• Computers and Concrete
• /
• 제33권3호
• /
• pp.265-273
• /
• 2024

Predicting fracture properties requires an understanding of structural failure behaviour in relation to specimen type, dimension, and notch length. Facture properties are evaluated using various testing methods, wedge splitting test being one of them. The wedge splitting test was numerically modelled three dimensionally using the finite element method on self compacting concrete specimens with varied specimen and notch depths in the current work. The load - Crack mouth opening displacement curves and the angle of rotation with respect to notch opening till failure are used to assess the fracture properties. Furthermore, based on the simulation results, failure curve was built to forecast the fracture behaviour of self-compacting concrete. The fracture failure curve revealed that the failure was quasi-brittle in character, conforming to non-linear elastic properties for all specimen depth and notch depth combinations.

• 터널과지하공간
• /
• 제29권6호
• /
• pp.523-531
• /
• 2019

암석역학이나 암반공학의 여러 활용 분야 중 발파, 천공 및 기계굴착의 경우에는 파괴인성이 중요한 요소이며, 암석의 파괴인성을 측정하기 위한 여러 가지 방법들이 제안되었다. 본 연구에서는 간단히 시험편을 제작할 수 있고, 압축 하중으로 암석의 모드 I 파괴인성을 구할 수 있도록 쐐기 분열 시험편(Wedge Splitting Test Specimen)을 이용하였다. 쐐기의 작용하는 연직하중에 의한 수직 및 수평하중 모두를 고려한 균열선단의 응력상태로부터 수치해석을 통한 응력확대계수의 식을 제안하였다. 쐐기 분열 시험편에 의해 구해진 모드 I 파괴인성값을 GD와 SENB 시험편의 시험 결과와 비교하여 시험법의 타당성을 확인하였다.

• 대한기계학회논문집A
• /
• 제40권3호
• /
• pp.253-258
• /
• 2016

입자강화복합재료를 이용하여 쐐기분열시험으로부터 얻은 파괴에너지, 균열진전 및 CTOD 에 대한 온도의 영향이 조사되었다. 이용된 재료는 고분자바인더, 산화제 및 알루미늄입자로 이루어져 있으며, 쐐기분열시편의 시험 속도는 50 mm/min 이고, 온도 조건은 $50^{\circ}C$, 상온, $-40^{\circ}C$, $-60^{\circ}C$이었다. 분열하중-CMOD 로부터 구한 파괴에너지는 $50^{\circ}C$에서 $-40^{\circ}C$까지 온도의 감소와 함께 증가한다. 또한 $-60^{\circ}C$에서 입자강화복합재료의 강도는 유리전이온도에 의해 급격히 증가하며 취성거동을 보였다. 그리고 디지털 이미지 상관법을 이용하여 균열 선단부근에 대한 변형률장이 분석되었다.

• Computers and Concrete
• /
• 제18권3호
• /
• pp.337-354
• /
• 2016

To study the influence on fracture properties of reinforced concrete wedge splitting test specimens by the addition of reinforcement, and the restriction of steel bars on crack propagation, 7 groups reinforced concrete specimens of different reinforcement position and 1 group plain concrete specimens with the same size factors were designed and constructed for the tests. Based on the double-K fracture criterion and tests, fracture toughness calculation model which was suitable for reinforced concrete wedge splitting tensile specimens has been obtained. The results show that: the value of initial craking load Pini and unstable fracture load Pun decreases gradually with the distance of reinforcement away from specimens's top. Compared with plain concrete specimens, addition of steel bar can reduce the value of initial fracture toughness KIini, but significantly increase the value of the critical effective crack length ac and unstable fracture toughness KIun. For tensional concrete member, the effect of anti-cracking by reinforcement was mainly acted after cracking, the best function of preventing fracture initiation was when the steel bar was placed in the middle of the crack, and when the reinforcement was across the crack and located away from crack tip, it plays the best role in inhibiting the extension of crack.

• Computers and Concrete
• /
• 제3권2_3호
• /
• pp.91-102
• /
• 2006

To place concrete overlays has become a standard application in the strengthening and rehabilitation of concrete structures such as bridges, tunnels, parking decks and industrial buildings. In general, connectors are used to ensure a monolithic behavior of the two concrete layers. Within the framework of the development of a new connector wedge splitting tests and shear tests were performed, in addition nonlinear finite element analyses were applied to investigate the load transfer behavior of the connectors for different prototypes. The numerical simulation results were compared to experimental data. The computed load-displacement curve demonstrates good correspondence with the curves obtained in the experiments, and the experimental crack patterns are reasonably simulated by the computed crack propagation. Both numerical and experimental investigations on the wedge splitting test and on the shear test served as basis for the development of new type of connectors.

