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Generalization of an Evaluation Formula for Bearing Pressures on the Rubble Mound of Gravity-Based Harbor Structures (중력식 항만구조물의 사석마운드 지반반력 평가식의 일반화)

  • Woo-Sun Park
    • Journal of Korean Society of Coastal and Ocean Engineers
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    • v.35 no.6
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    • pp.128-137
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    • 2023
  • In this study, the bearing pressure on the rubble mound of a gravity-based harbor structure with an arbitrarily shaped bottom was targeted. Assuming that the bottom of the structure is a rigid body, the rubble mound was modeled as a linear spring uniformly distributed on the bottom that resists compression only, and the bearing pressure evaluation formula was derived. It was confirmed that there were no errors in the derivation process by showing that when the bottom was square, the derived equation was converted to the equation used in the design. In addition, the validity of the derived equation was proven by examining the behavior and convergence value of the bearing pressure when an arbitrarily shaped bottom converges into a square one. In order to examine the adequacy of the method used in the current design, the end bearing pressure for the pre-designed breakwater cross-section was calculated and compared with the values in the design document. As a result, it was shown that the method used for design was not appropriate as it gave unsafe results. In particular, the difference was larger when the eccentricity of the vertical load was large, such as in the case of extreme design conditions.

Evaluation of Surface Temperature Variation and Heat Exchange Rate of Concrete Road Pavement with Buried Circulating Water Piping (열매체 순환수 배관이 매설된 콘크리트 도로 포장체의 표면 온도 변화와 방열량 평가)

  • Byonghu Sohn;Yongki Kim
    • Journal of the Korean Society for Geothermal and Hydrothermal Energy
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    • v.19 no.3
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    • pp.1-13
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    • 2023
  • Hydronic heated road pavement (HHP) systems have been well established and documented to provide road safety in winter season over the past two decades. However, most of the systems run on asphalt, only a few are tested with concrete, and there rarely is a comparison between those two common road materials in their performance. The aim of this study is to investigate the thermal performance of the concrete HHP systems, including surface temperature variations of experimental pavements in winter season. For preliminary study a small-scale experimental system was installed to evaluate the heat transfer characteristics of the concrete HHP in the test field. The system consists of 3 concrete slabs made of 1 m in width, 1 m in length, and 0.25 m in height. In these slabs, circulating water piping was embedded with different pipe depths of 0.08 m (Case A), 0.12 m (Case B), and 0.20 m (Case C) and same horizontal space of 0.16 m. Heating performance in winter season was tested with different inlet temperatures of 25℃, 30℃, 35℃ and 40℃ during the entire measurement period. Overall, the surface temperature of the concrete HHPs remained above 3℃ in all experimental conditions applied in this study. The results of the surface temperature measurement with respect to the pipe depth showed that Case B was the highest among the three cases. However, the closer the circulating water pipe was to the pavement surface, the greater the heat exchange rate. This results is considered that the heat is continuously accumulated inside the pavements and then the temperature inside the pavements increases, while the amount of heat dissipation decreases as the temperature difference between the inlet and outlet of circulating water decreases. In this preliminary test the applicability of the concrete HHP on road deicing was confirmed. Finally, the results can be used as a basis for studying the effects of various variables on road pavements through numerical analysis and for conducting large-scale empirical experiments.

Capabilities Required for Underground Facility Operations in Korean Megacities (한국 메가시티 지하시설 작전에 요구되는 능력)

