• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.31-45
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• 2012

This study was conducted to estimate the stability of a quay wall in case of wave overtopping under the combined action of an earthquake and tsunami using limit equilibrium method. The tsunami force was calculated by using a numerical program called TWOPM-3D (3-D one-field Model for immiscible TWO-Phase flows). Especially, the wave force acting behind the quay wall after a tsunami wave overtopping was estimated by treating back fill as a permeable material. The stability of the quay wall was assessed for both the sliding and overturning modes under passive and active conditions. The variation in the stability of the quay wall with time was determined by parametric studies, including those for the tsunami wave height, seismic acceleration coefficient, internal friction angle of the soil, wall friction angle, and pore water pressure ratio. When the earthquake and tsunami were considered simultaneously, the tsunami induced wave overtopping increased the stability of the quay wall under the passive condition, but in the active condition, the safety factors decreased.

• Journal of the Korean GEO-environmental Society
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• v.9 no.2
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• pp.47-59
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• 2008

Application of mechanically stabilized earth wall (MSEW) abutment has been rapidly increasing in United States of America, Pennsylvania since 2002. MSEW is effective for reducing construction cost and period compared to general concrete reinforced wall. In the paper, theoretical background and conventional criterion of MSEW abutment that is widely used abroad are analyzed. Based on the results, application of suitable MSEW abutment to domestic bridge type is examined. For the application of MSEW abutment in Korea, load interacting with upper shoe in domestic bridge types and structural analyses of beam seat and pile are investigated. As a result, all applications are possible except for PSC BOX Bridge that has heavy self-weight of girder. Through two and three dimensional numerical analyses, horizontal behaviour mechanisms between pile and MSEW were analyzed and field tests are also carried out for seven piles behind earth walls. From results of field tests, it is confirmed that an angle of internal friction of backfill material needs to be greater than 34 degree to use H-Pile as foundation of MSEW.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.9
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• pp.15-24
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• 1998

In this research. we have proposed a new technique to determine .the combination of design parameters for the process design of a hot forged product using artificial neural network(ANN) and statistical design of experiments(DOE). The investigated problem involves the adequate selection of the aspect ratio of billet, the ram velocity and the friction factor as design parameters. An optimal billet satisfying the forming limitation, die filling, load and energy as well as more uniform distribution of effective strain, is determined by applying the ability of artificial neural network and considering the analysis of mean and variation on the functional requirement. This methodology will be helpful in designing and controlling parameters on the shop floor which would yield the best design solution.

• Transactions of Materials Processing
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• v.33 no.2
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• pp.123-131
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• 2024

Plastic, the main material of FFF-type 3D printing, exhibits lower strength compared to metal. research aimed at increasing strength is needed for use in various industrial fields. This study analyzed three X-shape infill patterns(grid, lines, zigzag) with similar internal lattice structure. Moreover, tensile test considering weight and printing time was conducted based on the infill line multiplier and infill overlap percentage. The three X-shape infill patterns(grid, lines, zigzag) showed differences in nozzle paths, material usage and printing time. When infill line multiplier increased, there was a proportional increase in tensile strength/weight and tensile strength/printing time. In terms of infill overlap percentage, the grid pattern at 50% and the zigzag and lines patterns at 75% demonstrated the most efficient performance.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.3
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• pp.452-459
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• 2017

In recent years, to reduce self-weight of structural elements, the use of SCP (Steel Concrete Plate) instead of prestressed concrete is increasing. Because SCP has a complicated sectional shape and includes a large number of studs, the use of high-fluidity concrete is required. Therefore, in this study, to prevent the restrained shrinkage behavior by the stud, the effects of using an expansive agent (EA) and shrinkage reducing agent (SRA) were investigated, and the optimal mixture proportions to maximize the filling capacity were determined based on the fine aggregate ratio. The test results indicated that the combined use of EA and SRA exhibited the smallest shrinkage. The ratio of the crushed sand and washed sea sand was determined to be 5:5, and the proper fine aggregate ratio was found to be 55.6%, because when the ratio was too high, a decrease in strength and an increase in shrinkage strain were expected. The high-fluidity concrete effectively filled the large-sized SCP module.

