Non-Linear Structural Elements

FLAC3D 9 introduces new non-linear structural elements for ground support for beams and piles/rockbolts and for shells, geogrids, and liners. Simple plastic hinges have been supplemented with a numerical integration scheme.

BEAM-TYPE STRUCTURES

  • The beam-type plastic constitutive models update the internal element forces by integrating the internal stress over the beam volume using a numerical integration scheme.
  • The plasticity is induced by axial and bending deformations; twisting deformation induces an elastic response.
  • The beam may have either a rectangular or circular cross section.
  • Integration points are distributed throughout the volume of the beam elements.
  • There are three beam plastic constitutive models, each of which is a one-dimensional version of the corresponding 3D model used by the zones:
    • von Mises (steel beams)
    • Mohr Coulomb (concrete beams)
    • Strain Softening/Hardening Mohr Coulomb (concrete beams)

The following commands are for an rectangular cross-section aluminum ally beam:

struct beam cmodel assign von-mises

struct beam cmodel plastic-integration rectangular cross-section rectangular layout 3 5 3

struct beam property direction-y (0,1,0) young 68e9 poisson 0.33 strength-yield 270e6 modulus-plastic 0.0; 6061-T6 Al alloy

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SHELL-TYPE STRUCTURES

  • The plastic constitutive models update the internal element forces by integrating the internal stress over the shell volume using a numerical integration scheme.
  • There are a group of integration points distributed throughout the volume of each shell element.
  • There are three shell plastic constitutive models, each of which is a plane-stress version of the corresponding 3D model used by the zones:
    • von Mises (steel shells)
    • Mohr Coulomb (concrete shells)
    • Strain Softening/Hardening Mohr Coulomb (concrete shells)
  • Plasticity is provided by the DKT, CST and DKT-CST finite elements.

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