• Journal of the Korean GEO-environmental Society
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• v.20 no.11
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• pp.11-22
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• 2019

Limit state design (LSD) and allowable stress design (ASD) are two main types of soil nailing design methodologies. In the LSD method, stability is determined by applying individual coefficients to ground strength, working load and etc. The ASD method calculates the safety factor and compares it with the minimum safety factor to determine the stability. The global design trend of soil nailing system is changing from the ASD method to the LSD method. The design method in Korea still adopts the ASD philosophy while others mostly do the limit state design. In this study, four soil nail design methods, 'FHWA GEC 7' in U.S. (2015), 'Clouterre' in France (1991), 'Soil nailing - best practice guidance' in U.K. (2005), 'Geoguide 7' in Hongkong (2008), and 'Design guide for slope in construction work' in Korea (2016) were applied to the evaluation of the stability and the results were analyzed comparatively in brief. It is revealed that the design method of 'the overall stability of soil nail walls' in Korea is the most conservative and next those by FHWA, Clouterre and CIRIA become more conservative in order. However, the difference of results obtained from FHWA and Clouterre is negligible. Also, this study found out that efforts to improve domestic design criterion are needed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.3
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• pp.597-602
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• 2021

Even in the era of the 4th industrial revolution, the prevention of industrial accidents is still an important issue in industrial sites. In solving the problem of industrial safety, a product can be difficult to market if there is a lack of standard or method for a reliable performance evaluation. The purpose of this study was to develop and evaluate a test method for a wearable airbag product for protecting the body from falls that was newly developed to respond to fall accidents in industrial sites. As a research method, reliable evaluation standards were developed and applied through four stages of the evaluation and development process (Step 1: Product review, Step 2: Data research, Step 3: Expert meeting, Step 4: Drawing evaluation standard). In addition, the impact force was evaluated according to the developed evaluation standard. The fall impact force obtained through the evaluation showed a reduction effect of approximately 96% compared to the existing impact force. Therefore, the fall impact force was reduced significantly when the airbag was applied. This will enable new convergence products to be launched on the market and produce an environment where industrial workers can work safely.

• Journal of the Society of Disaster Information
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• v.19 no.1
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• pp.161-172
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• 2023

Safety education delivered to construction workers in a lecture manner has limitations in concentration and immersion, so delivery power and interest are low. In order to improve unstable behavior through education and prevent safety accidents, it is necessary to change the paradigm to hands-on education. Purpose: Experiential safety education aims to contribute to preventing accidents for construction workers by quickly recognizing risks, improving emergency response skills, and verifying the effectiveness of pre- and post-learning. Method: Based on a survey of workers who experienced the same work environment as the actual construction site, an opinion survey on the pre- and post-safety experience education and a variable measurement tool were planned, and a research hypothesis was established. Results: The Bayesian theory and MC simulation analysis were used to analyze the structural equation model, and the change in construction worker behavior was confirmed through the intended safety (A), non-experiential education in the sub-area of anxiety (B), average, standard deviation, and minimum and maximum values. Conclusion: The effect of education and industrial accidents are reduced only when construction workers are motivated to participate.

• Computers and Concrete
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• v.9 no.5
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• pp.327-340
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• 2012

The search for a design that meets both performance and safety, with minimal cost and lesser environmental impact was always the goal of structural engineers. In general, the design of conventional reinforced concrete structures is an iterative process based on rules of thumb established from the personal experience and intuition of the designer. However, such procedure makes the design process exhaustive and only occasionally leads to the best solution. In such context, this work presents the development and implementation of a mathematical formulation for obtaining optimal sections of reinforced concrete columns subjected to uniaxial flexural compression, based on the verification of strength proposed by the Brazilian standard NBR 6118 (ABNT 2007). To minimize the cost of the reinforced concrete columns, the Simulated Annealing optimization method was used, in which the amount and diameters of the reinforcement bars and the dimensions of the columns cross sections were considered as discrete variables. The results obtained were compared to those obtained from the conventional design procedure and other optimization methods, in an attempt to verify the influence of resistance class, variations in the magnitudes of bending moment and axial force, and material costs on the optimal design of reinforced concrete columns subjected to uniaxial flexural compression.

