• Proceedings of the Korean Geotechical Society Conference
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• 2010.09c
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• pp.72-77
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• 2010

The Incheon Bridge, which was opened to the traffic in October 2009, is an 18.4 km long sea-crossing bridge connecting the Incheon International Airport with the expressway networks around the Seoul metropolitan area by way of Songdo District of Incheon City. This bridge is an integration of several special featured bridges and the major part of the bridge consists of cable-stayed spans. This marine cable-stayed bridge has a main span of 800 m wide to cross the vessel navigation channel in and out of the Incheon Port. In waterways where ship collision is anticipated, bridges shall be designed to resist ship impact forces, and/or, adequately protected by ship impact protection (SIP) systems. For the Incheon Bridge, large diameter circular dolphins as SIP were made at 44 locations of the both side of the main span around the piers of the cable-stayed bridge span. This world's largest dolphin-type SIP system protects the bridge against the collision with 100,000 DWT tanker navigating the channel with speed of 10 knots. Diameter of the dolphin is up to 25 m. Vessel collision risk was assessed by probability based analysis with AASHTO Method-II. The annual frequency of bridge collapse through the risk analysis for 71,370 cases of the impact scenario was less than $0.5{\times}10^{-4}$ and satisfies design requirements. The dolphin is the circular sheet pile structure filled with crushed rock and closed at the top with a robust concrete cap. The structural design was performed with numerical analyses of which constitutional model was verified by the physical model experiment using the geo-centrifugal testing equipment. 3D non-linear finite element models were used to analyze the structural response and energy-dissipating capability of dolphins which were deeply embedded in the seabed. The dolphin structure secures external stability and internal stability for ordinary loads such as wave and current pressure. Considering failure mechanism, stability assessment was performed for the strength limit state and service limit state of the dolphins. The friction angle of the crushed stone as a filling material was reduced to $38^{\circ}$ considering the possibility of contracting behavior as the impact.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.20 no.3
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• pp.269-275
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• 2019

As the national industry is developing gradually due to the expansion of the economic scale, the construction of large and super high-rise structures for building social infrastructure has been increasing, and studies have been conducted actively to transmit the large loads at the upper portion to the lower bedrock. In this study, the PHC was extended to an ultra-high strength PHC, which increased the concrete compressive strength of the PHC from the conventional 80 MPa to 110 MPa, and the PHC, which extended the tip of the pile. After construction with the driving method and injected pile method, the tendency of the bearing capacity was tested through a load test. Measurements of the bearing capacity of the extended PHC using the pile driving method revealed the main surface friction force to be smaller than that of the general PHC, and the stet-up effect was also insignificant. On the other hand, the effect of the friction force on the ground surface when the injected pile method was applied is expected to increase the bearing capacity when the gap between the main surface and the ground is wide and the cement paste is filled tightly. In addition, the ultrahigh strength PHC showed higher bearing capacity than the conventional PHC, and the permissible pile stress was less than 60%. Therefore, it is possible to reduce the number of piles and reduce the construction cost and effect of shortening the length of the pile by designing the tip of the pile on the ground with the intensity of soft rock as a method for utilizing the increased strength of the ultra-high strength PHC.

• Journal of the Korean Geotechnical Society
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• v.39 no.3
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• pp.29-40
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• 2023

In this study, we investigated the reinforcing effects of waveform micropiles in a stratigraphic setting comprising buried soil, weathered soil, and weathered rock. We conducted a series of field load tests and determined that waveform micropiles exhibited sufficient bearing capacity through frictional resistance in the soil layer and demonstrated favorable constructability in conditions with deep bedrock layers. Moreover, the vertical stiffness of waveform micropiles was approximately 2.2 times higher than that of conventional micropiles when subjected to the same design load. Pile group load tests comprising conventional and waveform micropiles showed that micropiles with higher stiffness carried a greater proportion of the load. Although there was no significant difference in the bearing capacity between conventional and waveform micropiles under the same design load, waveform micropiles with higher stiffness showed a load-carrying capacity 1.7 to 3.2 times greater than that of conventional micropiles. These findings suggest that waveform micropiles can be effectively used for foundation reinforcement and reduce the risk of foundation failure when increased loads due to modifications such as expansion remodeling are expected.

