본 연구에서는 유압식 급속재하 시험 장치를 제작하여 변형 속도에 따른 후크형 강섬유 및 폴리아미드 섬유보강 시멘트 복합체의 압축강도 및 인장강도 특성을 평가하였다. 그 결과, 변형 속도가 증가함에 따라 압축강도, 최대 응력 점에서의 변형 및 탄성계수는 증가하였으 며, 섬유 종류 및 혼입률은 변형 속도에 의한 압축강도의 영향은 크지 않았다. 본 연구에서 평가된 압축강도의 DIF는 CEB-FIP model code 2010 에 비해 상회하였으며, ACI-349의 예측값과 유사한 경향이 나타났다. 인장특성의 경우에도 변형 속도가 증가함에 따라 인장강도와 변형능력 이 크게 향상되었다. 후크형 강섬유보강 시멘트 복합체는 변형 속도가 증가함에 따라 섬유와 매트릭스의 부착력이 증가하는 것에 의해 인장강 도와 변형능력이 크게 향상되었으며, 섬유가 매트릭스로부터 인발되는 파괴 특성이 나타났다. 한편, 폴리아미드 섬유보강 시멘트 복합체의 경 우 섬유와 매트릭스의 부착력이 크기 때문에 섬유가 매트릭스로부터 인발되지 않고 끊어지는 파괴 특성이 나타났으며, 폴리아미드 섬유보강 시멘트 복합체의 인장특성에 대한 변형 속도 효과는 섬유의 인장강도에 큰 영향을 받는 것으로 판단되었다. 이러한 결과로부터 폴리아미드 섬 유보강 시멘트 복합체의 인장강도에 대한 변형 속도의 효과는 후크형 강섬유의 부착력에 대한 민감도 보다 큰 것으로 사료된다.

본 연구에서는 국내 콘크리트구조기준(2012)에서 규정하고 있는 최소철근량 이하로 보강된 보에 강섬유를 혼입한 강섬유보강철 근콘크리트보의 휨파괴 실험을 수행하였다. 실험변수는 철근비와 강섬유의 혼입량으로 하였다. 철근보강비는 최소철근량의 44%, 66%, 78% 와 100%로 하였으며, 강섬유의 혼입량은 0.25%, 0.50%, 0.75% 및 1.00%이다. 실험결과, 강섬유는 균열저항성능을 크게 개선시키는 것으로 확 인되었다. 또한, 하중저항성능의 관점에서 강섬유는 항복하중의 증가에 기여하지만 극한하중의 증가에는 거의 기여하지 못하는 것을 확인하 였다. 강섬유로 인한 항복하중의 증가량은 철근 감소로 인한 항복하중의 감소량에 비하여 미미한 것으로 나타났다. 최소철근보에서 강섬유의 사용은 오히려 연성을 크게 감소시키는 것으로 확인되었다. 따라서 최소철근 휨부재에 강섬유를 사용하기 위해서는 연성도 확보를 위하여 철 근비를 증가시켜야 하는 것으로 확인되었다.

For the use of recycled aggregate concrete, the early strength is evaluated. The test variables are replacement ratio of recycled aggregate, steel fiber and blast furnace slag powder. For this, 6th concrete mixing plan is prepared. As a result, it is evaluated that the early strength depends on the steel fiber volume fraction and replacement ratio of blast furnace slag powder.

This paper provides the flexural test results of steel fiber reinforced concrete (SFRC) prisms with different aspect ratios of steel fibers (60 and 67). All mixtures have specific compressive strength of 40 MPa and steel fiber volume fraction of 0.75%. According to ASTM C 1609 and EN-14651, SFRC prisms with 150×150×550 mm were made and tested under bending loading. Test results indicated that the aspect ratio of hooked-end steel fibers has insignificant effect on the first-cracking strength and flexural behavior of SFRC prisms.

This paper presents the flexural test results of steel fiber reinforced concrete (SFRC) prisms with different lengths of steel fibers. The specified compressive strength of SFRC is 40 MPa. Two types of steel fiber used in this study have lengths (0.5 and 0.9mm). Test results indicated that steel fibers with longer length is more effective to improve the flexural performance of concrete prisms than steel fibers with shorter length.

It is known that all of structures be old enough not to use as time elapses, and the degree of deterioration depends on the environmental conditions and maintenance activity. Specific repair for deteriorated structures should be applied and the performances are greatly affected by materials used and location of members allocated. This study is to evaluate the enhancement of steel pipe pile in terms of performance when they are reinforced by carbon-fiber composite for underwater.

According to the KCI 2012, it is presented that steel fiber can replace minimum shear reinforcement when beams are designed. However, there is no standard for columns, and there is a lack of research on SFRC columns. Therefore, it is evaluated how much the capacity of columns increases according to the volume fraction of steel fiber through the cyclic lateral loading tests. Also, it is evaluated whether steel fiber can replace transverse reinforcements in concrete columns.

This paper examines the effect of steel fiber volume fraction on compressive and flexural properties of high-strength concrete with compressive strength of 40 MPa. The fiber volume fractions used in this study consist of 0.5, 0.75 and 1.0%. The prisms with 150x150x550 mm were made and tested in accordance with EN-14651.