  • Jun Hak Sim;Seung Jin Jo;Jun Woo Kim;Ji Woong Choi;Won Jun Choi;Sun Il Yang;Sang Hyuk Park
    • The Journal of the Convergence on Culture Technology
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    • v.10 no.2
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    • pp.267-272
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    • 2024
  • Recently, major advanced countries are fostering megacities through policy for reasons such as solving population problems, political and economic issues, and strengthening national competitiveness. The trend of change is accelerating. In Korea, following Seoul and Gyeonggi, mega city policies are being promoted in Busan, Ulsan, Gyeongnam, Daegu and Gyeongbuk, Gwangju and Jeonnam, and Daejeon, Sejong, South Chungcheong and North Chungcheong areas. Due to this urbanization phenomenon, military experts predict that the future battlefield environment will be space or a large city (mega city). From this perspective, Korea will not be able to effectively respond to the threats facing megacities if it does not prepare in advance. Therefore, underground facility operation capabilities optimized for the huge scale of the mega city and the characteristics of the underground operational environment are required. Against this background, the characteristics of the underground operational environment of mega cities and cases of preparation for underground facility operations in advanced military countries such as the United States and Israel were analyzed. Based on this, the capabilities required for underground facility operations suitable for the underground operational environment within Korean megacities are developed from an idea perspective to military organization and combat system, securing special equipment and materials to ensure combatant survival, developing small unit combat techniques, and establishing a training system. It was presented with priority given to.

Field Applicability Evaluation Experiment for Ultra-high Strength (130MPa) Concrete (초고강도(130MPa) 콘크리트의 현장적용성 평가에 관한 실험)

  • Choonhwan Cho
    • Journal of the Society of Disaster Information
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    • v.20 no.1
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    • pp.20-31
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    • 2024
  • Purpose: Research and development of high-strength concrete enables high-rise buildings and reduces the self-weight of the structure by reducing the cross-section, thereby reducing the thickness of beams and slabs to build more floors. A large effective space can be secured and the amount of reinforcement and concrete used to designate the base surface can be reduced. Method: In terms of field construction and quality, the effect of reducing the occurrence of drying shrinkage can be confirmed by studying the combination of low water bonding ratio and minimizing bleeding on the concrete surface. Result: The ease of site construction was confirmed due to the high self-charging property due to the increased fluidity by using high-performance water reducing agents, and the advantage of shortening the time to remove the formwork by expressing the early strength of concrete was confirmed. These experimental results show that the field application of ultra-high-strength concrete with a design standard strength of 100 MPa or higher can be expanded in high-rise buildings. Through this study, we experimented and evaluated whether ultra-high-strength concrete with a strength of 130 MPa or higher, considering the applicability of high-rise buildings with more than 120 floors in Korea, could be applied in the field. Conclusion: This study found the optimal mixing ratio studied by various methods of indoor basic experiments to confirm the applicability of ultra-high strength, produced 130MPa ultra-high strength concrete at a ready-mixed concrete factory similar to the real size, and tested the applicability of concrete to the fluidity and strength expression and hydration heat.

The Characteristics of the Rural Landscape of Daesan Plain Around the Japanese Colonial Era (일제강점기 전후 대산평야 농촌경관의 형성과 변화)

  • Jeong, Jae-Hyeon;Lee, Yoo-Jick
    • Journal of Korean Society of Rural Planning
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    • v.30 no.1
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    • pp.15-31
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    • 2024
  • The study primarily aims to examine the characteristics of the transition from natural landscape to modern agricultural landscape on the Daesan plain in Dong-myeon, Changwon-si, in the lower reaches of the Nakdong River. The periods covered in the transition include the late Joseon Dynasty, the early Japanese colonial period, and the late Japanese colonial period. The study concluded the following: It was found that the Daesan Plain used to function as a hydrophilic landscape before it formed into a rural landscape. This is characterized by the various water resources in the Plain, primarily by the Nakdong River, with its back marsh tributaries, the Junam Reservoir and Jucheon. To achieve its recent form, the Daesan Plain was subjected to human trial and error. Through installation of irrigation facilities such as embankments and sluices, the irregularly-shaped wetlands were transformed into large-scale farmlands while the same irrigation facilities underwent constant renovation to permanently stabilize the rural landscape. These processes of transformation were similarly a product of typical colonial expropriation. During the Japanese colonial period, Japanese capitalists initiated the construction of private farms which led to the national land development policy by the Governor-General of Korea. These landscape changes are indicative of resource capitalism depicted by the expansion of agricultural production value by the application of resource capital to undeveloped natural space for economic viability. As a result, the hierarchical structure was magnified resulting to the exacerbation of community and economic structural imbalances which presents an alternative yet related perspective to the evolution of landscapes during the Japanese colonial period. In addition, considering Daesan Plain's vulnerability to changing weather conditions, natural processes have also been a factor to its landscape transformation. Such occurrences endanger the sustainability of the area as when floods inundate cultivated lands and render them unstable, endangering residents, as well as the harvests. In conclusion, the Daesan Plain originally took the form of a hydrophilic landscape and started significantly evolving into a rural landscape since the Japanese colonial period. Human-induced land development and geophysical processes significantly impacted this transformation which also exemplifies the several ways of how undeveloped natural landscapes turn into mechanized and capitalized rural landscapes by colonial resource capitalism and development policies.

