• Journal of the Korean Geotechnical Society
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• v.40 no.2
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• pp.95-103
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• 2024

The global increase in population and subsequent scarcity of terrestrial living spaces necessitates exploration of alternative habitats. Research into the development of underwater living areas provides promising avenues for the expansion of human living spaces and the use of marine environments. This study focuses on the failure envelope of suction caisson foundations subjected to combined loads in a marine setting, utilizing finite element analysis. The foundation is assumed to be embedded in clay characterized by a linear increase in undrained shear strength with depth, employing the von Mises constitutive model for the clay. The resulting failure envelope is represented as a tilted ellipse which expands as the undrained shear strength increases, maintaining a constant ratio between the major and minor axes. A comparative analysis of two suction caisson foundations with varying length-to-diameter ratios revealed that this ratio influences the dimensions of the failure envelope, with a tendency for the major-to-minor axis ratio to increase as the length-to-diameter ratio increases. These findings are critical for the design of suction caisson foundations in offshore environments.

• Journal of the Korea Institute of Construction Safety
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• v.6 no.1
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• pp.7-11
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• 2024

Pump car is an equipment that transports concrete products as needed to the place where they are poured. In order to pour a large amount of concrete in a short period of time, using a pump car is the most efficient in terms of economic efficiency and quality control. However, recently, many casualties have occurred due to boom damage during concrete pouring, so this study suggests that improvements are needed in the equipment manufacturing stage, inspection standards for old equipment, and equipment rental system. The reason is that, as a result of the finite element analysis of the pump car, the significant stress acting at the second stage of the boom and the maximum stress at the top of the boom were found to be 895.39 MPa, and M.S. Since it was evaluated the lowest at 0.04, the need for reinforcement was recognized. And it was confirmed that the 2nd stage boom was the most stressful and vulnerable part of the 1st to 5th stage booms. Therefore, it is necessary to increase the thickness and rigidity of members at the design and manufacturing stage, and to reinforce the steel plates of currently used equipment. In addition, it is urgent to establish a system that makes non-destructive testing mandatory for all general construction machinery and holds inspection agencies responsible for missing boom defects during non-destructive testing and regular inspections.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.249-262
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• 2024

Retaining walls are widely used in the construction of underground structures. This study reviews the stability of the high-strength joint buried pile method at a site in Korea. [Consider giving details of the location.] The method is assessed by considering the amount of ground settlement, as calculated by finite element analysis and measured at the site. Comparison of the measured and numerical results confirmed the method's stability and field applicability. Settlement of 13.42~13.65 mm was calculated for seven cross-sections [The Abstract should be comprehensible without reference to the main text. The labels A-A' to G-G' should not be introduced here without explanation.] using numerical analysis, and the measured settlement reached a maximum of 2.00 mm. The observed differences and variations [Please state what differed/varied.] did not exceed the design expectations in any section. Instruments installed at the back of the excavation area were used to assess the conditions. An underground gradient meter recorded a cumulative horizontal displacement of between -0.40 and 0.60 mm, and an underground water meter recorded slight displacements of between -0.21 and 0.28 m compared with the initial measurements. A surface settlement meter observed very little movement, with a maximum of -2.00 mm compared with the initial measurement, thereby confirming the establishment of a stable state within the management criteria.

• Steel and Composite Structures
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• v.50 no.6
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• pp.705-720
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• 2024

