• 한국구조물진단유지관리공학회 논문집
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• 제1권1호
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• pp.97-105
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• 1997

The major object of this study is to analyze and investigate experimentally the experimenal equation for the estimate of compressive strength of concrete. The results are as follows. The relation between maturity scaled logarithm and compressive strength of concrete can be expressed in liner equation which show an good correlation. And combined method using rebound number, pulse velocity and water cement ratio also show an excellent correlation. The equation by combined method is same as the conclusions.

• 한국농공학회논문집
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• 제46권1호
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• pp.61-71
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• 2004

The performance evaluation and deflection of 3 spans concrete simplicity slab bridge analyzed by non-destructive and loading test. Compressive strength of slab and pier appeared in the range of each 353∼366 kgf/$cm^2$ and 152∼215 kgf/$cm^2$ in rebound number test. Also, it appeared that concrete quality of slab was good after performance improvement. The average compressive strength of slab by core picking appeared 229 kg/$cm^2$. In reinforcing bar arrangement test of span and member, it appeared that horizontal and vertical reinforcing bar was arranged to fixed interval. The value of calculation deflection that carried structural analysis with deflection analysis wave in static loading test appeared higher than that of experimental deflection and it appeared that hardness of this bridge was good. Maximum impact factor that estimated from deflection by running speed in dynamic loading test appeared by 0.216 in 10 km/hr running speed.

• 한국구조물진단유지관리공학회 논문집
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• 제6권4호
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• pp.91-98
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• 2002

Prediction for the compressive strength of concrete by non-destructive tests(NDT) has a tendency to show different outcomes according to various aggregates. The purpose of this study is to develop estimation equation by rebound number, ultrasonic velocity and combined method at concrete structures which used granite as coarse aggregates. The test variable is water/cement ratio(41.1%, 48.6%, 67.6%), curing method(moisture condition, dry condition) and age(7, 14, 28, 56). According to the test variable, new equation was suggested, and compared with the existing equations.

• 한국구조물진단유지관리공학회 논문집
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• 제3권3호
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• pp.157-165
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• 1999

The nondestructive testing methods are commonly used to determine the in-situ compressive strength of concrete. The correlation curves to evaluate the effect of aging on the development of concrete strength was proposed. Thirty two ${\Phi}10{\times}20cm$ cylinder specimens were cast from 5 batches having different strength levels. The correlation curves for rebound hammer method, ultrasonic pulse velocity method and combined method were derived from the laboratory tests and multiple regression analysis. To account for the change of condition such as surface hardness, internal moisture contents, the aging coefficients are applied to the correlation curves. From the comparison the nondestructive strength with the core strength taken from the existing reinforced concrete structures, the validity of the proposed correlation curves are verified.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 1997년도 가을 학술발표회 논문집
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• pp.97-110
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• 1997

• 자원ㆍ환경경제연구
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• 제26권2호
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• pp.173-203
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• 2017

본 연구는 2000~2013년까지 14년간 서울, 부산, 대구, 인천 4개 대도시에 대한 총 주행거리, 도로연장길이, 대중교통 이용객수, 지역내총생산, 지역인구, 석유류 소비량에 대한 횡단시계열자료를 활용하여 도로연장에 대한 반등효과가 우리나라에도 적용되는지를 실증분석하였다. 혼합효과모형으로 추정한 결과 도로연장은 총 주행거리와 동반상승관계에 있는 반면, 대중교통 이용량은 총 주행거리와 역관계에 있는 것으로 나타났다. 이는 도로연장을 중심으로 하는 공급관리형 교통정책이 도시 광역화로 자가운전의 편의성을 직접적으로 증진시키거나, "걷기 힘든" 환경조성을 통해 자가운전 외 교통수단 이용의 편의성을 절감시킴으로써 추가적인 도로이용을 유인함을 뜻한다. 즉, 교통혼잡 및 정체 개선을 위해서는 현재의 도로연장 중심의 정책보다는 대중교통의 편의성 증진을 골자로 하는 교통수요관리 정책에 맞추어야 함을 시사한다.

• 한국안전학회지
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• 제32권5호
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• pp.62-68
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• 2017

It is necessary to analyze on the compressive strength among material properties of concrete for confirming damages of architectures due to large explosion. A non destructive test is known as the representative methods estimating compressive strength and ultrasonic pulse velocity, rebound hardness test are widely used because of their simplicity, convenience. But combined method supplementing two types is applied at now as they are affected by the characteristics of test specimen. In this research to check damages on the members of structure before and after explosion, the characteristics of compressive strength are compared and analyzed through a real explosion test prior to full scale structures. The test results showed that the larger the TNT powder and the shorter the distance, the greater the decrease in strength before and after the explosion and that the largest displacement and moment for the explosive load and the greatest decrease in the strength at the central part. Due to the surface condition and the thickness variation of the concrete specimens, the standard deviation value is the smallest in the combining method of fusion of the ultrasonic method and rebound hardness method. Thus, the combining method can be one of appropriate methods to evaluate the strength in the reinforced concrete structures damaged by the explosion.

