very difficult. Also, laminate woven fabrics CFRP have unique failure mechanisms such as fiber bridging, fiber/matrix crack and so on. In particular, the delamination phenomenon of the composite materials is one of the most frequent failure mechanisms. So, we estimated interlaminar fracture and damage in composites using as ENF specimen by a 3 point bending test. And AE characteristics were examined for crack propagation on plain woven CFRP. We obtained the following conclusions from the results of the evaluation of the 3 point bending fracture test and AE characteristic estimation. AE counts of maximum crack length were obtained as $85.97{\times}10^4\;and\;93{\times}10^3\;for\;a_0/L=0.3$ and 0.6, respectively. Also the maximum amplitudes were over 80dB at both $a_0/L=0.3\;and\;0.6$. $G_{IIc}$ at that's $a_0/L$ ratio were obtained with $1.07kJ/m^2\;and\;3.79kJ/m^2$.

• Journal of Power System Engineering
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• v.18 no.5
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• pp.80-87
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• 2014

The pipelines are apt to erosion or corrosion because of the high-speed flow of water and steam with high temperatures or high pressures. This study was carried out a finite element analysis (FEA) and an experimental for the fracture behavior of T-joint pipes with local wall thinning under internal pressure. Local wall thinning was machined on the pipes in order to simulate erosion and corrosion of the metal. The configurations of the eroded area included an eroded ratio of d/t=0.80~0.963 and an eroded length of l=25 mm, 50 mm, and 102 mm. Three-dimensional elastic-plastic analyses were also carried out using FEA, which accurately simulates failure behaviors. In regards to the relationship between pressure and eroded, the criterion that indicates what can be used safely under operating pressure and design pressure were obtained from FEA. The FEA results were in relatively good agreement with that of the experiment.

• Earthquakes and Structures
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• v.18 no.1
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• pp.83-96
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• 2020

The main structural elements of historical masonry arch bridges are arches, spandrel walls, piers and foundations. The most vulnerable structural elements of masonry arch bridges under transverse seismic loads, particularly in the case of out-of-plane actions, are spandrel wall. The vulnerability of spandrel walls under transverse loads increases with the increasing of their length and height. This paper computationally investigates the out-of-plane nonlinear seismic response of spandrel walls of long-span and high masonry stone arch bridges. The Malabadi Bridge with a main arch span of 40.86m and rise of 23.45m built in 1147 in Diyarbakır, Turkey, is selected as an example. The Concrete Damage Plasticity (CDP) material model adjusted to masonry structures, and cohesive interface interaction between the infill and the spandrel walls and the arch are considered in the 3D finite element model of the selected bridge. Firstly, mode shapes with and without cohesive interfaces are evaluated, and then out-of-plane seismic failure responses of the spandrel walls with and without the cohesive interfaces are determined and compared with respect to the displacements, strains and stresses.

• Proceedings of the KSME Conference
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• 2008.11a
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• pp.13-19
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• 2008

A Wire-woven Bulk Kagome (WBK) is the new truss type cellular metal fabricated by assembling the helical wires in six directions. The WBK seems to be promising with respect to morphology, fabrication cost, and raw materials. In this paper, first, the geometric and material properties are defined as the main design parameters of the WBK considering the fact that the failure of WBK is caused by buckling of truss elements. Taguchi approach was used as statistical design of experiment(DOE) technique for optimizing the design parameters in terms of maximizing the compressive strength. Normalized specific strength is constant regardless of slenderness ratio even if material properties changed, while it increases gradually as the strainhardening coefficient decreases. Compressive strength of WBK dominantly depends on the slenderness ratio rather than one of the wire diameter, the strut length. Specifically the failure of WBK under compression by elastic buckling of struts mainly depended on the slenderness ratio and elastic modulus. However the failure of WBK by plastic failed marginally depended on the slenderness ratio, yield stress, hardening and filler metal area.

