• Structural Engineering and Mechanics
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• v.19 no.6
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• pp.653-677
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• 2005

Concrete filled steel tubular columns (CFT) are widely used in civil engineering works, especially in large scale of works because of high strength, deformation, toughness and so on. On the other hand, as a kind of strengthening measure for seriously damaged reinforced concrete piers of viaduct in Hansin-Awaji earthquake of Japan in 1995, reinforced concrete piers were wrapped with steel plate. Then, a new kind of structure appeared, that is, reinforced concrete filled steel tubular column (RCFT). In this paper, compression test and bending-shearing test on RCFT are carried out. The main parameters of experiments are (1) strength of concrete, (2) steel tube with or without rib, (3) width-thickness ratio and (4) arrangement of reinforcing bars. According to the experimental results, the effect of parameters on mechanical characteristics of RCFT is analyzed clearly. At the same time, strength evaluation formula for RCFT column is proposed and tested by experimental results and existed recommendations (AIJ 1997). The strength calculated by the proposal formula is in good agreement with test result. As a result, the proposed evaluation formula can evaluate the strength of RCFT column properly.

• Journal of the Korean Geographical Society
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• v.51 no.2
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• pp.185-200
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• 2016

The discipline of Geography is broadly concerned with the interconnections between people and the environment. Particularly, this unique human-environment relationship often can be typically reflected from, and well illustrated by, the dynamics of microstates' island environment. While Tuvaluans living on vulnerable, low-lying atolls in the Pacific are not primarily responsible for contributing to climate change, yet they are experiencing its dreadful effects. Population pressure, caused by the differences in population size, distribution, and composition, has been constantly affected by resource unavailability and environmental instability on the islands. It also represents one of our challenges in understanding the complex influence of population dynamics on the living environment. What can be learned from Tuvalu in the context of population geography and environmental geography as well as its relationship with other Pacific island microstates? What are Tuvaluans' migration responses to their atolls' environmental crisis as well as the carrying capacity scenarios related to overpopulation? What are the current living experiences and settlement situations of Tuvaluan internal and external migrants both at home and abroad? This research examines the contemporary migration literature in the context of Tuvalu's population geography, while analyzing Tuvaluan migration patterns, discourses and perspectives in relation to environmental change.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4A
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• pp.611-620
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• 2006

The composite two plate-girder bridges are generally defined as a non-redundant load path structure because the bridge can collapse if one of the two girders is seriously damaged by a fatigue crack. In this paper, a numerical study on the evaluation of the after-fracture redundancy of the composite two-girder bridges was accomplished. The evaluation has been performed on the simple and three-span continuous bridges with I-section cross beams which serve as transverse bracing, and with or without the bottom lateral bracing system. The load carrying capacities of the intact and damaged bridges with or without lateral bracing were evaluated from material and geometric nonlinear analysis, respectively and the redundancy was evaluated for each case. It was acknowledged from the analytical results that both simple and continuous intact two-girder bridges have sufficient redundancy even without lateral bracing, but it takes an important role to improve the redundancy of damaged bridges.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.10 no.6
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• pp.33-43
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• 2007

The revised Urban Park regulations newly adopt Theme Parks in order to enhance richness and diversities of urban services to communities. However, the regulations ambiguously define the main facilities and service programs of the theme parks. And there have been increasing concerns about confusions in terms of the main facilities and service programs of the theme parks among landscape designers/planners, local governments and relevant field of areas. Misunderstanding on the facilities and service programs of the theme parks may lead to ruin the purposes of the new urban park regulations. In the lights of these, this paper tries to reach a consensus for main facilities and service programs of two theme parks including athletic park and waterfront park, based on measured potential users' preferences with a conjoint choice model. For waterfront parks, potential users show low preferences or negative responses to facilities which are perceived as un-environment friendly. They also show high preferences on ecological areas sitting near to streams. For athletic parks, potential users show demand to introduce something different facilities and atmosphere from existing athletic parks. The demands are particularly high for children's play ground facilities and service facilities. This study also show some methodological examples to compute the carrying capacity with two hypothetical alternatives. This approach might be beneficial for local governments which are wish to alternate the park size on the basis of local conditions such as their financial conditions and land availability.

• Smart Structures and Systems
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• v.29 no.1
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• pp.17-28
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• 2022

The cable component of cable-stayed bridges is gradually impacted by weather conditions, vehicle loads, and material corrosion. The stayed cable is a critical load-carrying part that closely affects the operational stability of a cable-stayed bridge. Damaged cables might lead to the bridge collapse due to their tension capacity reduction. Thus, it is necessary to develop structural health monitoring (SHM) techniques that accurately identify damaged cables. In this work, a combinational identification method of three efficient techniques, including statistical analysis, clustering, and neural network models, is proposed to detect the damaged cable in a cable-stayed bridge. The measured dataset from the bridge was initially preprocessed to remove the outlier channels. Then, the theory and application of each technique for damage detection were introduced. In general, the statistical approach extracts the parameters representing the damage within time series, and the clustering approach identifies the outliers from the data signals as damaged members, while the deep learning approach uses the nonlinear data dependencies in SHM for the training model. The performance of these approaches in classifying the damaged cable was assessed, and the combinational identification method was obtained using the voting ensemble. Finally, the combination method was compared with an existing outlier detection algorithm, support vector machines (SVM). The results demonstrate that the proposed method is robust and provides higher accuracy for the damaged cable detection in the cable-stayed bridge.

