This study analyzed the characteristics of insulation resistance and operating time based on an accelerated degradation test of a low-voltage circuit breaker. The experimental sample used a molded case circuit breaker (MCCB) and an earth leakage circuit breaker (ELCB). After measuring the insulation resistance of the circuit breakers, the leakage current was affected by an external rather than an internal structure. Furthermore, the insulation resistance of the circuit breakers with accelerated degradation was measured using a Megger insulation tester. In the accelerated degradation test, aging times of five, ten, 15, and 20 years were applied according to a temperature derived using the Arrhenius equation. Circuit breakers with an equivalent life of ten, 15, and 20 years had increased insulation resistance compared to those with less degradation time. In particular, the circuit breaker with an equivalent life of ten years had the highest insulation resistance. Component analysis of the circuit breaker manufactured through an accelerated degradation test confirmed that the timing of the increase in insulation resistance and the time of additive loss were the same. Finally, after analyzing the operating time of the circuit breakers with degradation, it was confirmed that the MCCB did not change, but the ELCB breaker failed.

Qualifying quantities (upper tier (UT) and lower tier (LT)) are designated for the regulation of toxic substances. In this study, we aimed to establish systematic criteria for the qualifying quantities by comparing the South of Korea chemical control act with the European Seveso III Directive (Seveso III). In Seveso III, qualifying quantities are defined as "hazard categories" applying GHS (Globally Harmonized System of Classification and Labelling of Chemicals), and LTR (lower-tier requirements) and UTR (upper-tier requirements) are determined. The Pro HC (proposed hazard categories) were relevant to the GHS classification of toxic substances and were compared with the currently regulated qualifying quantities. Furthermore, we estimated the Pro LTR (proposed lower-tier requirements) and Pro UTR (proposed upper-tier requirements) corresponding to each Pro HC. Consequently, it was supposed that LT and UT were selected based on GHS like those of Seveso III. Therefore, designation criteria for qualifying quantities should be established by setting the Pro HC such as in Seveso III, rather than designating the qualifying quantities of toxic substances by itself individually. In addition, qualifying quantities should not be delegated to GHS classifications (H302, H341, H411) that do not meet the criteria for the designation of toxic substances, and the corresponding substances should be excluded from classification as toxic substances. This study provides insights into the selection of hazard categories and criteria for qualifying quantities of toxic substances.

Hydrogen is a clean fuel and is used in many applications in power systems such as fuel cells. It has unique properties such as wide flammability, high burning velocity, and difficulty to liquefy, which lead to critical safety issues. Fire and explosion are the most frequently occurring accidents and one of the major reasons is autoignition. In the ignition process, the chemistry of hydrogen combustion depends mainly on radical pools, and the temperature at which chain-branching and terminating rates are equal is called the crossover temperature. This study addresses the homogeneous autoignition of diluted hydrogen-air mixtures to investigate the effects of dilution on the crossover temperature to prevent explosions in the future. The new criterion for crossover temperature is introduced by only hydrogen radicals to adjust more simply. The detailed calculations indicate that the crossover temperatures are low at high dilutions of carbon dioxide and nitrogen because the concentrations of active radicals are reduced when an inert gas is added. This result is expected to contribute to hydrogen safety and realize a hydrogen society in the future.

In this study, the spill and leak system is developed to provide real-time remote monitoring of industrial complexes where chemical accidents have been occurring every year. The spill and leak monitoring system uses IR-RCD equipment mounted on a 70m-high steel tower to detect chemical substances, thereby detecting chemical accidents such as leaks, fires, and explosions in real time. If IR-RCD equipment can actually detect chemical substances at a long distance, accurate and rapid initial response can be expected. Therefore, in order to confirm that IR-RCD equipment can detect chemical leakage accidents occurring at a long distance, acetone was selected as the experimental substance and a detection experiment was designed. The experiment was conducted using the acetone pool evaporation method at the wharf which was located 1.5 km away from IR-RCD equipment, and it was confirmed whether IR-RCD equipment could detect acetone in real time through the control monitor.

