• 콘크리트학회지
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• 제8권2호
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• pp.139-150
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• 1996

본 연구의 목적은 프리캐스트 콘크리트(PC) 대형판 구조물의 축소모델 제작 및 실험기법에 관한 정보을 제공하는 것이다. 적용된 축소율은 1/5이며, 4가지의 실험이 수행되었다. : 모델 콘크리트와 모델 철근의 재료실험, 수평접합부의 압축실험, 수직접합부의 전단실험, 2층 부분구조물의 정적 주기 실험, 이들 실험결과를 기초로 다음의 결론을 도출하였다. : (1)모델 콘크리트는 일반적으로 예상보다 압축강도가 크게 나타났다. (2)모델 철근은 진공관을 사용하지 않고 열처리를 할 경우 연성의 저하를 보인다. (3)수평접합부와 수직접합부의 파괴모드는 실물크기와 모델이 거의 유사하였으나. 모델의 강도는 상사법칙에 의한 요구강도보다 크게 나타났다. (4) 실물크기와 유사하게 모델철근의 연성과 모델 콘크리트의 압축강도를 확보할 수 있다면, 1/5모델 부분구조물의 이력거동은 실물크리와 매우 근접되게 나타낼 수 있다.

• Structural Engineering and Mechanics
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• 제66권4호
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• pp.445-452
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• 2018

In this paper the effects of particle size and model scale of concrete have been investigated on point load index, tensile strength, and the failure processes using a PFC2D numerical modeling study. Circular and semi-circular specimens of concrete were numerically modeled using the same particle size, 0.27 mm, but with different model diameters of 75 mm, 54 mm, 25 mm, and 12.5 mm. In addition, circular and semi-circular models with the diameter of 27 mm and particle sizes of 0.27 mm, 0.47 mm, 0.67 mm, 0.87 mm, 1.07 mm, and 1.27 mm were simulated to determine whether they can match the experimental observations from point load and Brazilian tests. The numerical modeling results show that the failure patterns are influenced by the model scale and particle size, as expected. Both Is(50) and Brazilian tensile strength values increased as the model diameter and particle sizes increased. The ratio of Brazilian tensile strength to Is(50) showed a reduction as the particle size increased but did not change with the increase in the model scale.

• 한국전산구조공학회:학술대회논문집
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• 한국전산구조공학회 2004년도 봄 학술발표회 논문집
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• pp.301-308
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• 2004

The present study mainly focuses on the inelastic stress analysis of the 1/4 scale prestressed concrete containment vessel model(PCCV) under internal pressure and evaluates not only failure mode but also ultimate pressure capacity of the PCCV. Inelastic analysis is carried out 2D axisymmertic FE model and 3D FE model using four concrete material models which are Drucker-Prager Model, Chen-Chen Model, Damaged Plasticity Model and Menetrey-Willam Model. The uplift phenomenon of the basemat is considered in the 2D axisymmetric FE models. It is found from the 2D axisymmetric analysis results that both of Drucker-Prager model and Damaged Plasticity Model have a good performance and the uplift of the basemat is too small to influence on the global behavior of the PCCV. The FE analysis results on the ultimate pressure and failure mode have a good agreement with experimental results.

• 수산해양기술연구
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• 제47권4호
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• pp.281-289
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• 2011

The purpose of this study is to identify the flow resistance of the bottom trawl net. The bottom trawl net being used in the training ship of Chonnam National University was selected as a full-scale net, and model nets such as 1/10, 1/25 and 1/50 of the actual net were made. Total resistance of the net part, the height of the net mouth and the flow resistance of components of the net such as wing, bag and cod-end part was measured, converted into full-scale and compared. Additionally, the model rule of Tauti (1934), which has been most frequently used in fishing net modeling experiments, was applied to interpret flow resistance and scale effect of model experiment was investigated. Presumed that the flow resistance R is $R=kS{\upsilon}^2$ against the flow velocity of each net ${\upsilon}$, resistance coefficient k was calculated by substituting R, ${\upsilon}$ and S of the net. From the result, it was found that k decreases exponentially when u increases which makes $k=c{\upsilon}^{-m}$. Whereas m of each net is ranged between 0.13-0.16 and there was not significant difference between nets. c does not show big difference in 1/10 and 1/25 model and the value itself was relatively bigger than in 1/50 model. The height of the net mouth of 1/25 and 1/50 model net h decreases exponentially according as ${\upsilon}$ increases to make $h=d{\upsilon}^{-n}$. Whereas d and n values were almost same in two nets. Additionally, when resistance of cod-end, wing and bag part in 1/25 and 1/50 model nets, both nets showed big resistance in bag part when flow is 1m/s as more than 60%. Wing and cod-end part showed almost same value or wing part had little bit larger value. On the other hand, when reviewing the reasons why both models showed difference in 1/50 model while c value against the resistance coefficient k did not show big difference in 1/10 and 1/25 model, it is inferred that the difference occurred not from material difference but from the difference in net size according to scale. It was judged that they are the scale effects concomitant to the model experiments.

• 콘크리트학회논문집
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• 제11권3호
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• pp.47-57
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• 1999

The small-scale models have been utilized for the prediction of inelastic behavior of reinforced concrete structures for several decades. The parameters that affect the similitude between the model and prototype are various. Among them, the effect of bond between the model reinforcement and the model concrete is one of the most important factors. The study reported herein is addressed to verifying this similitude in bond behavior. The simple beams which have the lap splice at the midspan were made and flexural tests were performed under two-point loading. The length of lap splice are varied from 0.4ld through 0.7ld and up to 1.0ld where ld is the development length of the reinforcement. The selected scales are 1/1, 1/5, 1/10 and 1/12. Two prototype specimens and three models were tested in addition to the associated material tests and the test results are compared from the viewpoint of similitude.