• Journal of the Korean Geotechnical Society
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• v.39 no.5
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• pp.27-40
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• 2023

A pile is a structural element that is used to transfer external loads from superstructures and has been widely utilized in construction fields all over the world. The method of installing a pile into the ground should be selected based on geotechnical conditions, location, site status, environmental factors, and construction costs, among others. It can be divided into two types: direct hammering and preboring. The direct hammering method installs a pile into the bearing layer, such as rock, using a few types of hammer, generating a considerable amount of pile driving-induced vibration. The vibration from pile driving influences adjacent structures and the ground; therefore, quantitatively investigating the effects of vibration is inevitably required. In this study, two-dimensional dynamic numerical modeling and analysis are performed using the finite difference method to investigate the influence on the adjacent slope, including temporary supporting system. Time-dependent loading induced by pile driving is estimated and used in the numerical analysis. Consequently, large surface displacement is estimated due to surface waves and less wave deflection, and refraction at the surface. The total displacement decreases with the increase of the distance from the source. However, lateral displacement at the top of the slope shows a larger value than vertical displacement, and the overall displacement tends to be concentrated near the face of the slope.

• Economic and Environmental Geology
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• v.38 no.6 s.175
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• pp.717-729
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• 2005

Peak cooling load of large buildings is generally greater than their peak heating load. Internal and solar heat gains are used fur selection of adquate equipment in large building in cold winter climate like Canada and even Korea. The cost of geothermal heat exchanger to meet the cooling loads can increase the initial cost of ground source heat pump system to the extend less costly conventional system often chosen. Thermal ice storage system has been used for many years in Korea to reduce chiller capacity and shift Peak electrical time and demand. A distribution system designed to take advantage of heat extracted from the ice, and use of geothermal loop (geothermal heat exchanger) to heat as an alternate heat source and sink is well known to provide many benifits. The use of thermal energy storage (TES) reduces the heat pump capacity and peak cooling load needed in large building by as much as 40 to $60\%$ with less mechanical equipment and less space for mechanical room. Additionally TES can reduce the size and cost of the geothermal loop by 1/3 to 1/4 compared to ground coupled heat pump system that is designed to meet the peak heating and cooling load and also can eliminate difficuties of geothermal loop installation such as space requirements and thermal conditions of soil and rock at the urban area.

• The Journal of Korean Academy of Prosthodontics
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• v.50 no.1
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• pp.1-9
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• 2012

Purpose: The purpose of this study was to investigate the effects of a mouthguard on stress distribution under mandibular impact. Materials and methods: The FEM model of head consisted of skull, maxilla, mandible, articular disc, teeth, and mouthguard. The impact locations on mandible were gnathion, the center of inferior border, and the anterior edge of gonial angle. And the impact directions were vertical, oblique ($45^{\circ}$), and horizontal. The impact load was 800 N for 0.1 sec. Results: When vertical impact was applied, the similar stress and the distribution pattern was occurred without the relation of the mouthguard use (P>.05). The model with mouthguard was dispersed the stress to the teeth, the facial bone and the skull when the oblique ($45^{\circ}$) impacts were happened. However, the stress was centralized on the teeth in the model without mouthguard(P<.05). The model with mouthguard was dispersed the stress to the teeth, the facial bone and the skull when the horizontal impacts was occurred. However, the stress was centralized on the teeth without mouthguard (P<.05). For all impact loads, stress concentrated on maxillary anterior teeth in model without mouthguard, on the contrary, the stress was low in the model with mouthguard and distributed broadly on maxillary anterior teeth, facial bone, and skull. Conclusion: The mouthguard was less effective at shock absorbing when vertical impact was added. However, it was approved that mouthguard absorbed the shock regarded to the oblique ($45^{\circ}$) and horizontal impact by dispersing the shock to the broader areas and decreasing the stress.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.357-367
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• 2018

Recent earthquakes in Gyeongju and Pohang have raised interest in liquefaction in South Korea. Liquefaction, which is a phenomenon that excessive pore pressure is generated and the shear strength of soil is decreased by repeated loads such as earthquakes, causes severe problems such as ground subsidence and overturning of structures. Therefore, it is necessary to identify and prepare for the possibility of liquefaction in advance. In general, the possibility of liquefaction is quantitatively assessed using the Liquefaction Potential Index (LPI), but it takes a lot of time and effort for performing site response analysis which is essential for the liquefaction evaluation. In this study, a simple method to evaluate the liquefaction potential without executing the site response analysis in a downtown area with a lot of borehole data was proposed. In this simple method, the correlation between the average shear wave velocity of the target location ground and the LPI divided by thickness of liquefiable layer was established. And the applicable correlation equation for various rock outcrop accelerations were derived. Using the 104 boreholes information in Seoul, the correlation equation between LPI and the shear wave velocity (ground water level: 0m, 1m, 2m, 3m) is obtained and the possibility of liquefaction occurrence in Seoul and Gyeongju is evaluated. The applicability of the proposed simple method was verified by comparing the LPI values calculated from the correlation equation and the LPI values derived using the existing site response analysis. Finally, the distribution map of LPI calculated from the correlation was drawn using Kriging, a geostatistical technique.