• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 1994년도 가을 학술발표회 논문집
• /
• pp.99-104
• /
• 1994

Recently, nonlinear fracture mechanics was applied to analyze concrete structures more accurately, and new materials property such as fracture energy(Gf) was used for its application. The fracture energy was influenced by many parameters, especially the strength of concrete. Many researches on the relation between the strength of concrete and the fracture energy were performed. In spite of many researches on the relation between the strength of concrete and the fracture energy, there is no distinct conclusion. This research includes various the strength levels from low-strength of concrete to high-strength, and then intends to estimate relation between the strength of concrete and the fracture energy. Concrete used crushed sand is also included, which is going to be used much. In this research, the wedge splitting test method proposed by Prof. Linsbauer is adopted to investigate the fracture energy. Fracture behavior of concrete used natrual sand and crushed sand has the similar trend. In the strength range of 200~500 kg/$\textrm{cm}^2$, the fracture energy and the maximum splitting forces(F) increase as the strength of concrete increases. In the range of the higher strength, however, the maximum splitting forces(F) increases but the fracture energy decreases as the strength of concrete increases. Through this investigation the fracture energy of concrete was not proportional to the strength of concrete.

• 한국전산구조공학회:학술대회논문집
• /
• 한국전산구조공학회 1995년도 봄 학술발표회 논문집
• /
• pp.35-41
• /
• 1995

Fracture Mechanics does work for concrete, provided that a finite nonlinear zone at fracture front is being considered. The development of model for fracture process zone is most important to describe fracture phenomena in concrete. The fracture process zone is a region ahead of a traction-free crack, in which two major mechanisms, microcracking and bridging, play important rules. The toughness due to bridging is dominant compared to toughness induced by microcracking, so that the bridging is dominant mechanism governing the fracture process of concrete. In this paper the bridging zone, which is a part of extended macrocrack with stresses transmitted by aggregates in concrete, is model led by a Dugdale-Barenblatt type model with linear tension-softening curve. Two finite element techniques are shown for the model of fracture process zone in concrete.

• 콘크리트학회지
• /
• 제5권1호
• /
• pp.22-37
• /
• 1993

• 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.

• 전산구조공학
• /
• 제1권2호
• /
• pp.111-120
• /
• 1988

이 연구는 철근콘크리트보의 전단파괴 매카니즘에 대한 근본적인 성질을 밝히기 위해서 전단균열의 생성 및 진행과정을 해석적으로 연구하였다. 유한요소법에 파괴역학(fracture mechanics)을 결합시킨 program을 이용하여서, 철근 콘크리트 보에서 균열이 진행함에 따라 바꿔지는 내부응력상태와 균열정점에서의 stress intensity factors 등을 조사하여서, 전단균열의 생성 및 진행의 근본적인 이유를 밝히고자 하였다. 해석결과로 밝혀진 사실들을 간단한 실험으로 비교 검증하였다.

• Structural Engineering and Mechanics
• /
• 제19권5호
• /
• pp.519-533
• /
• 2005

The numerical simulations on the influence of mesoscopic structures on the macroscopic strength and fracture characteristics are carried out based on that the concrete is assumed to be a three-phase composite composed of matrix (mortar), aggregate and bond between them by using a numerical code named MFPA. The finite element program is employed as the basic stress analysis tool when the elastic damage mechanics is used to describe the constitutive law of meso-level element and the maximum tensile strain criterion and Mohr-Coulomb criterion are utilized as damage threshold. It can be found from the numerical results that the bond between matrix and aggregate has a significant effect on the macroscopic mechanical performance of concrete.

• Computers and Concrete
• /
• 제9권1호
• /
• pp.51-61
• /
• 2012

According to the results of three-point bending tests of rubberized concrete and plain concrete, the parameters such as total fracture energy ($G_F$), initial fracture energy ($G_f$), and tensile strength ($f_t$) are obtained for concrete material. Using ABAQUS software and a bilinear softening fictitious crack model, the crack propagation process was simulated and compared to the experimental results. It is found that the increase of AE hit count has a similar trend with the increase of energy dissipation in FEM simulation. For two types of concretes, both experimental results and numerical simulation indicate that the rubberized concrete has a better fracture resistance.

• Structural Engineering and Mechanics
• /
• 제54권6호
• /
• pp.1201-1216
• /
• 2015

This paper presents the details of size independent fracture energy and bi-linear tension softening relation for nano modified high strength concrete. Nano silica in powder form has been used as partial replacement of cement by 2 wt%. Two popular methods, namely, simplified boundary effect method of Karihaloo et al. (2003) and RILEM (1985) fracture energy with P-${\delta}$ tail correction have been employed for estimation of size independent fracture energy for nano modified high strength concrete (compressive strength ranges from 55 MPa to 72 MPa). It is found that both the methods gave nearly same values, which is an additional evidence that either of them can be employed for determination of size independent fracture energy. Bi-linear tension softening relation corresponding to their size independent fracture energy has been constructed in an inverse manner based on the concept of non-linear hinge from the load-crack mouth opening plots of notched three-point bend beams.

• Structural Engineering and Mechanics
• /
• 제48권1호
• /
• pp.17-39
• /
• 2013

In the present paper, a coaxial rotating smeared crack model is proposed for mass concrete in three-dimensional space. The model is capable of applying both the constant and variable shear transfer coefficients in the cracking process. The model considers an advanced yield function for concrete failure under both static and dynamic loadings and calculates cracking or crushing of concrete taking into account the fracture energy effects. The model was utilized on Koyna Dam using finite element technique. Dam-water and dam-foundation interactions were considered in dynamic analysis. The behavior of dam was studied for different shear transfer coefficients considering/neglecting fracture energy effects. The results were extracted at crest displacement and crack profile within the dam body. The results show the importance of both shear transfer coefficient and the fracture energy in seismic analysis of concrete dams under high hydrostatic pressure.

• Structural Engineering and Mechanics
• /
• 제11권6호
• /
• pp.591-604
• /
• 2001

In this paper, a finite element with embedded displacement discontinuity which eliminates the need for remeshing of elements in the discrete crack approach is applied for the progressive fracture analysis of concrete structures. A finite element formulation is implemented with the extension of the principle of virtual work to a continuum which contains internal displacement discontinuity. By introducing a discontinuous displacement shape function into the finite element formulation, the displacement discontinuity is obtained within an element. By applying either a nonlinear or an idealized linear softening curve representing the fracture process zone (FPZ) of concrete as a constitutive equation to the displacement discontinuity, progressive fracture analysis of concrete structures is performed. In this analysis, localized progressive fracture simultaneous with crack closure in concrete structures under mixed mode loading is simulated by adopting the unloading path in the softening curve. Several examples demonstrate the capability of the analytical technique for the progressive fracture analysis of concrete structures.