• Journal of the Korean Institute of Landscape Architecture
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• 제39권6호
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• pp.67-75
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• 2011

This study was carried out to investigate the changes in citizen satisfaction with parks and green spaces in Daegu. Three surveys were conducted using the same measurement tools in 1986, 2001, and 2010. Major results are as follows: 1. The overall satisfaction level with parks and green spaces increased remarkably over the last25years. Satisfaction levels with city spaces overall were higher than that of nearby surrounding areas. 2. Diversity of green spaces was the most distinguished indicator in increasing level of satisfaction while the management level of green space facilities showed the lowest improvement. 3. The factor analysis for individual variables for satisfaction resulted in two factors: functions and physical conditions were categorized as one factor, and indicators for the planning of green spaces were the other. Using a regression model, the major variables found for satisfaction were diversity, management level of woods, quantitative level, function of static recreation, and management level of facilities, respectively. 4. Regarding satisfaction level by the type of green spaces, green spaces by streets showed a remarkable increase while green spaces in industrial areas showed the lowest improvement. A factor analysis for each type of green space resulted in 3 factors: green spaces of urban parks, green spaces of urban recreational facilities, and green spaces of each district including residential areas and industrial areas.

• Journal of the Korean Geotechnical Society
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• 제28권10호
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• pp.5-16
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• 2012

Geotechnical buried structures with relatively light weight have been suffering from uplift damage due to liquefaction in the past earthquakes. The factor of safety approach by Koseki et al. (1997a), which is widely used in seismic design, predicts the triggering of uplift. However, a method for "quantitative" estimates of the uplift displacement has yet to be established. Estimation of the uplift displacement may be an important factor to be considered for designing underground structures under the framework of performance-based design (ISO23469, 2005). Therefore, evaluation of the uplift displacement of buried structure in liquefied ground during earthquakes is needed for a performance-based design as a practical application. In order to predict the uplift displacement quantitatively, a simplified method is derived based on the equilibrium of vertical forces acting on buried structures in backfill during earthquakes (Tobita et al., 2012). The method is verified through comparisons with results of centrifuge model tests and damaged sewerage systems after the 2004 Niigata-ken Chuetsu, Japan, earthquake. The proposed flow diagram for performance-based design includes estimation of the uplift displacement as well as liquefaction limit of backfill.

• Journal of the Korea Institute of Building Construction
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• 제20권2호
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• pp.137-145
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• 2020

The recent bridge construction projects demand thorough and systematic safety and risk management, due to the increase of risk factors following the introduction of new and complex construction methods and technologies. Among many types of damages that can occur in bridge construction projects, the damages to third parties who are not directly related to the existing property of the contractor construction project can also bring about critical loss in the project in order to compensate the damages. Therefore, risks that could be caused by the loss occurred to indemnify the third party damages should be clearly analyzed, although there are not subsequent amount of studies focusing on the issue. Based on the past record of insurance payment from domestic insurance companies for bridge construction projects, this study aimed to analyze the risk factors of bridge construction for loss caused to compensate the third-party damages happened in actual bridge construction projects and to develop a quantified and numerical predictive loss model. In order to develop the model, the loss ratio was selected as the dependent variable; and among many analyzed independent variables, the superstructure, foundation, flood, and ranking of contractors were the four significant risk factor variables that affect the loss ratio. The results produced can be used as an essential guidance for balanced risk assessment, supplementing the existing analysis on material losses in bridge construction projects by taking into account the third-party damage and losses.

• Proceedings of the Korean Institute Of Construction Engineering and Management
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• 한국건설관리학회 2006년도 정기학술발표대회 논문집
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• pp.154-160
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• 2006

There wasn't very successful practice cases for the quantity take-off based on the CAD system since the CAD system is used in the construction industry more than 20 years in Korea. It was also not easy to use 3D CAD system in design management and cost management in the construction industry although 3D CAD system is very successful in the manufacturing industry for those areas recently. It is important to construct 3D libraries and to supply those libraries for the designers in time. Architectural work is a kind of creative work. So, Architects like to create their own model. Unlike the manufacturing industry, 3D CAD system can not be survived in the construction industry without new 3D objects supply in the right time. Moreover, the estimation system for 3D must support the schematic design phase, detailed design phase and construction design phase. The product called "Constructor" of Graphisoft consist of modeller, estimator and scheduler based on 3D model. We applied the system to a real project and compared the estimation result and we made a very successful case study.

