Compression only joint springs

[randx]

I created this model perform a 2d frame analysis for a drain structure. I need to add joint springs in the bottom beam to represent the soil condition. What is the best way to do it?

 

[JoshPlumSE]

I usually base vertical soil spring stiffness off of the modulus of subgrade reaction of the soil. Though some geotechs are reticent to provide that information for some reason.

 

[Brad805]

If there are no load cases that will lead to the springs in tension, then a soil spring as Josh describes works fine. If your load cases lead to tension in the soil springs, then gap elements might work or you can add a short frame element that you can assign the tension = 0. There are useful videos on the CSI youtube page for gap elements.

 

[randx]

Brad805, If I use gap element, I have to use non-linear load case as well. For this kind of situation, which kind of load case should be applied?

 

[Brad805]

It is a non-linear problem if you want to relieve the tensile forces. During the NL load case the stiffness of the model changes to reduce the tensile forces to zero. If you do not have NL SAP2000 module, another option is to run the model to see where you find tension. Once you see where you have tension, simply delete those springs and re-run the model. It is a nuisance if you have many load cases. SAFE has compression only springs that are ideal for this problem.

I don't quite follow the loading for your structure or its dimensions. You would have to include that in your schematic for more useful advice. I would start with some hand calcs to see what you expect.