This study analyzed the relationship between occupational accidents in the construction industry and business cycle factors. Multiple regression analyses were conducted to achieve the research purpose; additionally, time-varying parameter estimations were performed to interpret the results. The results obtained for the construction industry revealed a statistically significant relationship between occupational accidents and wage increase rate, unemployment, construction starts, and other factors. The wage increase rate plays a role in reducing occupational accidents because efforts are made to prevent accidents owing to the increase in income loss due to accidents and the demand for increased safety levels. The number of construction starts affects occupational accidents with a time lag of 1 to 2 or 4 months; therefore, it is likely to be used as a leading indicator for estimating fatal accidents in the construction industry. This study highlighted the importance of monitoring socioeconomic changes that could affect the working conditions of workers and workplaces, and production activities in the workplace for the effective prevention of occupational accidents. This study also reveals the necessity of developing a method to operate prevention projects flexibly and the seasonality of industrial characteristics, particularly those of the construction industry where the highest number of fatal occupational injuries occur.

Simple statistical frequency based analysis, such as Pareto analysis, are widely used in conventional accident analysis. However, due to the dynamic and complex nature of construction works, many factors can simultaneously affect or involve the occurrence of accidents in construction projects. Therefore, the identification of the complex relationship between such factors is important to establish relevant and effective safety management policies and/or programs. In this study, characteristic factors and their relationships' contribution to non-fatal accidents in construction projects are analyzed using the association rule mining (ARM) technique. To this end, a total of 59,202 construction accident data are collected from 2015 to 2019 and the ARM is performed to retrieve specific relationships -named as association rules-among classified factors in the data. Characteristics of the retrieved relationships are analyzed and compared with the results of conventional Pareto analysis. Based on the results, it is found that both fall and trip are notable accident forms having characteristic relations with other factors for non-fatal accidents in construction projects. It is also found that small-scale construction, age of 50s, less than 1 month of working period, and architectural construction are important factors for non-fatal accidents in construction projects.

In the Construction Technology Promotion Act (CTPA) of the Republic of Korea, safety management cost is enforced as a statutory cost that must be included in the budget of construction projects. However, the construction of underground electric power transmission facilities (UEPTFs) is not included in the category of construction works defined in the CTPA. Consequently, the statutory safety management cost does not apply to the construction of UEPTFs. To overcome this limitation, the clients of UEPTF construction projects generally provide internal guidelines enabling the addition of the safety management cost in the project budget. Nevertheless, even after the execution of the internal guidelines, some important cost items are omitted from the budget owing to the incompleteness of the guidelines. In this context, this paper proposes a complete set of accounting items and their calculation methods for appropriate budgeting of the safety management cost of UEPTF construction projects. To this end, the current budgeting method of the safety management cost of UEPTF construction projects is analyzed, and a questionnaire study is performed to confirm the necessary cost items and their appropriate calculation methods. Based on the results of the questionnaire study, a set of accounting items and their calculation criteria for the budgeting of the safety management cost of UEPTF construction projects are proposed.

This paper proposes an optimal design method of a seismic reinforcement system for the seismic performance of adjacent asymmetric-stiffness structures with viscous dampers. The first method considers plan asymmetry for efficient seismic reinforcement, and evaluates the seismic performance of optimal design applied to two cases of modeling: adjacent stiffness-asymmetric structures and adjacent stiffness-symmetric structures. The second method considers the response of asymmetric structures to derive the optimal objective function, and evaluates seismic efficiency of the objective function applied to two cases of responses: horizontal displacement and torsion. Numerical analyses are conducted on 7- and 10-story structures with a uni-asymmetric-stiffness plan using six cases of historic earthquakes, normalized to 0.4g. The results indicate that the seismic performance is excellent as modeled by adjacent asymmetric-stiffness structures and how much horizontal displacement is applied as the objective function.

