• Structural Engineering and Mechanics
• /
• 제75권1호
• /
• pp.123-131
• /
• 2020

The bond performance of glass fibre reinforced polymer (GFRP) bars and that of steel bars embedded in Alkali Activated Cement (AAC) concrete are analysed and compared using pull-out specimens. The bond failure modes, the average bond strength and the free end bond stress-slip curves are used for comparison. Tepfers' concrete ring model is used to further analyse the splitting failure in ribbed steel bar and GFRP bar specimens. The angle the bond forces make with the bar axis was calculated and used for comparing bond behaviour of ribbed steel bar and GFRP bars in AAC concrete. The results showed that bond failure mode plays a significant role in the comparison of the average bond stress of the specimens at failure. In case of pull-out failure mode, specimens with ribbed steel bars showed a higher bond strength while specimens with GFRP bars showed a higher bond stress in case of splitting failure mode. Comparison of the bond stress-slip curves of ribbed steel bars and GFRP bars depicted that the constant bond stress region at the peak is much smaller in case of GFRP bars than ribbed steel bars indicating a basic bond mechanism difference in GFRP and ribbed steel bars.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 춘계 학술발표회 제16권1호
• /
• pp.120-123
• /
• 2004

The lap splice lengths of deformed steel reinforcing bars and GFRP bars were experimentally compared using beam specimens. The purpose was to evaluate the length required of the GFRP bar to develop strength at least equivalent to the conventional steel reinforcing bar. The main test variable was the lap splice length: 10, 20, 30 $d_b$ for the deformed steel bars and 20, 30, 40 $d_b$ for the GFRP bars. Two different types of GFRP bars were tested: (1) one with spiral-type deformation and (2) plain round bars. Elastic modulus was about 1/5 of the steel bars while the tensile strength was about 690 MPa for the GFRP bars. Nominal diameter of the GFRP bars and steel bars was 12.7 and 13 mm, respectively. Normal strength concrete (28-day $f_{cu}$ = 30 MPa) was used. For the conventional steel bars (SD400 grade), strength over 400 MPa in tension was developed using the lap splice length of 20 and 30 $f_{cu}$. Only $87\%$ of the nominal yield strength was reached with the lap splice length of 10 $d_b$. For the spiral-type deformed GFRP bars with $40-d_b$ lap splice length, 440 MPa in tension was determined. The maximum tensile strength developed of the GFRP bars with smaller lap splice lengths decreased. The plain GFRP bar was not effective in developing the tensile strength even with $40-d_b$ lap splice length. Development of the cracks on beam surface was clearly visible for the beams reinforced with the GFRP bars. Mid-span deflections, however, were significantly smaller than the comparable beams with conventional steel bars indicating potential ductility problem.

• 한국식품저장유통학회지
• /
• 제12권3호
• /
• pp.235-240
• /
• 2005

곡류의 기능성 소재를 바탕으로 칼로리가 낮고 조직감이 우수한 편의식 형태의 아침대용식 제품을 개발하기 위하여 9가지 곡물(옥수수, 통밀, 멥쌀, 흑미, 현미, 수수, 발아현미, 검은콩, 율무)을 이용하여 선식형과 퍼핑형 씨리얼바 2종류를 제조하여 수분함량, 색도, 조직감 등의 품질변화를 측정하였다. 씨리얼바의 제조는 9가지의 곡류 배합${\to}$부재료의 크림화${\to}$반죽${\to}$성형틀에 투입${\to}$굽기${\to}$냉각${\to}$견과류 토핑의 단계로 이루어졌다. 수분함량은 선식형 씨리얼바가 $9.4\%$, 퍼핑형 씨리얼바가 $10.1\%$였으며 색도 측정 결과 L값은 퍼핑형이 선식형보다 높았으며 a값은 프락토올리고당을 첨가한 선식형의 씨리얼바가 가장 강했으며 b값은 시료간에 유의적 차이를 보이지 않았다. 조직감에 있어 경도는 선식형보다 퍼핑형이 더 컸으며 선식형 씨리얼바의 경우에 프럭토올리고당을 첨가한 군이 가장 경도가 높았다. 관능검사 결과 전반적인 바람직성에 있어서 퍼핑형 씨리얼바가 선식형 씨리얼바보다 높은 기호도를 나타내었다.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2014년도 춘계 학술논문 발표대회
• /
• pp.80-81
• /
• 2014

Generally significant reinforcement is used for nuclear power plant structures and may cause potential problems when concrete is poured. In particular pouring concrete into structural member joint area is more difficult than other areas since the joint area is very congested due to hooked bars, embedded plates, and other reinforcements. The purpose of this study is to solve the problem by applying high-strength(ASTM A615 Gr. 75/80) bars. In addition large-sized(#14 & #18) headed deformed bar could be used as alternative of standard hooked bars to relieve the congestion to some extent. In order to apply headed deformed bars to nuclear power plant structures effectively, the large-sized diameter bars and the high-strength bars shall be used as thick as clear cover thickness 1". Therefore, test results were obtained by taking bar size, yield strength, and clear cover thickness as variables.

