| Application | PLAXIS 2D |
| Version | PLAXIS 2D CONNECT Edition V22 Update 2 PLAXIS 2D 2023.1 |
| Date created | 20 March 2023 |
| Date modified | 20 March 2023 |
Introduction
One of the greatest challenges in dynamic finite element analysis consists of the need to limit the theoretically unbounded wave propagation domain to a finite domain where waves are not unrealistically reflected at the boundaries. Concurrently, when the source of excitation is external to the model, such as in earthquake-induced loading, it is necessary to ensure that free field motion (i.e. dynamic motion in the absence of soil-structure interaction) is computed near the boundaries. In PLAXIS, free field boundary conditions can play this dual role. To improve their abilities, two modifications were recently introduced to the formulation implemented in PLAXIS 2D, one of them related to the equilibrium condition, while the other concerning the contribution of the boundaries to the damping matrix. The effects of the newly introduced modifications are explored in a case study concerning the response of two adjacent buildings resting on a saturated deposit of moderately loose sand subjected to an earthquake motion causing liquefaction. It is shown that:
- As intended, the newly revised formulation improves the deformation pattern and excess pore pressure profile obtained near the boundaries.
- For the present case study, it is possible to reduce the model width without affecting the accuracy of the obtained solution, while significantly reducing the run time.
1D site response analysis, deformed mesh (scaled up 5 times) and excess pore pressure ratio at the end of the dynamic phase obtained when using PLAXIS 2D CE V22.02 for a case study.
Note: Dynamics features such as earthquake analysis, vibrations and the mentioned Free Field elements are available in PLAXIS 2D Ultimate. See here for more details.