Since the 2000s, the demand for private demolition works has been gradually increasing as the apartment housing market has been led by redevelopment and reconstruction. In the case of the military, the Ministry of National Defense is consolidating troops from each military unit to reorganize the unit structure in accordance with Defense Reform 2.0; the plan includes reducing the garrison used by each unit to 70% of its current level. Accordingly, the demand for demolition work in the military is also expected to increase. However, the military regulations do not reflect the relevant laws that have been revised recently. This study identifies regulations and system improvements for demolition work suitable for the military based on an analysis of accident cases that have occurred during demolition work, of domestic and foreign laws and regulations related to military demolition work, and of the problems with current military safety management at each stage of planning, design, and construction. The study subsequently proposes improvements for military demolition work, including budget execution adjustment, the establishment of training courses, on-site inspections, the development of guidelines for military demolition work, the provision of risk assessment standards, and the need for the qualification of equipment operators.

It is necessary to better understand the effect of age-related degradation on the performance of reinforced concrete shear walls in nuclear power plants in order to ensure their structural safety in the event of earthquakes. Therefore, this paper studies seismic fragility of the typical shear wall in nuclear power plants under earthquake excitation Reinforced concrete shear wall is composed of wall, horizontal and vertical flanges. Due to characteristics of its geometry, it is difficult to predict the ultimate behavior of shear wall under earthquake excitation. In this study, for more realistic numerical simulation, the Latin Hyper-Cube (LHC) simulation technique was used to generate uncertain variables for the material properties of concrete shear walls. The effects of crack, characteristics of inelastic behavior of concrete, and loss of cross section were considered in the nonlinear finite element analysis. The effects of aging-related deterioration were investigated on the performance of reinforced concrete shear walls through analysis of undegraded concrete shear walls and degraded concrete shear walls. The resulting seismic fragility curves present the change of performance of concrete shear wall due to age-related degradation.

A method for measuring the length and slope of a temporary structure using an unmanned aerial vehicle (UAV) and 3D modeling method is proposed. The actual length and slope of the vertical member of the specimen were measured and compared with the measured values obtained by the proposed method for the specimens with and without the vertical protection net installed. Based on the result of measuring the length of the temporary structure specimen using the UAV and 3D modeling method, the measured value showed an error of 0.87% when compared to the actual length in the specimen without the vertical protection net installed. In addition, the error of the slope was 0.63°. It was thought that the proposed method could be usable for the purpose of finding parts in wrong installation state on the temporary structure and informing the manager in charge. However, in the case of the specimen with the vertical protection net, the measurement showed a 1.46% error in length and 2.77° difference in slope. Therefore, if a vertical protection net is to be installed in a temporary structure, the measurement accuracy should be improved by utilizing an image processing method, etc.

The Occupational Safety and Health Act holds that industrial safety helmets can be used as protective equipment to prevent the risk of injury in fall accidents. To better understand the importance given to PPE for the head, we analyzed the relevant regulations and guidelines in developed countries and reviewed the guidelines on testing safety helmets. The PPE regulations in Korea were notably different from those in other countries. First, except in Korea and Japan, safety helmets were used for protection against falling objects, flying objects, impact, or electric shock. However, the regulations did not recognize safety helmets as a PPE against fall hazards. Second, the impact energy applied on the helmet was within the range 50-100 J, and the helmet could protect only the upper part of the head against hazards such as the impact of falling objects, flying objects, etc. Third, in Korean regulations, the term "fall" was used in relation to the parts where the safety helmet was specified as a fall hazard PPE, unlike in other countries. We propose that the term "fall" should be revised to "shock" in Korean regulations for the safety helmet.

South Korea will soon be a super-aged society, as more than 20.6% of its population will be 65 years and older by 2025. As of 2022, 17.5% of the total population in South Korea is 65 years and older, which exceeds the set threshold for an aged society, where more than 14% of the population is 65 years and older. The proportion of older subway construction workers has increased. Aging workers and their work stress negatively impact their workability. A previous study demonstrated that the stress index measured using the uBioMacpa measurement device (Macpa stress index) had a significant correlation with work stress in South Korea. The device tests vascular health and measures stress levels via Macpa signal analysis. In this study, the pulse waves of subway construction workers were measured using uBioMacpa to identify their stress levels. The stress levels were analyzed by age, years of service, job position, employment type, and work type. Herein, these statistics could not be easily represented by a normal distribution; therefore, the Kruskal-Wallis test, a nonparametric statistical method, was used for the analysis of data. The results showed that age, job position, employment type, and working type affected the Macpa stress index and the stress levels of workers increased with age. In terms of job position, technical engineers were more stressed than other workers because of their poor working environment. In terms of employment type, daily-wage workers were more stressed than other workers. In terms of working type, tunneling, waterproofing, and construction scored the highest Macpa stress indexes without any significant difference, whereas earthworks scored the lowest. Based on the analysis of Macpa stress index, safety and health management plans were proposed to reduce the stress levels of workers. Moreover, a manual for efficient stress management must be developed for subway construction workers.

