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  • 1
    Electronic Resource
    Electronic Resource
    Damage analysis by boundary element method (1994)
    Springer
    Acta mechanica solida Sinica 7 (1994), S. 245-255 
    Details
    ISSN: 0894-9166
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The response of cracked bodies subjected to loading was investigated by the boundary element method in this paper. The two-law elastic-cohesive-softening model was used for crack propagation analysis. The interface conditions for uncracked, craze, open crack, adhesive crack and slid crack parts were discussed and the corresponding incremental iteration algorithm was given. A simplified damage propagation model was presented. The technique has been applied to some specific examples which give the evidence that the method is satisfactory and efficient.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208369
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  • 2
    Electronic Resource
    Electronic Resource
    Organisation Météorologique Internationale (O.M.I.) (1946)
    Springer
    Cellular and molecular life sciences 2 (1946), S. 512-512 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02137585
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  • 3
    Electronic Resource
    Electronic Resource
    Zur Thermodynamik der Trombenbildung (1945)
    Springer
    Cellular and molecular life sciences 1 (1945), S. 180-183 
    Details
    ISSN: 1420-9071
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Koschmieder's new thermodynamical theory of tornado formation (1940) makes it probable that a tornado (or a waterspout) develops when a warm air packet rises quickly within the convective mother cloud. In the present paper the three principle cases of conditions are indicated under which supplementary amounts of potential energy necessary to start a “daughter convection” in the cumulo-nimbus cloud can become available in the latter. Supply of moister air from below seems to be at least as important as that one of warmer air. However, the suddenness of the release of the said supplementary energy cannot be explained by the abrupt annihilation of an intercepting layer within the main body of the cumulo-nimbus, for the pre-existence of such a layer is incompatible with the general character of this type of cloud.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02164063
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  • 4
    Electronic Resource
    Electronic Resource
    Micromechanical identification of anisotropic damage evolution laws (1999)
    Springer
    International journal of fracture 98 (1999), S. 55-76 
    Details
    ISSN: 1573-2673
    Keywords: Anisotropic ; damage ; evolution ; crack tenso.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper deals with the establishment of anisotropic conjugate force based damage evolution laws in the framework of Rice's (1971) ‘normality structure’. The damage variable is the second-order crack tensor (Kachanov, 1980), which represents preexisting Griffith microcracks in a solid. The principal results include the deduced damage surfaces, potentials and kinetic equations for the basic internal variables and damage tensor during isothermal processes. The generalized pth order crack tensors and qth order energy release rates are introduced. The deduction in this paper is fully independent of the specific form of the free energy or Gibbs energy functions, so the deduced damage evolution laws have a wide applicable range including plasticity. Using the deviatoric stress as the conjugate force, the two well-established anisotropic yield surfaces, Karafillis and Boyce (1993) and Hill (1950), are recovered from the deduced damage surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018787705489
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  • 5
    Electronic Resource
    Electronic Resource
    Numerical model for rock bolts with consideration of rock joint movements (1995)
    Springer
    Rock mechanics and rock engineering 28 (1995), S. 145-165 
    Details
    ISSN: 1434-453X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: Summary The stability of any underground structure during and after excavation is the most important question for designers, because any kind of collapse may destroy large parts of a finished tunnel, causing major repairs and time loss. Preliminary calculations are therefore of great importance. A calculation is only useful, however, when the underlying numerical model correctly describes natural behaviour. The rock bolts used in tunnel excavations are mostly untensioned grouted bolts, and this type of bolt is the main focus of this work. From the model of the grouted bolt, other types of rock bolts can also be modelled by the theory presented herein. Bolt behaviour in intact rock mass is so different from behaviour when a bolt intersects a joint, that a model with two different elements is suggested for a numerical calculation; one element for the bolt in the rock mass and one as a bolt intersecting with a joint. The model for both elements is verified by the experimental results. The numerical results correspond favourably with the experimental work. A variation of the parameters important for the behaviour of the bolt in intersection with the joint is shown. As an implementation of the bolt model, the numerical simulation of excavation and stabilisation of one road tunnel is presented.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01020149
