Anker and Masses

[PiaKoerz]

Hi there,

I'm currentlich starting to learn SAP2000 and facing a few problems.
I'm trying to build a simple wall with frame elements (blue) and link-elements (green), which should act as springs. From some tests on real walls I know the behaviour of the walls and can describe this with hysteretic curves and a certain stiffness. These values are my input parameters for the link-elements. I want the frame elements to be infinite rigid and the joints to be flexible.
For the modelling of the foundation, I would like to model two different versions. One (like in the picture) is to simply use restraints. The other one is to assign two link-elements at the two bottom joints. The second version should simulate the behaviour of ankers that we also testet on the real walls. The ankers should only work in tension and be infinite rigid in compression. For the first try i set the values of the compression values to 10^8 and the tension like the values we got as results from the tests. Is there any other possibility such as blocking the compression completely?
And my second question would be how I should assign the weight of the wall. When assigning it to the link elements, it won't be taken into account for the modal analysis. I'd like to use load patterns as later in the tast I also need to assign more loads such as snow loads. Does anybody know the best way to do this?

Thanks in advance!!

 

[JoshPlumSE]

For the first try i set the values of the compression values to 10^8 and the tension like the values we got as results from the tests. Is there any other possibility such as blocking the compression completely?

I would have done it how you describe. Any compression related deflection should come out (effectively) as zero. So, I'd only start looking for other solutions if I were getting significant deflection there. Remember that the goal is to create a model that will get you the behavior you seek. It should not be to develop a "perfect" model (IMO), because no such model exists.

And my second question would be how I should assign the weight of the wall. When assigning it to the link elements, it won't be taken into account for the modal analysis. I'd like to use load patterns as later in the tast I also need to assign more loads such as snow loads. Does anybody know the best way to do this?

I have to admit that I've never really thought to DIRECTLY load a link element itself. I always think of them as not having any weight / mass. Though I do understand that having mass in the link can be helpful for Nonlinear time histories.

That being said, if I wanted to define gravity loads to a link, I would probably just do this with the link's self weight rather than trying to apply line loads or such.

Note: I probably should know more about links by now, but I don't. So, you should not take my reply as definitive. If others are experts, I welcome them to reply. If not, you might want to contact CSI's technical support group to make sure.

 

[PiaKoerz]

Thanks for the answer. For the compression deflection I also thought that it might be fine like this but as I'm fairly new I also thought that there might be a "cleaner" version.

With the load problem I also came up to not taking the weight into account for the link elements but rather for the upper and lower beams (each 50% of the weight of the wall). The problem now is that when I assign the weight as a line mass for the beams and choose the mass source to be "Element mass and additional masses" the answer of the modal analysis should be the same as if I assign the weight as distributed frame load (DEAD) and choose the mass source to be "Load case" and set it to DEAD load x1. But it's not the same. For the first one the natural frequency is 6,9 and for the second case it's 21,6Hz. I also calculated the frenquency by hand using the rayleigh method and came to the result of 10,0 so none of the results of the program is anywhere near this value
With the modal analysis I actually wanted to check if my mass assigns and the stiffness are correct but now I'm just totaly confused