• Journal of Korean Neurosurgical Society
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• 제57권3호
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• pp.197-203
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• 2015

Objective : The potassium disturbance associated with thiopental continuous infusion in neurosurgical patients is well known. However, the effect of propofol continuous infusion on serum potassium levels has not been investigated extensively. Methods : We reviewed the medical records of 60 consecutive patients who received coma therapy or deep sedation for intracranial pressure control using either thiopental or propofol between January 2010 and January 2012. Results : The overall incidence of hypokalemia (K<3.5 mmol/L) was comparable between thiopental and propofol groups (89.2% vs. 82.6%). But, the incidence of moderate to severe hypokalemia (K<3.0 mmol/L) was significantly higher in thiopental group (51.4% vs. 13.0%, p=0.003). The lowest potassium level (2.9 mmol/L vs. 3.2 mmol/L, p=0.020) was lower in thiopental group. The patients in the thiopental group required greater potassium replacement than the propofol group patients (0.08 mmol/kg/h vs. 0.02 mmol/kg/h, p<0.001). On multivariate analysis, thiopental [odds ratio, 95% confidence interval, 7.31 (1.78-27.81); p=0.005] was associated with moderate to severe hypokalemia during continuous infusion. The incidence of rebound hyperkalemia (K>5.0 mmol/L, 32.4% vs. 4.3%, p=0.010) and the peak potassium concentration (4.8 mmol/L vs. 4.2 mmol/L, p=0.037) after the cessation of therapy were higher in thiopental group. On multivariate analysis, thiopental [8.82 (1.00-77.81); p=0.049] and duration of continuous infusion [1.02 (1.00-1.04); p=0.016] were associated with rebound hyperkalemia once therapy was discontinued. Conclusion : Propofol was less frequently associated with moderate to severe hypokalemia after induction and rebound hyperkalemia following the cessation of continuous infusion than thiopental.

• 한국건설순환자원학회논문집
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• 제7권2호
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• pp.78-83
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• 2012

터널현장의 숏크리트 시공에 사용되는 강섬유 보강 숏크리트는 강섬유의 강성이 크고 중량이 무거워 숏크리트 시공상 어려움이 있으며, 강섬유의 부식과 높은 반발률 등이 개선사항으로 요구되고 있다. 이에 본 연구에서는 강섬유 보강 숏크리트의 단점을 개선하기 위하여 폴리아미드섬유를 혼입한 숏크리트를 제안하고, 현장 적용성 평가를 위하여 시험시공 결과를 제시하였으며, 그 결과 다음과 같은 결론을 얻었다. 1) 폴리아미드섬유 보강 숏크리트의 역학적 성능은 국내의 터널관련 설계기준을 만족하며, 기존 강섬유 보강 숏크리트와 동등 수준의 역학적 성능을 나타내었다. 2) 폴리아미드섬유 보강 숏크리트는 강섬유 보강 숏크리트에 비해 시공시 반발률이 저감되어 시공성 뿐만 아니라 경제성, 품질, 친환경성 측면에서 우수한 숏크리트라 할 수 있다.

• 화약ㆍ발파
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• 제21권2호
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• pp.21-30
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• 2003

현재 터널 굴착시 기초 지보수단으로 활용되고 있는 숏크리트는 암반의 굴착 특성상 조기에 얇은 두께로 타설하여도 높은 강도를 유지할 수 있다는 장점 때문에 그동안 우수한 장비와 재료가 개발되어 비약적인 발전을 거듭해 오고 있다. 또한, 계측기술의 발달로 지하암반 거동상태도 조기에 자세히 파악되어 강도와 두께 등 거의 정확한 설계가 이루어지고 있으며, 신소재의 보강재료도 지속적으로 개발되고 있다. 국내 석탄 화력발전소에서 발생되는 석탄회에는 fly ash와 bottom ash가 있으며, 이러한 석탄회는 시멘트, 골재, 건축, 토목 및 농수산 분야에 이르기까지 많은 분야에 기술개발이 되었으며, 연구가 활발히 진행 중에 있다. 따라서, 본 연구에서는 fly ash를 혼합한 콘크리트를 숏크리트 재료로서 활용하기 위해 기존의 숏크리트 배합설계에서 fly ash를 시멘트의 대체재로서 사용할 때, 압축강도의 향상 및 굴착면의 타설 리바운드 율을 저하시키는 최적의 함량에 대하여 실험을 실시하였다. 그 결과, fly ash를 시멘트에 15% 중량 치환했을 때, 약 10%의 압축강도의 향상과 리바운드 율이 6%감소되었다.