Analyzing the collapse behavior of thin-walled steel structures holds significant importance in ensuring their safety and longevity. Geometric imperfections present on the surface of metal materials can diminish both the durability and mechanical integrity of steel shells. These imperfections, encompassing local geometric irregularities and deformations such as holes, cavities, notches, and cracks localized in specific regions of the shell surface, play a pivotal role in the assessment. They can induce stress concentration within the structure, thereby influencing its susceptibility to buckling. The intricate relationship between the buckling behavior of these structures and such imperfections is multifaceted, contingent upon a variety of factors. The buckling analysis of thin-walled steel shell structures, similar to other steel structures, commonly involves the determination of crucial material properties, including elastic modulus, shear modulus, tensile strength, and fracture toughness. An established method involves the emulation of distributed geometric imperfections, utilizing real test specimen data as a basis. This approach allows for the accurate representation and assessment of the diversity and distribution of imperfections encountered in real-world scenarios. Utilizing defect data obtained from actual test samples enhances the model's realism and applicability. The sizes and configurations of these defects are employed as inputs in the modeling process, aiding in the prediction of structural behavior. It's worth noting that there is a dearth of experimental studies addressing the influence of geometric defects on the buckling behavior of cylindrical steel shells. In this particular study, samples featuring geometric imperfections were subjected to experimental buckling tests. These same samples were also modeled using Finite Element Analysis (FEM), with results corroborating the experimental findings. Furthermore, the initial geometrical imperfections were measured using digital image correlation (DIC) techniques. In this way, the response of the test specimens can be estimated accurately by applying the initial imperfections to FE models. After validation of the test results with FEA, a numerical parametric study was conducted to develop more generalized design recommendations for the stainless-steel shell structures with the initial geometric imperfection. While the load-carrying capacity of samples with perfect surfaces was up to 140 kN, the load-carrying capacity of samples with 4 mm defects was around 130 kN. Likewise, while the load carrying capacity of samples with 10 mm defects was around 125 kN, the load carrying capacity of samples with 14 mm defects was measured around 120 kN.

• Journal of the Korean Institute of Landscape Architecture
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• v.52 no.4
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• pp.56-68
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• 2024

This study aimed to derive the concept and types of school outdoor spaces in Seoul. The research results showed that the concept of school outdoor space can be viewed as an outdoor activity space in schools that secures the value of integrated public life and communal life, including "behavioral rights, walking rights, living rights, urban rights, landscape rights (viewing rights), and nature experience rights." It can also be defined as a basic educational space that reflects the value of education, which is the basic function of schools and the characteristics of the community. As a result of the analysis based on the general types of outdoor spaces, it was found that the outdoor spaces of Seoul schools can be divided into three major categories: walking space (movement function), educational space (educational activities), and rest and other spaces (other services). Based on this, outdoor spaces were categorized and subcategorized to serve as the basis for policy implementation. These classifications are characterized by 1) simplifying the classification of spaces by function into three (movement functions, educational activities, and other services) to enable the use of outdoor spaces for integrated purposes; 2) reflecting the complex use of spaces by subdividing educational spaces focusing on major activities, and in particular, discovering complex spaces due to the three-dimensionalization of buildings; and 3) enabling spatial-level planning and facility element-level access according to school characteristics. It is characterized by applying the recent trends and systems of general outdoor space projects to the current situation of schools.

• Wind and Structures
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• v.39 no.4
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• pp.259-269
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• 2024

The current research on the wind resistance of standing seam metal roofs primarily focuses on the failure modes of the entire roof panel and the contact areas between the seams and supports, with little consideration given to the synergy between the roof seam reinforcements, the web, and the supports. As a result, the failure mechanisms of roof systems cannot be accurately represented. This paper, based on wind uplift tests and ABAQUS simulation modeling, provides a detailed analysis of the wind resistance and failure mechanisms of reinforced standing seam metal roof systems. The study reveals that the deformation and failure of the roof system under wind load can be divided into three stages: elastic deformation, plastic deformation, and failure. In the elastic deformation stage, the areas with higher stress are mainly distributed in the mid-span of the roof panels and along the ribs, where the roof stress remains below the material's yield strength, and the displacement at the roof panel seams is minimal. During the plastic deformation stage, as the load increases, significant vertical deformations appear in the roof panels, the lateral displacement at the seams gradually increases, and the stress growth is pronounced. Without reinforcement, the roof panel withstands a maximum wind pressure of 3.2 kPa, with a central vertical displacement of 109 mm, while the ultimate lateral displacement at the seams reaches 2.3 mm, resulting in unseating failure, marking the structural failure. With reinforcement, the roof panel can withstand a maximum wind pressure of 4.3 kPa, corresponding to a central vertical displacement of 122 mm. The growth of lateral displacement at the seams slows down, and the reinforcement significantly suppresses seam displacement. As the load continues to increase, the reinforcements and the web work synergistically, exhibiting reciprocating counterclockwise and clockwise rotations, with the maximum lateral displacement at the seams increasing to 3.05 mm. Ultimately, unseating occurs at the roof panel seams or tearing at the web. Therefore, the reinforcement system significantly enhances the wind resistance of the roof system, providing theoretical guidance for wind-resistant design in roofing engineering.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.44 no.2
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• pp.191-201
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• 2024