• Steel and Composite Structures
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• v.18 no.3
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• pp.739-756
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• 2015

This paper presents investigations on the hysteretic behavior of concrete-filled circular tubular (CFCT) T-joints subjected to axial cyclic loading at brace end. In the experimental study, four specimens are fabricated and tested. The chord members of the tested specimens are filled with concrete along their full length and the braces are hollow section. Failure modes and load-displacement hysteretic curves of all the specimens obtained from experimental tests are given and discussed. Some indicators, in terms of stiffness deterioration, strength deterioration, ductility and energy dissipation, are analyzed to assess the seismic performance of CFCT joints. Test results indicate that the failures are primarily caused by crack cutting through the chord wall, convex deformation on the chord surface near brace/chord intersection and crushing of the core concrete. Hysteretic curves of all the specimens are plump, and no obvious pinching phenomenon is found. The energy dissipation result shows that the inelastic deformation is the main energy dissipation mechanism. It is also found from experimental results that the CFCT joints show clear and steady stiffness deterioration with the increase of displacement after yielding. However, all the specimens do not perform significant strength deterioration before failure. The effect of joint geometric parameters ${\beta}$ and ${\gamma}$ of the four specimens on hysteretic performance is also discussed.

• Nuclear Engineering and Technology
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• v.26 no.3
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• pp.411-419
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• 1994

The containment failure probability due to hydrogen burning during severe accidents proceeding in a low pressure sequence is calculated using Monte Carlo method. The probability distribution functions for this Monte Carlo calculation is obtained from the statistical method. The calculations are performed for Kori unit 2, and the sensitivity studies on the input variables-the amount of hydrogen generated at SFD, cerium diameter, cerium length, oxidation rate at FCI, and the amount of hydrogen generated during MCCI-are also performed. It is revealed that SFD is the main factor in hydrogen generation, but the other sources also cannot be neglected. The containment failure probability due to the hydrogen burning lies within 6% in case of Kori unit 2.

• Geomechanics and Engineering
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• v.33 no.2
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• pp.167-174
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• 2023

This study evaluated slope stability through a case study to determine the disaster risks associated with increased deforestation in structures, including schools and apartments, located in urban areas adjacent to slopes. The slope behind the ○○ High School in Gwangju, Korea, collapsed owing to heavy rain in August 2018. Historically, rainwater drained well around the slope during the rainy season. However, during the collapse, a large amount of seepage water flowed out of the slope surface and a shallow failure occurred along the saturated soil layer. To analyze the cause of the collapse, the images of the upper area of the slope, which could not be directly identified, were captured using unmanned aerial vehicles (UAVs). A digital elevation model of the slope was constructed through image analysis, making it possible to calculate the rainfall flow direction and the area, width, and length of logging areas. The change in the instability of the slope over time owing to rainfall lasting ten days before the collapse was analyzed through numerical analysis. Imaging techniques based on the UAV images were found to be effective in analyzing ground disaster risk maps in urban areas. Furthermore, the analysis was found to predict the failure before its actual occurrence.

• Computers and Concrete
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• v.33 no.6
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• pp.659-670
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• 2024

The mechanical behaviour of layered concrete samples containing an internal crack was numerically studied by modelling the geo-mechanical specimens in the particle flow code in two dimensions (PFC2D). The numerical modelling software was calibrated with the experimental results of the Brazilian tensile strengths gained from the laboratory disc-type specimens. Then, the samples with the bedding layers and internal notch were numerically simulated with PFC2D under uniaxial compressive loading. In each specimen, the layers' thickness was 10 mm but the layer's inclination angle was changed to 0°, 30°, 60°, 90°, 120° and 150°. Of course, the layers'interfaces are considered to have very low strengths. The internal notch was kept at 3 cm in length however, its inclination angle was changed to 0°, 40°, 60° and 90°. Therefore, a total, of 24 numerical models were made to study the failure mechanism of the layered concrete samples. Considering these results, it has been concluded that the inclination angles of both internal crack and bedding layers affect the failure mechanism and uniaxial compressive strength of the concrete.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10a
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• pp.418-423
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• 1998

This paper is intended to investigate the behavior of flexural-shear cracking in reinforced concrete beams without web reinforcement with FEM incorporated into a linear elastic fracture mechanics approach(LEFM). Each crack was propagated progressively by a finite length, then the quantitative reponses were examined. The results show that the horizontal crack was initiated by the bond-jnduced shear stress due to horizontal shearing action of the T-C force couple after the formation of the critical flexural crack. Also, the horizontal crack is considered to be a major factor of shear failure in slender reinforced concrete beams without web reinforcement.