Agent Model Construction Methods for Simulatable CPS Configuration (시뮬레이션 가능한 CPS 구성을 위한 에이전트 모델 구성 방법)

  • Jinmyeong Lee;Hong-Sun Park;Chan-Woo Kim;Bong Gu Kang
    • Journal of the Korea Society for Simulation
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    • v.33 no.2
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    • pp.1-11
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    • 2024
  • A cyber-physical system is a technology that connects the physical systems of a manufacturing environment with a cyber space to enable simulation. One of the major challenges in this technology is the seamless communication between these two environments. In complex manufacturing processes, it is crucial to adapt to various protocols of manufacturing equipment and ensure the transmission and reception of a large volume of data without delays or errors. In this study, we propose a method for constructing agent models for real-time simulation-capable cyberphysical systems. To achieve this, we design data collection units as independent agent models and effectively integrate them with existing simulation tools to develop the overall system architecture. To validate the proposed structure and ensure reliability, we conducted empirical testing by integrating various equipment from a real-world smart microfactory system to assess the data collection capabilities. The experiments involved testing data delay and data gaps related to data collection cycles. As a result, the proposed approach demonstrates flexibility by enabling the application of various internal data collection methods and accommodating different data formats and communication protocols for various equipment with relatively low communication delays. Consequently, it is expected that this approach will promote innovation in the manufacturing industry, enhance production line efficiency, and contribute to cost savings in maintenance.

PRC Maritime Operational Capability and the Task for the ROK Military (중국군의 해양작전능력과 한국군의 과제)

