• 제목/요약/키워드: embedded crack

검색결과 144건 처리시간 0.022초

콘크리트에서 국소화된 파괴해석을 위한 유한요소법 (A Finite Element Method for Localized Failure Analysis of Concrete)

  • 송하원;김형운;우승민
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1999년도 봄 학술발표회 논문집(I)
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    • pp.233-238
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    • 1999
  • Localized failure analysis of concrete structures can be carried out effectively by modeling fracture process zone of concrete during crack initiation and propagation. But, the analysis techniques are still insufficient for crack modeling because of difficulties in numerical analysis procedure which describe progressive crack. In this paper, a finite element with embedded displacement discontinuity is introduced to remove the difficulties of remeshing for crack propagation in discrete crack model during progressive failure analysis of concrete structures. The performance of this so-called embedded crack approach for concrete failure analysis is verified by several analysis examples. The analysis results show that the embedded crack approach retains mesh size objectivity and can simulate localized failure under mixed mode loading. It can be concluded that the embedded crack approach cab be an effective alternate to the smeared and discrete crack approaches.

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터빈축차내에 내재된 타원균열의 응력세기계수 결정 (Determination of Stress Intensity Factors for Embedded Elliptical Crack in Turbine Rotor)

  • 이강용;김종성;하정수
    • 대한기계학회논문집
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    • 제19권5호
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    • pp.1229-1242
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    • 1995
  • The thermal shock stress intensity factors of semi-elliptical surface crack in finite plate and the stress intensity fractors of embedded elliptical crack in turbine rotor is determined by means of Vainshtok weight function method. In case of semi-elliptical surface crack, the solution is compared with previous solution. The stress intensity factor for embedded elliptical crack in turbine rotor loaded by centrifugal and thermal loading is also determined. In this case, the value of stress intensity factor is larger at crack contour near internal radius surface and is almost constant at the crack contour farther from internal radius surface.

2D evaluation of crack openings using smeared and embedded crack models

  • Gamino, Andre Luis;Manzoli, Osvaldo Luis;de Oliveira e Sousa, Jose Luiz Antunes;Bittencourt, Tulio Nogueira
    • Computers and Concrete
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    • 제7권6호
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    • pp.483-496
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    • 2010
  • This work deals with the determination of crack openings in 2D reinforced concrete structures using the Finite Element Method with a smeared rotating crack model or an embedded crack model. In the smeared crack model, the strong discontinuity associated with the crack is spread throughout the finite element. As is well known, the continuity of the displacement field assumed for these models is incompatible with the actual discontinuity. However, this type of model has been used extensively due to the relative computational simplicity it provides by treating cracks in a continuum framework, as well as the reportedly good predictions of reinforced concrete members' structural behavior. On the other hand, by enriching the displacement field within each finite element crossed by the crack path, the embedded crack model is able to describe the effects of actual discontinuities (cracks). This paper presents a comparative study of the abilities of these 2D models in predicting the mechanical behavior of reinforced concrete structures. Structural responses are compared with experimental results from the literature, including crack patterns, crack openings and rebar stresses predicted by both models.

An embedded crack model for failure analysis of concrete solids

  • Dujc, Jaka;Brank, Bostjan;Ibrahimbegovic, Adnan;Brancherie, Delphine
    • Computers and Concrete
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    • 제7권4호
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    • pp.331-346
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    • 2010
  • We present a quadrilateral finite element with an embedded crack that can be used to model tensile fracture in two-dimensional concrete solids and the crack growth. The element has kinematics that can represent linear jumps in both normal and tangential displacements along the crack line. The cohesive law in the crack is based on rigid-plasticity with softening. The required material data for the concrete failure analysis are the constants of isotropic elasticity and the mode I softening curve. The results of two well known tests are presented in order to illustrate very satisfying performance of the presented approach to simulate failure of concrete solids.

콘크리트의 변형률 국소화 및 진행성 파괴에 관한 연구 (Study on Strain Localization and Progressive Failure of Concrete)

  • 송하원;김형운;우승민
    • 콘크리트학회논문집
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    • 제11권3호
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    • pp.181-192
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    • 1999
  • The progressive failure following strain localization in concrete can be analyzed effectively using finite element modeling of fracture process zone of concrete with a finite element embedded discontinuity. In this study, a finite element with embedded discontinuous line is utilized for the analysis of progressive failure in concrete. The finite element with embedded discontinuity is a kind of discrete crack element, but the difficulties in discrete crack approach such as remeshing or adding new nodes along with crack growth can be avoided. Using a discontinuous shape function for this element, the displacement discontinuity is embedded within an element and its constitutive equation is modeled from the modeling of fracture process zone. The element stiffness matrix is derived and its dual mapping technique for numerical integration is employed. Then, a finite element analysis program with employed algorithms is developed and failure analysis results using developed finite element program are verified through the comparison with experimental data and other analysis results.

