• Title/Summary/Keyword: 휨 시험

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Mechanical Properties of Very Rapid Hardening Polymer Mortar for Concrete Repair (보수용 초속경 폴리머 모르타르의 역학적 특성)

  • Hong, Kinam;Shin, Junsu;Han, Sanghoon;Seo, Dongwoo;Ahn, Kwangkuk
    • Journal of the Korean GEO-environmental Society
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    • v.15 no.8
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    • pp.31-37
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    • 2014
  • In this study, mechanical properties of Very-Rapid Hardening Polymer (VRHP) mortar were investigated. To do it, 75 VRHP mortar specimens were tested by the compressive test, bending test, bonding test, freezing and thawing test, length variation test, and water absorption test. From the test results, it was confirmed that the bond strength of VRHP was higher than that of normal concrete by 50 %, and the resistance of freezing and thawing of VRHP was more excellent than normal concrete. In addition, length variation ratio and water absorption ratio of VRHP were smaller than those of normal concrete by 20 %. Therefore, It should be mentioned that VRHP can be successfully used as the material for repairing the crack of concrete structure.

Structural Properties of High-Strength and Low-Yield-Steel Beam-Column for High-Rise Architecture Structure (건축구조용 저항복 고장력강 Beam-Column의 구조특성)

  • Kim, Jong-Sung;Meng, Ming Hua
    • Journal of Korean Society of Steel Construction
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    • v.24 no.1
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    • pp.13-21
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    • 2012
  • Recently, the development of high-strength thicker steel plate above 600MPa is becoming active due to the increase in both height and member size of architectural structure. However, such steel, which is being investigated in Korea nowadays, has possibility of limited practical application because of high design code strength and high-yield ratio. Therefore, this study performed the validation for the structural performance of beam-column with combined axial force and bending moment whether this beam-column might be attributable as an architectural purpose steel. This study was conducted from the result of monotonic loading test of beam-column, based on the material properties of low-yield, 600MPa class steel which was developed during 1988-1993 in Japan. This study might provide the fundamental database for practical research for these steel which are actively being tested in Korea.

A Simplified Analysis Method of GFRP Composites Deck (GFRP 복합소재 바닥판의 간편해석법)

  • Son, Byung Jik;Ji, Hyo Seon
    • Journal of Korean Society of Steel Construction
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    • v.25 no.4
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    • pp.359-368
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    • 2013
  • This paper presents a simplified analysis method using the elastic equivalent modelling not using the global finite element modelling of deck for the basic design GFRP composites deck with cellular tubes or sandwich structural type. In order to verify the validation of the simplified method ANSYS software package is used and compared the results analyzed on the global finite element modelling and the elastic equivalent modelling. And the laboratory testing by 4-point bending is conducted to compare the results based on the simplified analysis method proposed in this paper. The comparison of the results based on the analysis and the testing are discussed. It is found that the presented simplified analysis is applicable to the use in the basic design GFRP composite deck.

Influence of Blast Furnace Slag and Anhydrite on Strength of Shotcrete (고로슬래그와 무수석고가 숏크리트의 강도에 미치는 영향)

  • Ryu, Sung-Hee;Shin, Kyung-Joon;Kim, Yun-Yong
    • Journal of the Korea Concrete Institute
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    • v.24 no.1
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    • pp.87-95
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    • 2012
  • This study investigated the compressive strength, flexural strength, setting time, and rebound when blast furnace slag and anhydrite, which are widely used mineral admixtures for concrete, are applied to shotcrete. When Ordinary Portland Cement (OPC) was replaced at a rate of 10% with blast furnace slag and anhydrite, the initial and final setting time requirements were all satisfied. However, when OPC was replaced at a rate of 20%, final setting was delayed, revealing that this mixture was not suitable for shotcrete. Compressive strength test results showed that the mixture with 10% OPC replacement rate met the target strength at 1 day and 28 days for permanent tunnel support usage. Particularly, the mixture designed with OPC replacement by blast furnace slag and anhydrite at rates of 5% showed the highest compressive strength. Rebound measurements revealed that this mixture exhibited excellent performance with 23% reduction in the rebound compared to the shotcrete that was produced with only OPC binder.

Strength and Fatigue Properties of Recycled Concretes Under 50% Recycled Aggregate Ratio (재생골재 50% 이하 첨가된 재생콘크리트의 강도 및 피로저항 특성)

  • Doh, Young-Soo;Kim, Sung-Tae;Kim, Kwang-Woo
    • International Journal of Highway Engineering
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    • v.7 no.2 s.24
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    • pp.13-22
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    • 2005
  • Using recycled aggregate from demolished concrete structures provides a peat opportunity fur conserving natural resources. In many parts of world, virgin aggregate deposits have been depleted, and transporting aggregates over long distances can be much more expensive than using a low-cost recycled aggregate. In Korea, about 7-million tons of concrete occurs annually, out of this, about 2-3 million tons are available for recycling. This study is to present the method of utilizing the recycled aggregate. The recycled aggregate concretes were made for compressive strength test, flexural strength test and fatigue test using w/c of 40, 50 and 60%. The replacing rates of recycled aggregate to virgin aggregate were 0, 25 and 50%. The purpose of this study is to compare the fatigue lift of recycled aggregate concrete with that of virgin aggregate concrete. It was shown that the fatigue life of recycled concrete was function of recycled aggregate replacement ratio and water cement ratio.

