• 한국도로학회논문집
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• 제18권1호
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• pp.57-62
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• 2016

PURPOSES : Reflection cracking has been one of the major causes of distress when asphalt pavement is laid on top of concrete pavement. This study evaluated the reflection cracking resistance of asphalt mixtures reinforced with asphalt embedded glass fiber and carbon fiber using a Texas Transportation Institute (TTI) overlay tester. METHODS : Different asphalt mixtures such as polymer-modified mastic asphalt (PSMA) and a dense graded asphalt mixture were reinforced with asphalt-embedded carbon fiber and glass fiber. For comparison purposes, two PSMA asphalt mixtures and one dense graded asphalt mixture were evaluated without fiber reinforcement. Two different overlay test modes, the repeated overlay test (R-OT) and monotonic overlay test (M-OT), were used to evaluate the reflection cracking resistance of asphalt mixtures at $0^{\circ}C$. In the R-OT test, the number of repeated load when the specimen failed was obtained. In the M-OT test, the tensile strength at the peak load and tensile strain were obtained. RESULTS : As expected, the fiber-reinforced asphalt mixture showed a higher reflection cracking resistance than the conventional nonreinforced asphalt mixtures based on the R-OT test and M-OT test. The dense graded asphalt mixture showed the least reflection cracking resistance and less resistance than the PSMA. CONCLUSIONS : The TTI overlay tester could be used to differentiate the reflection cracking resistance values of asphalt mixtures. Based on the R-OT and M-OT results, the carbon-fiber-reinforced asphalt mixture showed the highest reflection cracking resistance among the nonreinforced asphalt mixtures and glass-fiber-reinforced asphalt mixture.

• Journal of Welding and Joining
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• 제23권3호
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• pp.34-39
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• 2005

It is required for the steel materials used in the sour environment to have sufficient resistance to hydrogen induced cracking(HIC). For line pipe steels, HIC resistance could be varied during pipe making process due to the large plastic deformation applied in the thick-wall pipe. In order to figure out such effect, HIC tests were performed not only in the plate condition but in the pipe condition and their results were compared in terms of cracking ratio. Test results demonstrated a detrimental effect of plastic deformation to HIC resulting in a substantial increase in the cracking ratio after pipe forming process. All of the cracks found in the pipe material were located in the outer layer of pipe where the tensile strain was resulted during pipe forming stage. In order to understand the HIC resistance of the pipe but in the plate condition, it was suggested to pre-strain the plate to some extent before the HIC test.

• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
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• pp.587-592
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• 2002

Fiber reinforced concrete has been used for tunnel lining and rehabilitation of old structures. Recently, structural synthetic fiber was developed to overcome the corrosive properties of steel fibers. Fibers play a role to increase the tensile and cracking resistance of concrete structures. The Post cracking behavior must be clarified to predict cracking resistance of fiber reinforced concrete. The purpose of the present study is to develop a realistic analysis method for post cracking behavior of synthetic fiber reinforced concrete members.

• International Journal of Concrete Structures and Materials
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• 제1권1호
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• pp.3-9
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• 2007

Fiber-reinforced self-compacting concrete (FRSCC) is a new type of concrete mix that can mitigate two opposing weaknesses: poor workability in fiber-reinforced concrete and cracking resistance in plain SCC concrete. This study focused on early-age cracking of FRSCC due to restrained drying shrinkage, one of the most common causes of cracking. In order to investigate the effect of fiber on shrinkage cracking of FRSCC, ring shrinkage tests were performed for polypropylene and steel fiber-reinforced SCC. In addition, finite element analyses for those specimens were carried out considering drying shrinkage based on moisture diffusion, creep, cracking resistance of concrete, and the effect of fiber. The analysis results were verified via a comparison between the measured and calculated crack width. From the test and analysis results, the effectiveness of fiber with respect to reducing cracking was confirmed and some salient features on the shrinkage cracking of FRSCC were obtained.

• 대한토목학회논문집
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• 제36권6호
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• pp.1109-1116
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• 2016

아스팔트 콘크리트 포장의 반사균열 저항성을 평가하기 위해 다양한 방법이 적용되고 있다. 반복직접인장시험은 기존실험에 비해 저렴하고 간편하게 아스팔트 콘크리트 포장의 반사균열 저항성을 평가할 수 있는 장점이 있다. 국내에 반복직접인장시험을 도입하기 위해서는 파괴기준의 결정이 필요하다. 반복직접인장시험의 파괴횟수를 결정하기 위해 다양한 방법을 검토한 결과 초기하중의 10%일 때를 파괴시점으로 산정할 경우 10% 이내의 반복횟수 편차를 나타내었다. 아스팔트 콘크리트의 두께가 30 mm에서 50 mm로 증가할 경우 파괴횟수는 13.6배 증가하여 포장두께가 반사균열 저항성에 큰 영향을 미치는 것을 알 수 있었다. 또한 재하변형의 크기가 클수록 반사균열의 진전속도가 증가하는 것으로 나타났다. 반복직접인장시험은 포장 두께, 변형크기, 재료적 특성에 따라 반사균열저항성을 정량적으로 평가할 수 있기 때문에 포장설계시 반사균열 저항성 평가 방법으로 적용 가능한 것으로 나타났다.