• Advances in Computational Design
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• v.1 no.1
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• pp.105-117
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• 2016

The objective of this work is to study the restraining effect in fire resistance of framed structures and to evaluate the global response of reinforced concrete frames when exposed to fire based on advanced finite element method. To study the response a single portal frame is analyzed. The effect of floor slab on this frame is studied by modeling a beam-column-slab assembly. The evolution of temperature distribution, internal stresses and deformations of the frame subjected to ISO 834 standard fire curve for both the frames are studied. The thermal and structural responses are evaluated and a comparison of results of individual members and entire structure is done. From the study it can be seen that restraining forces has significant influence on both stresses and deflection and overall response of the structure when compared to individual structural member. Among the various structural elements, columns are the critical members in fire and failure of column causes the failure of entire structure. The fire rating of various structural elements of the frame is determined by various failure criteria and is compared with IS456 2000 tabulated fire rating.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.310-315
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• 2017

Although studies evaluating the effects of the blasting vibration on the adjacent structures from various angles have continued, cases of securing the safety of the adjacent buildings and researching the proper blasting method for the field condition by analyzing the vibration waveform of the measuring field while performing the open pit blasting are poor. Therefore, it is necessary to present a remedy for blasting pattern selection through test blasting that is appropriate for field conditions, and is economical and efficient. In this study, open pit blasting work was conducted based on the separation distance applied according to the standard blasting method by test blasting and the vibration regulation standard in the road expansion construction site to measure the blasting vibration value, and the vibration prediction equation by blasting methods was examined using a regression analysis computer program to calculate K, N, and R of the confidence level 95%. By setting the blasting allowed vibration standard of the test blasting target area to 0.3cm/sec, and the charring weight and blasting method by the separation distances according to the blasting vibration estimation equation of the open pit blasting guideline and the blasting vibration estimation equation of the test blasting were compared/analyzed, it was possible to identify the factors that increased the working expenses. In addition, the measurement and analysis of the adjacent structures during open pit blasting and the blasting vibration were performed after selecting the most adjacent structure to the open pit blasting spot to analyze the problems on the test blasting procedure and analysis method in the open pit blasting design/construction guidelines, which appeared in the process of completing open pit blasting construction, and a remedy is presented.

• Safety and Health at Work
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• v.10 no.4
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• pp.452-460
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• 2019

Background: Monitoring and control of PM_2.5 are being recognized as key to address health issues attributed to PM_2.5. Availability of low-cost PM_2.5 sensors made it possible to introduce a number of portable PM_2.5 monitors based on light scattering to the consumer market at an affordable price. Accuracy of light scatteringe-based PM_2.5 monitors significantly depends on the method of calibration. Static calibration curve is used as the most popular calibration method for low-cost PM_2.5 sensors particularly because of ease of application. Drawback in this approach is, however, the lack of accuracy. Methods: This study discussed the calibration of a low-cost PM_2.5-monitoring device (PMD) to improve the accuracy and reliability for practical use. The proposed method is based on construction of the PM_2.5 sensor network using Message Queuing Telemetry Transport (MQTT) protocol and web query of reference measurement data available at government-authorized PM monitoring station (GAMS) in the republic of Korea. Four machine learning (ML) algorithms such as support vector machine, k-nearest neighbors, random forest, and extreme gradient boosting were used as regression models to calibrate the PMD measurements of PM_2.5. Performance of each ML algorithm was evaluated using stratified K-fold cross-validation, and a linear regression model was used as a reference. Results: Based on the performance of ML algorithms used, regression of the output of the PMD to PM_2.5 concentrations data available from the GAMS through web query was effective. The extreme gradient boosting algorithm showed the best performance with a mean coefficient of determination (R²) of 0.78 and standard error of 5.0 ㎍/㎥, corresponding to 8% increase in R² and 12% decrease in root mean square error in comparison with the linear regression model. Minimum 100 hours of calibration period was found required to calibrate the PMD to its full capacity. Calibration method proposed poses a limitation on the location of the PMD being in the vicinity of the GAMS. As the number of the PMD participating in the sensor network increases, however, calibrated PMDs can be used as reference devices to nearby PMDs that require calibration, forming a calibration chain through MQTT protocol. Conclusions: Calibration of a low-cost PMD, which is based on construction of PM_2.5 sensor network using MQTT protocol and web query of reference measurement data available at a GAMS, significantly improves the accuracy and reliability of a PMD, thereby making practical use of the low-cost PMD possible.