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Acoustic Emission Signal Analysis for Damage Assessment of the Reinforced Concrete Slab Structures (철근 콘크리트 슬래브 구조 손상 평가를 위한 음향방출 신호분석)

  • Kim, Jeong-Hee;Han, Byeong-Hee;Seo, Dae-Cheol;Yoon, Dong-Jin
    • Journal of the Korean Society for Nondestructive Testing
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    • v.29 no.4
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    • pp.360-367
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    • 2009
  • The acoustic emission(AE) behavior of reinforced concrete slab under flexural loading was investigated to assess the integrity. This study was aimed at identifying the characteristics of AE response associated with damage development. By applying cyclic loading in various load steps, it was able to differentiate each AE source such as distributed micro crack initiation, friction, flexural crack and localized diagonal tension crack. The secondary peak and the change of AE hit rate gave valuable criteria fur assessment. From the analysis of the felicity ratio, furthermore, it was shown that this values can be used for evaluating the degree of concrete damage. Based on the experimental results, this approach for practical AE application may provide a promising method for estimating the level of damage and distress in concrete structures.

Self-Diagnosis for Fracture Prediction of Concrete Reinforced by New Type Rib CFGFRP Rod and CF Sheet (신형 리브재 CFGFRP 보강근 및 CF 보강시트로 보강된 콘크리트의 파괴예측 자가진단)

  • Park, Seok-Kyun
    • Journal of the Korean Society for Nondestructive Testing
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    • v.27 no.2
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    • pp.115-123
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    • 2007
  • For investigating self-diagnosis applicability, a method based on monitoring the changes in the electrical resistance of carbon fiber reinforced concrete has been tested. Then after examining change in the value of electrical resistance at each flexural weight-stage of carbon fiber in CFGFRP (carbon fiber and glass fiber reinforcing plastic) with new type rib and carbon sheet for concrete reinforcing, the correlations of electrical resistance and load as a function of strain, deflection were analyzed. As the results, it is clarified that when carbon fiber rod, rib and sheet fracture, the electrical resistance of it increase largely, and specially in case of CFGFRP, afterwards glass fiber tows can be resist the load due to the presence of the hybrid (carbon and glass) reinforced fiber. Therefore, it can be recognized that reinforcing bar and new type rib of CFGFRP and sheet of CF could be applied for self-diagnosis of fracture in reinforced FRP concrete.

An Experimental Study on Failure Behavior of TP316 Stainless Steel Pipe with Local Wall Thinning and Cracking (국부 감육과 균열이 발생한 TP316 스테인리스강 배관의 파괴거동에 관한 실험적 연구)

  • Cheung, Jin Hwan;Kim, In Tae;Choi, Seock Jin;Choi, Hyung Suk;Kim, Hee Sung
    • Journal of Korean Society of Steel Construction
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    • v.24 no.6
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    • pp.647-657
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    • 2012
  • Although nuclear power plant piping system is designed conforming to design specifications, the piping systems are deteriorated with increase in service life. In this study, monotonic and cyclic loading tests were carried out on TP316 stainless steel pipe specimens, and the effect of local wall thinning and cracking on failure behavior was investigated. In the tests, 0%, 35% and 75% wall thinning and cracking of initial thickness were artificially introduced to inside elbow and straight pipe specimens, and internal pressures of 20MPa were applied to simulate real operation condition. From the test results, the effect of local wall thinning and cracking on failure mode, ultimate load, number of cycle and strain energy was presented, and maximum bending moment was compared with allowable bending moment calculated by ASME code.

Deterioration Characteristic of Shotcrete Immersed in Chemical Solution (화학적 침식에 의한 숏크리트의 열화특성 분석 - 단기거동)

  • Lee, Gyu-Phil;Kim, Dong-Gyou;Bae, Gyu-Jin;Shin, Hyu-Soung
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.7 no.2
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    • pp.143-152
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    • 2005
  • Shotcrete for support of tunnel structures may contact with groundwater. The hazardous components in groundwater may cause corrosion of shotcrete. Also, the hazardous components may deteriorate the engineering properties of shotcrete, such as compressive strength, bond strength, flexural strength and so forth. The more the effect of the hazardous components on the shotcrete may increase, the more the stability of tunnel structure may decrease. The specimens were artificially immersed in various chemical solutions including hazardous components after the specimens were made at the tunnel construction site. It was performed to analyze the effect of the hazardous components in ground water on the engineering properties of shotcrete. The uniaxial compressive strength test, XRD, SEM were conducted to evaluate the durability and corrosion of shotcrete.

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Experimental Study on the Strength Improvement and the Long Term Durability of Shotcrete mixed Micro-Silica Fume (실리카 흄을 혼입한 숏크리트의 강도증진과 장기내구특성에 관한 실험적 연구)

  • Ma, Sang-Joon;Kim, Dong-Min;Jang, Phil-Sung;Choi, Jae-Seok
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.8 no.2
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    • pp.165-182
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    • 2006
  • In this study, field test was performed to investigate the strength-improvement effect of shotcrete mixed Micro-silica fume and shotcrete quality was estimated by EFNARC standard. Deterioration test combined the Freezing-thawing and Carbonation was also performed in order to investigate a long-term durability of high-strength shotcrete. As a result of test, the compressive strength of shotcrete using Micro-silica fume was 45.2~55.8MPa and flexible strength was 5.01~6.66MPa, so a promotion ratio of strength was 37~79%, 17~61% respectively. And the strength-improvement effect of strength by silica fume addition ratio of 7.5~10% for cement mass was more superior to the others. Due to relative dynamic modulus, mass decrease rate and carbonation progress of shotcrete mixed Micro-silica fume, it was especially realized that Micro-silica fume reduced deterioration caused by steel fiber and improved a long-term durability of shotcrete.

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