  • Kim, Min-Seok
    • Strategy21
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    • s.33
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    • pp.65-112
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    • 2014
  • Recent trends show that the PRC has stepped aside its "army-centered approach" and placed greater emphasis on its Navy and Air Force for a wider range of operations, thereby reducing its ground force and harnessing its economic power and military technology into naval development. A quantitative growth of the PLA Navy itself is no surprise as this is not a recent phenomenon. Now is the time to pay closer attention to the level of PRC naval force's performance and the extent of its warfighting capacity in the maritime domain. It is also worth asking what China can do with its widening naval power foundation. In short, it is time to delve into several possible scenarios I which the PRC poses a real threat. With this in mind, in Section Two the paper seeks to observe the construction progress of PRC's naval power and its future prospects up to the year 2020, and categorize time frame according to its major force improvement trends. By analyzing qualitative improvements made over time, such as the scale of investment and the number of ships compared to increase in displacement (tonnage), this paper attempts to identify salient features in the construction of naval power. Chapter Three sets out performance evaluation on each type of PRC naval ships as well as capabilities of the Navy, Air Force, the Second Artillery (i.e., strategic missile forces) and satellites that could support maritime warfare. Finall, the concluding chapter estimates the PRC's maritime warfighting capability as anticipated in respective conflict scenarios, and considers its impact on the Korean Peninsula and proposes the directions ROK should steer in response. First of all, since the 1980s the PRC navy has undergone transitions as the focus of its military strategic outlook shifted from ground warfare to maritime warfare, and within 30 years of its effort to construct naval power while greatly reducing the size of its ground forces, the PRC has succeeded in building its naval power next to the U.S.'s in the world in terms of number, with acquisition of an aircraft carrier, Chinese-version of the Aegis, submarines and so on. The PRC also enjoys great potentials to qualitatively develop its forces such as indigenous aircraft carriers, next-generation strategic submarines, next-generation destroyers and so forth, which is possible because the PRC has accumulated its independent production capabilities in the process of its 30-year-long efforts. Secondly, one could argue that ROK still has its chances of coping with the PRC in naval power since, despite its continuous efforts, many estimate that the PRC naval force is roughly ten or more years behind that of superpowers such as the U.S., on areas including radar detection capability, EW capability, C4I and data-link systems, doctrines on force employment as well as tactics, and such gap cannot be easily overcome. The most probable scenarios involving the PRC in sea areas surrounding the Korean Peninsula are: first, upon the outbreak of war in the peninsula, the PRC may pursue military intervention through sea, thereby undermining efforts of the ROK-U.S. combined operations; second, ROK-PRC or PRC-Japan conflicts over maritime jurisdiction or ownership over the Senkaku/Diaoyu islands could inflict damage to ROK territorial sovereignty or economic gains. The PRC would likely attempt to resolve the conflict employing blitzkrieg tactics before U.S. forces arrive on the scene, while at the same time delaying and denying access of the incoming U.S. forces. If this proves unattainable, the PRC could take a course of action adopting "long-term attrition warfare," thus weakening its enemy's sustainability. All in all, thiss paper makes three proposals on how the ROK should respond. First, modern warfare as well as the emergent future warfare demonstrates that the center stage of battle is no longer the domestic territory, but rather further away into the sea and space. In this respect, the ROKN should take advantage of the distinct feature of battle space on the peninsula, which is surrounded by the seas, and obtain capabilities to intercept more than 50 percent of the enemy's ballistic missiles, including those of North Korea. In tandem with this capacity, employment of a large scale of UAV/F Carrier for Kill Chain operations should enhance effectiveness. This is because conditions are more favorable to defend from sea, on matters concerning accuracy rates against enemy targets, minimized threat of friendly damage, and cost effectiveness. Second, to maintain readiness for a North Korean crisis where timely deployment of US forces is not possible, the ROKN ought to obtain capabilities to hold the enemy attack at bay while deterring PRC naval intervention. It is also argued that ROKN should strengthen its power so as to protect national interests in the seas surrounding the peninsula without support from the USN, should ROK-PRC or ROK-Japan conflict arise concerning maritime jurisprudence. Third, the ROK should fortify infrastructures for independent construction of naval power and expand its R&D efforts, and for this purpose, the ROK should make the most of the advantages stemming from the ROK-U.S. alliance inducing active support from the United States. The rationale behind this argument is that while it is strategically effective to rely on alliance or jump on the bandwagon, the ultimate goal is always to acquire an independent response capability as much as possible.

A Study of Urban Park Development and Management through Public-Private Partnership (민.관 파트너십 도시공원 조성 및 관리방식 연구)

  • Kim, Yong-Gook;Han, So-Young;Zoh, Kyung-Jin
    • Journal of the Korean Institute of Landscape Architecture
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    • v.39 no.3
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    • pp.83-97
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    • 2011
  • The purpose of this study is to perform a gap analysis between public-private partnership urban parks of Korea currently in their initial stage and various foreign cases that have been established in terms of planning(formation of public-private partnership${\rightarrow}$creation of parks${\rightarrow}$operation and management of parks) and to propose improvements for each process of planning. As a result of the gap analysis on domestic and foreign public-private partnership urban parks, the future course to be followed by urban Korean parks can be summarized as follows. First, if the public-private urban parks that exist at present were led by a single or small number of partners centered on local government entities, urban parks from that point on must be created and managed based on efficient multi-sector partnerships. Since urban parks are public spaces where public benefit is more important than profit, diverse voices of public-private sectors must be reflected with a long-term perspective. Second, urban parks are not a place to be completed but a public space which continues to develop. Therefore, they must be approached with a focus on the process instead of the result. The existing concept of domestic public-private partnership is inclined to creation of urban parks. This suggests than the government had been focusing only on quantitative increase in urban parks. In order to create values as a public space for local communities, public-private partnership is also required in operation and management of urban parks. Third, public-private partnership management of urban parks can become more effective through active community participation. Participation by local communities takes long time because transition in the consciousness about values of urban parks must be presumed. Thus in Korea, non-profit organization like Seoul Green Trust should accumulate successful creation and management of small and large urban parks through public-private partnership will settle in our nation.