• Structural Engineering and Mechanics
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• 제47권2호
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• pp.247-263
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• 2013

It is evident that torsional resistance of a reinforced concrete (RC) member is attributed to both concrete and steel reinforcement. However, recent structural design codes neglect the contribution of concrete because of cracking. This paper reports on the results of an experimental and numerical investigation into the torsional capacity of concrete beams reinforced only by longitudinal rebars without transverse reinforcement. The experimental investigation involves six specimens tested under pure torsion. Each specimen was made using a cast-in-place concrete with different amounts of longitudinal reinforcements. To create the torsional moment, an eccentric load was applied at the end of the beam whereas the other end was fixed against twist, vertical, and transverse displacement. The experimental results were also compared with the results obtained from the nonlinear finite element analysis performed in ANSYS. The outcomes showed a good agreement between experimental and numerical investigation, indicating the capability of numerical analysis in predicting the torsional capacity of RC beams. Both experimental and numerical results showed a considerable torsional post-cracking resistance in high twist angle in test specimen. This post-cracking resistance is neglected in torsional design of RC members. This strength could be considered in the design of RC members subjected to torsion forces, leading to a more economical and precise design.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2002년도 Proceedings of the International Welding/Joining Conference-Korea
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• pp.266-272
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• 2002

This study reviews the factors controlling the weld metal cracking and shows the difference from those of HAZ cracking. It further reviews the recent progresses made in consumable design for improving the crack resistance in the high strength weld metal. Previously the controlling factors for weld metal cracking were regarded as weld metal strength, diffusible hydrogen and weld metal height. However an overall review presented in this article shows that the cold crack resistance can be improve significantly through the microstructural control and that an increase in tensile strength is not necessarily related to a decrease in the resistance to cold cracking.

• 한국도로학회논문집
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• 제6권3호
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• pp.9-15
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• 2004

아스팔트 혼합물의 균열 저항성은 일반적으로 인장 강도, 스티프니스와 같은 단일 물성치를 측정함으로써 평가된다. 그러나, 아스팔트 혼합물의 균열 성능을 평가함에 있어서 단일 물성치의 이용은 의문시되어 왔다. 따라서 본 연구에서는 아스팔트 혼합물의 균열 저항성과 관련이 있는 주요 특성치를 좀 더 심도 있게 규명하고자 하였다. 이를 위해 다양한 하중 조건 하에서 파괴 시험 크리프 시험, 강도 시험이 일반 아스팔트 혼합물과 개질 아스팔트 혼합물에 대해서 수행되었다. 시험 결과, 혼합물의 균열 저항성은 주로 미세 손상 축적 속도에 영향을 받음을 알 수 있었으며, 이 값은 파괴 에너지 한계에 영향을 주지 않으면서 m값에 반영됨을 알 수 있었다. 또한, 짧은 하중 재하 시간 (탄성거동) 동안 얻어지는 스티프니스는 혼합물의 균열 저항성의 차이를 규명하는데 한계가 있음을 알 수 있었다. 따라서 아스팔트 혼합물의 균열 저항성을 보다 명확히 평가하기 위해서는 혼합물의 크리프 거동과 파괴 한계점을 동시에 고려하는 것이 필수적임을 알 수 있었다. 또한 수퍼페이브 간접 인장 강도 시험으로부터 구한 잔여 소멸 에너지는 비교적 손쉬운 실험을 통해 아스팔트 혼합물의 균열 저항성의 상대적인 차이를 보여줄 수 있는 유용한 물성치임을 알 수 있었으며, 장기 크리프 시험에서 얻어지는 파괴 변형률은 아스팔트 혼합물의 크리프 거동과 파괴 한계점을 동시에 고려함으로써 균열 저항성을 평가할 수 있는 유용한 물성치 임을 알 수 있었다.

• 수산해양기술연구
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• 제26권4호
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• pp.372-379
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• 1990

The effect of primary solidification phase on the solidification cracking sensitivity, corrosion resistance and toughness at cryogenic temperature was investigated for the austenitic stainless steel welds. The conclusions were summarized as follows; 1. Soldification crack sensitivity of austenitic stainless steel welds depends on the primary solidification mode. 2. Austenitic stainless steels were very susceptible to solidification cracking in case of solidification as primary ${\gamma}$ and immune when solidified as primary $\delta$. 3. When the ratio of Creq/Nieq is in the range of 1.46 to 1.55, the most resistance against solidification cracking was obtained. These results agreed well with the relationship between primary solidification mode, corrosion resistance and toughness at cryogenic temperature. 4. Optimum toughness, corrosion and solidification cracking resistance can be obtained when alloys having chemical compositions described above and solidifies as primary $\delta$ containing no ferrite at room temperature.

• Journal of Welding and Joining
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• 제15권5호
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• pp.46-55
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• 1997

This study has evaluated the liquation cracking behavior in the heat affected zone of several Ni base superalloys (Incoloy 825, Inconel 718 and Inconel 600). 304 and 310S austenitic stainless steels were also included for comparison. In addition, the mechanism of liquation cracking in the HAZ was postulated based on the extensive microstructural examinations with SEM, EDAX and TEM. The liquation cracking resistance of Ni base alloys was found to be far inferior to that of austenitic stainless steels. The liquation cracking of Incoloy 825 and Inconel 718 was believed to be closely related with the Laves-austenite(Ti rich in 825 and Nb rich in 718) and MC-austenitic eutectic phases formed along the grain boundaries by constitutional liquation and incipient melting under rapid welding thermal contraction. Further, liquation cracking resistance of the HAZ was dependent not only upon the type and amount of low melting phases but also on the grain size.