Footfall analysis on floor plate - Damping

[lbasil]

Hi everyone.

I am working on the development of a script which will assess the response of a (timber) floor plate to successive walking loads of given rate. I have managed to get reasonable acceleration values, but the diagrams I get from the output data seem a bit weird. I have used the Rayleigh command to introduce a damping ratio (D) of 0.02%. More specifically I solved the equation: D=aK+bM, where K is the stiffness matrix and M the mass matrix to get the partial factors a and b. (rayleigh 0.0037 0.02 0.00 0.0). I am still not sure how this command works, but the acceleration/time diagram I get doesn't look right. On the other hand, when I use a=b=0.001 I get much more 'reasonable' distribution.

I would appreciate any help as I am currently trying to finish it and get results for my thesis.

Thank you in advance.