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Journal Article

Finite element fracture modelling of concrete gravity dams

01 Mar 2008-Journal of The South African Institution of Civil Engineering (South African Institution of Civil Engineering (SAICE))-Vol. 50, Iss: 1, pp 13-24
TL;DR: In this article, a smeared crack model based on nonlinear fracture mechanics was developed which allows for either linear or bilinear softening and assumes shear retention dependent on the strain normal to a crack.
Abstract: A smeared crack model, based on non-linear fracture mechanics, was developed which allows for either linear or bilinear softening and assumes shear retention dependent on the strain normal to a crack. A mesh objectivity verification study proves that the proposed crack modelling method is mesh objective. The crack model and its computational procedure is verified for a benchmark concrete gravity dam model and an existing concrete gravity dam by comparing the results with those of numerical investigations obtained by other researchers. Furthermore, an existing concrete gravity dam in South Africa is analysed and evaluated with regard to dam safety in terms of the maximum overflow level. A higher imminent failure flood is predicted in the analysis than that obtained by classical strength-based methods. The study proves the usefulness and applicability of the proposed crack model and implementation procedure in predicting crack response and evaluating the safety of concrete gravity dams. A sensitivity study on the material fracture properties and fracture parameters is included for the purpose of investigating the uncertainties often encountered in this type of analysis. The influence of the fracture properties and parameters on the cracking response and the overall structural behaviour is discussed.

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Citations
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Journal ArticleDOI
Jianbo Li, Xin Gao, Xing-an Fu, Chenglin Wu, Gao Lin 
TL;DR: In this paper, a nonlinear extended scaled boundary finite element method (X-SBFEM) was developed incorporating the cohesive fracture behavior of concrete, which consists of an iterative procedure to accurately model the traction distribution within the fracture process zone (FPZ) accounting for the cohesive interactions between crack surfaces.
Abstract: Fracture mechanics is one of the most important approaches to structural safety analysis. Modeling the fracture process zone (FPZ) is critical to understand the nonlinear cracking behavior of heterogeneous quasi-brittle materials such as concrete. In this work, a nonlinear extended scaled boundary finite element method (X-SBFEM) was developed incorporating the cohesive fracture behavior of concrete. This newly developed model consists of an iterative procedure to accurately model the traction distribution within the FPZ accounting for the cohesive interactions between crack surfaces. Numerical validations were conducted on both of the concrete beam and dam structures with various loading conditions. The results show that the proposed nonlinear X-SBFEM is capable of modeling the nonlinear fracture propagation process considering the effect of cohesive interactions, thereby yielding higher precisions than the linear X-SBFEM approach.

16 citations

Journal ArticleDOI
TL;DR: In this paper, a 3D finite element method (3-D FEM) is developed to simulate the temperature and thermal stress distribution in the concrete overflow dam during the construction period.

9 citations

Journal ArticleDOI
TL;DR: In this article, the Drucker-Prager non-linear finite element method (DP NL FEM) yield model is presented as a method to overcome the problem of the stress peaks at singularity points, and to produce more realistic stresses at the base of the dam wall.
Abstract: For many decades the 'classical' method has been used to design gravity dams. This method is based on the Bernoulli shallow beam theory. The finite element method (FEM) has become a powerful tool for the dam design engineer. The FEM can deal with material properties, temperatures and dynamic load conditions, which the classical method cannot analyse. The FEM facilitates the design and optimisation of new dams and the back analysis of existing dams. However, the linear elastic FEM has a limitation in that computed stresses are sensitive to mesh density at 'singularity points'. Various methods have been proposed to deal with this problem. In this paper the Drucker-Prager non-linear finite element method (DP NL FEM) yield model is presented as a method to overcome the problem of the stress peaks at singularity points, and to produce more realistic stresses at the base of the dam wall. The fundamentals of the DP NL FEM are presented. Benchmark studies of this method demonstrate the method's viability to deal with zones in a structure with stresses beyond the elastic limit where yielding of the material occurs. A case study of a completed gravity dam is analysed, comparing several analysis techniques. The service and extreme load cases are investigated. Different material properties for the concrete and rock, including weathered material along the base of the wall, are considered. The application and merits of the DP NL FEM are presented. The calculation of the critical factor of safety against sliding is done with a more realistic determination of the conditions along the base of the wall.