• Fire Science and Engineering
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• v.20 no.1 s.61
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• pp.6-14
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• 2006

The data of city gas accidents has been collected and analysed for not only predictions of the fire and explosion accidents but also the criteria of societal risk. The accidents of the recent 11 years have been broken up into such 3 groups roughly as "release", "explosion", "fire" d 16 groups in detail. Owing to the Poisson probability distribution functions, 'careless work-explosion-pipeline' and 'joint loosening & erosion-release-pipeline' items respectively have turned out to record the lowest and most frequency among the recent 11-years accidents. And thus the proper counteractions must be carried out. In order to assess the societal risks tendency of the fatal gas accidents and set the more obvious safety policies up, the D. O. Hogon equation and the regression method has been used to range the acceptable range in the F-N curve of the cumulative casualties. The further works requires setting up successive database on the fire and explosion accidents systematically to obtain reliable analyses. Also the standard codification will be demanded.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.34 no.2
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• pp.166-178
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• 2024

Objectives: The 12 occupational exposure limits(OELs) for chromium and its compounds in Korea were set by applying the American Conference of Governmental Industrial Hygienists (ACGIH) Threshold Limit Values (TLVs). However, this is significantly different from the TLVs after the existing TLVs were integrated and withdrawn in 2018, so it is necessary to review the revision. Methods: Various documents related to chromium OELs were reviewed, including the ACGIH TLV Documentations for chromium and its compounds. A field survey was conducted targeting workplaces handling chromium and its compounds. Based on this, a revised OELs were proposed and a socio-economic evaluation was conducted. Results: The OELs for chromium compounds in Korea was first enacted in 2002, and in 2007, the OELs for chromium (hexavalent) compounds (insoluble) was lowered from 0.05 mg/m³ to 0.01 mg/m³. In 2008, the OELs for strontium chromate was newly established as 0.0005 mg/m³, and in 2018, the OELs for calcium chromate was newly established as 0.001 mg/m³. Total chromium and hexavalent chromium were measured for each of 6 samples at 2 welding sites, 4 plating sites, and 2 spray coating sites. When omparing the average of the results measured by ICP, a total chromium analysis method, and the analysis results by IC, a hexavalent chromium analysis method, only workplace 4 was the same, and total chromium was evaluated more, and total chromium was evaluated at 0.0004 to 0.0027 mg/m³. And hexavalent chromium was evaluated as non-detection ~ 0.0014 mg/m³. Amendment ①: The exposure standard for hexavalent chromium is not divided into water soluble, insoluble, chromium ore processing, and other hexavalent chromium compounds, and is integrated into 0.01 mg/m³, which is the level of chromium (hexavalent) compound (insoluble)., OELs for chromium (metal) and chromium (trivalent) compounds are integrated into chromium (trivalent) compounds, and the exposure level is maintained. Amendment ②: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.005 mg/m³, which is the OELs of OSHA, and there is a grace period of 4 years. Amendment ③: As in the amendment ①, the OELs are integrated, but the level is lowered to 0.0002 mg/m³, which is the exposure standard of ACGIH, and there is a grace period of 5 years. Conclusions: Amendment ①: The change in the OELs is insignificant, so the cost required is small, and the benefit/cost ratio is greater than 1, so there is no problem in applying the amendment. Amendment ②: In all scenarios except chromium 6(insoluble), the benefit/cost ratio is greater than 1, so it is thought that there will be no major problem in applying the amendment. Amendment ③: Since the benefit/cost ratio is less than 1 in all scenarios, it is thought that the total social benefit that can be obtained when applying the amendment is not large.

• Korean Journal of Construction Engineering and Management
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• v.23 no.1
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• pp.89-97
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• 2022

Recently, various problems such as reduced productivity, insufficient inflow of skilled manpower, reduced quality, and concerns about increasing safety accidents have appeared in the domestic construction industry. Stakeholder of construction project are considering the Off-Site Construction (OSC) method rather than the conventional on-site construction as an alternative. Despite the importance of decision making in the early stage of the adoption of OSC, there is a lack of methodologies for rational decision making. In this study, a decision making system has been developed to derive the final construction cost score by deriving the project characteristics, selecting the construction difficulty index, and developing a cost model for each construction method alternatives to calculate the standard construction cost. Using this system, the OSC method can be effectively evaluated in terms of its feasibility in the early stage of construction