• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.1
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• pp.93-102
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• 2002

Steel fiber and polymer are used widely for reinforcement material of RC structures because of its excellences of the durability, serviceability as well as mechanical properties. The purpose of this study is to investigate the shear behavior of polymer cement high strength concrete beams mixed with steel fiber. The compressive strength of concrete was based on the 100$\times$200 mm cylinder specimens. The compressive strength of concrete are 320$kgf/cm^2$, 436 $kgf/cm^2$ and 520 $kgf/cm^2$ in the 28 days. The static test was carried out to measure the ultimate load, the initial load of flexural and diagonal cracking, crack patterns and fracture modes. Also, load-strain and load-deflection examined. During the test cracks were sketched against the load values according to the growth of crack. result are as follows; (1) The failure modes of the specimens are increased in rigidity and durability with mixing steel fiber and polymer. (2) The load of initial crack was similar a theory of shear-crack strength. (3) The deflection and strain at failure load of Polymer-steel fiber high strength concrete beams were increased, improving the brittleness of the high strength concrete.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.19 no.3
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• pp.195-201
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• 2009

To identify relationship between the airborne concentrations of formaldehyde and the causal factors in the endoscope unit of hospitals, a total of 48 workers selected from 4 hospitals (3 university hospitals and 1 national hospital) were investigated. Airborne formaldehyde samples were collected using passive samplers and subsequently analyzed by HPLC according to the OSHA method 1007. The geometric mean(GM) of airborne formaldehyde concentrations was 0.056 ppm (range: 0.003~0.923 ppm). The rates of exceeding exposure limits of OSHA PEL-TWA and NIOSH REL-TWA were 4.2 % and 83.3%, respectively. The STEL GM concentration was 1.428 ppm(range: 0.103~14.773 ppm). Ventilation condition (p=0.001) and temperature (p=0.017) were statistically significant causal factors for the airborne exposure concentration of formaldehyde in the endoscope unit of hospitals. In conclusion, the workers in the endoscope unit of hospitals were highly exposed to formaldehyde, and adequate controls such as appropriate management of ventilation and temperature are recommended to reduce over exposure to formaldehyde.

• Journal of Korean Society of Steel Construction
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• v.18 no.5
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• pp.625-631
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• 2006

Residual stresses in structural materials are stresses that exist in the objective without the application of any service or other external loads. Manufacturing processes are the most common causes of residual stress. To examine the effect and the distribution of residual stress due to press forming and welding in the production of a 600MPa-class steel tube, a residual stress evaluation test was performed. The measurement used the Hole-Drilling Strain Gauge Method and evaluated the distribution of residual stress, which measured a total of 59 places near the welding line.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.9 no.6
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• pp.82-88
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• 2000

The effect of the welding for the offshore structure in the TMCP steel on the fatigue crack propagation rate and crack opening-and-closure behavior was examined. The welding anisotropy of the TMCP steel and crack propagation characteristics of the excessive loading were reviewed. (1) It seemed that a heat which was generated by the welding made a compressive residual stress over the base metal, so fatigue crack propagation rate was placed lower than in case of the base metal. (20 In the base metal, an effect of the anisotropy which has an effect of fatigue crack propagation rate of the excessive load and the constant amplitude laos was not found but in the welding material case, fatigue crack propagation rate of the excessive load in the specimen of the width direction was located in the retard side as compared with a specimen rolling direction. (3) A crack opening ratio of the used TMCP stel in this study was not changed after excessive loading but a retard phenomenon of crack propagation was observed. Consequently, it was thought that all of the retard phenomenon of crack propagation did not only a cause of the crack opening-and-closure phenomenon.

• 월간산업보건
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• s.247
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• pp.16-19
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• 2008

파라티온(Parathion)은 폭넓고 다방면으로 사용되는 유기 인계 해충 진드기의 살충제이다. 파라티온의 첫 번째 생물학적 반응은 콜린에스테라아제 효소의 활성도 저감이다. 파라티온의 다양한 수준의 동물 노출 실험 결과, 경구 투여량 0.5-6 mg/kg 수준에서 악영향이 관찰되었다. 인간의 경우 파라티온 0.1 mg/kg 이하 수준에서는 RBC 콜린에스테라아제 효소의 활성도 감소가 나타나지 않았다. $0.2-0.8\;mg/m^3$의 작업장 노출 수준에서는 RBC 콜린에스테라아제 효소의 감소가 관찰되었다. 본 연구 결과에 근거하여 흡입 노출농도 $0.35\;mg/m^3$에 해당되는 0.05 mg/kg 이하 용량에서는 파라티온과 관련한 건강상의 생물학적 장애 증상이 유발되지 않았다. 따라서 흡입성 에어로졸과 증기상 형태로 $0.05\;mg/m^3$의 TLV-TWA가 파라티온의 작업장 노출기준으로 권고되었다. 이 노출기준은 부교감 신경의 이상과 다른 생물학적 장애 증상을 예방하는 목적에서 설정되었다. 이 수치는 인간을 대상으로 한 연구에서 얻어진 NOAEL로부터 근거를 둔 것이고, 작업자들의 RBC 콜린에스테라아제 효소의 활성도 저하를 방지하는 용량에 해당되는 것으로 예상된다. 이러한 접근은 RBC 콜린에스테라아제 효소의 억제가 단독 사용자에게서는 나타나지 않는다는 것을 확인하는데 이용되는 Biological Exposure Index의 활용과 일치된다. 인간에게 있어 파라티온 피부노출이 죽음까지도 이를 수 있다는 임상적 증세와 연관되어 있기 때문에 피부경고주석이 권고되었다. 쥐들을 대상으로 한 사료 공급 연구들에서 파라티온의 노출을 통한 명확한 종양의 발생 증가가 관찰되지 않아 비발암성 물질(A4)로 설정하였다. 파라티온의 TLV-STEL과 SEN notation을 설정하기에는 아직 충분한 데이터가 확보되어 있지 않고 있으며 파라티온의 작업 노출 모니터링에 대한 자세한 정보를 얻으려면 아세털콜린에스터라제 억제 농약의 BEI 문서들을 참고하는 것이 필요하다.

