• Advances in concrete construction
• /
• v.7 no.2
• /
• pp.87-96
• /
• 2019

Self-compacting concretes (SCC) are highly fluid concrete which can flow without any vibration. Their composition requires a large quantity of fines to limit the risk of bleeding and segregation. The use of crushed sand rich in limestone fines could be an adequate solution for both economic and environmental reasons. This paper investigates the influence of quarry limestone fines from manufactured crushed sand on rheological, mechanical and durability properties of SCC. For this purpose, five mixtures of SCC with different limestone fines content as substitution of crushed sand (0, 5, 10, 15 and 20%) were prepared at constant water-to-cement ratio of 0.40 and $490kg/m^3$ of cement content. Fresh SCC mixtures were tested by slump flow test, V-funnel flow time test, L-box height ratio, segregation resistance and rheological test using a rheometer. Compressive and flexural strengths of SCC mixtures were evaluated at 28 days. Regarding durability properties, total porosity, capillary water absorption and chloride-ion migration were studied at 180 days. For the two test modes in fresh state, the results indicated compatibility between slump flow/yield stress (${\tau}_0$) and V-funnel flow time/plastic viscosity (${\mu}$). Increasing the substitution level of limestone fines in SCC mixtures, contributes to the decrease of the slump flow and the yield stress. All SCC mixtures investigated achieved adequate filling, adequate passing ability and exhibit no segregation. Moreover, the inclusion of limestone fines as crushed sand substitution reduces the capillary water absorption, chloride-ion migration and consequently enhances the durability performance.

• Journal of the Korean GEO-environmental Society
• /
• v.20 no.12
• /
• pp.57-64
• /
• 2019

A man-made slope has been increased due to the construction of road. This slope lies at risk of rock falling, induced mostly by heavy rainfall. The MOLIT (Ministry of Land, Infrastructure and Transport) recommends the specific dimension of rockfall protection fence (post, wire-rope, and mesh) which should resist 48~61 kJ. However, the energy absorption capacity of each component of rockfall protection fence is not clearly presented. Hence, this study made an effort to compute the energy absorption capacity of each component in analytical and numerical method, and compared with each other.

• Journal of Radiation Protection and Research
• /
• v.46 no.1
• /
• pp.24-31
• /
• 2021

Decommissioning efforts are underway at the reactor where the accident occurred, namely the damaged Tokyo Electric Power Company (TEPCO) Fukushima Daiichi Nuclear Power Plant (FDNPP). However, a large amount of groundwater flowing into the site has become contaminated with radioactive substances and is stored in tanks on site, which has hampered the decommissioning work. Although the inflow of groundwater has been greatly reduced through measures such as the construction of frost walls, approximately 170 ㎥ of water treated by the Advanced Liquid Processing System (ALPS) is being stored in tanks, each day. The tanks used to store this treated water are expected to become full by around the summer of 2022. It is not easy to get people to understand the efforts of all concerned parties, and providing clear information to these concerned parties is also a challenge. Questions have also been raised regarding whether other alternatives have been fully explored in the ALPS subcommittee. Some people have commented that the answers to the questions raised regarding the biological effects of tritium transmutation are inadequate. Some suspect that the answers are too detailed and incomprehensible, and that the respondents may be manipulating the public with some malicious intent. In any case, each possible plan presents both advantages and disadvantages, depending on the people who are involved. That makes it an ethical and vexing issue that can sway decisions, as perspectives change. While the environmental release plan is scientifically safe, it may represent a painful alternative. On the other hand, a more careful and imaginative approach to the idea of continued storage in tanks or other forms of storage may reveal some troublesome hidden disadvantages. Under these circumstances, experts must be prepared to answer people's questions in a comprehensive and robust manner.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.35 no.2
• /
• pp.3-11
• /
• 2019

The recent earthquake of Pohang (M5.4) and the Gyeongju earthquake (M5.8) suggested the possibility of a strong earthquake in Korea and reminded us that the Korea is no longer an earthquake-safe zone. In the disaster recovery stage in a disaster like an earthquake, the investigation of the damage situation and the safety assessment of the building serve to provide important information for the initial action such as establishment of the recovery strategy and rescue of the survivor. However, the research that depends on manpower can not cope with the difficulty of processing a large number of doses in a short time, and the expertise of the manpower must be taken into consideration, which may result in delayed initial action. In this study, we propose an rapid safety evaluation technique of building using unmanned aerial vehicle which evaluates the performance and safety of buildings by integrating conventional safety inspection method with unmanned aerial vehicle technology and developed evaluation method of each evaluation factor. In order to verify this, the buildings damaged by the earthquake in Pohang were checked and compared using this system. The results are consistent with the results of the existing emergency earthquake risk assessment. As a result, the possibility of checking the emergency safety using the unmanned aerial vehicle for the damaged structures in case of a large-scale disaster such as an earthquake was confirmed.