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  • 6
    Electronic Resource
    Electronic Resource
    ROBUST PRECONDITIONERS FOR LINEAR ELASTICITY FEM ANALYSES (1997)
    Chichester [u.a.] : Wiley-Blackwell
    International Journal for Numerical Methods in Engineering 40 (1997), S. 2109-2127 
    Details
    ISSN: 0029-5981
    Keywords: preconditioned conjugate gradients ; incomplete factorization ; unstructured irregular grids ; finite elements ; linear elasticity ; Engineering ; Numerical Methods and Modeling
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: This paper deals with two forms of preconditioner which can be easily used with a Conjugate Gradient solver to replace a direct solution subroutine in a traditional engineering finite element package; they are tested in such a package (FINAL) over a range of 2-D and 3-D elasticity problems from geotechnical engineering. Quadratic basis functions are used.A number of modifications to the basic Incomplete Choleski [IC(0)] factorization preconditioner are considered. An algorithm to reduce positive off-diagonal entries is shown in numerical experiments to ensure stability, but at the expense of slow convergence. An alternative algorithm of Jennings and Malik is more successful, and a relaxation parameter ο is introduced which can make a further significant improvement in performance while maintaining stability. A heuristic for determining a near-optimal value of ο is proposed. A second form of preconditioning, symmetrically scaled element by element, due to Bartelt, is also shown to perform robustly over a range of problems; it does not require assembly of the global stiffness matrix, and has great potential for parallelization. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Simulation of arch dam - foundation interaction with a new friction interface element (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 18 (1994), S. 601-617 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: A new model for three-dimensional non-linear contact problems with irreversible friction is presented here for the interaction between the rock foundation and an arch dam structure. Based on the finite element method and load incremental theory, a constraint contact element with displacements and contact stresses as node parameters is developed. In this approach, four contact conditions are considered, i.e. fixed, slip, free and mixed. This model can simulate frictional slippage, decoupling and re-bonding of two bodies initially mating at a common interface or with any initial gaps. Furthermore boundary conditions for this element are discussed and treatment measures proposed. This method is shown to be effective and to have the advantage of being easily implemented into standard finite element programs. Solutions are obtained for a centrally loaded, simply supported composite beam and for an end-loaded elastica with initial gaps in regional contact with a rigid surface. The results obtained for these examples are compared to the plane stress solutions by contact friction analysis. As an application example, Quanshui arch dam located in Ruyuan County of Guangdong Province in southern China is simulated with the new element.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610180903
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  • 8
    Electronic Resource
    Electronic Resource
    Rheological analysis of tunnel excavations by means of coupled finite element (FEM)-boundary element (BEM) analysis (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    International Journal for Numerical and Analytical Methods in Geomechanics 11 (1987), S. 115-129 
    Details
    ISSN: 0363-9061
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Geosciences
    Notes: To facilitate the practical numerical analysis of tunnel structures by means of the finite element method in the case of viscoplastic properties of the rock mass and viscoelastic properties of the shotcrete, this method is coupled to boundary elements. In this way, the unchanged properties of the boundary element region provide enormous savings in computing time. In order to improve the numerical stability of such calculations, a variable time-step analysis was employed for each time step with an iterative correction method. Characteristic values are obtained from measured values by back-analysis.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/nag.1610110202
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  • 9
    Electronic Resource
    Electronic Resource
    Nonlinear beam element for r/c structures (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Communications in Applied Numerical Methods 3 (1987), S. 397-406 
    Details
    ISSN: 0748-8025
    Keywords: Engineering ; Engineering General
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mathematics , Technology
    Notes: A simple 2-node beam element with 6 degrees-of-freedom has been developed for solving static problems of r/c beams efficiently and fast.1 This integrated beam element considers, in the element stiffness matrix, the nonlinearity of the concrete and reinforcement. Cracks are ‘smeared out’ in a continous fashion along the element length, so that cracking does not cause geometrical changes of the system. Tension stiffening is implemented by modifying the stress-strain curve either of concrete or of steel.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cnm.1630030507
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