• Journal of the Korea institute for structural maintenance and inspection
• /
• v.25 no.1
• /
• pp.33-40
• /
• 2021

In recent years, many construction projects become large and complicated, and construction accidents also steadily increase, which grows interest in the safety and maintenance during construction. Many of the construction accidents are related to temporary construction and structures, but the safety evaluation and management during construction are unclear and indefinite due to the short operating period and continuous change in the formation of the temporary structure. The system support, which is one of the temporary structures to support the pouring load of concrete, was proposed to easily install and dismantle members with connection parts pre-manufactured. The use of the system support is increasing to improve the safety of the temporary structure during construction. However, the system support, which consists of multiple members, still has uncertainties in connectivity between members and supports of vertical members. Therefore, this study analyzed the structure, load, and accident cases of the system support to define the damage scenarios for member connection, support condition, and lateral displacement. The decrease rate of the critical load was analyzed according to the damage scenarios based on the defined unit structure of the system support. In addition, this study provided vulnerable members for each damage scenario, which could induce instability of the temporary structures during design, construction, and operation of the structure.

• Korean Journal of Construction Engineering and Management
• /
• v.18 no.2
• /
• pp.81-90
• /
• 2017

In Imjin River basin, three floods occurred between 1996 and 1999, causing many casualties and economic losses of 900 billion won. In Korea, flood damage is expected to increase in the future due to climate change. This study used the climate scenarios to estimate future flood damage costs and suggested a real options-based economic assessment method. Using proposed method, the flood control infrastructures in Imjin River basin were selected as a case study site to analyze the economic feasibility of the investment. Using RCP (Representative Concentration Pathway) climate scenarios, the future flood damage costs were estimated through simulated rainfall data. This study analyzed the flood reduction benefits through investment in the flood control infrastructures. The volatility of flood damage reduction benefits were estimated assuming that the RCP8.5 and RCP4.5 climate scenarios would be realized in the future. In 2071, the project option value would be determined by applying an extension option to invest in an upgrading that would allow the project to adapt to the flood of the 200-year return period. The results of the option values show that the two investment scenarios are economically feasible and the project under RCP8.5 climate scenario has more flood damage reduction benefits than RCP4.5. This study will help government decision makers to consider the uncertainty of climate change in the economic assessment of flood control infrastructures using real options analysis. We also proposed a method to quantify climate risk factors into economic values by using rainfall data provided by climate scenarios.

• Journal of Conservation Science
• /
• v.33 no.3
• /
• pp.189-201
• /
• 2017

This study focused on the Gaya mural tomb located in Goa-ri, Goryeong-gun, North Gyeongsang Province, Republic of Korea. Environmental factors such as ambient temperature, relative humidity and surface temperature, and microbial distribution on mural tombs were monitored for one year to gather data on the conservation environment of the mural tombs. The average internal temperature difference with reference to the ambient outer temperature was observed to be $11.7^{\circ}C$ for the monitoring period and the internal temperature of the tomb was found to change periodically every one or two months in response to the outer temperature. The highest temperature was observed in September and the lowest in March. The relative humidity in the mural tomb remained constant at 100%. Between December and April, condensation occurred on the ceiling of the main room of the tomb, where the murals are located. On the ceiling of the aisle, the condensation occurred throughout the year. The inside and surface wall were isolated from microorganisms, which could grow when a suitable growth environment suitable is established. Based on microbial growth temperature conditions, risk periods of microbial hazards were established, where in the period from August to October was identified as the most dangerous.

