Dynamic Analysis

The dynamic analysis option permits three-dimensional, fully dynamic analysis with FLAC3D. The calculation is based on the explicit finite difference scheme (as discussed in Theoretical Background) to solve the full equations of motion using lumped gridpoint masses derived from the real density of surrounding zones (rather than fictitious masses used for static solution). This formulation can be coupled to the structural element model, thus permitting analysis of soil-structure interaction brought about by ground shaking. The dynamic feature can also be coupled to the groundwater flow model. This allows, for example, analyses involving time-dependent pore pressure change associated with liquefaction (see Dynamic Pore-Pressure Generation). The dynamic model can likewise be coupled to the optional thermal model in order to calculate the combined effect of thermal and dynamic loading. The dynamic option extends FLAC3D’s analysis capability to a wide range of dynamic problems in disciplines such as earthquake engineering, seismology and mine rockbursts.

The fully nonlinear analysis method used by FLAC3D contrasts with the more commonly accepted “equivalent-linear” method used in earthquake engineering. Relation to Equivalent-Linear Methods compares the two methods and provides a review of recent applications of the fully nonlinear method. Background information on the Dynamic Formulation of the fully nonlinear method implemented in FLAC3D is also provided.

This volume includes discussions on the various features and considerations associated with the dynamic option in FLAC3D (i.e., dynamic loading and boundary conditions, wave transmission and mechanical damping). These features are described separately in Dynamic Modeling Considerations.

The user is strongly encouraged to become familiar with the operation of FLAC3D for simple mechanical, static problems before attempting to solve problems involving dynamic loading. Dynamic analysis is often very complicated and requires a considerable amount of insight to interpret correctly. A recommended procedure for conducting dynamic numerical analysis with FLAC3D is provided in Solving Dynamic Problems. Example analyses are also presented in this section to illustrate the procedure. These examples cover several of the features and considerations described in Dynamic Modeling Considerations.

Validation problems illustrating the accuracy of the dynamic model are provided . (The data files in this volume are stored in the directory “Itasca\Flac3d600\datafiles\Dynamic” with the extension “.f3dat.” A project file (with extension “.f3prj”) is provided for each example. In order to run the example, open the project file in FLAC3D.