Negative Soil Pressure and Uplift

[derek.plehal]

I am designing a large mat slab in Robot and using the elastic foundation option to model the soil. However, when I analyze the model I get negative soil pressures on the slab. When I select the option to allow uplift and prevent these negative pressures the model will not converge and give me any results. Am I missing some options or something else in the model that is preventing it from running correctly.

Any thoughts or advice would be greatly appreciated.

[length zero]

Well
First jou must verify overall stability of structure and if u can give as more informations of what are u analysing.
Maybe surface of slab which are loaded in compression is less than tension loaded surface and this affect overall stability of your structure.
In this case ( uplift analysis) program goes at nonlinear analysis phase, and you shortly must check some criterions for convergence problems,
Im thinking that you must predefine some criterions to stop analysis, in this case maximum displacements, which by default in robot is 10 cm, and maybe your real displacement exceed this valuue and you will have not convergence of results.

Hope it Help