9 citations

Journal ArticleDOI
TL;DR: In this paper, a two-step approach for discrete crack analysis of concrete gravity dams under earthquake force is presented, based on the intuitive conjecture that the effect of cracks on structural acceleration in gravity dams is small, thus allowing the actual inertia force (the product of mass and acceleration) to be approximately obtained by linear response analysis.

9 citations

Journal ArticleDOI
TL;DR: Fiber Bragg Grating (FBG) strain sensor is presented to obtain the strain of small-scale model during testing and shows advantages of ease for installation, high sensitivity, and reliability compared with traditional resistance strain gauge.
Abstract: A 203-m-high gravity dam being built in earthquake-prone areas needs to be investigated very carefully to determine its dynamic responses, damage mechanism, and safety evaluation. The dynamic characteristics, seismic responses, failure mode, and safety evaluation of the above structure are presented through dynamic fracture test for small-scale model on shaking table. Because the strength of the model material is very low, the traditional strain gauge is also not easy to be glued to the surface of model. It is difficult to measure the accurate strain data of small-scale model during testing. Therefore, Fiber Bragg Grating (FBG) strain sensor is presented to obtain the strain of small-scale model during testing, due to its high sensitivity. The dynamic strain and residual strain are obtained with the FBG sensors embedded in model. The FBG sensor is adhered to model material completely and shows advantages of ease for installation, high sensitivity, and reliability compared with traditional resistance strain gauge. The model during testing is submitted with earthquake wave from the Chinese Code. In the experiment, the peak ground acceleration (PGA) of the first crack in the model indicates the safety level of the gravity dam. The crack locations and forms determine the damageable part of gravity dam under intense earthquake. After the final analysis, the safety evaluation result of the gravity dam under strong earthquake is given in order to guide the implementation of the project.

6 citations

References
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Book
01 Jan 1980

1,072 citations


"Finite element fracture modelling o..." refers methods in this paper

  • ...Four-noded quadrilateral plane strain elements were used and a modified Newton-Raphson solution technique was adopted for the non-linear equations (Owen & Hinton 1980)....

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  • ...Non-linear FE analysis using material plasticity models such as Drucker-Prager, Mohr-Coulomb (see, for example, Owen & Hinton 1980) and contact simulation of cracking are also often adopted to predict cracking in concrete dams....

    [...]

26 Sep 1988

708 citations


"Finite element fracture modelling o..." refers methods in this paper

  • ...Constitutive relationship during cracking The multi-directional crack model proposed by De Borst and Nauta (1985) and Rots (1988), which is well established, is adopted and has the following main features: a new crack will be initiated whenever the angle between the normal to the crack plane of the…...

    [...]

  • ...The shear retention factor is defined as a decreasing function of the crack normal strain in equation (3), which is similar to that used by Rots and Blaauwendraad (1989), except that a maximum shear retention factor βmax is defined here to limit the maximum shear allowed in a crack....

    [...]

Journal ArticleDOI
TL;DR: In this paper, a new model for handling non-orthogonal cracks within the smeared crack concept is described, based on a decomposition of the total strain increment into a concrete and into a crack strain increment.
Abstract: A new model for handling non‐orthogonal cracks within the smeared crack concept is described. It is based on a decomposition of the total strain increment into a concrete and into a crack strain increment. This decomposition also permits a proper combination of crack formation with other non‐linear phenomena such as plasticity and creep and with thermal effects and shrinkage. Relations are elaborated with some other crack models that are currently used for the analysis of concrete structures. The model is applied to some problems involving shear failures of reinforced concrete structures such as a moderately deep beam and an axisymmetric slab. The latter example is also of interest in that it confirms statements that ‘reduced integration’ is not reliable for problems involving crack formation and in that it supports the assertion that identifying numerical divergence with structural failure may be highly misleading.

