2023 – Impact of Element Size and Frequency Content of Input Earthquake on the Dynamic Modelling of Embankment Dams

Ryan Morrish, Mahdi Zoorabadi, Francisco Lopez

The dynamic analysis of embankment dams subject to seismic events has evolved greatly over the years. However, as with all methods for numerical modelling, the quality of the results is highly dependent on the quality of the input data and model parameters. The most common method for modelling the dynamic behaviour of an embankment dam is the Finite Element Method (FEM). In the case of FEM, the size of each element of the model affects both the quality of the results and the computation running time. Therefore, the selection of an appropriate element size is a fundamental aspect in order to obtain the right balance between the required precision in the results and the model processing times.

A well-established empirical method for calculating the maximum element size of the FEM is to divide the wavelength of the highest frequency by 10. However, current literature is divided on what the correct frequency to adopt is to calculate the maximum element size.

This paper details the methodology and results for a sensitivity analysis of an embankment subject to an earthquake loading using FEM, where the frequency and wavelength to element size ratio are adjusted in order to seek clarification on what is the appropriate ratio of frequency to element size that provides an acceptable compromise between the accuracy of results and required running times.

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