• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.491-502
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• 2006

This paper summarizes full-scale test results on CFT column-to- flat plate connections has gained wide acceptance subjected to gravity loading. CFT construction has gained wide acceptance in a relatively short time in domestic building construction practice due to its various structural and construction advantages. However, efficient details for CFT column to flat plate connections have not been proposed yet. Based on the strategies that maximize economical field construction, several connecting schemes were proposed and tested. Test results showed strength and connection stiffness exceeding those of R/C flat p late counterparts. A semi-analytical procedure is presented to model the behavior of CFT column-to-flat plate connections. The five parameters to model elastic to post-punching catenary action range are calibrated based on the limited test data of t to progressive collapse prevention design is also illustrated.

• Journal of Korean Society of Steel Construction
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• v.18 no.6
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• pp.677-686
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• 2006

In this paper, a more practical and realistic method is proposed to establish the lifetime optimum maintenance strategies of the deteriorating bridges considering the life-cycle performance as well as life-cycle cost. The genetic algorithm is applied to generate the set of maintenance scenarios that is the multi-objective combinatorial optimization problem related to lifetime performance and cost as separate objective functions, and the technique to select optimum tradeoff maintenance scenario is presented. Optimum maintenance scenarios could be generated not only at the individual member level but also at the system level of the bridge. Through the analytical results of applying the proposed methodology to the existing bridge, it is expected that the methodology will be effectively used to determine the optimum maintenance strategy for introducing a real preventive maintenance system and overcoming the limits of existing maintenance methods.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.553-562
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• 2006

Lateral loading due to wind or earthquake is a major factor that affects the design of high-rise buildings. This paper highlights the problems associated with the seismic design of high-rise buildings in regions of strong wind and moderate seismicity. Seismic response analysis and performance evaluation were conducted for wind-designed concentrically braced steel high-rise buildings in order to check the feasibility of designing them per elastic seismic design criterion (or strength and stiffness solution) in such regions. Review of wind design and pushover analysis results indicated that wind-designed high-rise buildings possess significantly increased elastic seismic capacity due to the overstrength resulting from the wind serviceability criterion. The strength demand-to-capacity study showed that, due to the wind design overstrength, high-rise buildings with a slenderness ratio of larger than four or five can elastically withstand even the maximum considered earthquake (MCE) with the seismic performance level of immediate occupancy under the limited conditions of this study. A step-by-step seismic design procedure per the elastic criterion that is directly usable for practicing design engineers is also recommended.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.28 no.2
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• pp.200-210
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• 2018

Objectives: The purpose of this study is to assess the exposure to ozone and total volatile organic compounds(TVOCs) generated during welding work at a shipyard and recommend respiratory protective equipment(RPE) adequate against these hazards. Method: Ozone was collected for about 30 minutes at two-minutes intervals using a direct reading instrument, specifically an ozone analyzer(Serinus 10, Ecotech, Australia). TVOCs were collected for about 30 minutes at three-minute intervals using a portable GC (Alpha 115, Synspec BV, the Netherlands), and were determined simultaneously by area sampling at the welding plume closest to the welder's breathing zone. The total measurements were 162 for ozone($CO_2$ welding 47, TIG 60, stick 55), and 136 for TVOCs($CO_2$ 65, TIG 50, stick 21). Based on these measurements, a literature survey was conducted to assess the adequacy of RPE. Results: Relative to Korean OEL, measurements above STEL 0.2 ppm were 23.4% for $CO_2$, 63.3% for TIG and 14.5% for stick welding. There were significant differences(p=<0.0001) among welding types. Compared with ACGIH peak exposure of 0.4 ppm for ozone, which is not applied in Korea, $CO_2$ welding exceeded it by 10.6%, TIG by 40.0% and stick by 7.3%. Although it was not feasible to compare them directly since there are no Korean OEL, TVOCs had very high levels similar to the concentrations before moving into a new apartment and about 10-20 times the indoor air quality recommendations for some individual measurements. Conclusions: As ozone removal RPE has been recommended in welding environments for a long time(Lunau, 1967), this fact was demonstrated based on the results of the on-site work environment measurements(ozone and TVOCs). In conclusion, for all welding at a shipyard, gas/vapor and particulate combination RPE are recommended. If this is not possible, it should at least be present for TIG welding.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.29 no.4
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• pp.442-451
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• 2019

