José Abell's research blog

Paper03 - Earthquake Soil Structure Interaction of Nuclear Power Plants, differences in response to 3-D, 3 × 1-D, and 1-D excitations

Finally! First paper since PhD was accepted for publication. I’ll take this opportunity to start a tradition and review my own papers here. I think its important that I do this for several reasons. First, there are discussions that come up during peer review that are important but don’t make it into the paper. Misconceptions about the presented work can be clarified to a broader audience here. Also, I can say whatever I want, specially opinions and thoughts that come from intuition and might not make it through peer-review, I’ll be as critical as possible about these …

Talk Given at IngeoKring 2016 - Physics-Based Earthquake-Soil-Structure Interaction for Near-Field Induced Seismicity

This is a talk given at the IngeoKring 2016 Autumn symposium, hosted at TU Delft.

Simulation of a surface wave (Rayleigh)

This simulation, done in the UCD ESSI simulator and visualized in VisIt using VisIt-ESSI plugin, shows the passage of a surface wave (Rayleigh wave). The simulation consists on a surface impact on an elastic domain of 900m by 1800m depth, and a shear wave velocity of 1000km/s. Elliptical-retrograde motion can be seen as an illustration of Rayleigh waves.

VisIt can be obtained here, and the plugin here.

Visualizing ESSI output with VisIt-ESSI

VisIt-ESSI is a plugin for the VisIt post-processor created my CompGeoMech. It allows for remote (soon parallel also) visualization of outputs produced by ESSI in the HDF5 format (*.h5.feioutput).

VisIt can be obtained here, and the plugin here.

NTS-02. On Rayleigh damping coefficients for FE analysis

Note to self. How to compute Rayleigh damping coefficients for given damping ratios $\xi_1$ and $\xi_2$ at frequencies $f_1$ and $f_2$.

This is textbook content, I just need to remind myself too often how this is done and end up re-deriving the equations.

Given the second-order system of differential equations representing the FE model

$$ M \ddot{u} + C \dot{u} + K u = F(t) $$

The damping matrix $C$ can be written as a Rayleigh damping matrix:

$$ C = a_0 M + a_1 K $$

$a_0$ and $a_1$ are Rayleigh damping coefficients found by solving

$$ \left[ \begin{array}{cc} \dfrac{1}{2\pi f_1} & 2 \pi f_1 \ \dfrac{1}{2\pi f_2} & 2 \pi f_2 \end{array} \right] \left[ \begin{array}{c} a_0 \ a_1 \end{array} \right] = \left[ \begin{array}{c} \xi_1 \ \xi_2 \end{array} \right] $$

Which I do in the following code:

SNE # 01. Example of ESSI simulation and visualization with visitESSI

These are the results of a simple elastic-domain simulation. Mesh consists of

  • 154523 Nodes (46359 DOFs)
  • 1250 27 node bricks (LT formulation)
  • 1200 time-steps (dt = 0.01s)

Results were stored in the new format of output for ESSI simulator and visualized in VisIt post-processor where the movie was created.