초대형 컨테이너선의 해치 코밍 용접부의 내부 균열에 대한 파괴역학적 연구 (A Study on Embedded Crack at the Hatch Coaming FCA Butt Weldment in an Ultra Large Containership on the Basis of Fracture Mechanics)

  • 신상범;이주성
    • 대한용접접합학회:학술대회논문집
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    • 대한용접접합학회 2010년도 춘계학술발표대회 초록집
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    • pp.61-61
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    • 2010
  • The purpose of this study is to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in the ultra large containership during service life. In order to do it, the behavior of the embedded crack at the weldment under design loading conditions was evaluated in accordance with BS7910. Here, the level of primary stress induced by ship motion was evaluated by the design code of classification society and FEA. The level of residual stress as secondary stress was calculated in consideration of the restraint degree of weldment and welding heat input by using the predictive equation proposed by authors in the previous study. The fatigue crack growth rate at the weldment was evaluated using CT specimen in accordance with ASTM E647. According to the results, although the allowable defect for embedded crack specified in the classification society exists at the weldment, the occurrence possibility of unstable fracture at the weldment could not be negligible, regardless of CTOD value given in this study. So, in this study, the effect of initial defect size, welding heat input, restraint degree and CTOD on the fracture mechanical characteristics of embedded crack at the weldment was evaluated by the comprehensive fracture assessment. Based on the results, the design criteria including allowable defect, residual stress level and CTOD value was established to prevent the unstable fracture at the FCA butt weldment of hatch coaming deck in an ultra large containership during service life of 20years.

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Cracking of a prefabricated steel truss-concrete composite beam with pre-embedded shear studs under hogging moment

  • Gao, Yanmei;Zhou, Zhixiang;Liu, Dong;Wang, Yinhui
    • Steel and Composite Structures
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    • 제21권5호
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    • pp.981-997
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    • 2016
  • To avoid the cracks of cast-in-place concrete in shear pockets and seams in the traditional composite beam with precast decks, this paper proposed a new type of prefabricated steel truss-concrete composite beam (ab. PSTC beam) with pre-embedded shear studs (ab. PSS connector). To study the initial cracking load of concrete deck, the development and distribution laws of the cracks, 3 PSTC beams were tested under hogging moment. And the crack behavior of the deck was compared with traditional precast composite beam, which was assembled by shear pockets and cast-in-place joints. Results show that: (i) the initial crack appears on the deck, thus avoid the appearance of the cracks in the traditional shear pockets; (ii) the crack of the seam appears later than that of the deck, which verifies the reliability of epoxy cement mortar seam, thus solves the complex structure and easily crack behavior of the traditional cast-in-place joints; (iii) the development and the distribution laws of the cracks in PSTC beam are different from the conventional composite beam. Therefore, in the deduction of crack calculation theory, all the above factors should be considered.

A local-global scheme for tracking crack path in three-dimensional solids

  • Manzoli, O.L.;Claro, G.K.S.;Rodrigues, E.A.;Lopes, J.A. Jr.
    • Computers and Concrete
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    • 제12권3호
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    • pp.261-283
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    • 2013
  • This paper aims to contribute to the three-dimensional generalization of numerical prediction of crack propagation through the formulation of finite elements with embedded discontinuities. The analysis of crack propagation in two-dimensional problems yields lines of discontinuity that can be tracked in a relatively simple way through the sequential construction of straight line segments oriented according to the direction of failure within each finite element in the solid. In three-dimensional analysis, the construction of the discontinuity path is more complex because it requires the creation of plane surfaces within each element, which must be continuous between the elements. In the method proposed by Chaves (2003) the crack is determined by solving a problem analogous to the heat conduction problem, established from local failure orientations, based on the stress state of the mechanical problem. To minimize the computational effort, in this paper a new strategy is proposed whereby the analysis for tracking the discontinuity path is restricted to the domain formed by some elements near the crack surface that develops along the loading process. The proposed methodology is validated by performing three-dimensional analyses of basic problems of experimental fractures and comparing their results with those reported in the literature.

내부 불연속 요소를 사용한 콘크리트의 파괴진행해석 (Analysis of Progressive Fracture in Concrete using Finite Elements with Embedded Discontinuous Line)

  • 송하원;우승민;김형운
    • 한국콘크리트학회:학술대회논문집
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    • 한국콘크리트학회 1998년도 가을 학술발표논문집(II)
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    • pp.450-455
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    • 1998
  • In this paper, finite element with embedded discontinuous line is introduced in order to avoid the difficulties of adding new nodal points along with crack growth in discrete crack model. With the discontinuous element using discontinuous shape function, stiffness matrix of finite element is derived and dual mapping technique for numerical integration is employed. Using the finite element program made with employed algorithms, algorithm is verified and fracture analysis of simple concrete beam is performed.

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유한요소 교호법을 이용한 임의 형상의 삼차원 균열의 피로균열 성장 해석 (Fatigue Crack Growth Simulation of Arbitrarily Shaped Three Dimensional Cracks Using Finite Element Alternating Method)

  • 박재학;김태순
    • 한국안전학회지
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    • 제21권1호
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    • pp.15-20
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    • 2006
  • The finite element alternating method is a convenient and efficient method to analyze three-dimensional cracks embedded in an infinite or a finite body because the method has the property that the uncracked body and cracks can be modeled independently. In this paper the method was applied for fatigue crack growth simulation. A surface crack in a cylinder was considered as an initial crack and the crack configurations and stress intensity factors during the crack growth were obtained. In this paper the finite element alternating method proposed by Nikishkov, Park and Atluri was used after modification. In the method, as the required solution for a crack in an infinite body, the symmetric Galerkin boundary element method formulated by Li and Mear was used. And a crack was modeled as distribution of displacement discontinuities, and the governing equation was formulated as singularity-reduced integral equations.