For the use of recycled aggregate concrete, the early strength is evaluated. The test variables are replacement ratio of recycled aggregate, steel fiber and blast furnace slag powder. For this, 6th concrete mixing plan is prepared. As a result, it is evaluated that the early strength depends on the steel fiber volume fraction and replacement ratio of blast furnace slag powder.

This paper provides the flexural test results of steel fiber reinforced concrete (SFRC) prisms with different aspect ratios of steel fibers (60 and 67). All mixtures have specific compressive strength of 40 MPa and steel fiber volume fraction of 0.75%. According to ASTM C 1609 and EN-14651, SFRC prisms with 150×150×550 mm were made and tested under bending loading. Test results indicated that the aspect ratio of hooked-end steel fibers has insignificant effect on the first-cracking strength and flexural behavior of SFRC prisms.

This paper presents the flexural test results of steel fiber reinforced concrete (SFRC) prisms with different lengths of steel fibers. The specified compressive strength of SFRC is 40 MPa. Two types of steel fiber used in this study have lengths (0.5 and 0.9mm). Test results indicated that steel fibers with longer length is more effective to improve the flexural performance of concrete prisms than steel fibers with shorter length.

It is known that all of structures be old enough not to use as time elapses, and the degree of deterioration depends on the environmental conditions and maintenance activity. Specific repair for deteriorated structures should be applied and the performances are greatly affected by materials used and location of members allocated. This study is to evaluate the enhancement of steel pipe pile in terms of performance when they are reinforced by carbon-fiber composite for underwater.

This paper describes the effects of tensile strength and aspect ratio of steel fiber on flexural behavior of high-strength SFRC notched beam. Test results indicated that flexural properties of SFRC improved with increasing in aspect ratio and tensile strength of steel fiber.

This study is to evaluate the enhancement of steel pile in terms of performance when reinforced by primer and impregnated epoxy developed for underwater. Through compressive strength test, the adhesion between original material and new one was to be investigated as well as reinforcing effects.

Based on the study of researchers carried about SFRC, it was found that SFRC was effective to achieve flexural toughness according to higher volume fraction. On the other hand, higher volume fraction did not effect at compressive strength and toughness.

이 논문의 목적은 압축강도 130 MPa급의 고강도 강섬유 보강 콘크리트 보의 휨거동 특성을 파악하는데 있다. 부피비 1.0%의 강섬 유와 철근비 0.02 이하의 철근으로 보강된 고강도 강섬유 보강 콘크리트의 휨거동 특성 실험결과를 제시하였다. 일반강도철근과 고강도철근 을 실험 부재에 사용하였다. 강섬유 보강 콘크리트의 압축 및 인장거동 재료 실험과 모델링을 수행하였다. 강섬유 보강 콘크리트의 하중-균열 개구변위 실험결과를 반영하여 가상균열모델에 근거한 역해석을 통해 인장거동모델링을 제시하였다. 실험결과는 강섬유 보강 콘크리트와 고 강도철근의 사용은 균열제어 및 연성 거동에 유리한 것을 나타낸다. 일반강도철근을 사용한 보의 휨강도 실험값에 대한 수치해석에 의한 예측 값의 비는 0.81~1.42를 나타내고, 고강도철근을 사용한 보의 휨강도 실험값에 대한 수치해석에 의한 예측값의 비는 0.92~1.07을 나타낸다. 수 치해석에 의한 휨강도는 실험결과를 합리적으로 예측하고 있는 것으로 판단된다.

The purpose of this experimental research is to evaluate the mechanical properties of high performance concrete using amorphous steel fiber and organic fiber. For this purpose, the hybrid fiber reinforced concrete containing amorphous steel fiber(ASF) and polyamide(PA) fiber were made according to their total volume fraction of 0.5% for water-binder ratio of 33%, and then the characteristics such as the workability, compressive strength, and direct tension strength of those were evaluated. It was observed from the test results that the workability and compressive strength was decreased with increasing ASF and decreasing PA fiber. but the direct tension strength was on the whole increased with increasing ASF and decreasing PA fiber.

The elastic modulus of high-strength steel fiber reinforced concrete was measured 37 GPa to 41.98 GPa. Comparing the difference value of the measured stress and the stress calculated by the regression analysis results were within ± 1 MPa. Measured data acorrding to applied LPF was more stable than unapplied LPF data. but, it was slightly different.

This research investigated the influence of adding hybrid steel fiber on the direct tensile behavior of UHPFRC(Ultra high performance fiber reinforced concrete). Test results revealed that the post cracking strength and peak toughness for the Lf: 20mm Df: 0.2mm_0.5% and Lf: 22mm Df: 0.22mm_1.0% were higher than incorporate with Lf: 20mm Df: 0.2mm_1.0% and Lf: 22mm Df: 0.22mm_0.5%

This paper presents an experimental study on the improvement of ductile and flexural strength for high performance fiber reinforced cementitous composites (HPFRCC). The test was evaluated by compressive and flexural behavior of HPFRCC(compressive strength : 180 MPa) according to aspect ratio and volume contents of steel fiber. The flexural strength was increased by aspect ratio near 100 or increasing volume contents of steel fiber while there is no clearly result on the compressive strength.