• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1999년도 학회창립 10주년 기념 1999년도 가을 학술발표회 논문집
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• pp.407-410
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• 1999

An experimental investigation to study the behavior of low rise structural walls using high strength concrete is presented. The test parameter included in the study were the level of constant axial load. The shear strength of walls is predicted by the design provision given in the current the American Concrete Institute Building Code ACI 318-95 and Architectural Institute Japan Code AIJ. The predictions are compared with the test results reported herein as well as those available in the literature.

• 한국지반공학회논문집
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• 제23권5호
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• pp.143-151
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• 2007

고결모래의 거동은 고결정도, 상대밀도, 응력조건, 그리고 입자특성 등에 의해 영향을 받으며, 특히 고결모래의 강도에 영향을 끼치는 고결결합은 응력에 의해 파괴되기 때문에 고결모래의 강도정수는 응력조건을 고려하여 평가되어야 한다. 일반적으로 고결모래의 마찰각은 고결결합에 의해 영향을 받지 않기 때문에 미고결 상태의 마찰각과 동일한 반면, 점착력은 고결결합에 의해 증가하는 것으로 알려지고 있다. 따라서 본 연구에서는 석고를 고결유발제로 하는 고결시료를 조성하여 다양한 구속압 조건에서 배수전단시험을 실시함으로써, 구속압 변화에 따른 고결모래의 강도정수를 평가하였다. 실험결과 고결모래의 점착력은 고결정도와 구속압의 크기에 따라 고결지배구간, 천이구간, 응력지배구간에서 다르게 평가되었다. 또한 본 연구에서는 고결결합을 파괴시키지 않고 강도정수를 평가하기 위한 적정 구속압을 결정하기 위해 고결정도를 표현하는 일축압축강도와 고결결합을 파괴시키지 않는 최대 구속압의 관계를 결정하였다.

• 콘크리트학회논문집
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• 제28권1호
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• pp.105-113
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• 2016

순환골재를 사용한 콘크리트의 재료 및 역학 특성에 관한 대부분의 연구는 압축강도 40 MPa 이하의 콘크리트에 대하여 수행되었으며, 40 MPa 이상의 순환골재 콘크리트에 대한 역학적 특성에 대한 연구결과는 미비하다. 따라서, 이 연구에서는 순환골재 사용의 확대를 위해 40 MPa 이상의 순환골재 콘크리트의 압축강도 및 역학 특성을 파악하였다. 순환골재 콘크리트의 역학 특성을 파악하기 위하여 콘크리트 압축강도 및 순환굵은골재 치환율을 실험변수로 고려하였다. 실험변수로서 콘크리트의 압축강도는 45 및 60 MPa이고, 순환골재 치환율은 30, 50, 70 및 100%이다. 실험변수에 따른 순환골재 콘크리트의 압축강도, 탄성계수, 인장강도 및 파괴계수 특성을 분석하였다. 실험결과는 고강도 콘크리트일수록 순환골재 치환율에 따른 압축강도 감소량이 작은 것을 나타낸다. 탄성계수 실험결과와 기존설계코드에 의한 탄성계수 예측결과를 비교하였으며, 설계코드에 의한 예측결과는 실험결과를 과다평가하고 있다. 반면에 설계코드에 의한 파괴계수 예측결과와 실험결과는 잘 일치한다.

• 한국산업보건학회지
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• 제8권1호
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• pp.146-154
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• 1998