In this study, three-dimensional finite element analysis was used to analyze the behavior of existing and reinforcing piles according to the pile support conditions for vertical extension remodeling. Cap support conditions (group pile, piled raft foundation) and pile tip conditions (rock, soil embedment) were considered as factors influencing existing and reinforcing piles behavior. For the quantitative analysis of existing and reinforcing piles, the displacement, load distribution ratio, and axial force by depth according to the analysis stage were analyzed. As a result of the analysis, it was confirmed that the largest settlement occurred in the reinforcing pile due to the pre-loading method. In particular, a large amount of settlement occurred in group piles regardless of the embedment conditions. In the piled raft foundation, it was confirmed that the displacement and load distribution ratio of existing piles and reinforcing piles were reduced due to the influence of the raft. The axial force by depth showed a difference between group pile and piled raft foundation, which appears to be a major factor affecting displacement and load distribution ratio. Based on the numerical analysis results, it was confirmed that cap support conditions and pile tip embedment conditions should be considered in the design of pile foundations for vertical extension remodeling.

• The Journal of the Convergence on Culture Technology
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• v.10 no.5
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• pp.61-69
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• 2024

The Geonjae Old House Garden of Asan Oeam Village contains historical and academic values as a major element of the village's landscape, along with the village's feng shui geographical conditions and artificial roads that pass through the village, which represent the village. Although some have been maintained over a long period of time, many of them have been lost, disturbed, and distorted. The main houses of Oeam Village had traditional gardens, but the garden of the Geonjae Old House is a place where different garden cultures coexist in one place due to the creation of Japanese-style gardens in Japanese colonial era. This study predicts the past through genetic analysis of the garden of the Geonjae Old House, and establishes a restoration plan for the garden of the Geonjae Old House through historical restoration of the results. In addition, the purpose of this study is to suggest a way to avoid damage in restoring the original form of cultural properties as much as possible and to facilitate the preservation and management of cultural properties. As a result of contrast with past photographs and on-site evidence, it was found that the garden of the Geonjae Old House has a different shape from its previous appearance due to repeated distortion and damage. In addition, it was possible to suggest a restoration method that could reproduce the appearance of the past through genetic analysis.

• Proceedings of the Korean Geotechical Society Conference
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• 1991.10a
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• pp.87-102
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• 1991