• Journal of Korean Society of Steel Construction
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• v.20 no.1
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• pp.33-42
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• 2008

Buckling-Restrained Braces (BRB) has been developed to inhibit buckling and exhibit stable behavior underboth tensile and compresive cycles. In this study, an experime nt has been conducted by using the strength of its members and loading protocols as parameters to evaluate the structural performance of BRB (without in-filed concrete). Specimens are composed of an inner core and an outer tube with diferent steel strengths. When high-strength steels were used as iner cores, the ductility of BRB decreased, and the requirements (Cumulative Plastic Ductility) of the AISC Seismic Provisions were not satisfied. however, when high-strength steels were used as inner cores instead of conventional strength stel cores, the maximum capacity increased significantly and displayed similar performance in total energy dissipation.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.358-364
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• 2009

본 연구에서는 우리나라 주요 침엽수종인 소나무(Pinus densiflora)와 활엽수종인 굴참나무(Quercus variabilis)의 낙엽에 대해 FTIR(Fourier Transform Infrared) 분광계를 이용하여 배출 연소가스 종류 및 농도를 측정하였다. 실험결과 소나무와 굴참나무 낙엽에서 Carbon monoxide, Carbon dioxide, Acetic acid, Butyl acetate, Ethylene, Methane, Methanol, Nitrogen dioxide, Ammonia, Hydrogen Fluoride, Sulfur dioxide, Hydrogen bromide 등 13개 연소가스가 검출되었고 굴참나무 낙엽에서는 Nitrogen monoxide가 추가로 검출되었다. 방출된 연소가스의 전체 농도는 소나무 낙엽이 굴참나무 낙엽에 비해 4.5배 많이 검출되었다. 특히, 시간가중평균가스농도(TWA : Time-weighted average, ppm) 기준을 초과하는 연소가스는 Carbon monoxide, Carbon dioxide, Butyl acetate가 검출되었고 단시간노출기준(STEL : Short Term Exposure Limit, ppm) 기준을 초과하는 연소가스는 Carbon monoxide, Carbon dioxide로 소나무 및 굴참나무 모두에서 나타났다. 이에 산불에서의 낙엽층 지표화 연소시 전체 가스 방출량의 99% 이상을 차지하고 있는 Carbon monoxide, Carbon dioxide의 건강 위험성이 높은 것으로 나타났다. 하지만, 검출된 다른 건강 위험성 가스의 경우에도 연소물질의 양이 증가할수록 연소가스의 농도가 높아져 건강안정성에 해가 있을 것으로 판단되며 또한 검출된 연소가스 중 나무의 주요구성 원소가 아닌 Bromide, Fluoride 화합물에 대해서는 토양으로부터의 오염 또는 분석과정에서의 노이즈로 인한 검출 등에 대한 보다 면밀한 검토가 필요할 것으로 판단된다.

• Journal of Korean Society of Steel Construction
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• v.18 no.4
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• pp.457-468
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• 2006

An experimental study was performed to investigate the maximum energy dissipation and the ductility capacity of shear-dominated steel plate walls with thin web plates. Three specimens of three-story plate walls with thin web plates were tested. The parameters for the test specimens were the aspect ratio of the web plate and the shear strength of the column. A concentrically braced frame and a moment-resisting frme were a also tested for comparison. The steel plate walls exhibited much better ductility and energy dissipation capacity than the concentrically braced frame and the moment-resisting frame. The results showed that unlike other structural systems, the sh as well as strength, and can therefore be used as an effective earthquake-resisting system. A method of predicting the energy dissipation capacity of a steel plate wall was proposed.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.289-299
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• 2006

Orthotropic steel decks are manufactured by welding thin plates therefore it is inevitable that there are abundant works of welding process. On connection of transverse rib web, crossing point of longitudinal rib, transverse rib and deck plate and cut-out parts of transverse rib are the significant position of stress concentration phenomenon because of out of plane and oil-caning deformation caused by longitudinal rib distortion with shear force and distortion. In order to reduce the stress concentration phenomenon and improving fatigue performance at the crosing point and cut-out, structural analysis was performed considering the existence of scalop at conection and diaphragm which have same plane with transverse rib placed inside of longitudinal rib. Result o f the analysis show that there are the largest efect of stres concentration reduction when diaphragms are installed without scallop at connection, therefore these detail can improve the fatigue performance of orthotropic steel decks.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.385-393
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• 2006

In Korea, the effective utilization of wod structure is encour aged to preserve natural resources and the global environment.ote demand for wod. The efective combination of structural la minated timber and other materials is expected to extend the potential of building structures. This research examines the moment resis tance-type jointing method using structural laminated timber and H-section stel aiming at development of the two-direction frame for lar ge 9 mm and 12 mm) of the H section. Therefore, we conducted the experiment with bending test of the joints to investigate the s tifnes, strength, strain distributions of laminated timber an d of the flange of the H section, and failure paterns. As shown in the results, t he joints with a flange thicknes of 9 mm and 12 m have superi or strength with a flange thicknes of 9 mm and 12 mm were very large, whic h confirmed the high level of energy absorption of such structure s.