352 citations


"Finite element fracture modelling o..." refers methods in this paper

  • ...Constitutive relationship during cracking The multi-directional crack model proposed by De Borst and Nauta (1985) and Rots (1988), which is well established, is adopted and has the following main features: a new crack will be initiated whenever the angle between the normal to the crack plane of the last crack and the current principal stress direction exceeds a pre-defined threshold angle or the inclined maximum principal stress σ1 violates the crack onset criterion....

    [...]

  • ...Constitutive relationship during cracking The multi-directional crack model proposed by De Borst and Nauta (1985) and Rots (1988), which is well established, is adopted and has the following main features: a new crack will be initiated whenever the angle between the normal to the crack plane of the…...

    [...]

Book
01 Jan 1995
TL;DR: In this paper, a linear elastic fracture mechanics application of LEFM to concrete nonlinear fracture theories for concrete approximate non-linear fracture models test methods for the determination of fracture parameters brittleness and size effect of concrete structures determination of the tension softening response of concrete application to plain concrete structure application to reinforced concrete structures application to high performance cementitious materials.
Abstract: Linear elastic fracture mechanics application of LEFM to concrete nonlinear fracture theories for concrete approximate nonlinear fracture models test methods for the determination of fracture parameters brittleness and size effect of concrete structures determination of the tension softening response of concrete application to plain concrete structures application to reinforced concrete structures application to high performance cementitious materials.

351 citations


"Finite element fracture modelling o..." refers background in this paper

  • ...(See for example Karihaloo 1995 for a background to fracture mechanics.)...

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Journal ArticleDOI
TL;DR: In this paper, a series of tests on the size effect due to blunt fracture is reported and analyzed, and the fracture energy is defined as the specific energy required for crack growth in an infinitely large specimen.
Abstract: A series of tests on the size effect due to blunt fracture is reported and analyzed. It is proposed to define the fracture energy as the specific energy required for crack growth in an infinitely large specimen. Theoretically, this definition eliminates the effects of specimen size, shape, and the type of loading on the fracture energy values. The problem is to identify the correct size-effect law to be used for extrapolation to infinite size. It is shown that Bazant's recently proposed simple size-effect law is applicable for this purpose as an approximation. Indeed, very different types of specimens, including three-point bent, edge-notched tension, and eccentric compression specimens, are found to yield approximately the same fracture energy values. Furthermore, the R-curves calculated from the size effect measured for various types of specimens are found to have approximately the same final asymptotic values for very long crack lengths, although they differ very much for short crack lengths. The fracture energy values found from the size effect approximately agree with the values of fracture energy for the crack band model when the rest results are fitted by finite elements. Applicability of Bazant's brittleness number, which indicates how close the behavior of specimen or structure of any geometry is to linear elastic fracture mechanics and to plastic limit analysis, is validated by test results. Comparisons with Mode II shear fracture tests are also reported.

332 citations


"Finite element fracture modelling o..." refers methods in this paper

  • ...This beam was tested experimentally by Bažant and Pfeiffer (1987) and modelled numerically by Bhattacharjee and Leger (1993) and Cai et al (2006). The model parameters used are listed in table 2....

    [...]

  • ...This beam was tested experimentally by Bažant and Pfeiffer (1987) and modelled numerically by Bhattacharjee and Leger (1993) and Cai et al (2006). The model parameters used are listed in table 2. The mesh objectivity verification analyses carried out by Bhattacharjee and Leger (1993) and Cai et al (2006) have the following limitations: Sn cr...

    [...]

  • ...This beam was tested experimentally by Bažant and Pfeiffer (1987) and modelled numerically by Bhattacharjee and Leger (1993) and Cai et al (2006)....

    [...]