• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2000년도 봄 학술발표회 논문집
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• pp.533-538
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• 2000

In R.C. flat slab system, a brittle punching failure is a very fatal problem. But there is no generally well-defined answer to the problem and there are wide differences in current practical design codes. therefore, in this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. Therefore, In this study, the factors affecting to punching failure mechanism have been studied to find out the punching shear behavior in R.C. flat slabs by comparing other investigations and practical design codes. The conclusions in this study are summarized as follows; 1) The factors affecting to punching shear are concrete strength ($f_\alpha$), ratio of column side length to slab depth (c/d), ratio of distance from column center to radial contraflexure (l/d), yield strength of steel ($f_y$), flexural reinforcement ratio ($\rho$) and size effects. 2) It is shown that th use of $\surd{f_{ck}}$in applying($f_\alpha$ to punching shear strength estimation may be more sensitive in high concrete strength. 3) The effects of l/d, ($f_y$, size are no clear in the punching failure mechanism, so in the future, it should be investigated with the effects of various composed load.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2005년도 춘계 학술발표회 논문집
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• pp.916-923
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• 2005

In this study, to observe aging effect of undrained shear behavior for Nak-Dong River sand, undrained static and cyclic triaxial tests were performed with changing relative density ($D_r$), consolidation stress ratio($K_c$) and consolidation time. As a result of the test, the modulus of elasticity to all samples estimated within elastic zone by the micro strain of about 0.05% in case of static shear behavior increased with the lapse of consolidation time significantly, so aging effect was shown largely. Also strength of phase transformation point(S_{PT}$) and strength of critical stress ratio point($S_{CSR}$) increased with the lapse of consolidation time. Undrained cyclic shear strength($R_f$) obtained from the failure strain 5% increased in proportion to relative density($D_r$) and initial static shear stress($q_{st}$), $R_f$ of consolidated sample for 1,000 minutes increased about 10.6% compared to that for 10 minutes at the loose sand, and $R_f$ increased about 7.0% at the medium sand. In situ application range of $R_f$ to the magnitude of earthquake for Nak-Dong River sand was proposed by using a increasing rate of $R_f$ as being aging effect shown from this test result.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2001년도 봄 학술발표회 논문집
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• pp.138-145
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• 2001

This paper presents F.E.M. analysis result about the behavior of R.C. beam repaired with steel plate and fiber sheet. The effect of repairing varies with reinforcement ratio of R.C. beam, plate thickness, numbers of fiber sheet, and repairing length, etc. F.E.M. analysis using a program, DIANA, was carried out taking these factors as parameter in this study. Analysis result shows that repaired R.C. beam behaves differently according to parameters and certain cases imply that repairing is useless or may lay structure in dangerous condition. F.E.M. model considers that interfacial behavior between different two parts of repaired beam is rigid based on an assumption that adhesive failure does not appear before yielding of reinforcement and its analysis shows the result coincides with that of experiment.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 1992년도 가을 학술발표회 논문집
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• pp.106-110
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• 1992

This paper is an experimental study on shear capacity of the high strength R/C beams with a shear span-depth ratio between 1.5 and 2.5. a total of 15 beams was tested to determine diagonal cracking and ultimate shear strength. The major variables are shear span-depth ratio (a/d=1.5, 2.0. 2.5) , vertical shear reinforcements ratio(Vs = 0 , 25, 50, 75, 100% ( Vs = Pv/Pv(ACI)), and concrete compressive strength (f'c= 747㎏/㎠). Test results indicate that ACI 318-89 Eq(11-31) generally underestimates shear strength carried by vertical shear reinforcements, and the mode of failure may change from shear tension to shear compression for the beams having higher Vs than 75%, thus the effectiveness of r-fy on ultimate shear strength (vu) decreased.