• Journal of the Architectural Institute of Korea Structure & Construction
• /
• v.33 no.12
• /
• pp.91-98
• /
• 2017

In this study, the effect of window installation position in the residential building with the external insulation was numerically investigated in terms of insulation performance and heating/cooling energy consumption. For different window positions, 2-D heat transfer simulation was conducted to deduce the linear thermal transmittance, which was inputted to the dynamic energy simulation in order to analyze heating/cooling energy consumption. Simulation results showed that the linear thermal transmittance ranges from 0.05 W/mK to 0.7 W/mK, and is reduced as the window is installed near the external finish line. Indoor surface temperature and TDR analysis showed that the condensation risk is the lowest when the window is installed at the middle of the insulation and wall structure. It was also found that the window installation near the external finish can reduce the annual heating/cooling energy consumption by 12~16%, compared with the window installation near the interior finish. Although the window installation near the external finish can achieve the lowest heating/cooling energy consumption, it might lead to increased condensation risks unless additional insulation is applied. Thus, it can be concluded that the window should be installed near the insulation-wall structure junction, in consideration of the overall performance including energy consumption, condensation prevention and constructability.

• Journal of Korean Society of Disaster and Security
• /
• v.13 no.4
• /
• pp.93-104
• /
• 2020

Climate change has emerged as a social issue, and efforts have been made to overcome it in various ways. However, climate change due to global warming is likely to accelerate further than we expected, and the associated damage is also likely to increase. This tendency is expected to continue in the future, leading to difficulties for the existing water resource management system based on historical data. The precipitation in 2020 caused property damage and loss of life due to the extreme rainfall exceeding the design rainfall with the very unusual prolonged rainy days. With this 2020 flood, we should no longer be passive in managing flood risk due to uncertainties in climate change.

• Journal of Convergence for Information Technology
• /
• v.11 no.3
• /
• pp.107-124
• /
• 2021

This study is a study on the innovation resistance that may arise in connection with the introduction and use of smart factory-related technologies by SMEs. It is to study the effect of the leading factors of innovation resistance on innovation resistance and the effect of innovation resistance on use intention by using the extended innovation resistance model. A total of 176 survey data were used for the study, and the study was conducted using SPSS 25 and Smart PLS 2.0. Relative advantage, suitability, perceived risk, social impact, and organizational characteristics have a significant effect on innovation resistance, and innovation resistance was tested to have a significant effect on the intention to use. As an implication according to the research, a plan to improve the level of introduction and use of smart factories using the expanded innovative storage model was presented by dividing positive and negative factors, and factors that should be improved and factors that should be reduced are presented. It was specifically presented.

• Journal of the Korean Institute of Gas
• /
• v.26 no.1
• /
• pp.7-19
• /
• 2022

Hydrogen purification is generally performed through chemical and physical methods. Among various types of purification method PSA(Pressure Swing Adsorption) is widely used with its purification capacity and economic efficiency. In Korea, most of the hydrogen used in automobiles and power generation fuel cells is purified using PSA. Hydrogen produced in petrochemical complexes has difficulties in transportation. The government is planning to install hydrogen extractors that produce hydrogen directly from consumers in connection with the city gas supply chain, and companies are also installing related research and demonstration facilities one after another. Europe and others have recently established safety standards related to PSA and are making efforts for systematic safety management at the construction and operation stage, but domestic safety standards related to PSA are still insufficient. This study aims to identify problems of existing facilities through surveys and risk assessment by companies operating existing PSA, and to prepare domestic technical standards including them in overseas technical standards to promote the safety of new and existing PSA systems.

• Journal of Soil and Groundwater Environment
• /
• v.27 no.spc
• /
• pp.64-74
• /
• 2022

The conceptual site model (CSM) is used as a key tool to support decision making in risk based management of contaminated sites. In this work, CSM was applied in Jeonju Industrial Complex where site investigation for groundwater contamination was conducted. Site background information including facility types, physical conditions, contaminants spill history, receptor exposure, and ecological information were collected and cross-checked with tabulated checklist necessary for CSM application. The CSM for contaminants migration utilized DNAPL transport model and narrative CSMs were constructed for source to receptor pathway, ecological exposure route, and contaminants fate and transport in the form of a diagram or flowchart. The component and uncertainty of preliminary CSM were reviewed using the data gap analysis while taking into account the purpose of the survey and the site management stage at the time of the survey. Through this approach, the potential utility of CSM was demonstrated in the site management process, such as assessing site conditions and planning follow-up survey work.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.42 no.1
• /
• pp.135-144
• /
• 2022

This paper aimed to analyze the type of urban shrinkage over the past 20 years for four case cities designated as abandoned mining area promotion zones and present the direction of future urban spatial policies through the analysis of shrinking status. According to the analysis of urban shrinkage in the past 20 years, all of the case cities were analyzed as fixed-type shrinking cities, showing a population decrease of more than 30% over the past 40 years compared to the peak population. Despite the decrease in population, the designated area of urbanization and non-urban areas is increasing every year, and the development permit and construction permit in non-urban areas are also increasing, requiring efficient management and operation of urban space. It is necessary to study military-level cities in the high-risk phase of extinction in the future, and to develop various indicators for segmentation of urban shrinkage types and analysis of status by type.