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Modeling compression only spring

Modeling compression only spring

Modeling compression only spring

(OP)
Hello everyone
I'm modeling a self-centering steel plate shear wall using abaqus.
As you know, in this system Post-tensioned strands create self centering property.
Beam to column connection type is rocking connection and to simulate it, used comprresion only spring.

This text is from thesis Patricia M. Clayton "Self-Centering Steel Plate Shear Walls:
Subassembly and Full-Scale Testing" :

The “compression-only springs” at the beam flanges were modeled using axial connectors with nonlinear behavior representing a high elastic stiffness in compression and very low elastic stiffness in tension

please guide me.
Please see attached photo

RE: Modeling compression only spring

Can anyone understand what hojati is talking about? I haven't got a clue.

BA

RE: Modeling compression only spring

I thought maybe a "compression only spring" with nonlinear behavior sounded like a regular helical compression spring near coilbind with simple cup or cone seats, but really, beyond that, no clue here, either.





Mike Halloran
Pembroke Pines, FL, USA

RE: Modeling compression only spring

All i have programming this far remains within linear behaviour so i really don't know how to do it. Some of the reading i have done uses the following:

Stepwise procedures dividing time or loads on an increasing range, and checking each component step by step. You will need a nice iterative approach in order to solve() your data. It may worth the effort on a dynamic analysis i suppose.

But also i been thinking to set limits to the load. Maybe determining the yield load (or the one of your interest) as first load input and then a second load of interest. It's pretty similar to the above but with less steps and could be useful when stiffness is multilinear.

Good luck!

RE: Modeling compression only spring

First question, how does one physically construct a compression only "spring" in the field? Secondly, if its compression only, that does not seem conducive to the cyclic action of a seismic event. In other words, if the building sways back and forth, wouldn't the spring also see tension?

RE: Modeling compression only spring

Hi hojati, i'll like to know if you solved this and any commentary you'll like to give as. Thanks!

RE: Modeling compression only spring

I don't know abaqus but modelling a compression only spring would be non-linear (giving the spring a non-linear response).

you can bound the problem with two linear runs ...
1) use a simple spring, if compression load then ok, else
2) delete the spring and run again; if +ve displacement (indicating the spring would be in tension) then ok.
but if 2) gives a compression displacement then you need to model the spring properly.

another day in paradise, or is paradise one day closer ?

RE: Modeling compression only spring

Quote (hojati)

The “compression-only springs” at the beam flanges were modeled using axial connectors with nonlinear behavior representing a high elastic stiffness in compression and very low elastic stiffness in tension

So, the way I interpret this comment is that this axial member is intended only to represent the non-linear connectivity between two elements. If the member is in compression it acts as a rigid link. If the member is in tension, it has a near zero sttiffness.... likely to help with convergence issues in the abaqus solution.

RE: Modeling compression only spring

rb1957, how fast your view would work with several elements under multilinear behaviour?

RE: Modeling compression only spring

I'd "suck it and see". try running with normal springs ... do any of them see tension ? try no springs, do all of them displace to create tension ?

most likely, unfortunately, some will misbehave and you'll be stuck with the NL run.

another day in paradise, or is paradise one day closer ?

RE: Modeling compression only spring

what a strange perception

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