Modeling soil

[lotsofquestions]

I'm trying to model soil under a 4m x 4m concrete slab foundation in SAP2000. I am using a shell element to model the slab. I know I can use springs to model the soil but am unclear on the specifics of how to do so. There are lots of spring options in SAP2000.

Should I use joint springs or area springs?
If I use area springs, should I use a simple spring (compression & tension, only compression, only tension) or link property?
Should I have springs in all three directions?

 

[IJR]

Depends on what you are looking for.

For area springs you enter K in force/cubic length units
for joint springs you enter k in force /linear length units

If you are sure you will not have tension in the soil and linear analysis is fine with you, use simple spring
if you want to get rid of tension then say only compression, but saying that may require you do a nonlinear analysis.
To do links, learn first.

hope this helps

 

[jsha811]

Area spring is just a quick way for you to assign the spring to the area. At then end, the spring stiffness will be lumped at each joint.

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