• International Journal of Fluid Machinery and Systems
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• 제4권2호
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• pp.229-234
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• 2011

For Lift-type Vertical Axis Wind Turbine (VAWT), it is difficult to evaluate the performance through the scale-model wind tunnel tests, because of the scale effect relating to Reynolds number. However, it is beneficial to figure out the critical value of Reynolds number or minimum size of the Lift-type VAWT, when designing this type of micro wind turbine. Therefore, in this study, the performance of several scale-models of Lift-type VAWT (Reynolds number : $1.5{\times}10^4$ to $4.6{\times}10^4$) was investigated. As a result, the Reynolds number effect depends on the blade chord rather than the inlet velocity. In addition, there was a transition point of the Reynolds number to change the dominant driving force from Drag to Lift.

• Wind and Structures
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• 제12권2호
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• pp.151-177
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• 2009

The International Hurricane Research Center (IHRC) at Florida International University (FIU) is pursuing research to better understand hurricane-induced effects on residential buildings and other structures through full-scale aerodynamic and destructive testing. The full-scale 6-fan Wall of Wind (WoW) testing apparatus, measuring 4.9 m tall by 7.3 m wide, is capable of generating hurricane-force winds. To achieve windstorm simulation capabilities it is necessary to reproduce mean and turbulence characteristics of hurricane wind flows. Without devices and methods developed to achieve target wind flows, the full-scale WoW simulations were found to be unsatisfactory. To develop such devices and methods efficiently, a small-scale (1:8) model of the WoW was built, for which simulation devices were easier and faster to install and change, and running costs were greatly reduced. The application of such devices, and the use of quasiperiodic fluctuating waveforms to run the WoW fan engines, were found to greatly influence and improve the turbulence characteristics of the 1:8 scale WoW flow. Reasonable reproductions of wind flows with specified characteristics were then achieved by applying to the full-scale WoW the devices and methods found to be effective for the 1:8 scale WoW model.

• 수산해양기술연구
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• 제51권2호
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• pp.203-211
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• 2015

The purpose of this study is to identify the flow resistance of the bottom pair trawl nets. The bottom pair trawl nets being used in fishing vessel (100G/T, 550ps) was selected as a full-scale net, and 1/10, 1/25 and 1/50 of the model nets were made. Converted into the full-scale net by Tauti's modeling rule and Kim's modeling rule, when resistance coefficient k of each net was calculated by substituting into above equation for flow resistance R and wall area of nets S values of each net ${\upsilon}$. Because resistant coefficient k decreases exponentially according as flow velocity ${\upsilon}$ increases to make $k=c{\upsilon}^{-m}$, c and m values of each net were compared. As a result, as the model was smaller, c and m values was smaller in the two rule into standard of 1/10 model value, decrease degree of 1/25 model was almost same in the two rule, decrease degree of 1/50 model was very big in Tauti's modeling rule. Therefore, in the result of experiment, because average of c and m values for similarly 1/10 and 1/25 model were given $c=4.9(kgf{\cdot}s^2/m^4)$ and m=0.45, R (kgf) of bottom pair trawl net could show $R=4.9S{\upsilon}^{1.55}$ using these values. As in the order of cod-end, wing and bag part for 1/25 and 1/50 model net were removed in turn, measured flow resistance of each, converted into the full-scale, total resistance of the net and the resistance of each part net were calculated. The resistance ratio of each part for total net was not same in 1/25 and 1/50 model each other, but average of two nets was perfectly same area ratio of each part as the wing, bag and cod-end part was 43%, 45% and 12%. However, the resistance of each part divided area of the part, calculated the resistance of per unit area, wing and bag part were not big difference each other, while the resistance of cod-end part was very large.

• 콘크리트학회지
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• 제3권4호
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• pp.133-142
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• 1991

원형(prototype) 철근콘크리트 구조물의 거동을 축소모형실험을 이용하여 연구하기 위해서는 모든 구성재료의 물리적 성질들이 특정상사(similitude)관계 또는 1:1로 복제된 모형재료를 사용하여야 한다. 원형과 모형의 물리적 특성에 관한 상사성에 대해 사전 연구가 되어져야만 축소모형실험결과 해석에 적용할 수 있다. 본 연구는 철근콘크리트 구조물을 축소모형화하는데 따른 구성재료의 물리적 성질과 기본 거동에 관한 문제점들을 파악하고, 개선된 방법을 찾기 위한 것이다. 모형콘크리트에서 발견되는 큰 인장강도를 최소화하기 위해 배합비를 변화시켜서 원형콘크리트에 가장 가까운 모형콘크리트의 제작기법과 모형철근의 표면형태에 따른 거동의 차이를 단순보를 이용하여 연구하였다.

• Computers and Concrete
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• 제19권4호
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• pp.375-385
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• 2017

In the present paper experimental and numerical analysis of hook-ended steel fiber reinforced concrete is carried out. The experimental tests are performed on notched beams loaded in 3-point bending using fiber volume fractions up to 1.5%. The numerical analysis of fiber reinforced concrete beams is performed at meso scale. The concrete is discretized with 3D solid finite elements and microplane model is used as a constitutive law. The fibers are modelled by randomly generated 1D truss finite elements, which are connected with concrete matrix by discrete bond-slip relationship. It is demonstrated that the presented approach, which is based on the modelling of concrete matrix using microplane model, able to realistically replicate experimental results. In all investigated cases failure is due to the pull-out of fibers. It is shown that with increase of volume content of fibers the effective bond strength and slip capacity of fibers decreases.