• 천문학회보
• /
• 제39권1호
• /
• pp.38.2-38.2
• /
• 2014

Radial light profiles of bars are known to be related to the morphology of their host galaxies in a way that bars in early type disk galaxies show flat radial light profile, while bars in late type disk galaxies show exponential profile. To quantify how flat or steep bar profiles are, we have performed detailed two-dimensional decompositions on 3.6 micron images for 144 barred galaxies from the Spitzer Survey of Stellar Structure in Galaxies (S4G), and then modeled bar profiles with Sersic functions. We find that bars in classical bulge, higher bulge-to-total (B/T) galaxies are flatter than bars in bulgeless, lower B/T galaxies. In particular, we find that the presence of a bulge almost always guarantees that the bar is flat. Conversely, bulgeless galaxies, mostly have bars with steep profiles. This implies that the light profile of bars may be a dynamical age indicator of bars. We also find that the shape of bars are boxy and do not change with B/T. This indicates that as galaxies evolve, bars change their light profile while keeping their outermost shape boxy.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.449-452
• /
• 2004

The lap splice lengths of deformed steel reinforcing bars and GFRP bars with two different to surface type were experimentally compared using beam specimens. The purpose was to evaluate the length required of the GFRP bar to develop strength equivalent to the conventional steel reinforcing bar. The main test variable was the lap splice length. Two different GFRP bar surfaces were tested: (1) spiral-type GFRP bars and (2) sand coated GFRP bars. For the conventional steel bars (SD400 grade), strength over 400 MPa in tension was reached using the lap splice length of $30d_b$. Splice failure was observed in the specimen with the lap splice length of $20d_b$. For the spiral-type and sand coated GFRP bars, the tensile strength developed in the GFRP bars decreased with decreasing splice lengths. Development of the cracks on beam surfaces was clearly visible for the beams reinforced with the GFRP bars. Mid-span deflections, however, were significantly smaller than the comparable beams with conventional steel bars indicating potential ductility problem.

• 한국해안해양공학회지
• /
• 제8권1호
• /
• pp.61-71
• /
• 1996

해안선의 횡방향 표사이동에 대하여 장시간 관측된 자료를 이용하여 연안사주와 관련된 제반 특성들을 해석하였다. 전체적으로, 발생된 내부 연안사주는 시간이 지남에 따라 외해쪽으로 이동하다가 임의의 위치에서 외부 연안사주를 형성하게 된다. 이와 같이 외부 연안사주가 형성된 후, 내부 연안사주는 반대로 시간에 따라 해안선 쪽으로 진행하면서 동시에 많은 양의 표사가 해안선과 외부 연안사주방향으로 이동 소멸되어 외부 연안사주가 다시 내부 연안사주로 변화되는 과정을 거친다. 또한 외부 연안사주의 존재여부에 따라 내부 연안사주의 계절적인 변화특성이 매우 다르게 나타났다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계학술발표회 논문집(I)
• /
• pp.278-281
• /
• 2006

The aims of this study are to investigate rib geometries of reinforcing bars commercially available in Korea, Japan and USA, and evaluate bond performance using beam-end test specimens. Measurement of rib geometries of the bars include nominal area, average distance of rib, height of rib and an angle of rib perpendicular to bar axis. The result of this study show that rib height of Korean reinforcement bars are much less than those of Japan and USA resulting in the lowest value of relative rib area. Average bond strength of Korean D25 deformed bars is known as 9 % less than that of bars produced in USA. Bond strength depends primarily on the relative rib area. Bond strength of the high relative rib area bars produced in USA show 18% higher than that of bars produced in Korea.

• International Journal of Concrete Structures and Materials
• /
• 제2권2호
• /
• pp.99-105
• /
• 2008

Southern exposure test specimens were used to evaluate corrosion performance of epoxy-coated reinforcing bars in chloride contaminated concrete by electrochemical impedance spectroscopy method. The test specimens with conventional bars, epoxy-coated bars and corrosion inhibitors were subjected 48 weekly cycles of ponding with sodium chloride solution and drying. The polarization resistance obtained from the Nyquist plot was the key parameter to characterize the degree of reinforcement corrosion. The impedance spectra of specimens with epoxy-coated bars are mainly governed by the arc of the interfacial film and the resistance against the charge transfer through the coating is an order of magnitude higher than that of the reference steel bars. Test results show good performance of epoxy-coated bars, although the coatings had holes simulating partial damage, and the effectiveness of corrosion-inhibiting additives. The corrosion rate obtained from the impedance spectroscopy method is equivalent to those determined by the linear polarization method for estimating the rate of corrosion of reinforcing steel in concrete structures.

• 한국응용곤충학회지
• /
• 제20권1호
• /
• pp.37-41
• /
• 1981

콩의 흑색뿌리썩음병을 일으키는 Cylindrocladium crotalariae은 감자한천배지와 콩의 조직을 함유한 한천 배지를 서로 다르게 Water potential를 조절하여 이 병원균을 접종한 결과 균사신장과 대형분생포자형성은 -14bars에서 좋았고 $30^{\circ}C$에서는 -100bars $25^{\circ}C$에서는 -80bars $20^{\circ}C$에서는 -64bars에서 균사신장이 중지되었으며 포자형성도 -64bars에서 중지되었다. 자낭각과 미소균핵형성은 소금을 첨가하지 않은 -1.4나 -3.0bars에서 잘 되었고 이 균에 대한 포자발아율은 -1.4bars에서 -20bars의 모든 Water potential에서 똑 같이 좋았고 -20bars에서 Water potential이 낮아지므로 발아율이 떨어지다가 -60bars에서 억제되었다.