• Steel and Composite Structures
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• v.20 no.2
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• pp.379-397
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• 2016

Due to creep and shrinkage of the concrete core, concrete-filled steel tubular (CFST) arches continue to deform in the long-term under sustained loads. This paper presents analytical investigations of the effects of geometric nonlinearity on the long-term in-plane structural performance and stability of three-pinned CFST circular arches under a sustained uniform radial load. Non-linear long-term analysis is conducted and compared with its linear counterpart. It is found that the linear analysis predicts long-term increases of deformations of the CFST arches, but does not predict any long-term changes of the internal actions. However, non-linear analysis predicts not only more significant long-term increases of deformations, but also significant long-term increases of internal actions under the same sustained load. As a result, a three-pinned CFST arch satisfying the serviceability limit state predicted by the linear analysis may violate the serviceability requirement when its geometric nonlinearity is considered. It is also shown that the geometric nonlinearity greatly reduces the long-term in-plane stability of three-pinned CFST arches under the sustained load. A three-pinned CFST arch satisfying the stability limit state predicted by linear analysis in the long-term may lose its stability because of its geometric nonlinearity. Hence, non-linear analysis is needed for correctly predicting the long-term structural behaviour and stability of three-pinned CFST arches under the sustained load. The non-linear long-term behaviour and stability of three-pinned CFST arches are compared with those of two-pinned counterparts. The linear and non-linear analyses for the long-term behaviour and stability are validated by the finite element method.

• Journal of the Korea Institute of Information Security & Cryptology
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• v.27 no.6
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• pp.1441-1455
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• 2017

In order to build a secure electric vehicle charging infrastructure, security research is required because various data including charging and payment data are transmitted in the electric vehicle charging infrastructure. However, previous researches have focused on smart grid related security research such as power system infrastructure rather than charging infrastructure for electric vehicle charging. In addition, research on charging infrastructure is still lacking, and research using a systematic methodology such as threat modeling is not yet under way. Therefore, it is necessary to apply threat modeling to identify security threats and systematically analyze security requirements to build a secure electric vehicle charging infrastructure. In this paper, we analyze the electric vehicle charging infrastructure by accurately identifying possible threats and deriving objective security requirements using threat modeling including Data Flow Diagram, STRIDE, and Attack Tree.

• Journal of The Korean Society of Agricultural Engineers
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• v.61 no.5
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• pp.49-55
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• 2019

This study attempted to investigate the changes in the perception of local government officials about agricultural infrastructure improvement projects due to the financial policy changes. A total of 141 local government officials were surveyed on the priority, the current status of the agricultural infrastructure improvement projects. Irrigation facilities renovation project and Small drainage improvement project had generally high priority, while Support project of cultivation basis for upland crops in paddy, Large scale land readjustment project, and Upland infrastructure improvement project had low priorities. After the introduction of the block grant system, agricultural infrastructure improvement projects had often been conducted by collecting opinions from local residents. The officials in charge of local governments recognized that the agricultural infrastructure improvement projects were reduced due to lack of financial resources and project potential sites. In response to the changes in the agricultural infrastructure improvement projects, most of the surveys showed that the influence of cities and provinces was strengthened. In addition, respondents most needed to improve the subsidy rate and there were a large number of cases requiring differential support to meet the characteristics of the local government. Therefore, it will be necessary to present a new perspective on the agricultural infrastructure improvement projects and to suggest differentiated projects for each regions.

• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.17-29
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• 2020

The objective of this study was to find an optimum methane yield condition in anaerobic digestion of sewage sludge with microwave pretreatment. The pretreatment process was carried out using a lab scale industrial microwave unit (2,450 MHz frequency). The digestion efficiency of pretreated sludge was evaluated by biochemical methane potential (BMP) test. Box-Behnken design and Response Surface Analysis (RSA) were applied to determine the optimal combination of sludge mixing ratio (0 to 100%), power (400 to 1600 W), holding time (0 to 10 min) and pretreatment temperature (60 to 100℃). BMP test results showed that Volatile Solid (VS) removal efficiency was up to 48% at a condition of 0% for mixing ratio, 1600 W for power, 5 min for holding time, and 80℃ for pretreatment temperature. Methane production was up to 832.3 mL/g VS_removed at a condition of 50% for mixing ratio, 1000 W for power, 5 min for holding time, and 80℃ for pretreatment temperature. The results of the variance analysis (ANOVA) showed that the p-value of the power and pretreatment temperature among the independent variables were significant (p<0.05), and in particular, the pretreatment temperature significantly affected on the solubilization and methane production. The optimum condition for the maximum methane yield (847 mL/g VS_removed) was consist of 38.4% of mixing ratio, 909.1 W of power, 4.1 min of holding time, and 80℃ of temperature within the design boundaries.

• The Journal of The Korea Institute of Intelligent Transport Systems
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• v.21 no.6
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• pp.194-210
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• 2022

The user-centered EV charging infrastructure construction policy the government is aiming for can increase convenience for electric vehicle users and bring new electric vehicle users into the market. This study was conducted to provide an in-depth understanding of the charging behaviors of actual electric vehicle users, which can be used as basic information for the electric vehicle charging infrastructure. Based on charging diary data collected for a week, the charging of electric vehicles was analyzed on a daily and weekly basis, and sequence analysis and latent class analysis were used. As a result, five daily charging profiles and four weekly charging profiles were identified, which are expected to contribute to revitalizing the electric vehicle market by providing key information for decision-making by potential electric vehicle users as well for establishing user-centered charging infrastructure policies in the future.