This study was conducted to examine the influence of different styles of attribution to fine dust on preventive behaviors. In addition, the mediating effect of risk perception on the relationship between attribution styles and preventive behaviors was examined. Survey data was collected from 930 Korean people from a variety of ages and regions, and a hierarchical multiple regression analysis was used to test the hypothesis. The results indicated that both external and internal attribution to fine dust had a significant positive effect on preventive behavior. The multiple regression analysis revealed that both knowledge and dread had a significantly positive effect on preventive behaviors. In addition, risk perception (knowledge and dread) partially mediated the relationship between the external attribution to fine dust and preventive behavior. However, internal attribution showed only a direct effect on protection behaviors. The significance and limitations of the study were also discussed.

This study analyzes the characteristics of occupational accidents of food delivery via motorcycle in terms of accident probability and work-days. Depending on their employment status, food-delivery workers were divided into "employed" workers (who work for restaurants) and "special-type" workers (who work for delivery platforms). Collected data include occupational accident-information during the last two years (1,468 cases for employed workers and 4,899 cases for special-type workers) and their risk information such as age, work experience, accident location, season of the accident, and weather conditions. The study finds that special-type workers had a significantly higher accident probability for the younger age group (80.8%), while employed workers had more accidents in both 20's or younger (34.9%) and 50's or older (25.4%). The number of work-days-lost was higher for special-type workers with less work experience, and it decreased with increasing work experience. Moreover, the chance for accidents was higher at night time (55%) than for day time (45%) for special-type workers as well as for employed workers. The number of work-days-lost was higher in foreign workers (180.79 days) than in Korean workers (121.44 days). Accident probability (30.7%) and work-days-lost (136.2 days) was higher in winter than in other seasons. In addition, accidents-per-day was higher on snowy days (12.7 cases per day) than rainy (8.1) and windy days (7.1). In addition, it was found that deadly accidents mainly caused injuries to face, head, and chest, while non-deadly accidents affected mainly the legs and feet. This study enables the development of better policies to prevent accidents of food delivery workers.

The comparative evaluation of occupational accident fatality rates (OAFRs) of different countries is complicated owing to the differences in their level of socio-economic development. However, such evaluation is necessary to assess the national occupational safety and health system of a country. This study proposes a statistical method to compare the OAFRs of countries taking into consideration the difference in their level of socio-economic development. We first collected data on the socio-economic indicators and OAFRs of 11 countries over a 30-year period. Next, based on literature survey and statistical correlation analysis, we selected the significant independent variables and built multiple linear regression models to predict OAFR. We also determined the groups of countries having heterogeneous relationships between the independent variables and OAFRs, which are represented by the regression models. The proposed method is demonstrated by comparing the OAFR of Korea with the OAFRs of 10 other developed countries.