This study was designed to investigate the workers' exposure level to electromagnetic field(EMF) in accordance with the VDT arrangement in the work place and distance from VDT. Author compared the exposure strength of EMF in line group(workers exposed to EMF from both front and back side) and in shielding group(workers exposed to EMF exclusively from front side). The levels of EMF at 30cm and 50cm from front side and at 30cm from back side of VDT were also measured. The result were as follows: 1. Mean distance between a monitor and a worker in shielding group ($47.7{\pm}8.7cm$) significantly longer than that in line group($44.3{\pm}7.2cm$). Strength of EMF in shielding group [$1.3{\pm}0.7V/m$ (electric field) and $18.2{\pm}11.5mA/m$ (magnetic field) were lower than in line group [$1.4{\pm}0.6V/m$ and $26.6{\pm}11.6mA/m$, respectively] at the workers' position. 2. The strength of EMF was decreased with the distance from VDT. The strength at 70cm from VDT was nearly the same as the background strength in the ordinary office rooms. 3. Working distance from 9 inch monitor was significantly shorter than that from 14 inch and wider sized monitors. 4. The strength of EMF in extremely low frequency spectrum of color monitors was higher then that of black and white monitor. 5. Metal coated filters significantly decreased the electric field strength of EMF when earth line was connected. Metallic shield was effectively decreased the EMF strength from VDT, but wooden shield was not. From the above results, line type arrangement of VDT in the work place using metallic shield at the back side of VDT, and metal coated filter to monitor with application of earth line were recommended. It is also recommended to maintain workers position to be 60cm or more distance from monitor and 140cm or more between VDTs for minimizing workers' exposure to EMF.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2008년도 춘계 학술발표회 제20권1호
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• pp.781-784
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• 2008

최근 고강도콘크리트의 현장적용이 증가하면서 현장 콘크리트의 품질확인을 위한 강도 측정시 고강도콘크리트 공시체와 안전진단시 채취되는 비표준형 공시체의 사용이 증가하고 있다. 이에 본 연구에서는 콘크리트의 가장 기본적인 재료특성인 압축강도 특성을 공시체에 대한 크기 효과와 강도수준을 고려하여 합리적인 관계식을 적립하고자 하였다. 실험결과, 공시체 크기 1mm 증가시마다 압축강도는 기준강도 24MPa에서 0.05MPa, 40MPa에서 0.1MPa, 80MPa에서 0.3MPa씩 감소시키는 것으로 나타나, 강도수준이 고강도화 될수록 압축강도 감소량은 증가하는 것으로 나타났다. 또한 공시체 높이/직경비가 1.0 증가시마다 압축강도는 24MPa에서 2.9MPa, 40MPa에서 3.7MPa, 80MPa에서 9.8MPa 감소되어 고강도콘크리트일수록 높이/직경비의 영향을 크게 받는 것으로 나타났다.

• Geomechanics and Engineering
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• 제18권1호
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• pp.71-83
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• 2019

This investigation presented conventional triaxial and creep-permeability tests on sandstones considering thermally-induced damage (TID). The TID had no visible effects on rock surface color, effective porosity and permeability below $300^{\circ}C$ TID level. The permeability enlarged approximately two orders of magnitude as TID increased to $1000^{\circ}C$ level. TID of $700^{\circ}C$ level was a threshold where the influence of TID on the normalized mass and volume of the specimen can be divided into two linear phases. Moreover, no prominent variations in the deformation moduli and peak strength and strain appeared as TID< $500^{\circ}C$ level. It is interesting that the peak strength increased by 24.3% at $700^{\circ}C$ level but decreased by 11.5% at $1000^{\circ}C$ level. The time-related deformation and steady-state creep rate had positive correlations with creep loading and the TID level, whereas the instantaneous modulus showed the opposite. The strain rates under creep failure stresses raised 1-4 orders of magnitude than those at low-stress levels. The permeability was not only dependent on the TID level but also dependent on creep deformation. The TID resulted in large deformation and complexity of failure pattern for the sandstone.

