Modelling Soils with Springs

[shaheed]

As an extension to the question already asked by "Sepultura" how would one model the soil spring as compression only - using ETABS. Any hints/thoughts would be extremely appreciated.

 

[stressed]

There is no automated way to do this like in SAFE. However, you can define Link properties, Gap type, and do joint assignments to put them at joints on your basemat. The stiffness values for the gap links would be determined by soil subgrade modulus, size of element and tributary area. The gap type links are nonlinear compression only joint springs. If you can live without the nonlinear compression-only analysis, ETABS lets you assign area springs on your basemat (modeled as slab/shell) in which you input subgrade modulus for vertical springs. Thing is, you have to remember to restrain the basemat in the local 1 and 2 lateral directions too, using area or joint springs or joint restraints, to prevent instabilities.