It has been reported that the failure of Carsington Dam in Eng1and occured due to the existence of a thin yellow clay layer which was not identified during the design work, and due to pre-existing shears of the clay layer. The slope stability analyses during the design work, which utilized traditional circular arc type failure method and neglected the existence of the clay layer, showed a safety factor of 1.4. However, the post-failure analyses which utilized translational failure mode considering the clay layer and the pre-existing shear deformation revealed the reduction of safety factor to unity. The post-failure analysis assumed 10。 inclination of the horizontal forces onto each slice based on the results of finite element analyses. In this paper, Bishop's simplified method, Janbu method, and Morgenstern-Price method were used for the comparison of both circular and translational failure analysis methods. The effects of the pre-existing shears and subsquent movement were also considered by varying the soil strength parameters and the pore pressure ratio according to the given soi1 parameters. The results showed factor of safefy 1.387 by Bishop's simplified method(STABL) which assumed circular arc failure surface and disregarding yellow clay layer and pre-failure material properties. Also the results showed factor of safety 1.093 by Janbu method(STABL) and 0.969 by Morgenstern-Price method(MALE) which assumed wedge failure surface and considerd yellow clay layer using post failure material properties. In addition, dam behavior was simulated by Cam-Clay model FEM program. The effects of pore pressure changes with loading and consolidation, and strength reduction near or at failure were also considered based on properly assumed stress-strain relationship and pore pressure characteristics. The results showed that the failure was initiated at the yellow clay layer and propagated through other zones by showing that stress and displacement were concentrated at the yel1ow clay layer.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.29 no.6
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• pp.327-340
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• 2017

This article reviews the papers published in the Korean Journal of Air-Conditioning and Refrigeration Engineering during 2016. It is intended to understand the status of current research in the areas of heating, cooling, ventilation, sanitation, and indoor environments of buildings and plant facilities. Conclusions are as follows. (1) The research works on the thermal and fluid engineering have been reviewed as groups of flow, heat and mass transfer, the reduction of pollutant exhaust gas, cooling and heating, the renewable energy system and the flow around buildings. CFD schemes were used more for all research areas. (2) Research works on heat transfer area have been reviewed in the categories of heat transfer characteristics, pool boiling and condensing heat transfer and industrial heat exchangers. Researches on heat transfer characteristics included the results of the long-term performance variation of the plate-type enthalpy exchange element made of paper, design optimization of an extruded-type cooling structure for reducing the weight of LED street lights, and hot plate welding of thermoplastic elastomer packing. In the area of pool boiling and condensing, the heat transfer characteristics of a finned-tube heat exchanger in a PCM (phase change material) thermal energy storage system, influence of flow boiling heat transfer on fouling phenomenon in nanofluids, and PCM at the simultaneous charging and discharging condition were studied. In the area of industrial heat exchangers, one-dimensional flow network model and porous-media model, and R245fa in a plate-shell heat exchanger were studied. (3) Various studies were published in the categories of refrigeration cycle, alternative refrigeration/energy system, system control. In the refrigeration cycle category, subjects include mobile cold storage heat exchanger, compressor reliability, indirect refrigeration system with $CO_2$ as secondary fluid, heat pump for fuel-cell vehicle, heat recovery from hybrid drier and heat exchangers with two-port and flat tubes. In the alternative refrigeration/energy system category, subjects include membrane module for dehumidification refrigeration, desiccant-assisted low-temperature drying, regenerative evaporative cooler and ejector-assisted multi-stage evaporation. In the system control category, subjects include multi-refrigeration system control, emergency cooling of data center and variable-speed compressor control. (4) In building mechanical system research fields, fifteenth studies were reported for achieving effective design of the mechanical systems, and also for maximizing the energy efficiency of buildings. The topics of the studies included energy performance, HVAC system, ventilation, renewable energies, etc. Proposed designs, performance tests using numerical methods and experiments provide useful information and key data which could be help for improving the energy efficiency of the buildings. (5) The field of architectural environment was mostly focused on indoor environment and building energy. The main researches of indoor environment were related to the analyses of indoor thermal environments controlled by portable cooler, the effects of outdoor wind pressure in airflow at high-rise buildings, window air tightness related to the filling piece shapes, stack effect in core type's office building and the development of a movable drawer-type light shelf with adjustable depth of the reflector. The subjects of building energy were worked on the energy consumption analysis in office building, the prediction of exit air temperature of horizontal geothermal heat exchanger, LS-SVM based modeling of hot water supply load for district heating system, the energy saving effect of ERV system using night purge control method and the effect of strengthened insulation level to the building heating and cooling load.