• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 가을 학술발표회 논문집
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• pp.239-242
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• 2002

This study is intended to investigate the relationship between rebound value of P type schmidt hammer and the compressive strength with various aggregates, and a series of experiments about early strength quality control by P type schmidt hammer was performed. According to the results, the compressive strength of concrete using basalt and limestone aggregate is higher by 3% and lower by 4% than that of concrete using granite aggregate respectively. Concrete using basalt and lime stone aggregate show high rebound value in vertical strike. Estimation of the compressive strength does not show differences in horizontal strike, but the compressive strength is estimated high in order of granite, basalt and limestone aggregate in vertical strike. A good correlation between the rebound value of schmidt hammer and the compressive strength is confirmed regardless of aggregate types, so it could be possible to control the quality of concrete by P type schmidt hammer test when basalt and limestone aggregates are used at the same time.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.157-162
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• 2002

This study is intended to present a reference data for effective quality control of concrete through comparing the rebound value of P type schmidt hammer with the compressive strength with variation of mix proportion and curing condition. According to the results, the air-curing specimen shows the higher rebound value than standard specimen except high strength in the whole. Also the vertical stroke shows higher rebound value than horizontal stroke in standard specimen, however, the rebound value of the two does not show prominent difference in air-curing specimen. The estimation equation of compressive strength derived from this experiment estimates the compressive strength more largely than the estimation equation in P type schmidt hammer manual. Therefore it is thought that the new estimation equation that fits our condition will have to be presented.

• International Journal of Advanced Culture Technology
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• 제12권2호
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• pp.16-29
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• 2024

Mogao Grottoes in Dunhuang, China is one of the world cultural heritage, is the largest ancient grottoes art group in the world, and is a natural and cultural place with outstanding universal value for mankind all over the world. Dunhuang music and dance derived from the murals of Mogao Grottoes is an artistic representation of its thousand-year-old glorious history and an indispensable historical material for research. As one of the iconic images of Dunhuang music and dance, the "rebound lute behind the back" dance posture has unique charm value both in the original mural composition and the stage image. This paper analyzes the characters holding pipa in Dunhuang murals by case analysis, comparative research and other relevant research methods, then studies the stage image and posture of "rebound lute behind the back", and finally analyzes the stage works of "rebound lute behind the back". It is concluded that the dance image of "rebound lute behind the back" is a dynamic stage art work gradually formed by artists from the static Dunhuang murals through refining, developing, processing and transforming. This is to revive the image of Dunhuang music and dance murals, to provide reference and reference for the inheritance and development of Dunhuang culture, and then to enhance and enrich the artistic value of excellent traditional Chinese culture and world cultural heritage.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2002년도 학술.기술논문발표회
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• pp.11-15
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• 2002

This study is intended to analyze the relationship between the rebound value of P type schmidt hammer and the compressive strength for a quality control of concrete. According to the results, the compressive strength of standard curing specimen increases in proportion to age, but that of air curing specimen hardly increases after 28 days. The rebound value of P type schmidt hammer, however, increases due to carbonation of concrete in air curing specimen. The correlativity between the rebound value and the compressive strength is very favorable in the case of standard curing specimen, but drops remarkably in the case of air curing specimen. Thus, as application of age coefficient is required for exact estimation of the compressive strength, the age coefficient is derived from this study. The age coefficient of P type schmidt hammer is higher at the age of 3 and 7days, and drops significantly, compared with the age of 28days. And it is lower before 28days than that of N type schmidt hammer suggested in Japan, and shows the similar tendency after 28days.

• 한국건설순환자원학회논문집
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• 제10권2호
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• pp.143-151
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• 2022

동결융해에 의한 콘크리트 손상 발생 시기를 평가하기 위하여 상대동탄성계수와 표면반발경도를 이용하여 비교하였다. 비교 결과 W/C 70 실험체군에서는 표면반발경도에 의한 콘크리트 손상 발생 평가가 200 싸이클 이상 빠르게 나타나는 것으로 관찰되었다. 뿐만 아니라 이후 점점 심해지는 동해를 표현할 수 있는 데이터를 지속적으로 제공해주어 동해 발생하는 초기 시점부터 동해를 확인할 수 있다는 것을 나타냈다. W/C 60과 50 실험체군에서도 표면반발경도가 콘크리트 동해 손상을 상대동탄성계수 보다 빠르게 평가했으며, 물-시멘트비에 변화에 상관없이 전반적으로 동결융해 손상시기 상대적으로 빠르고 정확하게 평가한 것으로 판단된다.