• 한국농공학회지
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• 제36권3호
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• pp.90-99
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• 1994

To investigate the undrained shear strength characteristics of marine soils with high water content, high compressibility and weak bearing capacity, a series of undrained triaxial tests with pore pressure measurements on undisturbed and disturbed Banwol marine clay in normally consolidated and overconsolidated states is carried out. The results and main conclusions of this study are summarized as follows : 1 . When the consolidation pressure is increased, the maximum deviator stress of disturbed and undistubed clay in normally consolidated state is increased. Pore pressure parameters and internal friction angle of undisturbed clay are greater than those of disturbed clay. 2. The relationship between pore pressure and axial strain of undisturbed clay in normally consolidated state can be expressed as a hyperbolic function like stress-strain relation proposed by Kondner. 3. In the pore pressure-axial strain relation of disturbed clay in normally consolidated state, failure ratio R'f is greatly deviated in the range of 0.7~0.9 proposed by Christian and Desai. 4. For overconsolided clay, when overconsolidation ratio (OCR) is increased, normalized maximum deviator stress is increased and maximum pore pressure is decreased gradually. 5. Cohesion of overconsolidated clay is greater than that of nomally consolidated clay and internal friction angle slightly is decreased. 6. Pore pressure parameter at failure (Af) of overconsolidated clay is varied with OCR, Af becomes negative values with increment in OCR

• 한국철도학회:학술대회논문집
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• 한국철도학회 2011년도 정기총회 및 추계학술대회 논문집
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• pp.2573-2580
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• 2011

SMRT(Seoul Metropolitan Rapid Transit Corporation) changed PC-oriented office system to Smart-Phone oriented mobile office system(STnF: SMRT Talk & Flash), and provided smart phone to all staffs. STnF make it possible not only voice communication between staff, but also to input and inquiry all kind of information related to work(ex: Facility maintenance, Rolling Stock management, office management, Finance, human resource etc.) based on smart phone. STnF conquers the limitation of time and space. All staffs can commute to the site directly to reduce moving time and to share information between staffs, so SMRT improve speed and reliability of work by making a quick decision and action on the spot. After introduction of STnF, within 1 year, the equipment failure ratio fell to 47%. Mobile office system reduced and level-off the step of approval. so enhanced civil customer service. Quantification and scientific movement of work make it fast evolution and development. These business improvement make it possible to put more outstanding manpower on new business and R&D project, and this contributes to company's management effectiveness.

• Computers and Concrete
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• 제13권2호
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• pp.255-270
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• 2014

Impact performance of high-performance concrete (HPC) and SFRC at 28-day and 56-day under the action of repeated dynamic loading was studied. Silica fume replacement at 10% and 15% by mass and crimped steel fiber ($V_f$ = 0.5%- 1.5%) with aspect ratios of 80 and 53 were used in the concrete mixes. Results indicated that addition of fibers in HPC can effectively restrain the initiation and propagation of cracks under stress, and enhance the impact strengths and toughness of HPC. Variation of fiber aspect ratio has minor effect on improvement in impact strength. Based on the experimental data, failure resistance prediction models were developed with correlation coefficient (R) = 0.96 and the estimated absolute variation is 1.82% and on validation, the integral absolute error (IAE) determined is 10.49%. On analyzing the data collected, linear relationship for the prediction of failure resistance with R= 0.99 was obtained. IAE value of 10.26% for the model indicates better the reliability of model. Multiple linear regression model was developed to predict the ultimate failure resistance with multiple R= 0.96 and absolute variation obtained is 4.9%.

• 대한토목학회논문집
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• 제29권6C호
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• pp.321-329
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• 2009

국내 암석의 일축응력상태와 삼축응력상태의 한계변형률 특성을 연구하고자 국내에 분포하는 6종류의 암석을 대상으로 실내 일축 및 삼축압축시험을 실시하였다. 일축압축실험에 의한 일축압축강도는 대부분 1~100MPa의 범위이었고, 한계변형률도 0.1~1.0%에 위치하여 전반적으로 Sakurai(1982)가 제시한 상 하부 경계선 내에 분포하였다. 그리고 암석의 파괴/한계변형률의 비(${\varepsilon}_f/{\varepsilon}_0$)는 일축강도에 따라 1.0~1.8의 범위로 모두 1.0 이상 나타났다. 삼축압축실험에 의한 한계변형률은 모든 암석에서 0.8%이하로 일축압축실험에서의 최대 한계변형률 1.0% 보다 작은 값을 보였으며, 일축 및 삼축압축실험로부터 산정된 값은 거의 대부분의 암석시료에서 1.0~8.0정도의 범위였다. 본 연구를 통하여 삼축응력상태인 암반의 파괴변형률(${\varepsilon}_{f3}$)은 일축응력상태의 파괴변형률(${\varepsilon}_{f1}$)에 비하여 1.0~8.0배 정도 크고, ${\varepsilon}_{f1}$은 일축응력상태의 한계변형률(${\varepsilon}_{01}$)보다 1.0~1.8배정도 크게 나타나 암반터널 변위계측에 의한 안정성 기준치를 일축강도에 따른 한계변형률(${\varepsilon}_{01}$)로 규정하는 것은 안정측 관리기준이 되는 것으로 판단된다.