• Korean Journal of Construction Engineering and Management
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• 제16권3호
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• pp.11-23
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• 2015

Construction Management(CM) and Building Information Management(BIM) have a lot in common that they need to establish a cooperation system among different disciplines and promote smooth communication among project stakeholders throughout the project life-cycle. BIM can be an effective information management tool for CM's business and improve their service value. However, BIM uses by Construction Managers(CMr) are very limited. The objective of this study is to analyze the intention of CMrs to adopt BIM and establish effective BIM use strategy in the CMr's point of view. This study utilizes Technology Acceptance Model(TAM) as a research method, and the results show that 1) CMrs think it is more important whether BIM is required to be adopted in their business process at the social or industry level than that BIM can improve their personal competence, recognition, and impressions through their voluntary BIM adoption; 2) that CMrs think it is important to figure out business processes where BIM can be smoothly incorporated; and 3) that CMrs hesitate the use and trial of BIM in their realworld business although they agree that BIM needs to be eventually adopted in their business in the future. Based on these results, directions for establish a strategy for BIM adoption were proposed at the CMr's point of view

• Journal of Korea Water Resources Association
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• 제48권5호
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• pp.409-423
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• 2015

In this study the very short-term rainfall forecasting and storm water forecasting using the weather radar data were implemented in an urban stream basin. As forecasting time increasing, the very short-term rainfall forecasting results show that the correlation coefficient was decreased and the root mean square error was increased and then the forecasting model accuracy was decreased. However, as a result of the correlation coefficient up to 60-minute forecasting time is maintained 0.5 or higher was obtained. As a result of storm water forecasting in an urban area, the reduction in peak flow and outflow volume with increasing forecasting time occurs, the peak time was analyzed that relatively matched. In the application of storm water forecasting by radar rainfall forecast, the errors has occurred that we determined some of the external factors. In the future, we believed to be necessary to perform that the continuous algorithm improvement such as simulation of rapid generation and disappearance phenomenon by precipitation echo, the improvement of extreme rainfall forecasting in urban areas, and the rainfall-runoff model parameter optimizations. The results of this study, not only urban stream basin, but also we obtained the observed data, and expand the real-time flood alarm system over the ungaged basins. In addition, it is possible to take advantage of development of as multi-sensor based very short-term rainfall forecasting technology.

• The Journal of the Korea Contents Association
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• 제12권11호
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• pp.446-457
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• 2012

Recently, BIM(Building Information Modeling),which has been an issue in construction work, has been focused on as a new alternative of building industry for way out of crisis by slowing down and decreasing of orders in construction industry. Research for introducing BIM to the architectural field is already proceeding actively at home and abroad. However, civil engineering is so nonrecurring, horizontal, and different from regular construction works that it a large amount of information occurs because of wide range of project, which causes construction firms and design engineers to have some questions whether their initial investment cost would work or not and feel uncomfortable with the cost. In this study, technology level in engineering firms were surveyed for adapting BIM to domestic civil engineering. Development direction of BIM standard information model was drawn through awareness change analysis of BIM in civil engineering, as well. Deduced development direction is composed of guide development, system development, deliverable check and international standard proposal. The outcome will be employed as preliminary data for the study on development of infrastructure BIM standard and deliverable check system in civil engineering.