• Proceedings of the KSR Conference
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• 2011.05a
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• pp.1572-1581
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• 2011

Since 'The Act on Private Investment of The Infrastructure' was established in 1994, private investment as well as government's investment has been active on transport infrastructure. But investment of transport infrastructure has more risks than others due to overforecast of transport demand for ensuring project validity, and cost uncertainty arising from financial crisis, commodity prices and so on. In the case of Incheon international airport express, after 2 years and 6 months, Incheon international airport express is opened, Korail take over equity stake in private investor due to the problems of MRG(Minimum Revenue Guarantee) be contracted with private investor. Not only that, in other case of Yong-in light rail, it is ongoing for legal disputes between Yong-in local government and private investor on account of opening delaying. On current Investment Assessment System of Transport Infrastructure, Risk Management system on investment of transport infrastructure is inadequate because Sensitivity Analysis in economic efficiency have been performed on the simple method which only changes benefits, expense and social discount rate. For this reason, this study analyze risks for investment of transport infrastructure demand forecast, and rise to the management practice for every particular item.

• Journal of the Earthquake Engineering Society of Korea
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• v.17 no.6
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• pp.293-303
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• 2013

This paper deals with steel braced frame as increasing the lateral strength and ductility in order to seismic retrofit of existing buildings and discusses the designing criteria and calculation method of retrofitted buildings. The addition of steel braced frame can be effective for increasing the lateral strength and ductility of existing buildings. However, There is a problem in utilizing this method. It is the approach to provide an adequate connection between the existing RC frame and the installed steel braced frame, because global strength by failure mode(three type) depends on detail of connection and strength of existing RC frame. So, the designer must be confirmed if it satisfies the required performance or not. Failure mode of type I is the most appropriate for increasing the lateral strength and ductility. Seismic performance evaluation and strength calculation of seismic retrofit are performed by guideline by KISTEC(Korea Infrastructure Safety & Technology)'s "seismic performance evaluation and rehabilitation of existing buildings" and Japan Building Disaster Prevention Association. Buildings are modeled and non-linear pushover analysis are performed using MIDAS program.

• Journal of the Korean BIBLIA Society for library and Information Science
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• v.14 no.2
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• pp.119-140
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• 2003

The purpose of this paper is to suggest guidelines for building up an integrated information network(IIN) model that enables to enhance production, flow and use of knowledge and information. The IIN consists of four areas of key infrastructure, such as, education, labor market, school-industry cooperation, and lifelong education information infrastructure. Based on the analysis of current situations and problems of each information infrastructure, this paper raises variety of issues and solutions for the IIN model. Directions for building up the IIN includes both information base infrastructure and information support infrastructure.

• International conference on construction engineering and project management
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• 2009.05a
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• pp.83-90
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• 2009

Natural disasters, such as the recent floods in the Midwest, Hurricane Ike in the Gulf coast region (U.S.), and the earthquake in Sichuan (China), cause severe damage to the infrastructure as well as the associated industries and communities that rely on the infrastructure. The estimated damages due to Hurricane Ike in 2008 were a staggering $27 billion, the third worst in U.S. history. In addition, the worst earthquake in three decades in Sichuan resulted in about 90,000 people dead or missing and $20 billion of the estimated loss. A common observation in the analyses of these natural disaster events is the inadequacy of critical infrastructure to withstand the forces of natural calamities and the lack of mitigation strategies when they occur on the part of emergency-related organizations, industries, and communities. If the emergency-related agencies could identify and fortify the vulnerable critical infrastructure in the preparedness stage, the damage and impacts can be significantly reduced. Therefore, it is important to develop a decision support system (DSS) for identifying region-specific mitigation strategies based on the inter-relationships between the infrastructure and associated industries and communities in the affected region. To establish effective mitigation strategies, relevant data were collected from the affected areas with respect to the technical, social, and economic impact levels. The data analysis facilitated identifying the major factors, such as vulnerability, criticality, and severity, for developing a DSS. Customized mitigation strategies that will help agencies prepare, respond, and recover according to the disaster response were suggested.

• International conference on construction engineering and project management
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• 2022.06a
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• pp.984-991
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• 2022

The use of the sustainability rating systems in infrastructure construction projects is not as common in comparison to building construction projects. While the sustainability rating systems share some commonalities, they differ from one another in certain ways. Thus, project teams cannot make reliable decisions when choosing the best sustainability rating tools for a given infrastructure projects. The Department of Transportation (DOT) in several states are developing its own rating system to address the infrastructure sustainability, but not in the case of California. Therefore, this paper presents the statistical results on the important sustainability determinants that affects the success of meeting sustainability goals of infrastructure construction projects. The authors conducted an online survey using the structured questionnaires. The categories considered include site, water/wastewater, energy, materials/resources, environmental, and others. The statistical analyses such as Kruskal-Wallis and ANOVA are conducted using a total of 25 valid and complete data out of 59 surveys collected. The results demonstrate several factors under each of six major sustainable categories have received higher ranks than other factors. The results also show that a statistically significant difference can be found from water, energy, and environmental categories against the other category based on the pairwise comparisons.