• Journal of the Korea Concrete Institute
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• v.29 no.3
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• pp.249-257
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• 2017

The purpose of this study was to contribute to the field application cost effectively and reasonably by developing the functional piles that make up for the defects of PHC piles. CFP (Concrete Filled Pretensioned Spun High Strength Concrete Pile with Ring type Composite shear connectors) piles developed in this study increases the compressive stress through enlarged cross section by rearranging composite shear connectors and filling the hollow part of PHC pile with concrete. And it improved shear and bending performance placing the rebar (H13-8ea) within the PHC pile and the hollow part of PHC pile of rebar (H19-8ea). In addition, the composite shear connectors were placed for the composite behavior between PHC pile and filled concrete. Placing Rebars (H13-8ea) of PHC pile into composite shear connector holes are sleeve-type mechanical coupling method that filling the concrete to the gap of the two members. Nonlinear finite element analyzes were performed to verify the performance of shear and bending moments and it deduced the spacing of the composite shear connectors. Through a various interpretation of CFP piles, it's proved that the CFP pile can increase the shear and bending stiffness of the PHC pile effectively. Therefore, this can be utilized usefully on the construction sites.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.10 no.3
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• pp.87-98
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• 1990

The present Study dealt with the earthquake-resistant design of cantilever retaining walls supporting cohesionless soils. With design examples of three different types of cantilever retaining walls, the factors of safety against sliding were computed at various values of horizontal acceleration coefficient and compared with each other. The horizontal inertia effect due to the weights of concrete wall itself and a portion of backfill was taken into account in the analyses, and also Mononobe-Okabe pseudo-static solution method was modified to deal with various states different from limiting equilibrium state. From the analyses of safety against sliding, it was found that a cantilever retaining wall with sloped base was the most efficient type in earthquake resistant design. It was also found that by sloping the base, the width of the base slab could be reduced, resulting in the least volume of concrete, excavation and backfill as compared to the other types of walls. In the case of a cantilever retaining wall with sloped feel, the efficiency similar to that of a wall with sloped base could be expected under static loading as well as at relatively low level of earthquake loading. However, this efficiency became vanished with the increase of horizontal acceleration coefficient, since the rate of reduction in developed earth pressures on the heel became smaller. In addition, the design charts with different soil friction angles as well as with different earthquake resistant design criteria of safety factor against sliding were presented for the design of cantilever retaining walls sith sloped base.

• Journal of Internet of Things and Convergence
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• v.6 no.4
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• pp.21-26
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• 2020

An autonomous driving system is based on the deep learning system built by big data which are obtained by various IoT sensors. The miniaturization and high performance of the IoT sensors are needed for diverse devices including the autonomous driving system. Specially, the miniaturization of the sensors leads to compel the miniaturization of the fixer structures. In the viewpoint of the miniaturization, metallic structure is a best solution to attach the small IoT sensors to the main body. However, it is hard to manufacture the small metallic structure with a conventional machining process or manufacturing cost greatly increases. As one of solutions for the problems, in this work, metallic FDM (Fused depositon modeling) based on metallic filament was proposed and the FDM process was investigated to fabricate the small metallic structure. Final part was obtained by the post-process that consists of debinding and sintering. In this work, the relationship between infill rate and the density of the part after the post-process was investigated. The investigation of the relationship is based on the fact that the infill rate and the density obtained from the post-processing is not same. It can be said that this work is a fundamental research to obtain the higher density of the printed part.

• Journal of the Korea Institute of Building Construction
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• v.23 no.4
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• pp.465-476
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• 2023

This study introduces the development of a precast concrete double-wall, applicable to basement construction in apartment buildings. Unlike traditional precast concrete double walls, the developed double-wall doesn't require specialized manufacturing equipment such as a lathe. The constructability of these advanced technologies was validated through a full-scale mock-up test using the precast concrete double wall. The test specimens were constructed to represent a structural wall with a thickness of 250mm. It was observed that the quality of the in-situ concrete, filled between two single panels of 110mm thickness each, was excellent. The construction efficiency of the developed double-wall system for basement construction in an apartment building was also examined. Expert interviews about installation times of precast concrete elements were conducted to evaluate the speed of the basement floor's installation. The results showed that installation of precast concrete elements, including the proposed double walls, could be completed within 20 to 29 days for a basement in an apartment building. This indicates a three-fold increase in construction efficiency compared to traditional methods relying on in-situ casting.

• Geophysics and Geophysical Exploration
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• v.23 no.4
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• pp.253-260
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• 2020

The five-story stone pagoda in Tamni-ri located in Uiseong County in Gyeongsangbuk-do had an unstable upper structure, and the structural deformation of the foundation stone and the stylobate was severe. In order to repair the base of the pagoda, it must be confirmed if there are support stones inside the base. Resistivity survey was performed to study the inner base stone structure during the repair work. The stylobate was exposed soil and broken stones after removing the walls and the cover of the stylobate. Modified pole-dipole array II was used for the resistivity survey, and compared with the typical pole-dipole array method. And in this study, a physical scale-down model experiment was performed to compare and analyze distortions caused by severe topographical undulations such as right-angled lines. The results show that the stylobate of Five-story Stone Pagoda in Tamni-ri Uiseong has base stones inside the reinforced filling soil and are located beneath the pillar of the body and supporting the pagoda.