• Wind and Structures
• /
• v.23 no.2
• /
• pp.157-169
• /
• 2016

The structural integrity of tube bundles represents a major concern when dealing with high risk industries, such as nuclear steam generators, where the rupture of a tube or tubes will lead to the undesired mixing of the primary and secondary fluids. Flow-induced vibration is one of the major concerns that could compromise the structural integrity. The vibration is caused by fluid flow excitation. While there are several excitation mechanisms that could contribute to these vibrations, fluidelastic instability is generally regarded as the most severe. When this mechanism prevails, it could cause serious damage to tube arrays in a very short period of time. The tubes are therefore stiffened by means of supports to avoid these vibrations. To accommodate the thermal expansion of the tube, as well as to facilitate the installation of these tube bundles, clearances are allowed between the tubes and their supports. Progressive tube wear and chemical cleaning gradually increases the clearances between the tubes and their supports, which can lead to more frequent and severe tube/support impact and rubbing. These increased impacts can lead to tube damage due to fatigue and/or wear at the support locations. This paper presents simulations of a loosely supported multi-span U-bend tube subjected to turbulence and fluidelastic instability forces. The mathematical model for the loosely-supported tubes and the fluidelastic instability model is presented. The model is then utilized to simulate the nonlinear response of a U-bend tube with flat bar supports subjected to cross-flow. The effect of the support clearance as well as the support offset are investigated. Special attention is given to the tube/support interaction parameters that affect wear, such as impact and normal work rate.

• Asian Pacific Journal of Cancer Prevention
• /
• v.15 no.13
• /
• pp.5253-5257
• /
• 2014

Formaldehyde (FA) is an economically important chemical, and has been found to cause various types of toxic damage to the body. Formaldehyde-induced toxic damage involves reactive oxygen species (ROS) that trigger subsequent toxic effects and inflammatory responses, which may increase risk of cancer. Therefore, in the present study, we aimed to investigate the possible toxic mechanism in bone marrow caused by formaldehyde. In accordance with the principle of randomization, the mice were divided into four groups of 6 mice per group. One group was exposed to ambient air and the other three groups were exposed to different concentrations of formaldehyde (20, 40, $80mg/m^3$) for 15 days in the respective inhalation chambers, 2h a day. At the end of the 15-day experimental period, all mice were killed. Bone marrow cells were obtained. Some of those were used for the determination of blood cell numbers, bone marrow karyote numbers, CFU-F, superoxide dismutase (SOD) activity and malondialdehyde (MDA) content; others were used for the determination of mitochondrial membrane potential (MMP), cell cycle and Bcl-2, Bax, CytC protein expression. WBC and PLT numbers in median and high dose groups were obvious reduced, but there was no change on RBC numbers. There was also reduced numbers of bone marrow karyotes and CFU-F in the high dose group. SOD activity was decreased, but MDA content was increased. MMP and Bcl-2 expression were decreased with increasing formaldehyde concentration, while expression of Bax and Cyt C was increased. We also observed change in cell cycling, and found that there was S phase arrest in the high dose group. Our study suggested that a certain concentration of formaldehyde could have toxic effects on the hematopoietic system, with oxidative stress as a critical effect.

• Journal of the Korean Society of Safety
• /
• v.39 no.3
• /
• pp.1-6
• /
• 2024

Polyester round slings are widely utilized in various work environments due to their lightweight, flexible nature and smooth surface that minimizes the risk of cargo abrasion or damage. However, specific guidelines intended to protect round slings from the damage caused by the sharp edges of cargo, thus preventing accidents in case the cargo falls, are lacking in South Korea. In this study, a comparative analysis was conducted on the regulations and guidelines related to round slings in South Korea and the United States. Further, experiments were carried out to determine the relationship between round slings and lifting accessories. The research identified specific shortcomings in the user manuals provided by round-sling manufacturers. Accordingly, certain measures were proposed for enhancing the operational safety of round slings: 1) establish criteria for edge protection of polyester round slings and 2) recommend standardization of the information provided by manufacturers. As developing new standards is a time-consuming task, this study proposes a method for enhancing the operational safety of round slings in the short term by introducing established safety standards from the United States-where safety has been proven over a considerable period of time-into the domestic context. In addition, it is recommended that edge criteria be permanently printed on the labels of round slings.

• Journal of Korean Society of Disaster and Security
• /
• v.16 no.4
• /
• pp.33-43
• /
• 2023

The impact of prolonged rainfall, such as during the monsoon season or intense concentrated rainfall over a short period, can lead to mountainous disasters such as landslides and debris flows. These events, such as landslides and debris flows, cause both human and material damage, prompting the implementation of various measures and research to prevent them. In the context of researching debris flow disasters, numerical models for debris flows provide a relatively simple way to analyze the risk in a study area. However, since empirical equations are applied in these models, yielding different results and variations in input variables across models, the validation of numerical models becomes essential. In this study, a numerical model for debris flows was employed to compare and analyze the mitigation effects of facilities such as check dams and water channel work, aiming to reduce the damage caused by debris flows.