Objectives: The aim of this study was to review the reduction methods for ammonia (NH₃) and hydrogen sulfide (H₂S) exposure in livestock. Methods: By reviewing domestic and international research reports from Korea and China, reducing ammonia and hydrogen sulfide in livestock pens was analyzed in terms of ventilation, deodorant, and feed additives. In addition, exposure limits in Korea and China were examined through a comparison between 'TLV-TWA and STEL under the Industrial Safety and Health Act in Korea' and 'Management Standards for Air of Livestock Pens in China'. Results and Discussion: In order to effectively control hazardous gases and odors in livestock pens, the enhancement of natural ventilation or the addition of ventilation fans at the pollution source are being examined. Deodorants are used as adsorbents or masking deodorants. Additives to feed were zeolite powder, FeSO₄·7H₂O, enzymes, and microbial preparations. Use of feed additives was low-cost and had significant effects compared to other methods. Zeolite was the most commonly used in feed additive in Chinese cases and proved to be low-cost and effective for reducing harmful gases. Enzyme preparations were shown to stimulate the growth of livestock, but were expensive. Conclusions: This study reviewed and examined domestic and international research papers in Korea and China for reducing ammonia and hydrogen sulfide concentrations in livestock pens. More diverse research and the development of feed additives are needed.

• Journal of Korean Society of Steel Construction
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• v.18 no.2
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• pp.147-160
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• 2006

GA-based fuzzy optimum design algorithm incorporated with the refined plastic hinge analysis method is presented in this study. In the refined plastic hinge analysis method, geometric nonlinearity is considered by using the stability functions of the beam-column members. Material nonlinearity is also considered by using the gradual stiffness degradation model, which considers the effects of residual stresses, moment redistribution through the occurence of plastic hinges, and the geometric imperfections of the members. In the genetic algorithm, the tournament selection method and the total weight of the steel frames. The requirements of load-carrying capacity, serviceability, ductility, and constructabil ity are used as the constraint conditions. In fuzzy optimization, for crisp objective function and fuzzy constraint s, the tolerance that is accepted is 5% of the constraints. Furthermore, a level-cut method is presented from 0 to 1 at a 0 .2 interval, with the use of the nonmembership function, to solve fuzzy-optimization problems. The values of conventional GA optimization and fuzzy GA optimization are compared in several examples of steel structures.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.20 no.3
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• pp.147-155
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• 2010

This study was conducted to investigate the benzene exposure levels in coal chemical and petrochemical refining industries during BTX turnaround (TA) processes where benzene was being produced. Three companies producing benzene were selected, one coal chemical and two petrochemical industries. TA processes were classified into three stages: shut down, maintenance, and start up. Data was analyzed by classifying the refining method into 2 groups (Petrochemistry, Coal chemistry) for 823 workers. Comparing the data from petrochemical industries with data from a coal chemical refining industry, while benzene concentration levels of long-term samples during TA were not statistically different (p> 0.05), those levels of short-term samples were significantly different (p< 0.001). About 4.79 % of data in petrochemical industries exceed the occupational exposure limits (OELs) of benzene, 1 ppm. In a coal refining methods, about 15.7% exceeded the benzene OELs. The benzene concentrations in maintenance and start up stage of TA for petrochemical refineries were higher than those in a coal chemical refinery (p <0.01). These findings suggest that the coal chemical refining site requires more stringent work practice controls compare to petrochemical refining sites during TA processes. Personal protective equipments including organic respirators should be used by TA workers to protect them from benzene overexposure.

