Importance of free field boundary conditions to the finite element modelling of surface topography effects on incident waves

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4. Importance of free field boundary conditions to the finite element modelling of surface topography effects on incident waves

Surface topography effects have been associated with extreme peak accelerations recorded during strong earthquake, often resulting in severe structural damage. Although emerging as a natural choice for the performance-based design of this type of problems, given its robustness, ability to capture the interaction between different physical systems and wide availability, the accurate and cost-efficient finite element (FE) modelling of surface topography effects on incident waves is often challenging due to the need to truncate the theoretically unbounded wave propagation domain to a computationally feasible size. In effect, for earthquake-induced loading, these artificial boundaries should be able to apply free field motion to the main domain, while absorbing any spurious reflections. In this paper, a series of FE analyses are performed to investigate the performance of the newly revised PLAXIS 2D free field boundary conditions (BCs). It is firstly shown that the obtained results are consistent with independent benchmark solutions. Subsequently, the impact of the BCs on the computed solution is assessed by simulating the same problem with other BCs and comparing the obtained results against each other. It is concluded that the absorption capability at the boundary is a key ingredient to achieve accurate results in this type of problems.

10th European Conference on Numerical Methods in Geotechnical Engineering (NUMGE2023)

4. Geotechnical earthquake engineering