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Tension/Compression Springs to Model Pier Axial Deformation for Core Wall Deflections

Tension/Compression Springs to Model Pier Axial Deformation for Core Wall Deflections

Tension/Compression Springs to Model Pier Axial Deformation for Core Wall Deflections

(OP)
It appears that the joint spring assign function does not allow for multiple stiffness values for springs under tension and compression.

I am attempting to model the effects of a deep foundation on a tall core wall providing lateral stability of a building. I am concerned with building drift. I will model the "compression" spring to represent the axial stiffness of the pier (concrete) and the "tension" spring to represent the axial stiffness of the pier steel only (since under full tension load, the pier will undoubtedly have some level of tension cracking).

Can someone provide some feedback/guidance to my process as described below?:

I have modeled short 3 ft rigid frame members under each core wall support (essentially a short pier with rigid properties, pinned at it's base, and restricted against all lateral translation at its connection to the core wall). I then assigned "line spring" properties to those frame elements. Though, this method seems to be giving counterintuitive results. I would expect larger deflection since I am softening the springs for the pier tension case, but I am getting smaller deflections (when I compare this to using a blanket spring stiffness equal to the pier compressive stiffness).

Anybody have experience in modeling something similar to this!? Is there a different way to capture this behavior?

Any feedback is appreciated. Thank you.

RE: Tension/Compression Springs to Model Pier Axial Deformation for Core Wall Deflections

(OP)
So I don't think I correctly understood what a line spring is. Appears to be more applicable for modeling a frame element on soil or something similar to that.

Back to where I started. Any thoughts on how to model different stiffness values for springs in ten/comp???

RE: Tension/Compression Springs to Model Pier Axial Deformation for Core Wall Deflections

(OP)
Use JOINT LINK properties to model non-linear springs.

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