• 산업기술연구
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• 제29권B호
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• pp.57-64
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• 2009

This study has analysed actual overbreak, shotcrete rebound and the ratio between the actual quantity of shotcrete to designed shotcrete measured during a NATM tunnel construction. The measured shotcrete rebound was about 7.2% in average which was about half the allowable rebound (15%), showing shotcrete spraying was performed well. Based on the measurement of excavated tunnel shape, average overbreak was about 28.5cm after tunnel excavation by drill and blasting method. This was about 260% of allowable overbreak. In addition, due to the rebound and overbreak actual amount of shotcrete used in the tunnelling work was about 116.5 % of the designed value. According to the field measurement the ratio of actual shotcrete to designed value showed some relation with standard support pattern, but the size of overbreak did not show the correlation with standard support pattern. Hence current design specifications stating the size of overbreak based entirely on standard support pattern should perhaps be reestablished. The insight into the design guideline regarding overbreak and shotcrete.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문 발표회
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• pp.23-26
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• 2003

This study is intended to investigate the properties of early strength development by application of TEA to the field. According to the results, when TEA is added, fluidity is almost same to base concrete, and increases upto aimed slump after field flowing. Setting time does not differ in the case of base and TEA, but retarded after flowing. The time when compressive strength gains 5 MPa, which side form can be removed, is 23 hours, and so the removal time is shortened by I hours in comparison with plain concrete. But compressive strength is almost same to that of plain concrete at 28 days. The rebound value of P type schmidt hammer show similar tendency to compressive strength, and the rebound value of structure is higher than that of standard curing specimen due to heat capacity effect and drying by the air outside. Therefore, it is thought that if the rebound value of P type schmidt hammer is controled. by about 26 in consideration of open air environment, it is very effective to determine the removal time of side forms.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2003년도 학술.기술논문발표회
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• pp.23.1-26
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• 2003

This study is intended to investigate the properties of early strength development by application of TEA to the field. According to the results, when TEA is added, fluidity is almost same to base concrete, and increases upto aimed slump after field flowing. Setting time does not differ in the case of base and TEA, but is retarded after flowing. The time when compressive strength gains 5 MPa, which side form can be removed, is 23 hours, and so the removal time is shortened by 1hours in comparison with plain concrete. But compressive strength is almost same to that of plain concrete at 28 days. The rebound value of P type schmidt hammer show similar tendency to compressive strength, and the rebound value of structure is higher than that of standard curing specimen due to heat capacity effect and drying by the air outside. Therefore, it is thought that if the rebound value of P type schmidt hammer is controled. by about 26 in consideration of open air environment, it is very effective to determine the removal time of side forms.

• 한국건설순환자원학회논문집
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• 제10권4호
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• pp.539-546
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• 2022

현행 시설물의 안전 및 유지관리 실시 세부지침(성능평가 편)에서는 표면부 콘크리트의 품질의 평가 수단으로 표면에 품질의 저하가 없는 건전부와 겨울철 우수나 누수 등으로 표면 손상이 발생한 비건전부에 대한 표면반발경도를 측정하고 측정값을 상대비교하여 손상도를 평가하도록 규정하고 있다. 그러나 이 판정법은 동결융해 촉진 모사환경으로부터 구한 실험 DB로 도출된 상관관계를 분석하여 제안한 방법으로 실제 현장에서 수집된 DB와 비교 검토하는 등의 현장 적용성에 대한 검토가 미흡한 채 제정되었다. 따라서 이 연구에서는 국내 21개 콘크리트 교량을 대상으로 현장 조사를 실시하고 현장 적용의 적정성을 분석하였다. 분석 결과로부터 동해 손상에 따른 건전부와 비건전부의 뚜렷한 표면반발경도의 차이를 확인할 수 있어 현행 판정법의 현장 적용이 적정함을 확인할 수 있었다. 뿐만 아니라 표면 반발경도의 측정 위치 및 방법의 구체적인 제시에 대한 필요성을 제안하고, 전체 교량을 대상으로 할 때 동해 판정 등급에 대한 유효성에 대하여도 분석하였다.

• 한국건설순환자원학회논문집
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• 제9권4호
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• pp.419-424
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• 2021

콘크리트의 압축강도 추정에 널리 사용하는 반발경도법을 이용하여 콘크리트 표면의 동해손상을 초기에 판정할 수 있는 가능성을 검토하고자 하였다. 이를 위하여 동결융해 열화조건에 다면으로 노출된 콘크리트와 단면으로 노출된 콘크리트에 대하여 반발경도와 상대동탄성계수를 측정하여 콘크리트 표면 손상도를 비교하였다. 반발경도에 의한 동해손상이 단면 노출 콘크리트 시험체에 대해서는 150싸이클 빠르게 계측되었으며, 다면 노출 시험체에 대해서는 50싸이클 빠르게 계측되었다. 따라서 반발경도법이 공명진동법보다 콘크리트 표면 손상을 신속하게 판정할 수 있는 것으로 사료된다