• 콘크리트학회논문집
• /
• 제14권1호
• /
• pp.58-66
• /
• 2002

본 연구의 목적은 유효탄성균열모델과 점성균열모델의 개념에 기초한 임계응력확대계수, 임계균열단개구변위와 파괴에너지, 이선형 연화 곡선같은 콘크리트의 파괴특성들을 초기재령 콘크리트에 관해 구명하는 것이다. 이를 위해 모드 I의 파괴를 일으킬 수 있는 쐐기쪼갬시험이 노치가 있는 육각형의 쐐기 시험체에 대하여 수행되었다. 강도와 재령의 변화에 따라 하중-균열입구변위 곡선이 얻어졌으며, 이것은 선형탄성 파괴역학과 유한요소법에 의해 분석되었다. 실험 결과를 분석한 결과, 재령 1일부터 재령 28일까지의 임계응력확대계수와 파괴에너지는 증가하였으며, 임계균열단개구변위는 감소하였다. 또한 수치해석을 통하여 재령 1일부터 재령 28일까지의 이선형 연화 곡선의 네 파라미터를 구할 수 있었다. 이렇게 얻어진 초개재령 콘크리트의 파괴특성치와 이선형 연화 곡선은 초기재령 콘크리트의 파괴 기준과 유한요소해석시의 입력 상수로서 사용될 수 있을 것이다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.423-426
• /
• 2001

In this paper a large scale direct tension test of plain concrete is represented. Two independently controlled actuators were used to ensure a homogeneous tensile field and to avoid secondary flexural stresses. Fracture energies evaluated by a classical prediction equation and this test are compared. The result indicated that the classical prediction equation is not adequate to predict the fracture energy of large sized specimens. From this test, it was determined that the fracture energy obtained from large scale direct tension tests is significantly higher than the one obtained in wedge splitting tests on laboratory sized specimens. But the tensile strength was about half the value determined from splitting tensile strength test with cylindrical specimens.

• International Journal of Concrete Structures and Materials
• /
• 제18권3E호
• /
• pp.191-198
• /
• 2006

The objective of this study is to examine fracture characteristics of concrete at early ages, i.g. critical stress intensity factor, critical crack-tip opening displacement, fracture energy, and bilinear softening curve based on the concepts of effective-elastic crack model and cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By experimenting with various strengths and ages, load-crack mouth opening curves were obtained, and the results were analyzed by linear elastic fracture mechanics and FEM(finite element method). The results from the test and analysis showed that critical stress intensity factor and facture energy increased while critical crack-tip opening displacement decreased with concrete aging from 1 day to 28 days. Four parameters of bilinear softening curve from 1 day to 28 days were obtained from a numerical analysis. The obtained fracture parameters and bilinear softening curves at early ages from this study are to be used as a fracture criterion and an input data for the finite element analysis of concrete at early ages.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 봄 학술발표회 논문집
• /
• pp.215-220
• /
• 2001

The objective of this study is to examine the fracture characteristics of concrete at early ages such as critical stress intensity factor, critical crack-tip opening displacement, fracture energy based on the concepts of the effective-elastic crack model and the cohesive crack model. A wedge splitting test for Mode I was performed on cubic wedge specimens with a notch at the edge. By varying strength and age, load-crack mouth opening displacement curves were obtained and the results were analyzed by linear elastic fracture mechanics. The results from the test and analysis showed that critical stress intensity factor and fracture energy increased, and critical crack-tip opening displacement decreased with concrete age from 1 day to 28 days. The obtained fracture parameters at early ages may be used as a fracture criterion and an input data for finite element analysis of concrete at early ages.

• 한국항공우주학회지
• /
• 제46권7호
• /
• pp.535-541
• /
• 2018

본 연구에서는 입자강화 복합재료의 파괴거동을 평가하기 위해 쐐기분열시험을 수행하였다. 균열 저항성을 분석하기 위해 균열선단열림변위(CTOD)와 균열선단열림각도(CTOA)를 이용하였다. 사용된 입자강화 복합재료는 특성상 온도와 하중속도에 영향을 많이 받기 때문에 다양한 온도($-60^{\circ}C{\sim}50^{\circ}C$)와 하중속도(5~500mm/min)조건에서 시험을 수행하였다. 또한 균열선단에 대한 변형률장을 분석하기 위해 디지털 이미지 상관법(DIC)을 이용하였다. 시험결과 파괴에너지는 온도가 감소할수록 증가하였으며, 하중속도가 증가할수록 균열저항성이 증가하였다.