• Journal of the Korea Concrete Institute
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• 제24권2호
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• pp.195-204
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• 2012

In the construction of high-rise buildings, bent re-bars are manually straightened to connect slabs to core-walls, which are usually cast before floor structures. During cold bending and straightening of re-bars, plastic deformation causing work hardening, Bauschinger effect and aging hardening is unavoidable. Tensile tests of coldly bent and straightened re-bars were conducted with test parameters of grade, diameter, and bend radius of re-bars as well as age between bending and straightening. Test results showed that proportional limits were lower and strain hardening occurred without yield plateaus. Inside and outside of re-bars with compression and tension deformations, respectively, during bending showed lower yield points due to Bauschinger effect and no yield plateaus due to work hardening, respectively. When re-bar grade was higher, yield point became significantly lower where Grade 400 re-bars had yield strengths lower than specified yield strength of 400 MPa. Because the surface of re-bar has higher strength than the core of re-bar, Bauschinger effect was more obvious for higher-grade re-bars. When age between bending and straightening was greater, yield strength increased and elongation decreased (i.e. embrittlement occurs). Using measured data, stress-strain relationship for straightened re-bars was developed based on Ramberg-Osgood model, which can be used to evaluate stiffness of joints when straightened re-bars are applied.

• Journal of the Korea Institute of Building Construction
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• 제20권1호
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• pp.83-91
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• 2020

The recent bridge construction projects is demanded more sophisticated risk management measures and loss forecasts to brace for risk losses from an increase in the trend of bridge construction. This study aims to analyze the risk factors that caused the loss of material in actual bridge construction and to develop a quantified predictive loss model, based on the past record of insurance payment by major domestic insurance companies for bridge construction projects. For the development of quantitative bridge construction loss model, the dependent variable was selected as the loss ratio, i.e., the ratio of insurance payout divided by the total project cost, while the independent variable adopted 1) Technical factors: superstructure type, foundation type, construction method, and bridge length 2) Natural hazards: typhoon and flood 3) Project information: construction period and total project cost. Among the selected independent variables, superstructure type, construction method, and project period were shown to affect the ratio of bridge construction losses. The results of this study can provide government agencies, bridge construction design and construction and insurance companies with the quantitative damage prediction and risk assessment services, using risk indicators and loss prediction functions derived from the findings of this study and can be used as a guideline for future basic bridge risk assessment development research.

• Ocean Systems Engineering
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• 제6권1호
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• pp.61-97
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• 2016

This is the second of two papers on the 3D numerical modeling of nearshore hydro- and morphodynamics. In Part I, the focus was on surf and swash zone hydrodynamics in the cross-shore and longshore directions. Here, we consider nearshore processes with an emphasis on the effects of oceanic forcing and beach characteristics on sediment transport in the cross- and longshore directions, as well as on foreshore bathymetry changes. The Delft3D and XBeach models were used with four turbulence closures (viz., ${\kappa}-{\varepsilon}$, ${\kappa}-L$, ATM and H-LES) to solve the 3D Navier-Stokes equations for incompressible flow as well as the beach morphology. The sediment transport module simulates both bed load and suspended load transport of non-cohesive sediments. Twenty sets of numerical experiments combining nine control parameters under a range of bed characteristics and incident wave and tidal conditions were simulated. For each case, the general morphological response in shore-normal and shore-parallel directions was presented. Numerical results showed that the ${\kappa}-{\varepsilon}$ and H-LES closure models yield similar results that are in better agreement with existing morphodynamic observations than the results of the other turbulence models. The simulations showed that wave forcing drives a sediment circulation pattern that results in bar and berm formation. However, together with wave forcing, tides modulate the predicted nearshore sediment dynamics. The combination of tides and wave action has a notable effect on longshore suspended sediment transport fluxes, relative to wave action alone. The model's ability to predict sediment transport under propagation of obliquely incident wave conditions underscores its potential for understanding the evolution of beach morphology at field scale. For example, the results of the model confirmed that the wave characteristics have a considerable effect on the cumulative erosion/deposition, cross-shore distribution of longshore sediment transport and transport rate across and along the beach face. In addition, for the same type of oceanic forcing, the beach morphology exhibits different erosive characteristics depending on grain size (e.g., foreshore profile evolution is erosive or accretive on fine or coarse sand beaches, respectively). Decreasing wave height increases the proportion of onshore to offshore fluxes, almost reaching a neutral net balance. The sediment movement increases with wave height, which is the dominant factor controlling the beach face shape.