• Journal of Industrial Convergence
• /
• v.21 no.7
• /
• pp.29-39
• /
• 2023

In the recent period, there have been numerous earthquakes both domestically and internationally, and buildings in South Korea are particularly vulnerable to seismic design and earthquake damage. Therefore, the objective of this study is to discover an effective method for assessing the seismic vulnerability of buildings and conducting a density analysis of high-risk structures. The aim is to model this approach and validate it using data from pilot area(Seoul). To achieve this, two modeling techniques were employed, of which the predictive accuracy of the statistical analysis technique was 87%. Among the machine learning techniques, Random Forest Model exhibited the highest predictive accuracy, and the accuracy of the model on the Test Set was determined to be 97.1%. As a result of the analysis, the district rating revealed that Gwangjin-gu and Songpa-gu were relatively at higher risk, and the density analysis of at-risk buildings predicted that Seocho-gu, Gwanak-gu, and Gangseo-gu were relatively at higher risk. Finally, the result of the statistical analysis technique was predicted as more dangerous than those of the machine learning technique. However, considering that about 18.9% of the buildings in Seoul are designed to withstand the Seismic intensity of 6.5 (MMI), which is the standard for seismic-resistant design in South Korea, the result of the machine learning technique was predicted to be more accurate. The current research is limited in that it only considers buildings without taking into account factors such as population density, police stations, and fire stations. Considering these limitations in future studies would lead to more comprehensive and valuable research.

• Earthquakes and Structures
• /
• v.12 no.5
• /
• pp.489-499
• /
• 2017

The effects of past earthquakes have demonstrated the seismic vulnerability of confined masonry structures (CMSs) to earthquakes. The results of experimental analysis indicate that damage to these structures depends on lateral displacement applied to the walls. Seismic evaluation lacks an analytical approach because of the complexity of the behavior of this type of structure; an empirical approach is often used for this purpose. Seismic assessment and risk analysis of CMSs, especially in area have a large number of such buildings is difficult and could be riddled with error. The present study used analytical and numerical models to develop a simplified nonlinear displacement-based approach for seismic assessment of a CMS. The methodology is based on the concept of ESDOF and displacement demand and is compared with displacement capacity at the characteristic period of vibration according to performance level. Displacement demand was identified using the nonlinear displacement spectrum for a specified limit state. This approach is based on a macro model and nonlinear incremental dynamic analysis of a 3D prototype structure taking into account uncertainty of the mechanical properties and results in a simple, precise method for seismic assessment of a CMS. To validate the approach, a case study was considered in the form of an analytical fragility curve which was then compared with the precise method.

• KCID journal
• /
• v.17 no.2
• /
• pp.105-114
• /
• 2010

Tidal land reclamation provided water resources and land for agriculture and contributed stable crop production. However, climate change by global warming disrupts the hydrologic circulatory system of the earth resulting in sea level rise and more frequent flood for reclaimed arable land. Recently, Suyu reclaimed paddy field in Jindo-gun experienced prolonged inundation after heavy rainfall and there is a growing risk of flood damage. Onsite survey and flood analysis using GATE_Pro model of Korea Rural Corporation were conducted to investigate causes of flooding. To perform the analysis, input data such as inflow hydrograph, the lowest elevation of paddy field, neap tide level, management level of Gunnae estuary lake at the time of the flood were collected. Flood analysis confirmed that current drainage facilities are not enough to prevent 20year return period flood. The result of analysis showed flooding more than 24hours. Therefore, flood mitigation alternatives such as sluice gate expansion, installation drainage pumping station, refill paddy land, and catch canal were studied. Replacing drainage culvert of Suyu dike to sluice gate and installing drainage pumping station at the Gunne lake were identified as an effective flood control measures. Furthermore, TM/TC (SCADA) system and expert for gate management are required for the better management of drainage for estuary dam and flood mitigation.