A Comparative Study on the Awareness of Concepts for Gardens and Parks between the Experts and General Publics (정원과 공원에 대한 전문가와 일반인 인식 비교 연구)

  • Miok, Park
    • Journal of the Korean Institute of Landscape Architecture
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    • v.46 no.5
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    • pp.1-9
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    • 2018
  • The purpose of this study was to identify differences of perceptions for gardens and parks between experts and the general public concerning several aspects including scope, scale, publicity, artistic and scientific nature, main materials, practicality and aesthetics, executive and management systems as well as legal understanding of garden and park. The properties of garden and park were derived through literature research, and the concept, similarity, and difference of gardens and the parks were recognized by the experts and the public viewpoint was clarified by questionnaire. As for the difference in the scope of the gardens and the parks, the expert group recognized it more widely than the general public. In general, the space recognized as a garden was the rooftop green space, and urban forests were recognized as a park. In addition, the general public recognized urban forests as gardens the same as they recognized parks, and the distinction was unclear. In the expert group, the perception that gardens were small and the parks were large was more prevalent. It was generally recognized that gardens were private spaces and the parks were public spaces. In the expert group, the gardens were more personal and the parks were more apparent to the public. In the general population, functional and scientific aspects rather than artistic creativity in both gardens and parks. In addition, both the general public and experts found that parks are more complex than gardens. The garden was centered on plant material, and the park was recognized as a center where the sculptural facilities were centered, or the plant material and the sculptural facilities were properly balanced. To the experts the view of the gardens was positive. Expert groups emphasized the aesthetics of the garden, and the parks were more practical, and the general population showed similar perceptions of utility and aesthetics when comparing gardens and parks. In addition, the utility of gardens in the general publics is more emphasized than the aesthetics of the park. Regarding the executive system the park was recognized as the public sector, and the difference was larger in the expert group. As for the management system, both experts and the general public perceive the management of the park or the garden to be carried out by the supporting organization, and it is necessary to discuss the diversification of the management subject. It is found that there is a certain difference in recognition with the mixture of concepts, and there is still a big difference in legal system and perception.

Determination of Equivalent Hydraulic Conductivity of Rock Mass Using Three-Dimensional Discontinuity Network (삼차원 불연속면 연결망을 이용한 암반의 등가수리전도도 결정에 대한 연구)

  • 방상혁;전석원;최종근
    • Tunnel and Underground Space
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    • v.13 no.1
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    • pp.52-63
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    • 2003
  • Discontinuities such as faults, fractures and joints in rock mass play the dominant role in the mechanical and hydraulic properties of the rock mass. The key factors that influence on the flow of groundwater are hydraulic and geometric characteristics of discontinuities and their connectivity. In this study, a program that analyzes groundwater flow in the 3D discontinuity network was developed on the assumption that the discontinuity characteristics such as density, trace length, orientation and aperture have particular distribution functions. This program generates discontinuities in a three-dimensional space and analyzes their connectivity and groundwater flow. Due to the limited computing capacity In this study, REV was not exactly determined, but it was inferred to be greater than 25$\times$25$\times$25 ㎥. By calculating the extent of aperture that influences on the groundwater flow, it was found that the discontinuities with the aperture smaller than 30% of the mean aperture had little influence on the groundwater flow. In addition, there was little difference in the equivalent hydraulic conductivity for the the two cases when considering and not considering the boundary effect. It was because the groundwater flow was mostly influenced by the discontinuities with large aperture. Among the parameters considered in this study, the length, aperture, and orientation of discontinuities had the greatest influence on the equivalent hydraulic conductivity of rock mass in their order. In case of existence of a fault in rock mass, elements of the equivalent hydraulic conductivity tensor parallel to the fault fairly increased in their magnitude but those perpendicular to the fault were increased in a very small amount at the first stage and then converged.