ITASCA Flac3D 7.00.151
Why Use FLAC3D for Dynamic Analysis?
FLAC3D is especially useful for performing dynamic analyses. This page provides a brief overview of some of the features that make FLAC3D ideal for dynamic analysis.
Full Non-linear Solution in Time Domain
FLAC3D will provide a fully non-linear and path-dependent solution in time domain. FLAC3D uses the full equations of motion in its solution process. For static analysis, additional damping and mass scaling are introduced to facilitate the process of approaching the static equilibrium. For a dynamic solution, FLAC3D uses real grid-point masses and physically realistic damping. In short, for most purposes dynamic versus static is simply a small variation in the solution process.
The non-linearity and path-dependency of the stress-strain response is determined based on the constitutive law used at each zone. For a comprehensive constitutive law, modulus degradation and variation in damping due to changes in strain are inherent to the constitutive law. For simpler constitutive laws however, use of hysteretic damping and/or Rayleigh damping is advised.
The approach utilized by FLAC3D for obtaining a non-linear path-dependent solution in the time domain contrasts with the equivalent-linear methods commonly used in earthquake engineering, where response is obtained in frequency domain and the effects of any non-linearities are included in an incremental fashion. For more information about the differences and similarities of the two methods see the “Dynamic Analysis” section of the FLAC3D Manual.
The sample code included below models 1-D wave propagation of a shear wave generated at the bottom of the model. The excitation is comprised of a single frequency pulse with a reflective boundary at the bottom and a free top boundary. The simulation is undamped, and none of the boundaries are absorbent, so the wave will propagate indefinitely.
The second plot shows the same model, but with a quiet boundary defined at the bottom of the model. Note that the wave travels upward, reflects back into the model from the free surface, returns to the bottom boundary and then vanishes.
Product:ITASCA Flac3D 7.00.151