The purpose of this study is to analyze four cases of firefighter burns in various fire scenes and to find prevention measures to decrease firefighter injuries. Among the analysis reports prepared by the National Fire Research Institute of Korea from 2016 to 2020, four burn-related accidents are summarized and the main causes are conveyed. The four accidents include second-degree burns from using extinguishers during containment of fires; nine firefighters burned due to re-ignition in the LPG car repair shop; two firefighters injured with third-degree burns from using fire extinguishers during life-saving events in residential housing; and injuries from the radiant heat of the tank BLEVE near the factory fire. These cases are comprehensively investigated in their respective scenes and analyzed based on the fire site investigation reports from the fire department and related theoretical explanations of risk for each accident scene. In the third case study, some experimental research is conducted to evaluate the risk involved with the use of safety gloves. This is evaluated by reviewing Fire Tactics and Standard Operational Procedures (SOP) to determine improvements and recommendations for an efficient firefighting response. Results show that the main causes of burn accidents are the insufficient use of personal protective equipment (PPE), such as safety gloves, and the failure to follow firefighting tactics or SOPs. Through the accident investigation and assessment, it is concluded that to reduce the frequency of burn accidents, the performance of firefighting equipment, SOPs, protection tactics, and safety policy systems require improvement.

Every year, particularly during the monsoon rainy season, landslides at the Chuncheon province of South Korea cause tremendous damage to lives, properties, and infrastructures. More so, the high rainfall intensity and long rainfall days that occurred in 2020 have increased the water content in the soil, thereby increasing the chances of landslide occurrences. Besides this, the rainfall thresholds and characteristics responsible for the initiation of landslides in this region have not been properly identified. Therefore, this paper addresses the rainfall thresholds responsible for the initiation of landslides at Chuncheon from a regional perspective. Using data obtained from rainfall measurements taken from 2002 to 2011, we identify a threshold relationship between rainfall intensity and rainfall duration for the initiation of landslides. In addition, we identify the relationship between the rainfall intensity using a 3-day, 7-day, and 10-day antecedent rainfall observation. Specifically, we estimate the rainfall data at 8 sites where debris flow occurred in 2011 by kriging. Following this, the estimated data are used to construct the relationship between the intensity (I), duration (D), and frequency (F) of rainfall. The results of the intensity-duration-frequency (IDF) analysis show that landslides will occur under a rainfall frequency below a 2-year return period at two areas in Chuncheon. These results will be effectively used to design structures that can prevent the occurrence of landslides in the future.

Eco-friendly policies proposed by the government of The Republic of Korea have encouraged the use of eco-friendly vehicles. Hydrogen vehicles have exhibited the highest growth rate, although the current number of registered vehicles is low. In hydrogen vehicles, a thermally activated pressure relief device (TPRD) is installed to prevent explosions in the hydrogen gas cylinder. When discharged due to low ignition energy, hydrogen gas readily forms a jet flame. The risks induced by such jet flames were analyzed through a numerical analysis. Jet flames can activate TPRDs installed in nearby hydrogen gas cylinders. As a result, high-voltage cables exposed in the lower area of a vehicle can ignite within seconds. There was a 9.5-kW/m2 area around the vehicle (which can result in casualties) at a distance of ~5 m from the hydrogen gas cylinder, and a 37.5-kW/m2 area (which can cause significant damage) in the form of an inverted triangle toward the lower section of the vehicle. We believe that the risk factors analyzed herein should be considered for addressing accidents in hydrogen vehicles.

A variety of input parameters are taken into consideration while performing a Level 3 PSA. Some parameters related to plume segments, spatial grids, and particle size distribution have flexible input formats. Fine modeling performed by splitting a number of segments or grids may enhance the accuracy of analysis but is time-consuming. Analysis speed is highly important because a considerably large number of calculations is required to handle Level 2 PSA scenarios for a single-unit or multi-unit Level 3 PSA. This study developed a sensitivity analysis supporting interface called MACCSsense to compare the results of the trials of plume segmentation with the results of the base case to determine its impact (in terms of time and accuracy) and to support the development of a modeling approach, which saves calculation time and improves accuracy. MACCSense is an automation tool that uses a large amount of plume segmentation analysis results obtained from MUST Converter and Mr. Manager developed by KAERI to generate a sensitivity report that includes impact (time and accuracy) by comparing them with the base-case result. In this study, various plume segmentation approaches were investigated, and both the accuracy and speed of offsite consequence analysis were evaluated using MACCS as a consequence analysis tool. A simultaneous evaluation revealed that execution time can be reduced using multi-threading. In addition, this study can serve as a framework for the development of a modeling strategy for plume segmentation in order to perform accurate and fast offsite consequence analyses.