• 한국도로학회논문집
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• 제16권2호
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• pp.11-18
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• 2014

PURPOSES : This study aims to develop a strength test method for irregularly shaped concrete block paver. METHODS : Ten (10) different types of concrete block pavers including porous and dense blocks were tested for strength capacities. Destructive and non-destructive methods were used to develop a strength test method for irregularly shaped concrete block paver. The flexural strength evaluation was conducted in accordance to KS F 4419, while compressive strength was conducted with a 45.7mm-diameter core specimen. The impact echo test method was used to evaluate the elastic modulus. Finally, regression analysis was used to investigate the relationship between flexural strength, compressive strength and elastic modulus based on their corresponding test results. RESULTS : The flexural strength of the tested block pavers ranged from 4MPa to 10MPa. At 95% confidence level, the coefficients of determination between compressive-flexural strength relationship and compressive strength-elastic modulus relationship were 0.94 and 0.84, respectively. These coefficients signified high correlation. CONCLUSIONS : Using the test method proposed in this study, it will be easier to evaluate the strength of irregularly shaped concrete block pavers through impact echo test and compressive test, instead of the flexural test. Relative to the flexural strength requirement of 5MPa, the minimum values of compressive strength and elastic modulus, as proposed, are 13.0MPa and 25.0GPa, respectively.

• 한국직업건강간호학회지
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• 제21권1호
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• pp.66-75
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• 2012

Purpose: This study is aimed at obtaining the information on the physical fitness level of female flight attendants at a local airline. Methods: The subjects are 2,409 female flight attendants who have had medical examination and physical fitness tests at an airline medical center from January 2 to December 30, 2008. The independent variables include socio-demographic & behavioral characteristics, and medical examination results, whereas the dependent variable is their physical strength score representing their fitness level. Results: Factors that affect the fitness strength score are age, flight hours per year, and fasting blood sugar level. It is found that physical fitness level is higher when the subjects are over 35, on board for over 850 hours per year and their fasting blood sugar level is over 100 mg/dL. Conclusion: It is concluded that for the improvement of flight attendants' health, more exercise to develop cardio-respiratory endurance and muscular strength is needed, and further study needs to be done to develop fitness enhancement programs considering flight attendants' job characteristics, working years, and flight hours per year, and programs for those returning to their workplace after a long-term leave, and new employees.

• 대한물리의학회지
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• 제6권3호
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• pp.341-351
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• 2011

Purpose : The purpose of this study was to determine the initial effects of deltoid inhibition taping to Pain, Function, Strength, ROM in shoulder impingement syndrome (SIS). Methods : This study is 28 patients(male 16, female 12) with shoulder impingement syndrome(SIS).The experimental group received deltoid inhibition taping and the control group had sham taping. Outcome variables measured degree of pain, disability, strength, and range of motion at pre-post intervention. The changes between pre-post interventions are analyzed by a repeated measure ANOVA test. Results : Pain and disability index significantly decreased (p<.05), and the rate of change in pain and disability level of the experimental group increased significantly more than control group (p<.05). Strength and range of motion significantly increased (p<.05), but the rate of change of the two groups showed no significant difference (p>.05). Conclusion : These results suggest that deltoid inhibition taping was initial effective in decreasing pain and disability in SIS patients.

• 한국학교보건학회지
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• 제29권2호
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• pp.107-115
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• 2016

Purpose: This study is a descriptive survey which attempts to understand family strength, parenting attitude, and the ego-identity perceived by female high school students and identify the factors influencing ego-identity of the students. Methods: Data collection was carried out through a questionnaire survey of 186 female high school students. The collected data were analyzed by descriptive statistics, t-test. ANOVA, correlation analysis, and multi-variate regression analysis while using SPSS 23.0 program. Results: Family strength and the ego-identity perceived by female high school students were at a mid-level, with an average of 207.76 and 149.72 points, respectively. Parenting attitude showed scores higher than the mid-level, recording 90.36 points in average. As a result of analyzing the correlation between the factors, the higher family strength and the ego-identity of female high school students were, the better were the patenting attitudes of perceived parents. Besides, family health, parenting attitude, and family form (nuclear family) were found to be the factors influencing ego-identity formation of female high school students with the explanatory power being 25.5% in total. Conclusion: Developing intervention programs which take into account family strength is considered necessary to help the youth form positive ego- identity.