Winkler type elements - line support stiffness

[hockley]

Maybe this is a bit of a basic question - but I'd be grateful if someone could give me some advice or, failing that, refer me to an appropriate source on the web.

When modelling a strip foundation in AxisVM (a 3D finite element package) if I use the default line support stiffness Rz of 1E+7kN/m/m the reactions I get are rather "peaky". I would like, if possible, to make the support elements a little bit softer but I am unsure of how they are working.

In the manual it mentions that the line support elements are Winkler type elements. For a given width of strip foundation and a given ground stiffness how should I calculate the parameter Rz?

Rz has dimensions kN/m/m - is this simply the stiffness modulus of the ground (Es in kN/sq. metre) multiplied by the width of the strip foundation or is there, as I suspect, more to it than that?

Also, if you could give me guidance on how one calculates the value of Rz for ground-bearing slabs (given a certain ground stiffness modulus) I would be very grateful.

 

[Denial]

A "Winkler" support under a beam or under a plate is one where the restoring pressure (in units F/L or F/L^2 respectively) is proportional to the tranverse displacement and depends upon nothing else. Continuity in the supporting medium is totally ignored.

The classic text for beam behaviour under this assumption is the book "Beams on Elastic Foundation" by M.Hetenyi, originally published by Uni of Michigan Press in 1961 (and, I think, since re-published).

Formulae for a range of special cases are presented in many books, including Roark's "Formulas for Stress and Strain". If searching, try use "beam on elastic foundation" rather than "winkler" as your search term.

I can give you no guidance on Rz values. You will probably need specialist geotechnical assistance for that.

 

[Denial]

Correction. Hetenyi's book was first published in 1946. Republished in 1961. (Doesn't time fly when you're having fun?)