• Archives of Pharmacal Research
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• 제28권4호
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• pp.483-487
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• 2005

The aim of this study was to investigate the pharmacokinetic changes of verapamil and its major metabolite, norverapamil, after oral administration of verapamil (10 mg/kg) in rabbits with slight, moderate and severe hepatic failure induced by carbon tetrachloride. The plasma verapamil concentrations in all groups of hepatic failure were significantly higher (p<0.01) than the control. However, the plasma norverapamil concentrations in severe hepatic failure were significantly higher (p<0.05) than the control. The peak concentrations ($C_{max}$) and the areas under the plasma concentration-time curve (AUC) of verapamil in the rabbits were significantly (p<0.01) higher than the control. The absolute bioavailability ($F_{A.B}$) and the relative bioavailability ($F_{R.B}$) of verapamil in the rabbits with hepatic failure were significantly higher ($13.6-22.2\% and 150-244\%$, respectively) than the control ($9.1\% and 100\%$, respectively). Although the AUC and $C_{max}$ of its major metabolite, norverapamil, in slight, moderate hepatic failure were not significantly lower than the control, the metabolite-parent AUC ratio in all groups of hepatic failure was decreased significantly (p<0.05, in slight group; p<0.01, in moderate and severe group) than the control. This could be due to decrease in metabolism of verapamil in the liver because of suppressed hepatic function in the hepatic failure groups because verapamil is mainly metabolized in the liver. From our data, it would seem appropriate that in patients with liver disease, doses of verapamil should be decreased by degree of hepatic failure.

• 대한방사선기술학회지:방사선기술과학
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• 제22권2호
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• pp.33-39
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• 1999

This paper included a data analysis of the unit of medical devices using mainternance recording card that had medical devices of unit failure mode, hospital of failure mode and MTBF. The results of the analysis were as follows : 1. Medical devices of unit failure mode was the highest in QC/PM such A hospital as 33.9%, B hospital 30.9%, C hospital 30.3%, second degree was the Electrical and Electronic failure such A hospital as 23.5%, B hospital 25.3%, C hospital 28%, third degree was mechanical failure such A hospital as 19.5%, B hospital 22.5%, C hospital 25.4%. 2. Hospital of failure mode was the highest in Mobile X-ray device(A hospital 62.5%, B hospital 69.5%, C hospital 37.4%), and was the lowest in Sono devices(A hospital 16.76%, B hospital 8.4%, C hospital 7%). 3. Mean time between failures(MTBT) was the highest in SONO devices and was the lowest in Mobile X-ray devices which have 200 - 400 failure hours. 4. Anverage failure ratio was the highest in Mobile X-ray devices(A hospital 31.3%, B hospital 34.8%, C hospital 18.7%), and was the lowest in Sono(Ultrasound) devices (A hospital 8.4%, B hospital 4.2%, C hospital 3.5%). 5. Failure ratio results of medical devices according to QC/PM part of unit failure mode were as follows ; A hospital was the highest part of QC/PM (50%) in Mamo X-ray device and was the lowest part of QC/PM(26.4%) in Castro X-ray. B hospital was the highest part of QC/PM(56%) in Mobile X-ray device, and the lowest part of QC/PM(12%) in Gastro X-ray. C hospital was the highest part of QC/PM(60%) in R/F X-ray device, and the lowest a part of QC/PM(21%) in Universal X-ray. It was found that the units responsible for most failure decreased by systematic management. We made the preventive maintenance schedule focusing on adjustement of operating and dust removal.