• Journal of the Korean Geotechnical Society
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• v.28 no.9
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• pp.57-67
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• 2012

In the design for piled rafts, the load capacity of the raft is in general ignored and the load capacities of pile are only considered for the estimation of the total load carrying capacity of the piled raft. The axial resistance of piled raft is offered by the raft and group piles acting on the same supporting ground soils. As a consequence, pile - soil - raft and pile - soil interactions, occurring by stress and displacement duplication with pile and raft loading conditions, acts as a key element in the design for piled rafts. In this study, a series of centrifuge model tests has been performed to compare the axial behavior of group pile and raft with that of a piled raft (having 16 component piles with an array of $4{\times}4$) at the stiff and soft clays. From the test results, it is observed that the interactions of piles, soil, and raft has little influences on the load capacities of piles and raft in piled rafts compared with the load capacities of group piles and raft at the same clay soil condition.

• Journal of the Korean GEO-environmental Society
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• v.8 no.1
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• pp.33-40
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• 2007

Engineering behaviour of uplift-resisting ground anchors constructed in weathered rocks has been investigated by carrying out a series of full scale pull-out tests. The anchor was to resist uplift forces (buoyancy) associated with high groundwater table acting on the basement of a rail way station. The study has included the ultimate pull-out capacity of the anchors and shear stress transfer mechanism at the anchor-ground interface. The pull-out tests were conducted by changing bonded lengths of the anchor (2~7 m) and diameter of drilled borehole (108~165 mm) to investigate their effects on the behaviour of the anchor. The measured results showed that the ultimate capacity of the anchors was increased with an increase in the bonded length, diameter of drilled borehole as expected. The ultimate capacity of the anchors deduced from the pull-out tests ranged from 392 to 1,569 kN, depending on the above-mentioned factors. This corresponds to the interface shear strength of about 227~505 kPa. Interface shear stresses deduced from the pull-out test showed that the larger the pull-out force, the larger the mobilisation of the interface shear strength. The failure mode of the anchors heavily depended on the bonded lengths of the anchors. When the bonded length was short (2~3 m), a cone-type failure was observed, whereas when the bonded length increased (5~7 m), failure developed at the grout-ground interface.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.1
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• pp.12-22
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• 2000

Recently urbanization and industrialization around the Nak-dong river watershed have lead to the regional environmental problems. In this viewpoint, we took up variables which were related to watershed environment, and found out spatial and environmental properties of the Nak-dong river using factor analysis, ANOVA test and geographic information system. The results may be summarized as follows; three common factors which were named as urban, agricultural and industrial pollutant factor extracted from statistical methods. Spatial distribution of watershed environment could be found by connection attributes of factor scores derived from factor analysis to digital map using GIS. According to the results, distribution of pollutant sources were concentrated in the main stream of the Nak-dong river and its tributaries, Kum-ho river. So it is necessary to manage the watershed environment in due consideration of environmental carrying capacity.

• Journal of Korea Water Resources Association
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• v.41 no.2
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• pp.127-135
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• 2008

The objective of sewer rehabilitation is to improve its function while eliminating inflow/infiltration (I/I) and insufficient carrying capacity (ICC). Such rehabilitation efforts, however, have not been particularly successful due to a lack of sewer data and unsystematic field practices. The present study aimed to solve these problems by developing a decision making model consisting of two models: the rehabilitation weighting model (RWM) and the rehabilitation priority model (RPM). In RWM, the I/I of each pipe in a drainage district is estimated according to various defects, with each defect given an individual weighting factor using an analytic hierarchy process (AHP). RPM determines the optimal rehabilitation priority (ORP) using a genetic algorithm (GA). The developed models can be used to overcome the problems associated with unsystematic practices and, in practice, as a decision making tool for urban sewer system rehabilitation.

• Fire Science and Engineering
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• v.30 no.5
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• pp.54-59
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• 2016

Steel is a structural material that is inherently noncombustible. On the other hand, it has high thermal conductivity and the strength and stiffness of the material are reduced significantly when exposed to fire or high temperatures. Because the yield strength and modulus of elasticity of steel are reduced by 70% at $350^{\circ}C$ and less than 50% at $600^{\circ}C$, the load-carrying capacity of steel structure at high temperature rapidly lose. To be accepted as a fire-resisting construction, the fire test should be performed at the certificate authority. On the other hand, the fire test on a full-scale structure is limited by time, space, and high-cost. The analytical method was verified by a comparison with the fire test of H-section columns under compression and thermal analysis based on a finite element method using the ABAQUS program, and the numerical analysis method reported in this study was suggested as a complement of an actual fire test.