• Journal of Korean Society of Steel Construction
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• v.20 no.2
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• pp.333-345
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• 2008

concrete deck bridges are increasingly aplied to twin- girder bridges and open-stel box girder bridges.One of the most dificult isues in the design of shear conect ors is the mater of achieving ful composite action. Many connectors in smal area require a significant section los of precast decks resulting in difficult reinforcement details. In this closer spacing than the required minimum spacing in the design codes was evaluated through static tests. Test results s howed that the ultimate strength decreased as the conector spacing was reduced. The strength enhancement was observed due to aditional reinforcement for precast slabs or for shear pockets. Thus, the design of group stud shear connection needs to anticipate failure modes and the conector failure should be induced. Based on the test results, an empirical equation consi dering stud spacing was proposed to evaluate the ultimate strength of group stud shear conection. Fatigue tests showed n o reduction in fatigue life of the group stud shear conection in the range of this research. Details of the precast decks wer e enhanced using the findings of the study.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.4
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• pp.321-327
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• 2009

1,3-butadiene is classified as suspected human carcinogen, group A2(American Conference of Governmental Industrial Hygienists, ACGIH). In Korea, 1,3-butadiene has been used as a raw material; monomer, homopolymer, polybutadiene latex, acrylonitrile-butadiene-styrene(ABS) and styrene-butadiene rubber(SBR), in the petrochemistry and precision chemistry industry. As petrochemistry industry in Korea has been developed, the potential exposure possibility of 1,3-butadiene to workers can be increased. Therefore the purpose of this study is to evaluate airborne 1,3-butadiene concentration and workers' exposure levels in the workplace using 1,3-butadiene. Air samples were collected with 4-tert-butyl catechol(TBC) charcoal tube(100 mg/50 mg) and were analyzed by gas chromatograph/flame ionization detector(GC/FID) according to the Choi's method(2002). Geometric mean (GM) and arithmetic mean (AM) of total 59 workers' exposure concentrations to airborne 1.3-butadiene were 0.042 ppm and 1.51 ppm, respectively. Although most samples were lower than 1ppm, 2 samples(21.5ppm and 33.1ppm as 8hr-TWA) were exceeded the Korean standard(2ppm) over 10 times at the repair process in synthetic rubber and resin manufacture industry. 14 samples(41%) of total 34 short-term air samples were exceeded the Korean standard(10ppm as STEL) of Ministry Labor. 1,3-butadiene concentration(GM) in the synthetic rubber and resin manufacture industry(7.87ppm) was significantly higher than that in the monomer manufacure industry (0.35ppm)(p<0.05). Also in the sampling and repair process, each GM(range) was 1.39ppm(N.D.-469.6ppm) and 7.85ppm(N.D.-410.2ppm). In conclusion, it depends on the industry and process, 1,3-butadiene can be exposed to workers as high concentration for short-term.

• Safety and Health at Work
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• v.1 no.1
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• pp.51-60
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• 2010

Objectives: The level of benzene exposure in the petrochemical industry during regular operation has been well established, but not in turnaround (TA), where high exposure may occur. In this study, the characteristics of occupational exposure to benzene during TA in the petrochemical companies were investigated in order to determine the best management strategies and improve the working environment. This was accomplished by evaluating the exposure level for the workers working in environments where benzene was being produced or used as an ingredient during the unit process. Methods: From 2003 to 2008, a total of 705 workers in three petrochemical companies in Korea were studied. Long- and short-term (< 1 hr) samples were taken during TAs. TA was classified into three stages: shut-down, maintenance and start-up. All works were classified into 12 occupation categories. Results: The long-term geometric mean (GM) benzene exposure level was 0.025 (5.82) ppm (0.005-42.120 ppm) and the short-term exposure concentration during TA was 0.020 (17.42) ppm (0.005-61.855 ppm). The proportions of TA samples exceeding the time-weighted average, occupational exposure level (TWA-OEL in Korea, 1 ppm) and the short-term exposure limit (STEL-OEL, 5 ppm) were 4.1% (20 samples of 488) and 6.0% (13 samples of 217), respectively. The results for the benzene exposure levels and the rates of exceeding the OEL were both statistically significant (p < 0.05). Among the 12 job categories of petrochemical workers, mechanical engineers, plumbers, welders, fieldman and scaffolding workers exhibited long-term samples that exceeded the OEL of benzene, and the rate of exceeding the OEL was statistically significant for the first two occupations (p < 0.05). Conclusion: These findings suggest that the periodic work environment must be assessed during non-routine works such as TA.